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  • 1.
    Arora, Neha
    et al.
    Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    Dubey, Durgesh
    Centre of Biomedical Research, SGPGIMS, Lucknow 226014, Uttar Pradesh, India.
    Sharma, Meenakshi
    Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    Patel, Alok
    Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    Guleria, Anupam
    Centre of Biomedical Research, SGPGIMS, Lucknow 226014, Uttar Pradesh, India.
    Pruthi, Parul A.
    Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    Kumar, Dinesh
    Centre of Biomedical Research, SGPGIMS, Lucknow 226014, Uttar Pradesh, India.
    Pruthi, Vikas
    Department of Biotechnology and Centre for Transportation Systems, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    Poluri, Krishna Mohan
    Department of Biotechnology and Centre for Transportation Systems, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand, India.
    NMR-Based Metabolomic Approach To Elucidate the Differential Cellular Responses during Mitigation of Arsenic(III, V) in a Green Microalga2018In: ACS Omega, E-ISSN 2470-1343, Vol. 3, no 9, p. 11847-11856Article in journal (Refereed)
    Abstract [en]

    Nuclear magnetic resonance (NMR)-based metabolomic approach is a high-throughput fingerprinting technique that allows a rapid snapshot of metabolites without any prior knowledge of the organism. To demonstrate the applicability of NMR-based metabolomics in the field of microalgal-based bioremediation, novel freshwater microalga Scenedesmus sp. IITRIND2 that showed hypertolerance to As(III, V) was chosen for evaluating the metabolic perturbations during arsenic stress in both its oxidation states As(III) and As(V). Using NMR spectroscopy, we were able to identify and quantify an array of ∼45 metabolites, including amino acids, sugars, organic acids, phosphagens, osmolytes, nucleotides, etc. The NMR metabolomic experiments were complemented with various biophysical techniques to establish that the microalga tolerated the arsenic stress using a complex interplay of metabolites. The two different arsenic states distinctly influenced the microalgal cellular mechanisms due to their altered physicochemical properties. Eighteen differentially identified metabolites related to bioremediation of arsenic were then correlated to the major metabolic pathways to delineate the variable stress responses of microalga in the presence of As(III, V).

  • 2.
    Chandra, Rajesh
    et al.
    Bioenergy Research Laboratory, Polymer and Process Engineering Department, Indian Institute of Technology Roorkee (Saharanpur Campus), Saharanpur, 247001, Uttar Pradesh, India.
    Pradhan, Snigdhendubala
    Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Doha, Qatar.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ghosh, Uttam Kumar
    Bioenergy Research Laboratory, Polymer and Process Engineering Department, Indian Institute of Technology Roorkee (Saharanpur Campus), Saharanpur, 247001, Uttar Pradesh, India.
    An approach for dairy wastewater remediation using mixture of microalgae and biodiesel production for sustainable transportation2021In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 297, article id 113210Article in journal (Refereed)
    Abstract [en]

    The aim of this work is remediation of dairy wastewater (DWW) for biodiesel feedstock production using poly-microalgae cultures of four microalgae namely Chlorella minutissima (C. minutissima), Scenedesmus abundans (S. abundans), Nostoc muscorum (N. muscorum) and Spirulina sp. The poly-microalgae cultures were prepared as C. minutissima + N. muscorum (CN), C. minutissima + N. muscorum + Spirulina sp. (CNSS) and S. abundans + N. muscorum + Spirulina sp. (SNSS). Poly-microalgae culture CNSS cultivated on 70% DWW achieved 75.16, 61.37, 58.76, 84.48 and 84.58%, removals of biological oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and suspended solids (SS), respectively, at 12:12 h photoperiod that resulted into total biomass and lipid yield of 3.47 ± 0.07 g/L and 496.32± 0.065 mg/L. However, maximum biomass and lipid yields of 5.76 ± 0.06 and 1152.37 ± 0.065 mg/L were achieved by poly-microalgae culture CNSS cultivated on 70% DWW + 10 g/L of glucose at 18:6 h photoperiod. Fatty acid methyl ester (FAME) analysis shown presence of C14:0 (myristic acid) C16:0 (palmitic acid), C16:1 (palmitoleic acid), C18:0 (stearic acid), C18:2 (linoleic acid) and C18:3 (linolenic acid), it indicates that the lipids produced from poly-microalgae cultures are suitable for biodiesel production. Thus, poly-microalgae cultures could be more efficient than mono-microalgae cultures in the remediation of DWW and for biodiesel feedstock production.

  • 3.
    Chauhan, Ajeet Singh
    et al.
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan.
    Patel, Anil Kumar
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow, Uttar Pradesh, 226 029, India.
    Nimker, Vanshika
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan; Amity Institute of Biotechnology, Amity University, Noida, Uttar Pradesh, 201313, India.
    Singhania, Reeta Rani
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow, Uttar Pradesh, 226 029, India.
    Chen, Chiu-Wen
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan; Department of Marine Environmental Engineering, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan.
    Patel, Alok Kumar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Raj, Tirath
    Department of Agricultural and Biological Engineering, University of Illinois Urbana-Champaign, 1304 West Pennsylvania Avenue, Urbana, IL, 61801, USA.
    Dong, Cheng-Di
    Institute of Aquatic Science and Technology, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan; Department of Marine Environmental Engineering, College of Hydrosphere, National Kaohsiung University of Science and Technology, Kaohsiung City, 81157, Taiwan.
    Biorefining of essential polyunsaturated fatty acids from microbial sources: current updates and prospects2023In: Systems Microbiology and Biomanufacturing, ISSN 2662-7655Article, review/survey (Refereed)
    Abstract [en]

    The biorefinery approach ensures a sustainable source of valuable fatty acids and opens up new avenues for their application in healthcare industries. Recent studies highlight the health benefits of omega-PUFAs, spurring the search for cost-effective production methods. Microbial platforms are promising for high-yield PUFA production, with ω-3 dominating the market. ω-3 PUFAs offer antioxidant and anti-inflammatory effects, reducing illness risk, while all PUFAs contribute to cardiovascular health, diabetes prevention, cancer risk reduction, and more. ω-6 PUFAs, particularly linoleic acid (LA) and arachidonic acid (ARA), play vital roles in various aspects of health, making them high-demand bioavailable compounds. Additionally, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) exhibit potential benefits in brain development and COVID-19 prevention. This comprehensive review provides insights into the state-of-the-art microbial biorefinery strategies for ω-3 and ω-6 PUFA production and their wide-ranging health-related benefits.

  • 4.
    Dixit, Rishibha
    et al.
    Rani Durgavati Univ, Dept PG Studies & Res Biol Sci, Algal Biotechnol Lab, Jabalpur 482001, India.
    Singh, Surendra
    Rani Durgavati Univ, Dept PG Studies & Res Biol Sci, Algal Biotechnol Lab, Jabalpur 482001, India.
    Enamala, Manoj Kumar
    Bioserve Biotechnol India Private Ltd, Unit D4-7,1st Floor,Ind Estate, Hyderabad 500040, India.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Effect of Various Growth Medium on the Physiology and De Novo Lipogenesis of a Freshwater Microalga Scenedesmus rotundus-MG910488 under Autotrophic Condition2022In: Clean Technologies, E-ISSN 2571-8797, Vol. 4, no 3, p. 733-751Article in journal (Refereed)
    Abstract [en]

    The microalga Scenedesmus rotundus, isolated from Jabalpur, Madhya Pradesh, India was designated as Scenedesmus rotundus-MG910488 after morphological and molecular identification. In this study, the effects of various autotrophic growth media on the physiology and lipid accumulation of this microalga were investigated. The cell density, amount of photosynthetic pigments, the productivity of biomass and lipid content and the cell morphology of the microalga were shown to be significantly affected by the variation in growth media. The highest biomass of 754.56 +/- 14.80 mg L-1 with biomass productivity of 37.73 +/- 0.74 mg L(-1)day(-1) was achieved when this microalgae was cultivated in the Zarrouk's medium, whereas the highest lipid content of 33.30 +/- 1.21% was observed in the BG-11 medium. The results confirm that the BG-11 is a cost-effective and efficient growth medium for this microalga. It also shows that the ingredients of the growth medium and its concentration influence the growth and synthesis of biomolecules produced by microalga. The biodiesel produced from obtained lipids was qualitatively estimated by Gas Chromatography-Mass Spectroscopy (GC-MS), Nuclear Magnetic Resonance (H-1, C-13 NMR) and Fourier Transform-Infrared Spectroscopy (FT-IR), which indicate the presence of oleic acid methyl ester, linoleic acid methyl ester and palmitic acid methyl ester as the leading fatty acid methyl esters (FAME) in the samples, which make this strain an ideal feedstock for biodiesel production.

