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  • 1.
    Antonopoulou, Io
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Spanopoulos, Athanasios
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, Athens, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Single cell oil and ethanol production by the oleaginous yeast Trichosporon fermentans utilizing dried sweet sorghum stalks2020In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 146, p. 1609-1617Article in journal (Refereed)
    Abstract [en]

    The ability of the oleaginous yeast Trichosporon fermentans to efficiently produce lipids when cultivated in dried sweet sorghum was evaluated. First, lipid production was evaluated in synthetic media mimicking the composition of sweet sorghum stalks and optimized based on the nitrogen source and C: N ratio. Under optimum conditions, the lipid production reached 3.66 g/L with 21.91% w/w lipid content by using a mixture of sucrose, glucose and fructose and peptone at C: N ratio 160. Cultivation on pre-saccharified sweet sorghum stalks offered 1.97 g/L, while it was found that sweet sorghum stalks can support yeast growth and lipid production without the need for external nitrogen source addition. At an attempt to increase the carbon source concentration for optimizing lipid production, the Crabtree effect was observed in T. fermentans. To this end, the yeast was evaluated for its potential to produce ethanol under anaerobic conditions in synthetic media and sweet sorghum. The ethanol concentration at 100 g/L glucose was 40.31 g/L, while utilizing sweet sorghum by adding a distinct saccharification step and external nitrogen source offered ethanol concentration equal to 23.5 g/L. To the authors’ knowledge, this is the first time that the Crabtree effect is observed in T. fermentans.

  • 2.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bian, Bin
    Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA; Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Jimenez-Sandoval, Rodrigo
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Environmental Science and Engineering Program, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Katuri, Krishna P.
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Saikaly, Pascal E.
    Water Desalination and Reuse Center, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Environmental Science and Engineering Program, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
    Nature inspired catalysts: A review on electroactive microorganism-based catalysts for electrochemical applications2024In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 488, article id 144215Article, review/survey (Refereed)
  • 3.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krige, Adolf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Advances in cathode designs and reactor configurations of microbial electrosynthesis systems to facilitate gas electro-fermentation2022In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 354, article id 127178Article in journal (Refereed)
    Abstract [en]

    In gas fermentation, a range of chemolithoautotrophs fix single-carbon (C1) gases (CO2 and CO) when H2 or other reductants are available. Microbial electrosynthesis (MES) enables CO2 reduction by generating H2 or reducing equivalents with the sole input of renewable electricity. A combined approach as gas electro-fermentation is attractive for the sustainable production of biofuels and biochemicals utilizing C1 gases. Various platform compounds such as acetate, butyrate, caproate, ethanol, butanol and bioplastics can be produced. However, technological challenges pertaining to the microbe-material interactions such as poor gas-liquid mass transfer, low biomass and biofilm coverage on cathode, low productivities still exist. We are presenting a review on latest developments in MES focusing on the configuration and design of cathodes that can address the challenges and support the gas electro-fermentation. Overall, the opportunities for advancing CO and CO2-based biochemicals and biofuels production in MES with suitable cathode/reactor design are prospected.

  • 4.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krige, Adolf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dual cathode configuration and headspace gas recirculation for enhancing microbial electrosynthesis using Sporomusa ovata2022In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 287, Part 3, article id 132188Article in journal (Refereed)
    Abstract [en]

    High-rate production of acetate and other value-added products from the reduction of CO2 in microbial electrosynthesis (MES) using acetogens can be achieved with high reducing power where H2 appears as a key electron mediator. H2 evolution using metal cathodes can enhance the availability of H2 to support high-rate microbial reduction of CO2. Due to the low solubility of H2, the availability of H2 remains limited to the bacteria. In this study, we investigated the performances of Sporomusa ovata for CO2 reduction when dual cathodes were used together in an MES, one was regular carbon cathode, and the other was a titanium mesh that allows higher hydrogen evolution. The dual cathode configuration was investigated in two sets of MES, one set had the usual S. ovata inoculated graphite rod, and another set had a synthetic biofilm-imprinted carbon cloth. Additionally, the headspace gas in MES was recirculated to increase the H2 availability to the bacteria in suspension. High-rate CO2 reduction was observed at −0.9 V vs Ag/AgCl with dual cathode configuration as compared to single cathodes. High titers of acetate (up to ∼11 g/L) with maximum instantaneous rates of 0.68–0.7 g/L/d at −0.9 V vs Ag/AgCl were observed, which are higher than the production rates reported in literatures for S. ovata using MES with surface modified cathodes. A high H2 availability supported the high-rate acetate production from CO2 with diminished electricity input.

  • 5.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krige, Adolf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Microbial Electrosynthesis Using 3D Bioprinting of Sporomusa ovata on Copper, Stainless-Steel, and Titanium Cathodes for CO2 Reduction2023In: Fermentation, E-ISSN 2311-5637, Vol. 10, no 1, article id 34Article in journal (Refereed)
    Abstract [en]

    Acetate can be produced from carbon dioxide (CO2) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H2). However, the low solubility of H2 can limit the process. Using metal cathodes to generate H2 at a high rate can improve MES. Immobilizing bacteria on the metal cathode can further proliferate the H2 availability to the bacteria. In this study, we investigated the performances of 3D bioprinting of Sporomusa ovata on three metal meshes—copper (Cu), stainless steel (SS), and titanium (Ti), when used individually as a cathode in MES. Bacterial cells were immobilized on the metal using a 3D bioprinter with alginate hydrogel ink. The bioprinted Ti mesh exhibited higher acetate production (53 ± 19 g/m2/d) at −0.8 V vs. Ag/AgCl as compared to other metal cathodes. More than 9 g/L of acetate was achieved with bioprinted Ti, and the least amount was obtained with bioprinted Cu. Although all three metals are known for catalyzing H2 evolution, the lower biocompatibility and chemical stability of Cu hampered its performance. Stable and biocompatible Ti supported the bioprinted S. ovata effectively. Bioprinting of synthetic biofilm on H2-evolving metal cathodes can provide high-performing and robust biocathodes for further application of MES.

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  • 6.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krige, Adolf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Chapter 12 - Advances in gas fermentation processes2022In: Current Developments in Biotechnology and Bioengineering: Advances in Bioprocess Engineering / [ed] Sirohi, Ranjna; Pandey, Ashok; Taherzadeh, Mohammad J.; Larroche, Christian, Elsevier, 2022, p. 321-351Chapter in book (Other academic)
    Abstract [en]

    Microbial metabolism enables the sustainable synthesis of fuels and chemicals from gaseous substrates (H2, CO, and CO2), thus drastically diminishing the carbon load in the atmosphere. Various value-added biochemicals and biofuels, such as acetate, methane, ethanol, butanol, butyrate, caproate, and bioplastics, have been produced during the conversion of syngas or H2/CO2, using a variety of microorganisms as biocatalysts. Gas fermentation processes using acetogenic and methanogenic organisms are being extensively investigated. This chapter provides an overview of microbial CO and CO2 conversion technology, with an emphasis on recent developments and integration with renewable electricity for the generation of H2 or other forms of electron donors. A discussion on technological challenges in gas fermentation addresses issues, such as poor mass transfer, low microbial biomass, and low productivity. It also presents possible solutions based on the latest advances in bioelectrochemical processes including microbial gas electrofermentation. Finally, the chapter includes a sustainability analysis of the process and includes a brief update on commercially established companies operating gas fermentation systems. Overall, an integrated approach combining gas fermentation and renewable electricity offers an opportunity for the development of CO and CO2- based biochemical and biofuel production at commercial scale.

  • 7.
    Bazar, July Ann
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hrůzová, Kateřina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sand, Anders
    Boliden Mineral AB, SE-936 81 Boliden, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Organosolv Lignin Particles as a Partial Replacement of Xanthate Collector in a Copper Sulfide Ore Flotation: Scale-up StudyManuscript (preprint) (Other academic)
    Abstract [en]

    The transition to a sustainable, green economy indeed requires more access to strategic/critical metals for renewable energy technologies while simultaneously reducing reliance on fossil fuels and their byproducts. In mineral processing, various research for an environment-friendly flotation reagents have been ongoing for many years. In this paper, the potential of organosolv lignin particles (OLP) as a biobased reagent that can improve the grade and recovery of Cu was demonstrated using real sulfide ore. The main advantage of this process is that it requires low dosage of OLP in the tested condition and set-up. The initial laboratory batch flotation tests showed that potassium amyl xanthate (PAX) can be partially replaced with OLP by 50% and in the absence of depressant, lime. These results were further verified in semi-pilot flotation tests that showed an increase in recovery by 8% in the rougher stage and comparable grade in the final cleaner stage when using the OLP-PAX mixture with respect to PAX at full dosage. In general, this paper presents the progress towards validating the viability of OLP as a biobased flotation reagent suitable for industrial-scale applications.

  • 8.
    Bazar, July Ann
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hrůzová, Kateřina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sand, Anders
    Boliden Mineral AB, SE-936 81 Boliden, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Organosolv Lignin Particles as a Partial Replacement of Xanthate Collector in a Copper Sulfide Ore Flotation: Scale-up StudyManuscript (preprint) (Other academic)
    Abstract [en]

    The transition to a sustainable, green economy indeed requires more access to strategic/critical metals for renewable energy technologies while simultaneously reducing reliance on fossil fuels and their byproducts. In mineral processing, various research for an environment-friendly flotation reagents have been ongoing for many years. In this paper, the potential of organosolv lignin particles (OLP) as a biobased reagent that can improve the grade and recovery of Cu was demonstrated using real sulfide ore. The main advantage of this process is that it requires low dosage of OLP in the tested condition and set-up. The initial laboratory batch flotation tests showed that potassium amyl xanthate (PAX) can be partially replaced with OLP by 50% and in the absence of depressant, lime. These results were further verified in semi-pilot flotation tests that showed an increase in recovery by 8% in the rougher stage and comparable grade in the final cleaner stage when using the OLP-PAX mixture with respect to PAX at full dosage. In general, this paper presents the progress towards validating the viability of OLP as a biobased flotation reagent suitable for industrial-scale applications.

  • 9.
    Bhattacharyya, Shubhankar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Melt Stable Functionalized Organosolv and Kraft Lignin Thermoplastic2020In: Processes, ISSN 2227-9717, Vol. 8, no 9, article id 1108Article in journal (Refereed)
    Abstract [en]

    A shift towards an economically viable biomass biorefinery concept requires the use of all biomass fractions (cellulose, hemicellulose, and lignin) for the production of high added-value products. As lignin is often underutilized, the establishment of lignin valorization routes is highly important. In-house produced organosolv as well as commercial Kraft lignin were used in this study. The aim of the current work was to make a comparative study of thermoplastic biomaterials from two different types of lignins. Native lignins were alkylate with two different alkyl iodides to produce ether-functionalized lignins. Successful etherification was verified by FT-IR spectroscopy, changes in the molecular weight of lignin, as well as 13C and 1H Nuclear Magnetic Resonance (NMR). The thermal stability of etherified lignin samples was considerably improved with the T2% of organosolv to increase from 143 °C to up to 213 °C and of Kraft lignin from 133 °C to up to 168 °C, and glass transition temperature was observed. The present study shows that etherification of both organosolv and Kraft lignin with alkyl halides can produce lignin thermoplastic biomaterials with low glass transition temperature. The length of the alkyl chain affects thermal stability as well as other thermal properties.

  • 10.
    Bonturi, Nemailla
    et al.
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nilsson, Robert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Miranda, Everson Alves
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Single Cell Oil Producing Yeasts Lipomyces starkeyi and Rhodosporidium toruloides: Selection of Extraction Strategies and Biodiesel Property Prediction2015In: Energies, E-ISSN 1996-1073, Vol. 8, no 6, p. 5040-5052Article in journal (Refereed)
    Abstract [en]

    Single cell oils (SCOs) are considered potential raw material for the production of biodiesel. Rhodosporidium sp. and Lipomyces sp. are good candidates for SCO production. Lipid extractability differs according to yeast species and literature on the most suitable method for each oleaginous yeast species is scarce. This work aimed to investigate the efficiency of the most cited strategies for extracting lipids from intact and pretreated cells of Rhodosporidium toruloides and Lipomyces starkeyi. Lipid extractions were conducted using hexane or combinations of chloroform and methanol. The Folch method resulted in the highest lipid yields for both yeasts (42% for R. toruloides and 48% for L. starkeyi). Also, this method eliminates the cell pretreatment step. The Bligh and Dyer method underestimated the lipid content in the tested strains (25% for R. toruloides and 34% for L. starkeyi). Lipid extractability increased after acid pretreatment for the Pedersen, hexane, and Bligh and Dyer methods. For R. toruloides unexpected fatty acid methyl esters (FAME) composition were found for some lipid extraction strategies tested. Therefore, this work provides useful information for analytical and process development aiming at biodiesel production from the SCO of these two yeast species.

  • 11.
    Cao, Danyang
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhang, Jie
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Dong, Lisong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Zhu, Jiahua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Mu, Liwen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Biolubricant2023In: Sustainable Production Innovations: Bioremediation and Other Biotechnologies / [ed] Alok Kumar Patel; Amit Kumar Sharma, John Wiley & Sons, 2023, p. 1-56Chapter in book (Other academic)
  • 12.
    Cayenne, Aadila
    et al.
    Faculty of Mechanical and Process Engineering and Maritime Technologies, Flensburg University of Applied Sciences, Kanzleistr. 91-93, Flensburg, 24943, Germany.
    Monção, Maxwel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Thomsen, Mette H.
    Department of Energy Technology, Aalborg University, Niels Bohrs Vej 8, Esbjerg, 6700, Denmark.
    Uellendahl, Hinrich
    Faculty of Mechanical and Process Engineering and Maritime Technologies, Flensburg University of Applied Sciences, Kanzleistr. 91-93, Flensburg, 24943, Germany.
    Enhancing the Methane Yield of Salicornia spp. via Organosolv Fractionation as Part of a Halophyte Biorefinery Concept2024In: Energies, E-ISSN 1996-1073, Vol. 17, no 5, article id 1074Article in journal (Refereed)
    Abstract [en]

    The present research investigated the effect of organosolv pretreatment on two species of salt-tolerant Salicornia spp. biomass, Salicornia dolichostachya and Salicornia ramosissima, for increasing biomethane production through anaerobic digestion. The final biomethane yield of de-juiced green fibers of Salicornia spp. from wet fractionation increased by 23–28% after organosolv treatment. The highest methane yield of about 300 mL-CH4/gVS was found after organosolv treatment with 60% v/v ethanol solution at 200 °C for 30 min, or at 180 °C for 30 or 60 min treatment time. Furthermore, the methane production rate increased significantly, reducing the time until 95% of the final methane yield was reached from 20 days to 6–10 days for the organosolv-treated biomass. This research shows that the process of anaerobic digestion of halophyte biomass benefits from cascade processing of Salicornia fibers in a biorefinery framework by sequential wet and organosolv fractionation for full utilization of halophytic biomass.

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  • 13.
    Cayenne, Aadila
    et al.
    Faculty of Mechanical and Process Engineering and Maritime Technologies, Flensburg University of Applied Sciences, Kanzleistr. 91-93, Flensburg, 24943, Germany.
    Monção, Maxwel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Thomsen H., Mette
    Department of Energy Technology, Aalborg University, Niels Bohrs Vej 8, Esbjerg, 6700, Denmark.
    Uellendahl, Hinrich
    Faculty of Mechanical and Process Engineering and Maritime Technologies, Flensburg University of Applied Sciences, Kanzleistr. 91-93, Flensburg, 24943, Germany.
    Increasing the Biochemical Methane Potential of Salicornia Dolichostachya by Organosolv Fractionation in a Halophyte Biorefinery2023In: European Biomass Conference and Exhibition (EUBCE) Proceedings / [ed] I. De Bari; N. Scarlat; A. Grassi, ETA-Florence Renewable Energies , 2023, p. 560-565Conference paper (Refereed)
  • 14.
    Charisteidis, Ioannis
    et al.
    Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Lazaridis, Polykarpos
    Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Fotopoulos, Apostolos
    Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Pachatouridou, Eleni
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), Thessaloniki, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Triantafyllidis, Konstantinos
    Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Catalytic Fast Pyrolysis of Lignin Isolated by Hybrid Organosolv—Steam Explosion Pretreatment of Hardwood and Softwood Biomass for the Production of Phenolics and Aromatics2019In: Catalysts, E-ISSN 2073-4344, Vol. 9, no 11, article id 935Article in journal (Refereed)
    Abstract [en]

    Lignin, one of the three main structural biopolymers of lignocellulosic biomass, is the most abundant natural source of aromatics with a great valorization potential towards the production of fuels, chemicals, and polymers. Although kraft lignin and lignosulphonates, as byproducts of the pulp/paper industry, are available in vast amounts, other types of lignins, such as the organosolv or the hydrolysis lignin, are becoming increasingly important, as they are side-streams of new biorefinery processes aiming at the (bio)catalytic valorization of biomass sugars. Within this context, in this work, we studied the thermal (non-catalytic) and catalytic fast pyrolysis of softwood (spruce) and hardwood (birch) lignins, isolated by a hybrid organosolv–steam explosion biomass pretreatment method in order to investigate the effect of lignin origin/composition on product yields and lignin bio-oil composition. The catalysts studied were conventional microporous ZSM-5 (Zeolite Socony Mobil–5) zeolites and hierarchical ZSM-5 zeolites with intracrystal mesopores (i.e., 9 and 45 nm) or nano-sized ZSM-5 with a high external surface. All ZSM-5 zeolites were active in converting the initially produced via thermal pyrolysis alkoxy-phenols (i.e., of guaiacyl and syringyl/guaiacyl type for spruce and birch lignin, respectively) towards BTX (benzene, toluene, xylene) aromatics, alkyl-phenols and polycyclic aromatic hydrocarbons (PAHs, mainly naphthalenes), with the mesoporous ZSM-5 exhibiting higher dealkoxylation reactivity and being significantly more selective towards mono-aromatics compared to the conventional ZSM-5, for both spruce and birch lignin.

  • 15.
    Díaz, Sara
    et al.
    Departamento de Ingeniería Mecánica, Universidad de Las Palmas de Gran Canaria. Edificio de Fabricación Integrada, Las Palmas de Gran Canaria, Parque Científico – Tecnológico de la ULPGC, Campus universitario de Tafira Baja, 35017, Las Palmas, Spain.
    Ortega, Zaida
    Departamento de Ingeniería Mecánica, Universidad de Las Palmas de Gran Canaria. Edificio de Fabricación Integrada, Las Palmas de Gran Canaria, Parque Científico – Tecnológico de la ULPGC, Campus universitario de Tafira Baja, 35017, Las Palmas, Spain.
    Benítez, Antonio N.
    Departamento de Ingeniería Mecánica, Universidad de Las Palmas de Gran Canaria. Edificio de Fabricación Integrada, Las Palmas de Gran Canaria, Parque Científico – Tecnológico de la ULPGC, Campus universitario de Tafira Baja, 35017, Las Palmas, Spain.
    Marrero, María D.
    Departamento de Ingeniería Mecánica, Universidad de Las Palmas de Gran Canaria. Edificio de Fabricación Integrada, Las Palmas de Gran Canaria, Parque Científico – Tecnológico de la ULPGC, Campus universitario de Tafira Baja, 35017, Las Palmas, Spain.
    Carvalheiro, Florbela
    LNEG– Laboratório Nacional de Energia e Geologia, Unidade de Bioenergia, Estrada Do Paço Do Lumiar, 22, 1649-038, Lisboa, Portugal.
    Duarte, Luís C.
    LNEG– Laboratório Nacional de Energia e Geologia, Unidade de Bioenergia, Estrada Do Paço Do Lumiar, 22, 1649-038, Lisboa, Portugal.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krikigianni, Eleni
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Fernandes, Maria C.
    Centro de Biotecnologia Agrícola E Agro-Alimentar Do Alentejo (CEBAL)/Instituto Politécnico de Beja (IPBeja), Apartado 6158, 7801-908, Beja, Portugal; MED-Mediterranean Institute for Agriculture, Environment and Development, CEBAL—Centro de Biotecnologia Agrícola e Agro-Alimentar do Alentejo, Apartado 6158, 7801-908, Beja, Portugal.
    Oligosaccharides production by enzymatic hydrolysis of banana pseudostem pulp2023In: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 13, no 12, p. 10677-10688Article in journal (Refereed)
    Abstract [en]