  • 5.
    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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  • 6.
    Ghodke, Praveen Kumar
    et al.
    Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode, 673601, Kerala, India.
    Sharma, Amit Kumar
    Department of Chemistry, Centre for Alternate and Renewable Energy Research, R&D, University of Petroleum & Energy Studies (UPES), School of Engineering, Energy Acres Building, Bidholi, Dehradun, 248007, Uttarakhand, India.
    Pandey, J.K
    Department of Chemistry, School of Basic and Applied Sciences, Adamas University, Kolkata, 700 126, 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.
    Ashokkumarhi, Veeramuthu
    Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Department of Energy and Environmental Engineering, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, 600077, India.
    Pyrolysis of sewage sludge for sustainable biofuels and value-added biochar production2021In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 298, article id 113450Article in journal (Refereed)
    Abstract [en]

    The study deals with the pyrolysis of sewage sludge to produce eco-friendly and sustainable fuels along with value-added biochar products. The experiments were conducted in a fixed-bed cylindrical glass reactor in the temperature range of 250–700 °C and achieved the product yield of 22.4 wt% bio-oil, 18.9 wt % pyrolysis gases, and 58.7 wt% biochar at 500 °C optimum temperature. The chemical composition of bio-oil was investigated by gas chromatograph-mass spectroscopy and fourier transformation infrared techniques. The ASTM standard procedures were used to assess the fuel qualities of bio-oil, and they were found to be satisfactory. Bio-oil has a greater H/C ratio (3.49) and a lower O/C ratio (1.10), indicating that it is suitable for engine use. The gas chromatographic analysis of pyrolysis gases confirmed the presence of 41.16 wt % combustible gases, making it suitable for use in spark-ignition engines. X-ray fluorescence analysis of biochar showed that it had a good amount of carbon, nitrogen, phosphorus, and potassium along with some micro-and macro-nutrient which proves its potential to utilize as organic manure in the agriculture sector. In addition, the data obtained from the TGA analysis during the pyrolysis of sewage sludge was applied to calculate kinetic parameters via the Coats-Redfern method.

  • 7.
    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.

  • 8.
    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.

  • 9.
    Kadri, Mohammad Sibtain
    et al.
    Department of Education and Human Potential Development, National Dong Hwa University, Hualien, 974301, Taiwan.
    Singhania, Reeta Rani
    Institute of Aquatic Science and Technology, National Kaohsiung University of Science and Technology, Kaohsiung City 81157, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow 226 029, Uttar Pradesh, India.
    Anisha, Grace Sathyanesan
    Post-graduate and Research Department of Zoology, Government College for Women, Thiruvananthapuram 695014, Kerala, India.
    Gohil, Nisarg
    Department of Biosciences, School of Science, Indrashil University, Rajpur, Mehsana 382715, Gujarat, India.
    Singh, Vijai
    Department of Biosciences, School of Science, Indrashil University, Rajpur, Mehsana 382715, Gujarat, India.
    Patel, Alok Kumar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Patel, Anil Kumar
    Institute of Aquatic Science and Technology, National Kaohsiung University of Science and Technology, Kaohsiung City 81157, Taiwan; Centre for Energy and Environmental Sustainability, Lucknow 226 029, Uttar Pradesh, India.
    Microalgal lutein: Advancements in production, extraction, market potential, and applications2023In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 389, article id 129808Article, review/survey (Refereed)
  • 10.
    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.

  • 11.
    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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  • 12.
    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.

  • 13.
    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.

  • 14.
    Mehariya, Sanjeet
    et al.
    Department of Chemistry, Umeå University, Umeå, Sweden.
    Plöhn, Martin
    Department of Chemistry, Umeå University, Umeå, Sweden.
    Leon-Vaz, Antonio
    Department of Chemistry, Umeå University, Umeå, Sweden; Laboratory of Biochemistry, University of Huelva, Huelva, Spain.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Funk, Christiane
    Department of Chemistry, Umeå University, Umeå, Sweden.
    Improving the content of high value compounds in Nordic Desmodesmus microalgal strains2022In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 359, article id 127445Article in journal (Refereed)
    Abstract [en]

    Nordic Desmodesmus microalgal strains (2-6) and (RUC-2) were exposed to abiotic stress (light and salt) to enhance lipids and carotenoids. The biomass output of both strains increased by more than 50% during light stress of 800 μmol m-2 s-1 compared to control light. The biomass of Desmodesmus sp. (2-6) contained most lipids (15% of dry weight) and total carotenoids (16.6 mg g-1) when grown at moderate light stress (400 μmol m-2 s-1), which further could be enhanced up to 2.5-fold by salinity stress. Desmodesmus sp. (RUC-2) exhibited maximal lipid (26.5%) and carotenoid (43.8 mg L-1) content at light intensities of 400 and 100 μmol m-2 s-1, respectively. Salinity stress stimulated lipid accumulation by 39%. Nordic Desmodesmus strains therefore are not only able to tolerate stress conditions, but their biomass considerably improves under stress. These strains have high potential to be used in algal bio-factories on low-cost medium like Baltic seawater.

  • 15.
    Pal, Shashank
    et al.
    Department of Mechanical, School of Engineering Studies, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India.
    Kumar, Anil
    Department of Mechanical, School of Engineering Studies, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India.
    Sharma, Amit Kumar
    Department of Chemistry and Centre of Alternate Energy, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India.
    Ghodke, Praveen Kumar
    Department of Chemical Engineering, National Institute of Technology Calicut, Kozhikode 673601, Kerala, India.
    Pandey, Shyam
    Yogoda Satsanga Mahavidyalaya, Ranchi 834001, Jharkhand, India.
    Patel, Alok
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Recent Advances in Catalytic Pyrolysis of Municipal Plastic Waste for the Production of Hydrocarbon Fuels2022In: Processes, ISSN 2227-9717, Vol. 10, no 8, article id 1497Article in journal (Refereed)
    Abstract [en]

    Currently, the resources of fossil fuels, such as crude oil, natural gas, and coal, are depleting day by day due to increasing energy demands. Nowadays, plastic items have witnessed a substantial surge in manufacturing due to their wide range of applications and low cost. Therefore, the amount of plastic waste is increasing rapidly. Hence, the proper management of plastic wastes for sustainable technologies is the need of the hour. Chemical recycling technologies based on pyrolysis are emerging as the best waste management approaches due to their robustness and better economics. However, research on converting plastic waste into fuels and other value-added goods has yet to be undertaken, and more R&D is required to make waste-plastic-based fuels economically viable. In this review article, the current status of the plastic waste pyrolysis process is discussed in detail. Processcontrolling parameters such as temperature, pressure, residence time, reactor type, and catalyst dose are also investigated in this review paper. In addition, the application of reaction products is also described in brief. For example, plasto-oil obtained by catalytic pyrolysis may be utilized in various sectors, e.g., transportation, industrial boilers, and power generation. On the other hand, byproducts, such as solid residue (plasto-char), could be used as a road construction material or to make activated carbon or graphenes, while the non-condensable gases have a good potential to be utilized as heating/energy source.

  • 16.
    Patel, Alok
    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.
    Enman, Josefine
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Lipids detection and quantification in oleaginous microorganisms: an overview of the current state of the art2019In: BMC Chemical Engineering, ISSN 2524-4175, Vol. 1, article id 13Article in journal (Refereed)
    Abstract [en]

    Oleaginous microorganisms are among the most promising feedstocks for the production of lipids for biofuels and oleochemicals. Lipids are synthesized in intracellular compartments in the form of lipid droplets. Therefore, their qualitative and quantitative analysis requires an initial pretreatment step that allows their extraction. Lipid extraction techniques vary with the type of microorganism but, in general, the presence of an outer membrane or cell wall limits their recovery. This review discusses the various types of oleaginous microorganisms, their lipid accumulating capabilities, lipid extraction techniques, and the pretreatment of cellular biomass for enhanced lipid recovery. Conventional methods for lipid quantification include gravimetric and chromatographic approaches; whereas non-conventional methods are based on infrared, Raman, nuclear magnetic resonance, and fluorescence spectroscopic analysis. Recent advances in these methods, their limitations, and fields of application are discussed, with the aim of providing a guide for selecting the best method or combination of methods for lipid quantification.