    Banana production generates significant amounts of agricultural wastes, being fiber extraction one of the most relevant alternatives for their valorization. This process produces banana’s pseudostem pulp (BPP) as a byproduct, which shows an interesting composition for the biorefinery’s biochemical platform, with high polysaccharides (68%) and low lignin contents. This work deals with the enzymatic hydrolysis (EH) of raw and hydrothermally pre-treated BPP, focusing on the production of oligosaccharides (OS). Raw BPP hydrolysis with cellulase at different dosages rendered only 3.2% OS yields (OSY). Pectinase addition has not affected EH performance. On the other hand, EH of hydrothermally pre-treated BPP at 150 °C and 170 °C (P150 and P170) allowed to increase OSY up to 28% (P150, 1 FPU of cellulase/g dry biomass, 12 h), being 72% of the solubilized sugars in the form of cello-oligosaccharides. This last condition was subjected to a multi-stage EH strategy without improvements in OSY. An endo-glucanase was also tested, but obtained OSY were lower than cellulase results. Finally, obtained OS demonstrated to stimulate the growth of two Lactobacilli strains. The results show that BPP pre-treated under mild operational conditions is a good candidate for cello-oligosaccharides production by EH using 1 FPU/g DB of cellulase with a simple strategy.

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  • 16.
    Ghodke, Praveen Kumar
    et al.
    Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode 673601, Kerala, India.
    Sharma, Amit Kumar
    Center for Alternate Energy Research (CAER), Department of Chemistry, University of Petroleum and Energy Studies (UPES), Uttarakhand, Dehradun, 248007, India.
    Moorthy, Krishna
    Department of Mechanical Engineering, University of Petroleum and Energy Studies (UPES), Uttarakhand, Dehradun, 248007, India.
    Chen, Wei-Hsin
    Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung, 411, Taiwan.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Experimental Investigation on Pyrolysis of Domestic Plastic Wastes for Fuel Grade Hydrocarbons2023In: Processes, ISSN 2227-9717, Vol. 11, no 1, article id 71Article in journal (Refereed)
    Abstract [en]

    Plastics usage is rising daily because of increased population, modernization, and industrialization, which produces a lot of plastic garbage. Due to their various chemical structures, long chain polymeric compositions, and thermal/decomposition behavior, it is challenging to recycle these plastic wastes into hydrocarbon fuels. In the current work, domestic plastic waste was pyrolyzed at 473 to 973 K in a fixed bed reactor and compared with the three virgin plastics LDPE (low-density polyethylene), HDPE (high-density polyethylene), and PP (polypropylene), as well as a mixture of the three (virgin mixed plastics). The pyrolysis results showed that maximum liquid hydrocarbons obtained from HDPE, LDPE, PP, mixed plastic, and domestic waste were 64.6 wt.%, 62.2 wt.%, 63.1 wt.%, 68.6 wt.%, and 64.6 wt.% at 773 K, respectively. The composition of liquid fuels was characterized using FTIR and GC-MS, which showed a wide spectrum of hydrocarbons in the C8–C20 range. Furthermore, liquid fuel characteristics such as density, viscosity, fire and flash point, pour point, and calorific value were examined using ASTM standards, and the results were found to be satisfactory. This study provides an innovative method for recycling waste plastics into economical hydrocarbon fuel for use in transportation.

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  • 17.
    Havilah, Pulla Rose
    et al.
    Department of Chemical Engineering, School of Engineering, University of Petroleum and Energy Studies, Energy Acres Building, Bidholi, Dehradun 248007, India.
    Sharma, Amit Kumar
    Department of Chemistry, Centre for Alternate and Renewable Energy Research, R & D, University of Petroleum and Energy Studies (UPES), Energy Acres Building, Bidholi, Dehradun 248007, India.
    Govindasamy, Gopalakrishnan
    Department of Chemical Engineering, School of Engineering, University of Petroleum and Energy Studies, Energy Acres Building, Bidholi, Dehradun 248007, India.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Biomass Gasification in Downdraft Gasifiers: A Technical Review on Production, Up-Gradation and Application of Synthesis Gas2022In: Energies, E-ISSN 1996-1073, Vol. 15, no 11, article id 3938Article, review/survey (Refereed)
    Abstract [en]

    Rapid climate change and forecasted damage from fossil fuel combustion, forced researchers to investigate renewable and clean energy sources for the sustainable development of societies throughout the world. Biomass-based energy is one of the most important renewable energy sources for meeting daily energy needs, which are gaining in popularity daily. Gasification-based bioenergy production is an effective way to replace fossil fuels and reduce CO2 emissions. Even though biomass gasification has been studied extensively, there is still much opportunity for improvement in terms of high-quality syngas generation (high H2/CO ratio) and reduced tar formation. Furthermore, the presence of tar has a considerable impact on syngas quality. Downdraft gasifiers have recently shown a significant potential for producing high-quality syngas with lower tar concentrations. This article presents a comprehensive review on the advancement in biomass downdraft gasification technologies for high-quality synthesis gas. In addition, factors affecting syngas production and composition e.g., equivalency ratio, temperature, particle size, and gasification medium on synthesis gas generation are also comprehensively studied. The up-gradation and various applications of synthesis gas are also discussed in brief in this review article.

  • 18.
    Hruzova, Katerina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kolman, Krzysztof
    Nouryon Surface Chem, S-44485 Stenungsund, Sweden.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nordberg, Henrik
    Nouryon Surface Chem, S-44485 Stenungsund, Sweden.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Characterization of Organosolv Lignin Particles and Their Affinity to Sulfide Mineral Surfaces2023In: ACS Applied Nano Materials, E-ISSN 2574-0970, Vol. 6, no 19, p. 17349-18631Article in journal (Refereed)
    Abstract [en]

    Organosolv lignin nanoparticles have been recently evaluated for their use in mineral froth flotation as a flotation reagent, and as a result, the recovery of the target minerals was improved and the selectivity of the process was increased. However, the mechanism of lignin activity in mineral froth flotation is not known. Therefore, this study is the first step in understanding the interaction of organosolv lignin with the mineral surface. As such, the organosolv lignin was characterized by GPC and 31P NMR, where the structural differences between the birch and spruce lignins were determined. The molecular size and lignol unit composition were evaluated. Subsequently, the morphology and size of the organosolv lignin particles were examined for all 4 produced types: BN, BM, SN, and SM. The ? potential was measured in the pH range of 2-11. All particles had a high negative charge, which indicated good stability of the dispersion in the alkali range. The stability of their colloidal dispersion was observed under increasing concentrations of mono- and divalent cations, and electrostatic repulsion was identified as the main stabilization mechanism. Finally, QCM-D was used to study the interaction of the lignin particles with the mineral surfaces of chalcopyrite, pyrite, and galena, which gave insight into the possible mechanism during the flotation process.

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  • 19.
    Hruzova, Katerina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sand, Anders
    Boliden Mineral AB, SE-776 98 Garpenberg, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Organosolv lignin hydrophobic micro- and nanoparticles as a low-carbon footprint biodegradable flotation collector in mineral flotation2020In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 306, article id 123235Article in journal (Refereed)
    Abstract [en]

    Flotation is a key step during mineral separation. Xanthates are the most commonly used collectors for recovering Cu, Ni, and Zn from sulphide ores. However, xanthates are fossil-based and toxic for the environment. The aim of this study was to evaluate the use of lignin nanoparticles and microparticles as sustainable and environmentally friendly collectors. Lignin particles demonstrated good selectivity toward Cu (chalcopyrite), with total recoveries exceeding 80% and grades of up to 8.6% w/w from a Cu-Ni ore in rougher flotation tests. When floating Zn-Pb-Cu ore, lignin nanoparticles could reduce the use of xanthates by 50%. Moreover, they outperformed xanthates alone, achieving total recoveries of up to 91%, 85%, and 98% for Cu, Pb, and Zn, respectively. These results prove the potential of lignin as a flotation collector.

  • 20.
    Hruzova, Katerina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Masák, Jan
    Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic.
    Maťátková, Olga
    Department of Biotechnology, University of Chemistry and Technology Prague, Prague, Czech Republic.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    A novel approach for the production of green biosurfactant from Pseudomonas aeruginosa using renewable forest biomass2020In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 711, article id 135099Article in journal (Refereed)
    Abstract [en]

    The rising demand for surfactants by the pharmaceuticals and cosmetic industries has generated vast amounts of petroleum-based synthetic surfactants, which are often toxic and non-degradable. Owing to their low toxicity, stability in extreme conditions, and biodegradability, biosurfactants could represent a sustainable alternative. The present study aimed to maximize the production of rhamnolipids (RL) from Pseudomonas aeruginosa by optimizing glucose concentration, temperature, and C/N and C/P ratios. After 96 h of cultivation at 37 °C, the final RL concentration was 4.18 ± 0.19 g/L with a final yield of 0.214 ± 0.010 g/gglucose when pure glucose was used as a carbon source. At present, the main obstacle towards commercialization of RL production is economic sustainability, due to the high cost of downstream processes and media components. For this reason, a renewable source such as wood hydrolysates (from birch and spruce woodchips) was examined here as a possible source of glucose for RL production. Both hydrolysates proved to be adequate, resulting in 2.34 ± 0.17 and 2.31 ± 0.10 g/L of RL, respectively, and corresponding yields of 0.081 ± 0.006 and 0.089 ± 0.004 g/gsugar after 96 h. These results demonstrate the potential of using renewable biomass for the production of biosurfactants and, to the best of our knowledge, they constitute the first report on the use of wood hydrolysates for RL production.