  • 17.
    Patel, Alok
    et al.
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), India.
    Arora, Neha
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), India.
    Mehtani, Juhi
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), India.
    Assessment of fuel properties on the basis of fatty acid profiles of oleaginous yeast for potential biodiesel production2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 77, p. 604-616Article in journal (Refereed)
    Abstract [en]

    Over the last decade, there has been a huge upsurge of interest in sustainable production of biomass-based biofuels to fulfill the existing energy demand and simultaneously reducing the environmental deterioration. Earlier, vegetable oils and animal fats were utilized for biodiesel production, but due to food crisis and environmental sustainability, renewable sources such as neutral lipid derived from microbes are gaining much attention for budding biodiesel industries. Among various types of microorganisms, oleaginous yeasts are more promising feedstock to accomplish the current demand of biodiesel production and utilize a large number of cost-effective renewable substrates for their growth and lipid accumulation. However, biodiesel obtained from oleaginous yeasts have certain restrictions regarding their commercial utilization due to their unstable fuel properties such as oxidative stability, cetane number, viscosity and low-temperature performance etc. Numerous articles have been published in the public domain describing the fatty acid profiles of oleaginous yeast as feedstock for biodiesel production. However, the evaluation of quality parameters of biodiesel obtained from oleaginous yeasts is still in infancy. Although there is a huge disparity in a number of papers published for biodiesel production yet the reporting performance on diesel engines need to be verified in details. In this review article, attempt has been made to assess the important biofuel properties on the basis of the fatty acid profile of oleaginous yeast. Thus this evaluation would provide a guideline to the biodiesel producer to improve the production plans related to feedstocks for oleaginous yeast, culture conditions and biodiesel blending.

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  • 18.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee.
    Arora, Neha
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee.
    A novel rapid ultrasonication-microwave treatment for total lipid extraction from wet oleaginous yeast biomass for sustainable biodiesel production2019In: Ultrasonics sonochemistry, ISSN 1350-4177, E-ISSN 1873-2828, Vol. 51, p. 504-516Article in journal (Refereed)
    Abstract [en]

    Oleaginous yeasts have emerged as a sustainable source of renewable oils for liquid biofuels. However, biodiesel production from them has few constraints with respect to their cell disruption and lipid extraction techniques. The lipid extraction from oleaginous yeasts commonly includes dewatering and drying of cell biomass, which requires energy and time. The aim of this work was to establish a process for the lipid extraction techniques from wet biomass applying acid catalyzed hot water, microwave, rapid ultrasonication-microwave treatment together with conventional Bligh and Dyer method. In the wake of testing all procedures, it was revealed that rapid ultrasonication-microwave treatment has great potential to give high lipid content (70.86 % w/w) on the cell dry weight basis. The lipid profile after treatment showed the presence of appropriate quantities of saturated (10.39 ± 0.15%), monounsaturated (76.55 ± 0.19%) and polyunsaturated fatty acids (11.49 ± 0.23%) which further improves biodiesel quality compared to the rest of methods. To the best of our knowledge, this is the first report of using rapid ultrasonication-microwave treatment for the lipid extraction from wet oleaginous yeast biomass in the literature.

  • 19.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bettiga, Maurizio
    Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; Bioeconomy Division, EviKrets Biobased Processes Consultants, Landvetter, 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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Microbial genetic engineering approach to replace shark livering for squalene2022In: Trends in Biotechnology, ISSN 0167-7799, E-ISSN 1879-3096, Vol. 40, no 10, p. 1261-1273Article, review/survey (Refereed)
    Abstract [en]

    Squalene is generally sourced from the liver oil of deep sea sharks (Squalus spp.), in which it accounts for 40–70% of liver mass. To meet the growing demand for squalene because of its beneficial effects for human health, three to six million deep sea sharks are slaughtered each year, profoundly endangering marine ecosystems. To overcome this unsustainable practice, microbial sources of squalene might offer a viable alternative to plant- or animal-based squalene, although only a few microorganisms have been found that are capable of synthesizing up to 30% squalene of dry biomass by native biosynthetic pathways. These squalene biosynthetic pathways, on the other hand, can be genetically manipulated to transform microorganisms into 'cellular factories' for squalene overproduction.

  • 20.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Delgado Vellosillo, Irene
    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.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    A novel bioprocess engineering approach to recycle hydrophilic and hydrophobic waste under high salinity conditions for the production of nutraceutical compounds2022In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 431, no Part 1, article id 133955Article in journal (Refereed)
    Abstract [en]

    The recovery of hydrophobic substrates generated by industrial oily effluents and oil spills represents a growing issue. Here, we describe a low-cost, bio-based, and environmentally friendly method for the mitigation of oil-induced water pollution. We demonstrate that a marine thraustochytrid strain could survive and utilise a record 120 g/L waste cooking oil (WCO) under highly saline conditions. Moreover, the thraustochytrid strain could convert this low-quality oil into high-quality microbial lipids rich in docosahexaenoic acid (DHA) and squalene. DHA and squalene levels were further improved via the co-utilisation of hydrophilic and hydrophobic substrates via de novo and ex novo fermentation. Hydrophobic substrate such as WCO, and volatile fatty acids (VFAs) as hydrophilic substrates generated via acidogenic fermentation increased the DHA content to 40% of total lipids and squalene to 40.47 mg/L. These values are much higher than the 23.96% and 30.21 mg/L obtained with simultaneous de novo and ex novo fermentation using glucose and WCO. The presently described method for producing nutraceutical compounds has two important benefits: (i) it enables the bioremediation of hydrophobic waste from marine environments, and (ii) it offers a sustainable and economical alternative to the use of fish oils and liver from deep-sea sharks as sources of DHA and squalene.

  • 21.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Desai, Sneha Sawant
    Department of Biotechnology, University of Mumbai, Kalina, Santacruz (E), Mumbai, India.
    Mane, Varsha Kelkar
    Department of Biotechnology, University of Mumbai, Kalina, Santacruz (E), Mumbai, India.
    Enman, Josefine
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Futuristic food fortification with a balanced ratio of dietary ω-3/ω‰-6 omega fatty acids for the prevention of lifestyle diseases2022In: Trends in Food Science & Technology, ISSN 0924-2244, E-ISSN 1879-3053, Vol. 120, p. 140-153Article in journal (Refereed)
    Abstract [en]

    BackgroundOver the last three decades, consumption of total and saturated fat has steadily declined in Western diets as a proportion of calories intake. At the same time, omega (ω)-6 fatty acid intake has risen at the expense of ω-3 fatty acids, resulting in an ω-6/ω-3 ratio of 20:1 or higher.

    Scope and approachThe observed changes in fatty acids ratio coincide with a significantly increased prevalence of coronary heart disease, hypertension, cancer, diabetes, obesity, rheumatoid arthritis, and autoimmune or neurodegenerative disorders. The low intake of ω-3 fatty acids may be attributed to their absence from the diet or lack of awareness about suitable dietary sources.

    Key findings and conclusionsA sustainable and cost-effective way of reaching a large population with essential ω-3 fatty acids is fortification of staple foods. A variety of food items enriched with ω-3 have entered the market in recent years, including beef, fish, dairy products, cereals, cereal bars, and infant formula. The present review discusses the role of ω-3 and ω-6 fatty acids, as well as their ratio, on human health. Additionally, it focuses on the latest developments regarding dietary sources, innovative technologies, and challenges of food fortification with ω-3 fatty acids.

  • 22.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Enman, Josefine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Gulkova, Anna
    Boliden Mineral AB, SE- 936 32 Boliden, Sweden.
    Guntoro, Pratama Istiadi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Dutkiewicz, Agata
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ghorbani, Yousef
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical 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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Integrating biometallurgical recovery of metals with biogenic synthesis of nanoparticles2021In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 263, article id 128306Article in journal (Refereed)
    Abstract [en]

    Industrial activities, such as mining, electroplating, cement production, and metallurgical operations, as well as manufacturing of plastics, fertilizers, pesticides, batteries, dyes or anticorrosive agents, can cause metal contamination in the surrounding environment. This is an acute problem due to the non-biodegradable nature of metal pollutants, their transformation into toxic and carcinogenic compounds, and bioaccumulation through the food chain. At the same time, platinum group metals and rare earth elements are of strong economic interest and their recovery is incentivized. Microbial interaction with metals or metals-bearing minerals can facilitate metals recovery. Metal nanoparticles are gaining increasing attention due to their unique characteristics and application as antimicrobial and antibiofilm agents, biocatalysts, in targeted drug delivery, for wastewater treatment, and in water electrolysis. Ideally, metal nanoparticles should be homogenous in shape and size, and not toxic to humans or the environment. Microbial synthesis of nanoparticles represents a safe, and environmentally friendly, alternative to chemical and physical methods. In this review article, we mainly focus on metal and metal salts nanoparticles synthesized by various microorganisms, such as bacteria, fungi, microalgae, and yeasts, as well as their advantages in biomedical, health, and environmental applications.