  • 21.
    Hrůzová, Kateřina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bazar, July Ann
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sand, Anders
    Boliden Mineral AB, SE-936 81 Boliden, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Boosting Copper Sulfide Ore Flotation Efficiency through a Substantial Replacement of Xanthate Collectors with Organosolv Lignin ParticlesManuscript (preprint) (Other academic)
    Abstract [en]

    The green transition requires a lot of metals or minerals that must be mined and processed. One of the most widely used processes to recover sulfidic minerals is froth flotation. Flotation reagents are necessary for the selective recovery of target minerals. The main purpose of the study was to demonstrate a novel sustainable flotation process for selective extraction of chalcopyrite from sulfide ores, based on partial replacement of fossil-based xanthate flotation collectors with bio-based, biodegradable, and non-toxic organosolv lignin particles. The addition of organosolv lignin particles provided increased recovery of copper by almost 20 % with high selectivity in the rougher flotation. The amount of required xanthate was significantly lowered by 75% in the newly proposed process. In addition, the economical and environmental impact of the whole process could be improved by removal of lime, as pH adjustment through lime addition was not necessary to achieve good selectivity.

  • 22.
    Hrůzová, Kateřina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karnaouri, Anthi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Norén, Fredrik
    N-research AB, Gränsgatan 17, 453 30 Lysekil, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Second-Generation Biofuel Production from the Marine Filter Feeder Ciona intestinalis2020In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, no 22, p. 8373-8380Article in journal (Refereed)
    Abstract [en]

    Biofuels are essential for transitioning to a sustainable society. This switch can be achieved by introducing novel feedstocks and technologies for efficient and economically feasible biofuel production. Second-generation biofuels are particularly advantageous, as they are produced from nonedible lignocellulosic biomass derived primarily from agricultural byproducts. Ciona intestinalis, a marine filter feeder, is cultivated to produce fish feed from the invertebrate’s inner tissue body. This process generates also vast amounts of a renewable side stream, namely the tunicate’s external cellulose-rich tunic. The aim of the present study was to evaluate the potential of the C. intestinalis tunic as a novel feedstock for bioethanol production. For this purpose, organosolv fractionation of the tunic was optimized to increase cellulose content. Enzymatic saccharification of the pretreated biomass was assessed to identify the most promising materials, which were subsequently utilized as carbon source in fermentation trials. Under optimal conditions, a titer of 38.7 g/L of ethanol, with a yield of 78.3% of the maximum theoretical, was achieved. To the best of our knowledge, this is the first report whereby organosolv pretreated tunic biomass is valorized toward bioethanol production; the current work paves the way for incorporating tunicates in bioconversion processes for the generation of biofuels and other biobased chemicals.

  • 23.
    Hrůzová, Kateřina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karnaouri, Anthi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Norén, Fredrik
    N-Research AB, Gränsgatan 17, 453 30, Lysekil, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Valorization of outer tunic of the marine filter feeder Ciona intestinalis towards the production of second-generation biofuel and prebiotic oligosaccharides2021In: Biotechnology for Biofuels, E-ISSN 1754-6834, Vol. 14, article id 32Article in journal (Refereed)
    Abstract [en]

    Background

    One of the sustainable development goals focuses on the biomass-based production as a replacement for fossil-based commodities. A novel feedstock with vast potentials is tunicate biomass, which can be pretreated and fermented in a similar way to lignocellulose. Ciona intestinalis is a marine filter feeder that is cultivated to produce fish feed. While the inner tissue body is used for feed production, the surrounding tunic remains as a cellulose-rich by-product, which can be further separated into outer and inner tunic. Ethanol production from organosolv-pretreated whole-tunic biomass was recently validated. The aim of the present study was to evaluate the potential of organosolv pretreated outer-tunic biomass for the production of biofuels and cellobiose that is a disaccharide with prebiotic potential.

    Results

    As a result, 41.4 g/L of ethanol by Saccharomyces cerevisiae, corresponding to a 90.2% theoretical yield, was achieved under the optimal conditions when the tunicate biomass was pretreated at 195 °C for 60 min at a liquid-to-solid ratio of 50. In addition, cellobiose production by enzymatic hydrolysis of the pretreated tunicate biomass was demonstrated with a maximum conversion yield of 49.7 wt. %.

    Conclusions

    The utilisation of tunicate biomass offers an eco-friendly and sustainable alternative for value-added biofuels and chemicals. The cultivation of tunicate biomass in shallow coastal sea improves the quality of the water and ensures sustainable production of fish feed. Moreover, there is no competition for arable land, which leaves the latter available for food and feed production.

  • 24.
    Hrůzová, Kateřina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Organosolv fractionation of spruce bark using ethanol-water mixtures: towards a novel bio-refinery concept2021In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 341, article id 125855Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to assess the effect of hot water extraction followed by organosolv pretreatment on the enzymatic hydrolysability of spruce bark biomass. To this end, samples were pretreated at five different temperatures in the presence or not of acid catalyst. The cellulose content of pre-treated biomass reached 49.6% w/w. During the enzymatic hydrolysis trials with 3% w/w dry solids, the final hydrolysis yield reached up to 70.1%, which corresponded to the release of 7.8 g/L of glucose. Whereas, the final hydrolysis yield obtained during the high-gravity enzymatic hydrolysis reached up to 43.5%. The concentration of released glucose was in range of 33.3 – 40.0 g/L with a hemicellulose sugars in a range of 5.5 – 6.6 g/L. These values are suitable for downstream bioconversion processes and represent a significant improvement over existing steam pretreatment methods.

  • 25.
    Jakhwal, Parul
    et al.
    Department of Separation Science, LUT School of Engineering Science, LUT University, Sammonkatu 12, FI-50130, Mikkeli, Finland.
    Daneshvar, Ehsan
    Department of Separation Science, LUT School of Engineering Science, LUT University, Sammonkatu 12, FI-50130, Mikkeli, Finland.
    Skalska, Kinga
    Department of Separation Science, LUT School of Engineering Science, LUT University, Sammonkatu 12, FI-50130, Mikkeli, Finland.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Park, Yuri
    Department of Environmental Engineering, Seoul National University of Science and Technology, Seoul, 01811, South Korea.
    Bhatnagar, Amit
    Department of Separation Science, LUT School of Engineering Science, LUT University, Sammonkatu 12, FI-50130, Mikkeli, Finland.
    Nutrient removal and biomass production of marine microalgae cultured in recirculating aquaculture systems (RAS) water with low phosphate concentration2024In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 358, article id 120859Article in journal (Refereed)
    Abstract [en]

    This study was conducted to investigate the feasibility of microalgal biomass production and nutrient removal from recirculating aquaculture systems (RAS) water (RASW) with low phosphate concentration. For this purpose, Nannochloropsis oculata, Pavlova gyrans, Tetraselmis suecica, Phaeodactylum tricornutum, and their consortium were cultivated in RASW and RASW supplemented with vitamins (+V). Among them, N. oculata showed the maximum biomass production of 0.4 g/L in RASW. Vitamins supplementation significantly increased the growth of T. suecica from 0.16 g/L in RASW to 0.33 g/L in RASW + V. Additionally, T. suecica showed the highest nitrate (NO3–N) removal efficiency of 80.88 ± 2.08 % in RASW and 83.82 ± 2.08 % in RASW + V. Accordingly, T. suecica was selected for scaling up study of microalgal cultivation in RASW and RASW supplemented with nitrate (RASW + N) in 4-L airlift photobioreactors. Nitrate supplementation enhanced the growth of T. suecica up to 2.2-fold (day 15). The fatty acid nutritional indices in T. suecica cultivated in RASW and RASW + N showed optimal polyunsaturated fatty acids (PUFAs)/saturated fatty acid (SFAs), omega-6 fatty acid (n-6)/omega-3 fatty acid (n-3), indices of atherogenicity (IA), and thrombogenicity (IT)). Overall, the findings of this study revealed that despite low phosphate concentration, marine microalgae can grow in RASW and relatively reduce the concentration of nitrate. Furthermore, the microalgal biomass cultivated in RASW consisting of pigments and optimal fatty acid nutritional profile can be used as fish feed, thus contributing to a circular bioeconomy.

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  • 26.
    Jampala, Annie Modestra
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bajracharya, Suman
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bioelectrochemical treatment of acid mine drainage: Microbiome synergy influences sulfidogenesis and acetogenesis2024In: Sustainable Chemistry for the Environment, E-ISSN 2949-8392, Vol. 6, article id 100106Article in journal (Refereed)
    Abstract [en]

    Bioelectrochemical systems (BES) are emerging as potential technologies that can remediate acid mine drainage (AMD) by cathodic reduction of sulfates to metal sulfides. This study evaluated bioelectrochemical remediation of sulfate rich AMD at two applied cathode potentials; BES-1: −1.0 V and BES-2: −0.8 V. Sulfate reducing bacteria were selectively enriched to be used as biocatalyst in BES. Initially, lactate was fed as carbon source and switched to chemolithoautotrophy with only CO2-fed conditions. Both BESs were operated at 3±0.2 g/l of sulfate with synthetic AMD (SAMD) fed first, and gradually changed to 50% AMD from mining site with 50% SAMD. Sulfate reduction was relatively higher with BES-1: 82% than BES-2: 76% coupled with sulfidogenesis. Interestingly, acetogenesis (BES-1: 2.12±0.2 g/l, BES-2: 1.9±0.2 g/l) was also noticed with high reduction currents (BES-1&2: >-70 mA). Microbiome community analysis revealed the dominant presence of sulfate reducers, acetogens, syntrophic bacteria and Methanobacterium, probing microbial synergy aiding sulfate reduction. An added advantage was the iron-sulfide (FeS) particles formation on cathode, which might have contributed to increased reduction currents. This study reveals insights into microbial synergy for autotrophic sulfate reduction within mixed microbiome communities along with the impact of FeS particles as conducive facilitator for electron transfer in BES, thereby enhancing electrosynthetic acetate production.

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  • 27.
    Kalogiannis, Konstantinos G
    et al.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 6th km Harilaou-Thermi Rd, 57001 Thessaloniki, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Aspden, James
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lappas, Angelos A
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 6th km Harilaou-Thermi Rd, 57001 Thessaloniki, Greece.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Acid Assisted Organosolv Delignification of Beechwood and Pulp Conversion towards High Concentrated Cellulosic Ethanol via High Gravity Enzymatic Hydrolysis and Fermentation2018In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 23, no 7, article id 1647Article in journal (Refereed)
    Abstract [en]

    Background: Future biorefineries will focus on converting low value waste streams to chemical products that are derived from petroleum or refined sugars. Feedstock pretreatment in a simple, cost effective, agnostic manner is a major challenge.

    Methods: In this work, beechwood sawdust was delignified via an organosolv process, assisted by homogeneous inorganic acid catalysis. Mixtures of water and several organic solvents were evaluated for their performance. Specifically, ethanol (EtOH), acetone (AC), and methyl- isobutyl- ketone (MIBK) were tested with or without the use of homogeneous acid catalysis employing sulfuric, phosphoric, and oxalic acids under relatively mild temperature of 175 °C for one hour.

    Results: Delignification degrees (DD) higher than 90% were achieved, where both AC and EtOH proved to be suitable solvents for this process. Both oxalic and especially phosphoric acid proved to be good alternative catalysts for replacing sulfuric acid. High gravity simultaneous saccharification and fermentation with an enzyme loading of 8.4 mg/gsolids at 20 wt.% initial solids content reached an ethanol yield of 8.0 w/v%.

    Conclusions: Efficient delignification combining common volatile solvents and mild acid catalysis allowed for the production of ethanol at high concentration in an efficient manner

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  • 28.
    Kalogiannis, Konstantinos G.
    et al.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), Thessaloniki, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lappas, Angelos A.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), Thessaloniki, Greece.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Aromatics from Beechwood Organosolv Lignin through Thermal and Catalytic Pyrolysis2019In: Energies, E-ISSN 1996-1073, Vol. 12, no 9, article id 1606Article in journal (Refereed)
    Abstract [en]

    Biomass fractionation, as an alternative to biomass pretreatment, has gained increasing research attention over the past few years as it provides separate streams of cellulose, hemicellulose, and lignin. These streams can be used separately and can provide a solution for improving the economics of emerging biorefinery technologies. The sugar streams are commonly used in microbial conversions, whereas during recent years lignin has been recognized as a valuable compound as it is the only renewable and abundant source of aromatic chemicals. Successfully converting lignin into valuable chemicals and products is key in achieving both environmental and economic sustainability of future biorefineries. In this work, lignin retrieved from beechwood sawdust delignification pretreatment via an organosolv process was depolymerized with thermal and catalytic pyrolysis. ZSM-5 commercial catalyst was used in situ to upgrade the lignin bio-oil vapors. Lignins retrieved from different modes of organosolv pretreatment were tested in order to evaluate the effect that upstream pretreatment has on the lignin fraction. Both thermal and catalytic pyrolysis yielded oils rich in phenols and aromatic hydrocarbons. Use of ZSM-5 catalyst assisted in overall deoxygenation of the bio-oils and enhanced aromatic hydrocarbons production. The oxygen content of the bio-oils was reduced at the expense of their yield. Organosolv lignins were successfully depolymerized towards phenols and aromatic hydrocarbons via thermal and catalytic pyrolysis. Hence, lignin pyrolysis can be an effective manner for lignin upgrading towards high added value products

  • 29.
    Karageorgou, Dimitra
    et al.
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, 45100 Ioannina, Greece.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Katapodis, Petros
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, 45100 Ioannina, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Heterotrophic Cultivation of the Cyanobacterium Pseudanabaena sp. on Forest Biomass Hydrolysates toward Sustainable Biodiesel Production2022In: Microorganisms, E-ISSN 2076-2607, Vol. 10, no 9, article id 1756Article in journal (Refereed)
    Abstract [en]

    Environmental pollution, greenhouse gas emissions, depletion of fossil fuels, and a growing population have sparked a search for new and renewable energy sources such as biodiesel. The use of waste or residues as substrates for microbial growth can favor the implementation of a biorefinery concept with reduced environmental footprint. Cyanobacteria constitute microorganisms with enhanced ability to use industrial effluents, wastewaters, forest residues for growth, and concomitant production of added-value compounds. In this study, a recently isolated cyanobacterium strain of Pseudanabaena sp. was cultivated on hydrolysates from pretreated forest biomass (silver birch and Norway spruce), and the production of biodiesel-grade lipids was assessed. Optimizing carbon source concentration and the (C/N) carbon-to-nitrogen ratio resulted in 66.45% w/w lipid content when microalgae were grown on glucose, compared to 62.95% and 63.79% w/w when grown on spruce and birch hydrolysate, respectively. Importantly, the lipid profile was suitable for the production of high-quality biodiesel. The present study demonstrates how this new cyanobacterial strain could be used as a biofactory, converting residual resources into green biofuel.

  • 30.
    Karageorgou, Dimitra
    et al.
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, Ioannina 45110, Greece.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Katapodis, Petros
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, Ioannina 45110, Greece.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Benefits of supplementation with microbial omega-3 fatty acids on human health and the current market scenario for fish-free omega-3 fatty acid2023In: Trends in Food Science & Technology, ISSN 0924-2244, E-ISSN 1879-3053, Vol. 136, p. 169-180Article, review/survey (Refereed)
    Abstract [en]

    BackgroundGrowing evidence points to a link between specific fatty acids ingested through the diet and human health. Chain length, saturation degree, and position of double bonds in fatty acids determine their effect in humans. Omega-3 and omega-6 fatty acids have been recognized for their contribution to the prevention and/or treatment of diabetes, cancer, visual impairment, cardiovascular diseases, as well as neurological and musculoskeletal disorders.

    Scope and approachHumans cannot synthesize these fatty acids in sufficient amounts and need to absorb them through the diet. Oleaginous microalgae constitute a promising, sustainable source of such fatty acids, as they can accumulate up to 85% of lipids on a cell dry weight basis.

    Key findings and conclusionsThe present review summarizes the potential of oleaginous microalgae as a convenient, economical, and sustainable source of polyunsaturated fatty acids, and explores their beneficial role in human health. The growing prevalence of cardiovascular diseases and changing dietary preferences are driving the increasing demand for microbial omega-3 fatty acids. Following the COVID-19 pandemic, the importance of a healthy immune system has further strengthened the market for omega-3 fatty acids.

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  • 31.
    Karnaouri, Anthi C.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jalvo, Blanca
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden.
    Moritz, Philipp
    Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Höfft, Oliver
    Institute of Electrochemistry, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany.
    Sourkouni, Georgia
    Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany.
    Maus-Friedrichs, Wolfgang
    Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany.
    Mathew, Aji P.
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lytic Polysaccharide Monooxygenase-Assisted Preparation of Oxidized-Cellulose Nanocrystals with a High Carboxyl Content from the Tunic of Marine Invertebrate Ciona intestinalis2020In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, no 50, p. 18400-18412Article in journal (Refereed)
    Abstract [en]

    The tunicate species Ciona intestinalis is a fast-growing marine invertebrate animal that contains cellulose in its outer part - the tunic. The high crystallinity and microfibril aspect ratio of tunicate cellulose make it an excellent starting material for the isolation of nanocellulose. In the present work, tunic from C. intestinalis was subjected to organosolv pretreatment followed by bleaching and acid-hydrolysis steps for the isolation of nanocrystals. Applying an intermediate enzymatic treatment step with a lytic polysaccharide monooxygenase (LPMO) from the thermophilic fungus Thermothelomyces thermophila was proved to facilitate the isolation of nanocellulose and to improve the overall process yield, even when the bleaching step was omitted. LPMOs are able to oxidatively cleave the glycosidic bonds of a polysaccharide substrate, either at the C1 and/or C4 position, with the former leading to introduction of carboxylate moieties. X-ray photoelectron spectroscopy analysis showed a significant increase in the atomic percentage of the C═O/O-C-O and O-C═O bonds upon the addition of LPMO, while the obtained nanocrystals exhibited higher thermal stability compared to the untreated ones. Moreover, an enzymatic post-treatment with LPMOs was performed to additionally functionalize the cellulose nanocrystals. Our results demonstrate that LPMOs are promising candidates for the enzymatic modification of cellulose fibers, including the preparation of oxidized-nanocellulose, and offer great perspectives for the production of novel biobased nanomaterials. ©

  • 32.
    Karnaouri, Anthi C.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bühler, Saskja
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Muraleedharan, Madhu Nair
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Tailoring Celluclast (R) Cocktail's Performance towards the Production of Prebiotic Cello-Oligosaccharides from Waste Forest Biomass2019In: Catalysts, E-ISSN 2073-4344, Vol. 9, no 11, article id 897Article in journal (Refereed)
    Abstract [en]

    The main objective of this study focused on the sustainable production of cellobiose and other cellulose-derived oligosaccharides from non-edible sources, more specifically, from forest residues. For this purpose, a fine-tuning of the performance of the commercially available enzyme mixture Celluclast® was conducted towards the optimization of cellobiose production. By enzyme reaction engineering (pH, multi-stage hydrolysis with buffer exchange, addition of β-glucosidase inhibitor), a cellobiose-rich product with a high cellobiose to glucose ratio (37.4) was achieved by utilizing organosolv-pretreated birch biomass. In this way, controlled enzymatic hydrolysis combined with efficient downstream processing, including product recovery and purification through ultrafiltration and nanofiltration, can potentially support the sustainable production of food-grade oligosaccharides from forest biomass. The potential of the hydrolysis product to support the growth of two Lactobacilli probiotic strains as a sole carbon source was also demonstrated

  • 33.
    Karnaouri, Anthi C.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krikigianni, Eleni
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Valorization of waste forest biomass toward the production of cello-oligosaccharides with potential prebiotic activity by utilizing customized enzyme cocktails2019In: Biotechnology for Biofuels, E-ISSN 1754-6834, Vol. 12, no 1, article id 285Article in journal (Refereed)
    Abstract [en]

    Background

    Production of value-added materials from lignocellulosic biomass residues is an emerging sector that has attracted much attention as it offers numerous benefits from an environmental and economical point of view. Non-digestible oligosaccharides represent a group of carbohydrates that are resistant to gastrointestinal digestion, and therefore, they are considered as potential prebiotic candidates. Such oligosaccharides can derive from the biomass cellulose fraction through a controlled enzymatic hydrolysis that eliminates the yield of monomers.