  • 23.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Enman, Josefine
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Metal Nanoparticles for Dermatology and Cosmetics2022In: Engineered Nanomaterials for Innovative Therapies and Biomedicine / [ed] Hemen Sarma; Sonam Gupta; Mahesh Narayan; Ram Prasad; Anand Krishnan, Springer, 2022, p. 53-66Chapter in book (Refereed)
  • 24.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hruzova, Katerina
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sustainable biorefinery concept for biofuel production through holistic volarization of food waste2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 294, article id 122247Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to utilize the whole food waste in two stages. In the first stage, the carbohydrate and protein fractions of food waste recovered after enzymatic hydrolysis was used to cultivate heterotrophic microalgae, resulting in biomass yield of 0.346 ± 0.09 g/gsugars and lipid yield of 0.216 ± 0.06 g/gsugars. In the second stage, oil (14.15% w/w) was extracted from food waste after hydrolysis and converted to biodiesel by a two-step transesterification reaction that generated 135.8 g/kgfood waste of fatty acid methyl esters and 13.8 g/kgfood waste of crude glycerol. Finally, crude glycerol obtained from both processes was used at 20 g/L to cultivate heterotrophic microalgae, resulting in a cell dry weight and total lipid concentration of 6.23 g/L and 2.91 g/L, respectively. A total 248.21 g of fatty acid methyl esters were obtained from the 1 kg of food waste through this integrated process.

  • 25.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karageorgou, Dimitra
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, Ioannina, 45110, Greece.
    Katapodis, Petros
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, Ioannina, 45110, Greece.
    Sharma, Amit
    Department of Chemistry and Biofuels Research Laboratory, Centre for Alternate Energy Research, R&D, University of Petroleum and Energy Studies, Dehradun, 248007, Uttarakhand, India.
    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.
    Bioprospecting of thraustochytrids for omega-3 fatty acids: A sustainable approach to reduce dependency on animal sources2021In: Trends in Food Science & Technology, ISSN 0924-2244, E-ISSN 1879-3053, Vol. 115, p. 433-444Article in journal (Refereed)
    Abstract [en]

    Backgrounds

    Omega-3 and omega-6 fatty acids are examples of polyunsaturated fatty acids (PUFAs). The omega-3 α-linolenic acid and omega-6 linoleic acid cannot be generated by humans and, therefore, are considered essential fatty acids. Long-chain PUFAs, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), can be produced from α-linolenic acid in the human body, but at a level too low to meet daily requirements and must be supplemented through the diet. Daily intake of EPA and DHA reduces the risk of heart disease, Alzheimer's, bipolar disorder, schizophrenia, and type 2 diabetes; moreover, DHA is essential for proper visual and neurological postnatal development.

    Scope and approach

    Fish oil and seafood are the widely used as sources of omega fatty acids, which represents a two-fold problem. First, it depletes fish stocks and impacts negatively on the aquatic environment through excessive aquaculture. Second, the growing popularity of veganism and vegetarianism puts these consumers at risk of omega-3 fatty acid deficiency. Hence, alternative sources of long-chain PUFAs for human consumption should be found. Plants produce only a handful of PUFAs, such as linoleic acid, α-linolenic acid, γ-linolenic acid, and octadecatetraenoic acid.

    Key findings and conclusions

    Thraustochytrids, non-photosynthetic marine microorganisms often mislabeled as ‘algae’, represent a promising commercial source of omega-3 fatty acids due to their high content of PUFAs. In this review, we describe lipid synthesis in thraustochytrids and distinguish it from that of other microorganisms, including proper microalgae. Furthermore, we detail the advances in omega-3 fatty acids production from thraustochytrids at laboratory and industrial scale.

  • 26.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karageorgou, Dimitra
    Laboratory of Biotechnology, Department of Biological Applications and Technologies, University of Ioannina, Ioannina 45110, Greece.
    Rova, Emma
    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.
    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.
    An Overview of Potential Oleaginous Microorganisms and Their Role in Biodiesel and Omega-3 Fatty Acid-Based Industries2020In: Microorganisms, E-ISSN 2076-2607, Vol. 8, no 3, article id 434Article, review/survey (Refereed)
    Abstract [en]

    Microorganisms are known to be natural oil producers in their cellular compartments. Microorganisms that accumulate more than 20% w/w of lipids on a cell dry weight basis are considered as oleaginous microorganisms. These are capable of synthesizing vast majority of fatty acids from short hydrocarbonated chain (C6) to long hydrocarbonated chain (C36), which may be saturated (SFA), monounsaturated (MUFA), or polyunsaturated fatty acids (PUFA), depending on the presence and number of double bonds in hydrocarbonated chains. Depending on the fatty acid profile, the oils obtained from oleaginous microorganisms are utilized as feedstock for either biodiesel production or as nutraceuticals. Mainly microalgae, bacteria, and yeasts are involved in the production of biodiesel, whereas thraustochytrids, fungi, and some of the microalgae are well known to be producers of very long-chain PUFA (omega-3 fatty acids). In this review article, the type of oleaginous microorganisms and their expertise in the field of biodiesel or omega-3 fatty acids, advances in metabolic engineering tools for enhanced lipid accumulation, upstream and downstream processing of lipids, including purification of biodiesel and concentration of omega-3 fatty acids are reviewed.

  • 27.
    Patel, Alok
    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.
    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.
    Bioprocessing of volatile fatty acids by oleaginous freshwater microalgae and their potential for biofuel and protein production2022In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 438, article id 135529Article in journal (Refereed)
    Abstract [en]

    To address the issue of high organic carbon costs in heterotrophic cultivation of microalgae, we evaluated the hypotheses by employing microalgae as a biorefinery for proteins and advanced biofuels after cultivation on volatile fatty acids (VFAs) instead of pure glucose. To prevent the inhibitory effect of VFAs on lipid synthesis, strains capable of tolerating high levels of VFAs were selected. Growth and lipid synthesis by two freshwater microalgae, Auxenochlorella protothecoides and Chlorella sorokiniana, was optimized at different VFA concentrations. Maximum biomass and lipid content in A. protothecoides (10.66 g/L, 33.93%) and C. sorokiniana (7.98 g/L, 39.80%) were obtained by replacing glucose with 30 g/L acetate at C/N 60. The generated lipids were compliant with existing standards for biodiesel. Moreover, when grown on acetate, both microalgae contained the complete range of essential and non-essential amino acids. Finally, single-source commercial VFAs were replaced with VFAs mixture after acidogenic fermentation of waste lignocellulosic biomass from brewers’ spent grain. The mixture allowed successful mixotrophic and heterotrophic cultivation of both microalgae, demonstrating feasibility of this low-cost carbon source in fuel-grade biodiesel production.

  • 28.
    Patel, Alok Kumar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sharma, Amit KumarDepartment of Chemistry, University of Petroleum & Energy Studies, Energy Acres Building, Dehradun, Uttarakhand, India.
    Sustainable Production Innovations: Bioremediation and Other Biotechnologies2023Collection (editor) (Other academic)
  • 29.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Liefeldt, Stephan
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Co-production of DHA and squalene by thraustochytrid from forest biomass2020In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, article id 1992Article in journal (Refereed)
    Abstract [en]

    Omega-3 fatty acids, and specifically docosahexaenoic acid (DHA), are important and essential nutrients for human health. Thraustochytrids are recognised as commercial strains for nutraceuticals production, they are group of marine oleaginous microorganisms capable of co-synthesis of DHA and other valuable carotenoids in their cellular compartment. The present study sought to optimize DHA and squalene production by the thraustochytrid Schizochytrium limacinum SR21. The highest biomass yield (0.46 g/gsubstrate) and lipid productivity (0.239 g/gsubstrate) were observed with 60 g/L of glucose, following cultivation in a bioreactor, with the DHA content to be 67.76% w/wtotal lipids. To reduce costs, cheaper feedstocks and simultaneous production of various value-added products for pharmaceutical or energy use should be attempted. To this end, we replaced pure glucose with organosolv-pretreated spruce hydrolysate and assessed the simultaneous production of DHA and squalene from S. limacinum SR21. After the 72 h of cultivation period in bioreactor, the maximum DHA content was observed to 66.72% w/wtotal lipids that was corresponded to 10.15 g/L of DHA concentration. While the highest DHA productivity was 3.38 ± 0.27 g/L/d and squalene reached a total of 933.72 ± 6.53 mg/L (16.34 ± 1.81 mg/gCDW). In summary, we show that the co-production of DHA and squalene makes S. limacinum SR21 appropriate strain for commercial-scale production of nutraceuticals.

  • 30.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mahboubi, Amir
    Swedish Centre for Resource Recovery, University of Borås, Borås, Sweden.
    Sárvári Horváth, Ilona
    Swedish Centre for Resource Recovery, University of Borås, Borås, Sweden.
    Taherzadeh, Mohammad J.
    Swedish Centre for Resource Recovery, University of Borås, Borås, 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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Volatile Fatty Acids (VFAs) Generated by Anaerobic Digestion Serve as Feedstock for Freshwater and Marine Oleaginous Microorganisms to Produce Biodiesel and Added-Value Compounds2021In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 12, article id 614612Article in journal (Refereed)
    Abstract [en]

    Given an increasing focus on environmental sustainability, microbial oils have been suggested as an alternative to petroleum-based products. However, microbial oil production relies on the use of costly sugar-based feedstocks. Substrate limitation, elevated costs, and risk of contamination have sparked the search for alternatives to sugar-based platforms. Volatile fatty acids are generated during anaerobic digestion of organic waste and are considered a promising substrate for microbial oil production. In the present study, two freshwater and one marine microalga along with two thraustochytrids were evaluated for their potential to produce lipids when cultivated on volatile fatty acids generated from food waste via anaerobic digestion using a membrane bioreactor. Freshwater microalgae Auxenochlorella protothecoides and Chlorella sorokiniana synthesized lipids rich in palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), and linoleic acid (C18:2). This composition corresponds to that of soybean and jatropha oils, which are used as biodiesel feedstock. Production of added-value polyunsaturated fatty acids (PUFA) mainly omega-3 fatty acids was examined in three different marine strains: Aurantiochytrium sp. T66, Schizochytrium limacinum SR21, and Crypthecodinium cohnii. Only Aurantiochytrium sp. T66 seemed promising, generating 43.19% docosahexaenoic acid (DHA) and 13.56% docosapentaenoic acid (DPA) in total lipids. In summary, we show that A. protothecoides, C. sorokiniana, and Aurantiochytrium sp. T66 can be used for microbial oil production from food waste material.

  • 31.
    Patel, Alok
    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.
    A comparative study on de novo and ex novo lipid fermentation by oleaginous yeast using glucose and sonicated waste cooking oil2019In: Ultrasonics sonochemistry, ISSN 1350-4177, E-ISSN 1873-2828, Vol. 52, p. 364-374Article in journal (Refereed)
    Abstract [en]

    There are only a few reports available about the assimilation of hydrophobic substrates by microorganisms, however, it is well known that oleaginous microorganisms are capable of utilizing both hydrophilic and hydrophobic substrates and accumulate lipids via two different pathways namely de novo and ex novo lipid synthesis, respectively. In the present study, an oleaginous yeast, Cryptococcus curvatus, was investigated for its potentials to utilize a waste substrate of hydrophobic nature (waste cooking oil – WCO) and compared with its ability to utilize a hydrophilic carbon source (glucose). To facilitate the utilization of WCO by C. curvatus, the broth was sonicated to form a stable oil-in-water emulsion without adding any emulsifier, which was then compared with WCO samples without any ultrasound treatment (unsonicated) for the yeast cultivation. Ultrasonication reduces the size of hydrophobic substrates and improves their miscibility in an aqueous broth making them easily assimilated by oleaginous yeast. Under de novo lipid fermentation, the yeast synthesized 9.93 ± 0.84 g/L of cell dry weight and 5.23 ± 0.49 g/L lipids (lipid content of 52.66 ± 0.93% w/w) when cultivated on 40 g/L of glucose (C/N ratio of 40). The amount of cell dry weight, lipid concentration, and lipid content were considerably higher during the ex novo lipid synthesis. More specifically, the highest lipid content achieved was 70.13 ± 1.65% w/w with a corresponding dry cell weight and lipid concentration of 18.62 ± 0.76 g/L and 13.06 ± 0.92 g/L respectively, when grown on 20 g/L sonicated WCO. The highest lipid concentration, however, was observed when the yeast was cultivated on 40 g/L sonicated WCO. Under these conditions, 20.34 g/L lipids were produced with a lipid content of 57.05% w/w. On the other hand, lipid production with unsonicated WCO was significant lower, reaching 11.16 ± 1.02 g/L (69.14 ± 1.34% w/w of lipid content) and 12.21 ± 1.34 g/L (47.39 ± 1.67% w/w of lipid content) for 20 g/L and 40 g/L of WCO, respectively. This underpins the significance of the sonication treatment, especially at elevated WCO concentrations, to improve the accessibility of the yeast to the WCO. Sonication treatment that was used in this study assisted the utilization of WCO without the need to add emulsifiers, thus reducing the need for chemicals and in turn has a positive impact on the production costs. The microbial lipids produced presented a different fatty acid composition compared to the WCO, making them more suitable for biodiesel production as suggested by the theoretical estimation of the biodiesel properties.

  • 32.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, LeonidasLuleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nutraceutical Fatty Acids from Oleaginous Microalgae: A Human Health Perspective2020Collection (editor) (Other academic)
    Abstract [en]

    Over the past several years, extensive research has been done on the microbial production of polyunsaturated fatty acids (PUFA).  Regardless, research on the oleaginous microalgae used as feedstock for biofuels production and the overall story about the production of nutraceutical fatty acids from oleaginous microalgae has been very limited. This volume provides an exclusive insight on the production of nutraceutical fatty acids from oleaginous microalgae and their role on human health.

    Some saturated and monounsaturated fatty acids can be synthesized by humans, whereas long-chain polyunsaturated fatty acids (PUFAs) such as α-linolenic acid and linoleic acid cannot and are deemed essential. The products of these acids, such as DHA, which is important for early visual and neurological development, are extremely important to human health. Replacing SFAs with omega-3 and omega-6 fatty acids in the diet reduce the risk of cardiovascular diseases and prevent Alzheimer's, bipolar disorder, and schizophrenia, among other benefits.

    The ever-rising global demand for omega-3 & 6 PUFAs, however, cannot be met solely by fish oil, due to diminishing fish stocks and pollution of marine ecosystems, which has led to increased interest in alternative sustainable sources. Vegetable oils from genetically engineered plant oilseeds and microorganisms are two potential alternatives to fish oil, even though omega-3 PUFAs are highest in the latter.  Although transgenic plants present numerous advantages, their production is dependent on seasonal and climatic conditions and the availability of arable land. Moreover, there are public concerns regarding the cultivation of transgenic crops in open ecosystems. These, together with regulatory issues restrict the large-scale production of genetically modified crops. Microorganisms, however, are known natural producers of microbial oils similar to those obtained from plants and animals and a possible source of nutritionally important omega-3 & 6 PUFAs.

    This groundbreaking volume presents invaluable new research on essential fatty acids, their production from various oleaginous microorganisms, biochemical and metabolic engineering to improve PUFAs content in oil, extraction and purification of omega 3 fatty acids, and the current market scenario. Whether a veteran engineer or scientist using it as a reference or a professor using it as a textbook, this outstanding new volume is a must-have for any engineer or scientist working in food science.