    Results

    In the present study, hydrolysis of organosolv-pretreated forest residues (birch and spruce) was tested in the presence of four cellulases (EG5, CBH7, CBH6, EG7) and one accessory enzyme (LPMO). The optimal enzyme combinations were comprised of 20% EG5, 43% CBH7, 22% TtLPMO, 10% PaCbh6a and 5% EG7 in the case of birch and 35% EG5, 45% CBH7, 10% TtLPMO, 10% PaCbh6a and 5% EG7 in the case of spruce, leading to 22.3% and 19.1 wt% cellulose conversion into cellobiose, respectively. Enzymatic hydrolysis was applied on scale-up reactions, and the produced oligosaccharides (consisted of > 90% cellobiose) were recovered and separated from glucose through nanofiltration at optimized temperature (50 °C) and pressure (10 bar) conditions, yielding a final product with cellobiose-to-glucose ratio of 21.1 (birch) and 20.2 (spruce). Cellobiose-rich hydrolysates were tested as fermentative substrates for different lactic acid bacteria. It was shown that they can efficiently stimulate the growth of two Lactobacilli strains.

    Conclusions

    Controlled enzymatic hydrolysis with processive cellulases, combined with product recovery and purification, as well as enzyme recycling can potentially support the sustainable production of food-grade oligosaccharides from forest biomass.

  • 34.
    Karnaouri, Anthi C
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Topakas, Evangelos
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. School of Chemical Engineering, National Technical University of Athens.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Fine-tuned enzymatic hydrolysis of organosolv pretreated forest materials for the efficient production of cellobiose2018In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 6, article id 128Article in journal (Refereed)
    Abstract [en]

    Non-digestible oligosaccharides (NDOs) are likely prebiotic candidates that have been related to the prevention of intestinal infections and other disorders for both humans and animals. Lignocellulosic biomass is the largest carbon source in the biosphere, therefore cello-oligosacharides (COS), especially cellobiose, are potentially the most widely available choice of NDOs. Production of COS and cellobiose with enzymes offers numerous benefits over acid-catalyzed processes, as it is milder, environmentally friendly and produces fewer by-products. Cellobiohydrolases (CBHs) and a class of endoglucanases (EGs), namely processive EGs, are key enzymes for the production of COS, as they have higher preference toward glycosidic bonds near the end of cellulose chains and are able to release soluble products. In this work, we describe the heterologous expression and characterization of two CBHs from the filamentous fungus Thermothelomyces thermophila, as well as their synergism with proccessive EGs for cellobiose release from organosolv pretreated spruce and birch. The properties, inhibition kinetics and substrate specific activities for each enzyme are described in detail. The results show that a combination of EGs belonging to Glycosyl hydrolase families 5, 6 and 9, with a CBHI and CBHII in appropriate proportions, can enhance the production of COS from forest materials, underpinning the potential of these biocatalysts in the production of NDOs.

  • 35.
    Karnaouri, Anthi
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Topakas, Evangelos
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemical Engineering, Biotechnology Laboratory, National Technical University of Athens, Greece.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Development of Thermophilic Tailor-Made Enzyme Mixtures for the Bioconversion of Agricultural and Forest Residues2016In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 7, article id 177Article in journal (Refereed)
    Abstract [en]

    Even though the main components of all lignocellulosic feedstocks include cellulose, hemicellulose, as well as the protective lignin matrix, there are some differences in structure, such as in hardwoods and softwoods, which may influence the degradability of the materials. Under this view, various types of biomass might require a minimal set of enzymes that has to be tailor-made. Partially defined complex mixtures that are currently commercially used are not adapted to efficiently degrade different materials, so novel enzyme mixtures have to be customized. Development of these cocktails requires better knowledge about the specific activities involved, in order to optimize hydrolysis. The role of filamentous fungus Myceliophthora thermophila and its complete enzymatic repertoire for the bioconversion of complex carbohydrates has been widely proven. In this study, four core cellulases (MtCBH7, MtCBH6, MtEG5, and MtEG7), in the presence of other four “accessory” enzymes (mannanase, lytic polyssacharide monooxygenase MtGH61, xylanase, MtFae1a) and β-glucosidase MtBGL3, were tested as a nine-component cocktail against one model substrate (phosphoric acid swollen cellulose) and four hydrothermally pretreated natural substrates (wheat straw as an agricultural waste, birch, and spruce biomass, as forest residues). Synergistic interactions among different enzymes were determined using a suitable design of experiments methodology. The results suggest that for the hydrolysis of the pure substrate (PASC), high proportions of MtEG7 are needed for efficient yields. MtCBH7 and MtEG7 are enzymes of major importance during the hydrolysis of pretreated wheat straw, while MtCBH7 plays a crucial role in case of spruce. Cellobiohydrolases MtCBH6 and MtCBH7 act in combination and are key enzymes for the hydrolysis of the hardwood (birch). Optimum combinations were predicted from suitable statistical models which were able to further increase hydrolysis yields, suggesting that tailor-made enzyme mixtures targeted toward a particular residual biomass can help maximize hydrolysis yields. The present work demonstrates the change from “one cocktail for all” to “tailor-made cocktails” that are needed for the efficient saccharification of targeted feed stocks prior to the production of biobased products through the biorefinery concept.

  • 36.
    Katsimpouras, Constantinos
    et al.
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Zacharopoulou, Maria
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Topakas, Evangelos
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Sequential high gravity ethanol fermentation and anaerobic digestion of steam explosion and organosolv pretreated corn stover2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 244:1, p. 1129-1136Article in journal (Refereed)
    Abstract [en]

    The present work investigates the suitability of pretreated corn stover (CS) to serve as feedstock for high gravity (HG) ethanol production at solids-content of 24 wt%. Steam explosion, with and without the addition of H2SO4, and organosolv pretreated CS samples underwent a liquefaction/saccharification step followed by simultaneous saccharification and fermentation (SSF). Maximum ethanol concentration of ca. 76 g/L (78.3% ethanol yield) was obtained from steam exploded CS (SECS) with 0.2% H2SO4. Organosolv pretreated CS (OCS) also resulted in high ethanol concentration of ca. 65 g/L (62.3% ethanol yield). Moreover, methane production through anaerobic digestion (AD) was conducted from fermentation residues and resulted in maximum methane yields of ca. 120 and 69 mL/g volatile solids (VS) for SECS and OCS samples, respectively. The results indicated that the implementation of a liquefaction/saccharification step before SSF employing a liquefaction reactor seemed to handle HG conditions adequately.

  • 37.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Axelsson, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kinetic study of catalytic gasification of wood char impregnated with different alkali salts2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 118, p. 1055-1065Article in journal (Refereed)
    Abstract [en]

    Different concentrations (0.1 and 1 M K+/Na+) of salt solutions (K2CO3, Na2CO3, NaOH and NaCl) were used to impregnate alkali in sawdust. After devolatilization, char samples were gasified at different temperatures (750–900 °C) under CO2 in a macro-thermogravimetric analyzer for gasification kinetics. Morphologically, three classes of chars could be identified. Chars experiencing the highest catalytic influence were in Class-2 (0.5 M K2CO3 and 1 M NaOH) with a swollen and molten surface. In contrast, Class-1 (wood char like) and Class-3 (with salt deposits) chars showed moderate and low catalytic effect on gasification reactivity respectively. It is believed to be related to char surface swelling and alkali salt used. At 850 °C or below, the reactivity increased linearly (Class-1 and Class-3 Char) with initial alkali content up to 2200 mmol alkali/kg of char (except for NaCl). The same reaction rate was maintained until 3600 mmol/kg of char of alkali loading (Class-2) and then decreased. However, no trend was observed at 900 °C due to drastic change in reactivity of the samples, probably due to alkali transformation. Among the salts, K2CO3 (0.5 M) was found to be the most suitable for catalytic gasification due to its high catalytic activity in combination with relatively low carbon leaching.

  • 38.
    Kirtania, Kawnish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Axelsson, Joel
    Luleå University of Technology.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Alkali catalyzed gasification of solid biomass: influence on fuel conversion and tar/soot reduction2016In: Proceedings of the 24th European Biomass Conference and Exhibition, Amsterdam: ETA Florence Renewable Energies , 2016, p. 533-536Conference paper (Refereed)
    Abstract [en]

    Based on char gasification experiments in an isothermal thermogravimetric analyzer, a suitable concentration of alkali salt (K2CO3) was chosen for impregnation due to almost five-fold increase in gasification reactivity and relatively low amount of carbon leaching during impregnation. Furthermore, an optimum method for wet alkali impregnation was proposed based on the several tests performed by varying temperature and time. To study the catalytic effect on tar and soot yield, untreated and impregnated woody biomass were gasified under entrained flow condition between 900 oC and 1200 oC. Impregnation leads to 70% lower tar yield from gasification around 1000 oC and 1100 oC. The lowest amount of soot was detected for the same temperature range whereas the soot yield was one order of magnitude higher for untreated biomass. For tar, this influence became insignificant at a higher temperature (1200 oC). This defines the suitable temperature range for alkali catalyzed gasification without the loss of catalytic activity.

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  • 39.
    Krikigianni, Eleni
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Investigating the Bioconversion Potential of Volatile Fatty Acids: Use of Oleaginous Yeasts Rhodosporidium toruloides and Cryptococcus curvatus towards the Sustainable Production of Biodiesel and Odd-Chain Fatty Acids2022In: Applied Sciences, E-ISSN 2076-3417, Vol. 12, no 13, article id 6541Article in journal (Refereed)
    Abstract [en]

    Oleaginous yeasts have attracted increasing scientific interest as single cell oil (SCO) producers. SCO can be used as a fossil-free fuel substitute, but also as a source of rarely found odd-chain fatty acids (OCFAs), such as C15, C17, and C25 fatty acids which have a wide range of nutritional and biological applications. Volatile fatty acids (VFAs) have gained interest as sustainable carbon source for yeasts. This study aims to improve current knowledge on yeast species that yield high amounts of SCO using VFAs as a carbon source. Specifically, the growth of the promising yeasts Cryptococcus curvatus and Rhodotorula toruloides was evaluated on individual VFAs, such as acetic, propionic, and butyric acid. C. curvatus proved to be more tolerant in higher concentrations of VFAs (up to 60 g/L), while butyric acid favored biomass and lipid conversion (0.65 and 0.23 g/gsubstrate, respectively). For R. toruloides, butyric acid favored biomass conversion (0.48 g/gsubstrate), but lipid conversion was favored using acetic acid, instead (0.14 g/gsubstrate). Propionic acid induced the formation of OCFAs, which yielded higher amounts for C. curvatus (up to 2.17 g/L). VFAs derived from the anaerobic digestion of brewer’s spent grain were tested as a cost-competitive carbon source and illustrated the significance of the combination of different VFAs in the quality of the produced SCO, by improving the biodiesel properties and OCFAs production.

  • 40.
    Lage, Sandra
    et al.
    Swedish University of Agricultural Sciences, Umeå.
    Kudahettige, Nirupa P.
    Swedish University of Agricultural Sciences, Umeå.
    Ferro, Lorenza
    Umeå University, Umeå.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Funk, Christiane
    Umeå University, Umeå.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Gentili, Francesco G.
    Swedish University of Agricultural Sciences, Umeå.
    Microalgae Cultivation for the Biotransformation of Birch Wood Hydrolysate and Dairy Effluent2019In: Catalysts, E-ISSN 2073-4344, Vol. 9, no 2, article id 150Article in journal (Refereed)
    Abstract [en]

    In order to investigate environmentally sustainable sources of organic carbon and nutrients, four Nordic green microalgal strains, Chlorella sorokiniana, Chlorella saccharophila, Chlorella vulgaris, and Coelastrella sp., were grown on a wood (Silver birch, Betula pendula) hydrolysate and dairy effluent mixture. The biomass and lipid production were analysed under mixotrophic, as well as two-stage mixotrophic/heterotrophic regimes. Of all of the species, Coelastrella sp. produced the most total lipids per dry weight (~40%) in the mixture of birch hydrolysate and dairy effluent without requiring nutrient (nitrogen, phosphorus, and potassium-NPK) supplementation. Overall, in the absence of NPK, the two-stage mixotrophic/heterotrophic cultivation enhanced the lipid concentration, but reduced the amount of biomass. Culturing microalgae in integrated waste streams under mixotrophic growth regimes is a promising approach for sustainable biofuel production, especially in regions with large seasonal variation in daylight, like northern Sweden. To the best of our knowledge, this is the first report of using a mixture of wood hydrolysate and dairy effluent for the growth and lipid production of microalgae in the literature.

  • 41.
    Latham, Kenneth G.
    et al.
    Umeå University, Department of Chemistry, SE-901 87, Umeå, Sweden; Discipline of Chemistry, University of Newcastle, Callaghan NSW 2308, Australia.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Figueira, João
    Umeå University, Department of Chemistry, Scilife Lab, SE-901 87, Umeå, Sweden.
    Kozyatnyk, Ivan
    Umeå University, Department of Chemistry, SE-901 87, Umeå, Sweden; Occupational and Environmental Medicine Center, Department of Clinical and Experimental Medicine, Linköping University, SE-581 83, Linköping, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jansson, Stina
    Umeå University, Department of Chemistry, SE-901 87, Umeå, Sweden.
    Impact of Temperature and Residence Time on the Hydrothermal Carbonization of Organosolv Lignin2022In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 166, article id 105623Article in journal (Refereed)
    Abstract [en]

    Herein, we have investigated how pure lignin extracted from birch and spruce via a hybrid organosolv/steam explosion method reacts under hydrothermal carbonization (HTC) to produce hydrochar, a product that has found applications in environmental remediation, energy storage and catalysis. We subjected thirteen lignin samples obtained from birch and spruce under different extraction conditions to HTC at 260 ℃ for four hours. The yield of hydrochar varied between the different extraction conditions and source, although no clear correlation between extraction conditions and yield could be observed. For instance, lignin from birch pretreated in 60%v/v ethanol for 15 minutes resulted in a hydrochar yield of 39 wt%. Increasing the time to 30 and 60 resulted in a hydrochar yield of 27 wt% and 23 wt%, respectively. This suggested that small changes in the organosolv reaction conditions might produce highly structurally different lignin, resulting in the difference in HTC yield. Thus, we chose a subset of four lignin samples to investigate in-depth, subjecting these samples to a range of hydrothermal reaction temperatures and residence times. Solid State NMR and FTIR analysis indicated that the most significant structural changes occurred below 230 ℃ resulting in the breaking of C-O- linkages. Increasing the temperature or time had minimal impact, with no further C-O- linkages broken and no changes to the ring structure of C-C groups. Size exclusion chromatography indicated that the degree of micro and macromolecules in the liquid product varied significantly with lignin source and HTC reaction conditions. Overall, this study demonstrated that lignin has a large reaction range where it produces a very chemically similar solid product, with the only major difference being the yield of material. This is important for industry, as it indicates that a similar solid product can be easily achieved independently of extraction conditions allowing the HTC reaction to be tuned towards extracting the maximum benefit from products contained in the liquid.

  • 42.
    Latham, Kenneth G.
    et al.
    Umeå University, Department of Chemistry, SE-901 87, Umeå, Sweden. Discipline of Chemistry, University of Newcastle, Callaghan, NSW, 2308, Australia.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Figueira, João
    Umeå University, Department of Chemistry, Scilife Lab, SE-901 87, Umeå, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jansson, Stina
    Umeå University, Department of Chemistry, SE-901 87, Umeå, Sweden.
    Examination of how variations in lignin properties from Kraft and organosolv extraction influence the physicochemical characteristics of hydrothermal carbon2021In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 155, article id 105095Article in journal (Refereed)
    Abstract [en]

    Seven different lignin samples, three from Kraft extraction and four from organosolv extraction, were subjected to hydrothermal treatment at 260℃ for four hours to assess the impact of lignin type on the physicochemical properties of the hydrothermal material. The 13C Solid state NMR, XPS, FTIR and SEM analysis revealed that the different sources of lignin and the extraction conditions created variations in the degree of syringyl and guaiacyl subunits, inter-unit bonding arrangements, morphology and surface composition. Hydrothermal carbonization appeared to “normalize” the differences between each of the lignin samples, via breaking β-O-4 or α-O-4 linkages, removal of methoxy and syringyl subunits, and creation of C C and 4-O-5 linkages to polymerization into large 100−200 μm amorphous carbon particles. Overall, this study indicates that the source and extraction type have minimal influence on the physicochemical structure and morphology of the final hydrothermal product.

  • 43.
    Magalhães, Duarte
    et al.
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Gürel, Kaan
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Pisano, Italo
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland; Celignis Biomass Analysis Laboratory, Holland Road, Castletroy, Co. Limerick, Ireland.
    Leahy, J.J.
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland.
    Kazanç, Feyza
    Mechanical Engineering Department, Middle East Technical University, Ankara, Turkey.
    Trubetskaya, Anna
    Department of Chemical Sciences, University of Limerick, Limerick, Ireland.
    Prediction of yields and composition of char from fast pyrolysis of commercial lignocellulosic materials, organosolv fractionated and torrefied olive stones2021In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 289, article id 119862Article in journal (Refereed)
    Abstract [en]

    This study investigated the fast pyrolysis behaviour of torrefied olive stones, fractionated olive stones and lignocellulosic commercial compounds. Olive stones were reacted in a continuous industrial torrefaction unit. The olive stones were also fractionated into their main components in an organosolv reactor at temperatures from 170 to 190 °C in both the presence and absence of an acidic catalyst. All samples were reacted in a wire mesh reactor at different temperatures (800–1150 °C) and heating rates (400–1150 °C/s), and the solid product was characterised for its yield, morphology, and elemental composition. The char yields from fast pyrolysis of commercially available cellulose, hemicelluloses, and lignin were compared with yields of fractionated olive stones. A model was developed to compare the measured yields of olive stones with the predicted yields using fractionated or commercial components. The presence of acid during fractionation had a stronger effect than the temperature, particularly on the lignin fraction. The fractionated lignocellulosic compounds provided more accurate predictions of the char yields of olive stones, as compared to the commercial lignocellulosic compounds. The fractionation at 180 °C without acid catalyst gave the cellulose, hemicellulose, and lignin with highest degree of purity and resulted in the most accurate predictions of the experimental yields of olive stones. The results showed that interactions between the lignocellulosic components were not significant. The char yield of each fractioned compound and non-treated olive stones could be accurately predicted from the lignocellulosic content which has importance for biorefinery applications in which each fraction is used as a value-added product.