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  • 33.
    Patel, Alok
    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.
    Hruzova, Katerina
    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.
    Biosynthesis of Nutraceutical Fatty Acids by the Oleaginous Marine Microalgae Phaeodactylum tricornutum Utilizing Hydrolysates from Organosolv-Pretreated Birch and Spruce Biomass2019In: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 17, no 12, article id 119Article in journal (Refereed)
    Abstract [en]

    Polyunsaturated fatty acids (PUFAs) are essential for human function, however they have to be provided through the diet. As their production from fish oil is environmentally unsustainable, there is demand for new sources of PUFAs. The aim of the present work was to establish the microalgal platform to produce nutraceutical-value PUFAs from forest biomass. To this end, the growth of Phaeodactylum tricornutum on birch and spruce hydrolysates was compared to autotrophic cultivation and glucose synthetic media. Total lipid generated by P. tricornutum grown mixotrophically on glucose, birch, and spruce hydrolysates was 1.21, 1.26, and 1.29 g/L, respectively. The highest eicosapentaenoic acid (EPA) production (256 mg/L) and productivity (19.69 mg/L/d) were observed on spruce hydrolysates. These values were considerably higher than those obtained from the cultivation without glucose (79.80 mg/L and 6.14 mg/L/d, respectively) and also from the photoautotrophic cultivation (26.86 mg/L and 2.44 mg/L/d, respectively). To the best of our knowledge, this is the first report describing the use of forest biomass as raw material for EPA and docosapentaenoic acid (DHA) production.

  • 34.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India .
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Pruthi, Parul A
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India .
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India .
    Potential of aquatic oomycete as a novel feedstock for microbial oil grown on waste sugarcane bagasse2018In: Environmental Science and Pollution Research, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 25, no 33, p. 33443-33454Article in journal (Refereed)
    Abstract [en]

    Biodiesel production from vegetable oils is not sustainable and economical due to the food crisis worldwide. The development of a cost-effective non-edible feedstock is essential. In this study, we proposed to use aquatic oomycetes for microbial oils, which are cellulolytic fungus-like filamentous eukaryotic microorganisms, commonly known as water molds. They differ from true fungi as cellulose is present in their cell wall and chitin is absent. They show parasitic as well as saprophytic nature and have great potential to utilize decaying animal and plant debris in freshwater habitats. To study the triacylglycerol (TAG) accumulation in the aquatic oomycetes, the isolated water mold Achlya diffusa was cultivated under semi-solid-state conditions on waste sugarcane bagasse, which was compared with the cultivation in Czapek (DOX) medium. A. diffusa grown on waste sugarcane bagasse showed large lipid droplets in its cellular compartment and synthesized 124.03 ± 1.93 mg/gds cell dry weight with 50.26 ± 1.76% w/w lipid content. The cell dry weight and lipid content of this water mold decreased to 89.54 ± 1.21 mg/gds and 38.82% w/w, respectively, when cultivated on standard medium Czapek-Dox agar (CDA). For the fatty acid profile of A. diffusa grown in sugarcane bagasse and CDA, in situ transesterification (IST) and indirect transesterification (IDT) approaches were evaluated. The lipid profile of this mold revealed the presence of C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, C20:0, and C21:0 fatty acids, which is similar to vegetable oils. The biodiesel properties of the lipids obtained from A. diffusa satisfied the limits as determined by international standards ASTM-D6751 and EN-14214 demonstrating its suitability as a fuel for diesel engines.

  • 35.
    Patel, Alok
    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.
    A perspective on biotechnological applications of thermophilic microalgae and cyanobacteria2019In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 278, p. 424-434Article in journal (Refereed)
    Abstract [en]

    The importance of expanding our knowledge on microorganisms derived from extreme environments stems from the development of novel and sustainable technologies for our health, food, and environment. Microalgae and cyanobacteria represent a group of diverse microorganisms that inhabit a wide range of environments, are capable of oxygenic photosynthesis, and form a thick microbial mat even at extreme environments. Studies of thermophilic microorganisms have shown a considerable biotechnological potential due to their optimum growth and metabolisms at high temperatures (≥50 °C), which is supported by their thermostable enzymes. Microalgal and cyanobacterial communities present in high-temperature ecosystems account for a large part of the total ecosystem biomass and productivity, and can be exploited to generate several value-added products of agricultural, pharmaceutical, nutraceutical, and industrial relevance. This review provides an overview on the current status of biotechnological applications of thermophilic microalgae and cyanobacteria, with an outlook on the challenges and future prospects.

  • 36.
    Patel, Alok
    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.
    Heterotrophic cultivation of Auxenochlorella protothecoides using forest biomass as a feedstock for sustainable biodiesel production2018In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, no 1, article id 169Article in journal (Refereed)
    Abstract [en]

    Background

    The aim of this work was to establish a process for the heterotrophic growth of green microalgae using forest biomass hydrolysates. To provide a carbon source for the growth of the green microalgae, two forest biomasses (Norway spruce and silver birch) were pretreated with a hybrid organosolv-steam explosion method, resulting in inhibitor-free pretreated solids with a high cellulose content of 77.9% w/w (birch) and 72% w/w (spruce). Pretreated solids were hydrolyzed using commercial cellulolytic enzymes to produce hydrolysate for the culture of algae.

    Results

    The heterotrophic growth of A. protothecoides was assessed using synthetic medium with glucose as carbon source, where the effect of sugar concentration and the carbon-to-nitrogen ratio were optimized, resulting in accumulation of lipids at 5.42 ± 0.32 g/L (64.52 ± 0.53% lipid content) after 5 days of culture on glucose at 20 g/L. The use of birch and spruce hydrolysates was favorable for the growth and lipid accumulation of the algae, resulting in lipid production of 5.65 ± 0.21 g/L (66 ± 0.33% lipid content) and 5.28 ± 0.17 g/L (63.08 ± 0.71% lipid content) when grown on birch and spruce, respectively, after only 120 h of cultivation.

    Conclusions

    To the best of our knowledge, this is the first report of using organosolv pretreated wood biomass hydrolysates for the growth and lipid production of microalgae in the literature. The pretreatment process used in this study provided high saccharification of biomass without the presence of inhibitors. Moreover, the lipid profile of this microalga showed similar contents to vegetable oils which improve the biodiesel properties.

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  • 37.
    Patel, Alok
    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.
    Sartaj, Km
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology (IIT-R), Roorkee, India.
    Chandra, Rajesh
    Bioenergy Research Laboratory, Department of Polymer & Process Engineering, Indian Institute of Technology Roorkee (Saharanpur Campus), Saharanpur, India.
    Extraction of lipids from algae using supercritical carbon dioxide2020In: Green Sustainable Process for Chemical and Environmental Engineering and Science: Supercritical Carbon Dioxide as Green Solvent / [ed] Inamuddin, Abdullah M. Asiri, and Arun M. Isloor, Elsevier, 2020, p. 17-39Chapter in book (Other academic)
    Abstract [en]

    Microalgal oils are considered an important source of industrially valuable oleochemicals with significant applications ranging from the energy to pharmaceutical sectors. Industrial production of microalgal oil is emerging rapidly; however, the high cost associated with downstream processes may constrain this process. Oils are accumulated intracellularly in oleaginous microalgae in the form of lipid droplets, which in turn require cell wall disruption followed by extraction in order to recover them. Disruption of the microalgal cell is very challenging owing to its distinctive features like high water content, hard cell wall, presence of algaenan, and sporopollenin like biopolymers that in turn create hurdles in efficient extraction of lipids. Various conventional pretreatment methods have been explored to rupture the cellular integrity of microalgal cells to enhance lipid extraction, and each method has certain advantages and disadvantages. Supercritical fluid extraction is the oldest technique for the extraction of valuable compounds from microalgae and is considered an alternative to conventional solvent extraction methods. It has several advantageous features such as being free from organic solvents (and their disposal), environment-friendly, and operating at a mild range of temperature (40–80°C). CO2 is considered to be an ideal supercritical fluid due to its non-toxic, non-flammable, and lipophilic nature. In this chapter, use of supercritical carbon dioxide extraction of lipids from microalgae is discussed and compared with other available lipid extraction methods.

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  • 38.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mikes, Fabio
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Valorization of Brewers’ Spent Grain for the Production of Lipids by Oleaginous Yeast2018In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 23, no 12, article id 3052Article in journal (Refereed)
    Abstract [en]

    Brewers’ spent grain (BSG) accounts for 85% of the total amount of by-products generated by the brewing industries. BSG is a lignocellulosic biomass that is rich in proteins, lipids, minerals, and vitamins. In the present study, BSG was subjected to pretreatment by two different methods (microwave assisted alkaline pretreatment and organosolv) and was evaluated for the liberation of glucose and xylose during enzymatic saccharification trials. The highest amount of glucose (46.45 ± 1.43 g/L) and xylose (25.15 ± 1.36 g/L) were observed after enzymatic saccharification of the organosolv pretreated BSG. The glucose and xylose yield for the microwave assisted alkaline pretreated BSG were 34.86 ± 1.27 g/L and 16.54 ± 2.1 g/L, respectively. The hydrolysates from the organosolv pretreated BSG were used as substrate for the cultivation of the oleaginous yeast Rhodosporidium toruloides, aiming to produce microbial lipids. The yeast synthesized as high as 18.44 ± 0.96 g/L of cell dry weight and 10.41 ± 0.34 g/L lipids (lipid content of 56.45 ± 0.76%) when cultivated on BSG hydrolysate with a C/N ratio of 500. The cell dry weight, total lipid concentration and lipid content were higher compared to the results obtained when grown on synthetic media containing glucose, xylose or mixture of glucose and xylose. To the best of our knowledge, this is the first report using hydrolysates of organosolv pretreated BSG for the growth and lipid production of oleaginous yeast in literature. The lipid profile of this oleaginous yeast showed similar fatty acid contents to vegetable oils, which can result in good biodiesel properties of the produced biodiesel

  • 39.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mikes, Fabio
    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.
    An Overview of Current Pretreatment Methods Used to Improve Lipid Extraction from Oleaginous Microorganisms2018In: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 23, no 7, article id 1562Article in journal (Refereed)
    Abstract [en]

    Microbial oils, obtained from oleaginous microorganisms are an emerging source of commercially valuable chemicals ranging from pharmaceuticals to the petroleum industry. In petroleum biorefineries, the microbial biomass has become a sustainable source of renewable biofuels. Biodiesel is mainly produced from oils obtained from oleaginous microorganisms involving various upstream and downstream processes, such as cultivation, harvesting, lipid extraction, and transesterification. Among them, lipid extraction is a crucial step for the process and it represents an important bottleneck for the commercial scale production of biodiesel. Lipids are synthesized in the cellular compartment of oleaginous microorganisms in the form of lipid droplets, so it is necessary to disrupt the cells prior to lipid extraction in order to improve the extraction yields. Various mechanical, chemical and physicochemical pretreatment methods are employed to disintegrate the cellular membrane of oleaginous microorganisms. The objective of the present review article is to evaluate the various pretreatment methods for efficient lipid extraction from the oleaginous cellular biomass available to date, as well as to discuss their advantages and disadvantages, including their effect on the lipid yield. The discussed mechanical pretreatment methods are oil expeller, bead milling, ultrasonication, microwave, high-speed and high-pressure homogenizer, laser, autoclaving, pulsed electric field, and non-mechanical methods, such as enzymatic treatment, including various emerging cell disruption techniques.

  • 40.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mu, Liwen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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.
    Novel Biorefinery Approach Aimed at Vegetarians Reduces the Dependency on Marine Fish Stocks for Obtaining Squalene and Docosahexaenoic Acid2020In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, no 23, p. 8803-8813Article in journal (Refereed)
    Abstract [en]

    Squalene and docosahexaenoic acid (DHA) have gained substantial market share as dietary supplements and vital nutraceuticals due to their beneficial effects on human health. Marine fish are the main commercial source of these nutraceuticals, but a growing global demand, issues of sustainability, and an expanding vegan and vegetarian population has prompted the search for alternatives. Oils obtained from oleaginous microorganisms such as microalgae, diatoms, certain fungi, and thraustochytrids are alternatives to fish oils for omega-3 fatty acids. Among these, DHA is now being mined from thraustochytrids due to its highest proportion in their lipids, however, this strategy is not cost-effective. One way to offset such elevated production costs is to simultaneously extract other high value-added biological products from these oleaginous microorganisms. Here, we propose a novel biorefinery process based on single-step purification of squalene from total lipids extracted from an oleaginous thraustochytrid cultivated on non-edible forest biomass. To render the process economically feasible and sustainable, additional squalene-free lipids were exploited for enrichment of DHA; whereas leftover lipids generated as by-product during the process were tested as a novel biolubricant.

  • 41.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mu, Liwen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    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.
    Single-Cell Oils from Oleaginous Microorganisms as Green Bio-Lubricants: Studies on Their Tribological Performance2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 20, article id 6685Article in journal (Refereed)
    Abstract [en]

    Biolubricants refer to eco-friendly, biodegradable, and non-toxic lubricants. Their applications are still limited compared to mineral oils; however, their sustainable credentials are making them increasingly attractive. Vegetable oils are frequently used for this purpose. However, vegetable oils have issues of low lipid productivity, dependence on climatic conditions, and need for agricultural land. Microbial oils represent a more sustainable alternative. To ensure their widespread applicability, the suitability of microbial oils from a physicochemical point of view needs to be de-termined first. In this study, oils obtained from various oleagenic microbes—such as microalgae, thraustochytrids, and yeasts—were characterized in terms of their fatty acid profile, viscosity, friction coefficient, wear, and thermal stability. Oleaginous microalgal strains (Auxenochlorella protothe-coides and Chlorella sorokiniana), thraustochytrids strains (Aurantiochytrium limacinum SR21 and Au-rantiochytrium sp. T66), and yeast strains (Rhodosporidium toruloides and Cryptococcus curvatus) synthesized 64.5%, 35.15%, 47.89%, 47.93%, 56.42%, and 52.66% of lipid content, respectively. Oils from oleaginous microalgae (A. protothecoides and C. sorokiniana) and yeasts (R. toruloides and C. curvatus) possess excellent physicochemical and tribological qualities due to high amount of monounsatu-rated fatty acids (oleic acid C18:1 content, 56.38%, 58.82%, 46.67%, 38.81%) than those from oleaginous thraustochytrids (A. limacinum SR21 and Aurantiochytrium sp. T66; 0.96%, 0.08%, respectively) supporting their use as renewable and biodegradable alternatives to traditional mineral oil-based lubricants. Oil obtained from microalgae showed a lower friction coefficient than oils obtained from yeasts and thraustochytrids.

  • 42.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India;iofuel Laboratory, Centre for Transportation Systems, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Biotechnology Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, Uttarakhand, India.
    Innovative screening approach for the identification of triacylglycerol accumulating oleaginous strains2019In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 135, p. 936-944Article in journal (Refereed)
    Abstract [en]

    Currently, triacylglycerides (TAG) accumulation in the form of lipid droplets (LDs) in oleaginous microorganisms is of immense importance due to their ability to get transesterified into value-added products in the form of biodiesel. Hence, in order to search for oleaginous microorganisms having high lipid content among a wide range of samples from different niches, there is a compulsive need to develop simple, reliable and rapid methods for screening of TAG accumulating strains. Conventional methods require multistep processes for the isolation, cultivation, extraction and estimation of lipids to identify oleagenic strains. To overcome these challenges, we are proposing an easy, live cellimaging technique for the estimation of lipids via visualization of TAG accumulation in probable strains at the single cell level that gives real-time monitoring of intracellular lipid accumulation in yeasts. In this screening technique, only 100 μl of specific neutral lipid accumulating medium was used to grow the isolated culture in the microtiter plate. The harvested cells were stained with LipidTOX™ Green and visualized by a LED based digital inverted fluorescence microscope. Among 446 yeast colonies screened, maximum lipid producing yeast strains Rhodosporidium kratochvilovae HIMPA1 and Rhodotorula minuta,having supersized lipid body of 5.05 ± 0.87 μm and 4.46 ± 0.61 μm, respectively, were identified as potential candidates for biodiesel production. To the best of our knowledge, this is the first report of using LipidTOX™ Green for the staining of lipid droplets present in yeast cells as per the literature.