  • 44.
    Mariam, Iqra
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bettiga, Maurizio
    Department of Life Sciences – LIFE, Division of Industrial Biotechnology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; Innovation Unit, Italbiotec Srl Società Benefit, Milan, Italy.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ameliorating microalgal OMEGA production using omics platforms2024In: Trends in Plant Science, ISSN 1360-1385, E-ISSN 1878-4372Article, review/survey (Refereed)
    Abstract [en]

    Over the past decade, the focus on omega (ω)-3 fatty acids from microalgae has intensified due to their diverse health benefits. Bioprocess optimization has notably increased ω-3 fatty acid yields, yet understanding of the genetic architecture and metabolic pathways of high-yielding strains remains limited. Leveraging genomics, transcriptomics, proteomics, and metabolomics tools can provide vital system-level insights into native ω-3 fatty acid-producing microalgae, further boosting production. In this review, we explore ‘omics’ studies uncovering alternative pathways for ω-3 fatty acid synthesis and genome-wide regulation in response to cultivation parameters. We also emphasize potential targets to fine-tune in order to enhance yield. Despite progress, an integrated omics platform is essential to overcome current bottlenecks in optimizing the process for ω-3 fatty acid production from microalgae, advancing this crucial field.

  • 45.
    Mariam, Iqra
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krikigianni, Eleni
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rantzos, Chloe
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bettiga, Maurizio
    Department of Life Sciences – LIFE, Division of Industrial Biotechnology, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden; Innovation Unit, Italbiotec Srl Società Benefit, Milan, Italy.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Transcriptomics aids in uncovering the metabolic shifts and molecular machinery of Schizochytrium limacinum during biotransformation of hydrophobic substrates to docosahexaenoic acid2024In: Microbial Cell Factories, E-ISSN 1475-2859, Vol. 23, no 1, article id 97Article in journal (Refereed)
    Abstract [en]

    Background: Biotransformation of waste oil into value-added nutraceuticals provides a sustainable strategy. Thraustochytrids are heterotrophic marine protists and promising producers of omega (ω) fatty acids. Although the metabolic routes for the assimilation of hydrophilic carbon substrates such as glucose are known for these microbes, the mechanisms employed for the conversion of hydrophobic substrates are not well established. Here, thraustochytrid Schizochytrium limacinum SR21 was investigated for its ability to convert oils (commercial oils with varying fatty acid composition and waste cooking oil) into ω-3 fatty acid; docosahexaenoic acid (DHA).

    Results: Within 72 h SR21 consumed ~ 90% of the oils resulting in enhanced biomass (7.5 g L− 1) which was 2-fold higher as compared to glucose. Statistical analysis highlights C16 fatty acids as important precursors of DHA biosynthesis. Transcriptomic data indicated the upregulation of multiple lipases, predicted to possess signal peptides for secretory, membrane-anchored and cytoplasmic localization. Additionally, transcripts encoding for mitochondrial and peroxisomal β-oxidation along with acyl-carnitine transporters were abundant for oil substrates that allowed complete degradation of fatty acids to acetyl CoA. Further, low levels of oxidative biomarkers (H2O2, malondialdehyde) and antioxidants were determined for hydrophobic substrates, suggesting that SR21 efficiently mitigates the metabolic load and diverts the acetyl CoA towards energy generation and DHA accumulation.

    Conclusions: The findings of this study contribute to uncovering the route of assimilation of oil substrates by SR21. The thraustochytrid employs an intricate crosstalk among the extracellular and intracellular molecular machinery favoring energy generation. The conversion of hydrophobic substrates to DHA can be further improved using synthetic biology tools, thereby providing a unique platform for the sustainable recycling of waste oil substrates.

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  • 46.
    Maršík, Dominik
    et al.
    Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
    Thoresen, Petter Paulsen
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Maťátková, Olga
    Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
    Masák, Jan
    Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
    Sialini, Pavel
    Central Laboratories, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Tsikourkitoudi, Vasiliki
    Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jarošová Kolouchová, Irena
    Department of Biotechnology, University of Chemistry and Technology, 166 28 Prague, Czech Republic.
    Synthesis and Characterization of Lignin-Silver Nanoparticles2024In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 29, no 10, article id 2360Article in journal (Refereed)
    Abstract [en]

    Metal nanoparticle synthesis via environmentally friendly methods is gaining interest for their potential advantages over conventional physico-chemical approaches. Herein, we propose a robust green synthesis route for lignin-modified silver nanoparticles, utilizing the recovery of lignin as a renewable raw material and exploring its application in valuable areas. Through a systematic approach combining UV-Vis spectroscopy with AAS and DLS, we identified repeatable and scalable reaction conditions in an aqueous solution at pH 11 for homogeneous silver nanoparticles with high uniformity. The TEM median sizes ranged from 12 to 15 nm with circularity between 0.985 and 0.993. The silver nanoparticles yield exceeded 0.010 mol L−1, comparable with traditional physico-chemical methods, with a minimal loss of silver precursor ranging between 0.5 and 3.9%. Characterization by XRD and XPS revealed the presence of Ag-O bonding involving lignin functional groups on the pure face-centered cubic structure of metallic silver. Moreover, the lignin-modified silver nanoparticles generated a localized thermal effect upon near-infrared laser irradiation (808 nm), potentially allowing for targeted applications in the biomedical field. Our study showcases the potential of lignin as a renewable reducing and capping agent for silver nanoparticle synthesis, addressing some shortcomings of green synthesis approaches and contributing to the development of suitable nanomaterials.

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  • 47.
    Matsakas, Leonidas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antonopoulou, Io
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Evaluation of Myceliopthora thermophila as an enzyme factory for the production of thermophilic cellulolytic enzymes2015In: BioResources, E-ISSN 1930-2126, Vol. 10, no 3, p. 5140-5158Article in journal (Refereed)
    Abstract [en]

    Enzymatic hydrolysis is a key step in bioethanol production. Efficient hydrolysis requires a consortium of different enzymes that are able to hydrolyze cellulose and hemicellulose into fermentable sugars. Myceliopthora thermophila is a promising candidate for the production of thermophilic cellulolytic enzymes, the use of which could reduce the cost of ethanol production. The growth conditions of the fungus were optimized in order to achieve increased secretion of extracellular cellulases. Optimal conditions were found to be 7.0% w/v brewer’s spent grain as the carbon source and 0.4% w/v ammonium sulfate as the nitrogen source. The cellulases obtained were characterized for their optimum activity. The optimum temperature and pH for cellulase activity are 65 °C and pH 5.5, respectively. Studies on thermal inactivation of the crude extract showed that the cellulases of M. thermophila are stable for temperatures up to 60 °C. At this temperature the half-life was found to be as high as 27 h. Enzymatic hydrolysis of cellulose resulted in 31.4% hydrolysis yield at 60 °C after 24 h of incubation. Finally, the recalcitrance constant for cellulose and cellulose pretreated with ionic liquids was calculated to be 5.46 and 2.69, respectively.

  • 48.
    Matsakas, Leonidas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bonturi, Nemailla
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Miranda, Everson Alves
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    High concentrations of dried sorghum stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides2015In: Biotechnology for Biofuels, E-ISSN 1754-6834, Vol. 8, article id 8:6Article in journal (Refereed)
    Abstract [en]

    Background:Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for alarge fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.Results: Initially the ability of sweet sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of thepresence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20%w/w enzymatically liquefied sweet sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized.Conclusions: The use of sweet sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9%when dried stalks or stalk juice was used, respectively.

  • 49.
    Matsakas, Leonidas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ethanol Production from Enzymatically Treated Dried Food Waste Using Enzymes Produced On-Site2015In: Sustainability, E-ISSN 2071-1050, Vol. 7, no 2, p. 1446-1458Article in journal (Refereed)
    Abstract [en]

    The environmental crisis and the need to find renewable fuel alternatives have made production of biofuels an important priority. At the same time, the increasing production of food waste is an important environmental issue. For this reason, production of ethanol from food waste is an interesting approach. Volumes of food waste are reduced and ethanol production does not compete with food production. In this work, we evaluated the possibility of using source-separated household food waste for the production of ethanol. To minimize the cost of ethanol production, the hydrolytic enzymes that are necessary for cellulose hydrolysis were produced in-house using the thermophillic fungus Myceliophthora thermophila. At the initial stage of the study, production of these thermophilic enzymes was studied and optimized, resulting in an activity of 0.28 FPU/mL in the extracellular broth. These enzymes were used to saccharify household food waste at a high dry material consistency of 30% w/w, followed by fermentation. Ethanol production reached 19.27 g/L with a volumetric productivity of 0.92 g/L·h, whereas only 5.98 g/L of ethanol was produced with a volumetric productivity of 0.28 g/L·h when no enzymatic saccharification was used.

  • 50.
    Matsakas, Leonidas
    et al.
    National Technical University of Athens.
    Christakopoulos, Paul
    National Technical University of Athens.
    Fermentation of liquefacted hydrothermally pretreated sweet sorghum bagasse to ethanol at high-solids content2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 127, p. 202-208Article in journal (Refereed)
    Abstract [en]

    The ability of sweet sorghum bagasse to be utilized as feedstock for ethanol production at high initial dry matter concentration was investigated. In order to achieve high enzymatic hydrolysis yield, a hydrothermal pretreatment prior to liquefaction and saccharification was applied. Response surface methodology had been employed in order to optimize the pretreatment step, taking into account the yield of cellulose hydrolysis. Liquefaction of the pretreated bagasse was performed at a specially designed liquefaction chamber at 50 °C for either 12 or 24 h using an enzyme loading of 10 FPU/g·DM and 18% DM. Fermentation of liquefacted bagasse was not affected by liquefaction duration and leaded to an ethanol production of 41.43 g/L and a volumetric productivity of 1.88 g/L h. The addition of extra enzymes at the start up of SSF enhanced both ethanol concentration and volumetric productivity by 16% and 17% after 12 and 24 h saccharification, respectively.

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