  • 43.
    Patel, Alok
    et al.
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Vikas
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Pruthi, Parul A.
    Molecular Microbiology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee (IIT-R), India.
    Synchronized nutrient stress conditions trigger the diversion of CDP-DG pathway of phospholipids synthesis towards de novo TAG synthesis in oleaginous yeast escalating biodiesel production2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 139, p. 962-974Article in journal (Refereed)
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    Energy
  • 44.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Assessment of Fatty Acids Profile and Omega-3 Polyunsaturated Fatty Acid Production by the Oleaginous Marine Thraustochytrid Aurantiochytrium sp. T66 Cultivated on Volatile Fatty Acids2020In: Biomolecules, E-ISSN 2218-273X, Vol. 10, no 5, article id 694Article in journal (Refereed)
    Abstract [en]

    Thraustochytrids are considered natural producers of omega-3 fatty acids as they can synthesize up to 70% docosahexaenoic acids (DHA) of total lipids. However, commercial and sustainable production of microbial DHA is limited by elevated cost of carbon substrates for thraustochytrids cultivation. This problem can be addressed by utilizing low-cost renewable substrates. In the present study, growth, lipid accumulation and fatty acid profiles of the marine thraustochytrid Aurantiochytrium sp. T66 (ATCC-PRA-276) cultivated on volatile fatty acids (C1, formic acid; C2, acetic acid; C3, propionic acid; C4, butyric acid; C5, valeric acid and C6, caproic acid) and glucose as control were evaluated for the first time. This strain showed an inability to utilize C3, C5 and C6 as a substrate when provided at >2 g/L, while efficiently utilizing C2 and C4 up to 40 g/L. The highest cell dry weight (12.35 g/L) and total lipid concentration (6.59 g/L) were attained when this strain was cultivated on 40 g/L of butyric acid, followed by cultivation on glucose (11.87 g/L and 5.34 g/L, respectively) and acetic acid (8.70 g/L and 3.43 g/L, respectively). With 40 g/L butyric acid, the maximum docosahexaenoic acid content was 2.81 g/L, corresponding to 42.63% w/w of total lipids and a yield of 0.23 g/gcell dry weight (CDW). This marine oleaginous microorganism showed an elevated potential for polyunsaturated fatty acids production at higher acetic and butyric acid concentrations than previously reported. Moreover, fluorescence microscopy revealed that growth on butyric acid caused cell size to increase to 45 µm, one of the largest values reported for oleaginous microorganisms, as well as the presence of numerous tiny lipid droplets.

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    fulltext
  • 45.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    From Yeast to Biotechnology2022In: Bioengineering, E-ISSN 2306-5354, Vol. 9, no 12, article id 751Article in journal (Other academic)
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    fulltext
  • 46.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Introduction to Essential Fatty Acids2020In: Nutraceutical Fatty Acids from Oleaginous Microalgae: A Human Health Perspective / [ed] Alok Kumar Patel, Leonidas Matsakas, John Wiley & Sons, 2020, p. 1-22Chapter in book (Refereed)
    Abstract [en]

    Certain omega‐3 fatty acids, such as α‐linolenic acid (ALA), and omega‐6 fatty acids, such as linoleic acid (LA), cannot be synthesized in the human body and are recognized as essential fatty acids. While some long‐chain polyunsaturated fatty acids (LC‐PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can be synthesized from the parent omega‐3 fatty acids (ALA), this is done at a very low conversion rate, hence it must be taken through diet to fulfill the daily intake requirement. Both EPA and DHA have several vital activities in the human body, such as anti‐inflammatory effects and being the structural component of the cell membrane. The fatty acids DHA, arachidonic acid (AA), and LA accumulate most usually in tissues, whereas DHA mostly accumulates in retina and brain gray matters and it is important for proper visual and neurological development during gestation period and postnatal period. Replacement of saturated fatty acids with omega‐3 and omega‐6 fatty acids in daily diet reduces the risk of cardiovascular disease and prevents diseases such as Alzheimer's, bipolar disorder, and schizophrenia. Proper EPA and DHA content also help individuals with type 2 diabetes to reduce the elevated serum triacylglycerides. It also facilitates infants to reduce the risks of fatal myocardial infarction and other cardiovascular diseases. Hence, as recommended by the American Heart Association, it is necessary to consume fish, and especially oily fish at least twice per week as it is an excellent source of these fatty acids. Marine fishes of Salmonidae, Scombridae, and Clupeidae families are important sources of omega‐3 fatty acids but due to the increasing demand of PUFA and diminishing aquatic ecosystem, fishes are not a sustainable source to serve as a long‐term feed‐stock for omega‐3. Plants can synthesize some of PUFA such as oleic acid, LA, GLA (γ‐linolenic acid), ALA, and octadecatetraenoic acid but due to lacking some essential enzymes for PUFA synthesis such as desaturase and elongases, they are incapable of synthesizing EPA and DHA. Oleaginous microalgae and thraustochytrids could be a sustainable option to produce microbial EPA and DHA.

  • 47.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Microalgal lutein biosynthesis: Recent trends and challenges to enhance the lutein content in microalgal cell factories2022In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 9, article id 1015419Article, review/survey (Refereed)
    Abstract [en]

    Photosynthetic organisms such as eukaryotic microalgae and prokaryotic cyanobacteria synthesize a wide range of valuable chemicals. They are predicted to become efficient and renewable sources for valuable products in the future due to their high biomass synthesis using CO2 and solar energy. Microalgae are producers of several carotenoids including lutein, which is a xanthophyll carotenoid with several health advantages, including the prevention of age-related macular degeneration. Currently, it is extracted on commercial scale from marigold flower petals, however, production from plant sources is highly affected by seasonal variations, requires arable land, and has high production cost. Microalgae, on the other hand, are an ideal alternative for lutein synthesis due to their rapid growth and high biomass and lutein yield. It is, however, necessary to further improve lutein productivity, for a successful transition to commercial production. This article describes lutein biosynthesis in microalgae by using their native biochemical pathways, as well as possible target genes for genetic engineering to enhance lutein production. Understanding the processes behind lipid droplet synthesis in chloroplasts, as well as carotenoid transport across chloroplast membranes and carotenoid esterification, might lead to novel ways to boost lutein levels in microalgae.

  • 48.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mining of squalene as a value-added byproduct from DHA producing marine thraustochytrid cultivated on food waste hydrolysate2020In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 736, article id 139691Article in journal (Refereed)
    Abstract [en]

    The commercial production of docosahexaenoic acid (DHA) from oleaginous microorganisms is getting more attention due to several advantages over fish oils. The processing cost became a major bottleneck for commercialization of DHA from microorganisms. The most of cost shares in the feedstock to cultivate the microorganisms and downstream processing. The cost of feedstock can be compensated with the utilization of substrate from waste stream whereas production of value-added chemicals boosts the economic viability of nutraceutical production. In the present study, the docosahexaenoic acid (DHA)-producing marine protist Aurantiochytrium sp. T66 was cultivated on post-consumption food waste hydrolysate for the mining of squalene. After 120 h of cultivation, cell dry weight was 14.7 g/L, of which 6.34 g/L (43.13%; w/w) were lipids. DHA accounted for 2.15 g/L (34.05%) of total extracted lipids or 0.15 g/gCDW. Maximum squalene concentration and yield were 1.05 g/L and 69.31 mg/gCDW, respectively. Hence, utilization of food waste represents an excellent low-cost strategy for cultivating marine oleaginous thraustochytrids and produce squalene as a byproduct of DHA.

  • 49.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Role of Oleaginous Microorganisms in the Field of Renewable Energy2022In: Energies, E-ISSN 1996-1073, Vol. 15, no 16, article id 5984Article in journal (Other academic)
  • 50.
    Patel, Alok
    et al.
    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.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Simultaneous production of DHA and squalene from Aurantiochytrium sp. grown on forest biomass hydrolysates2019In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 12, no 1, article id 255Article in journal (Refereed)
    Abstract [en]

    Background

    Recent evidence points to the nutritional importance of docosahexaenoic acid (DHA) in the human diet. Thraustochytrids are heterotrophic marine oleaginous microorganisms capable of synthesizing high amounts of DHA, as well as other nutraceutical compounds such as squalene, in their cellular compartment. Squalene is a natural triterpene and an important biosynthetic precursor to all human steroids. It has a wide range of applications in the cosmetic and pharmaceutical industries, with benefits that include boosting immunity and antioxidant activity. Apart from its nutritional quality, it can also be utilized for high-grade bio-jet fuel by catalytic conversion.

    Results

    In the present study, the potential of thraustochytrid strain Aurantiochytrium sp. T66 to produce DHA and squalene was evaluated. When the strain was cultivated on organosolv-pretreated birch hydrolysate (30 g/L glucose) in flask, it resulted in 10.39 g/L of cell dry weight and 4.98 g/L of total lipids, of which 25.98% was DHA. In contrast, when the strain was grown in a bioreactor, cell dry weight, total lipid, and DHA increased to 11.24 g/L, 5.90 g/L, and 35.76%, respectively. The maximum squalene yield was 69.31 mg/gCDW (0.72 g/L) when the strain was cultivated in flask, but it increased to 88.47 mg/gCDW (1.0 g/L), when cultivation shifted to a bioreactor.

    Conclusions

    This is the first report demonstrating the utilization of low cost non-edible lignocellulosic feedstock to cultivate the marine oleaginous microorganism Aurantiochytrium sp. for the production of nutraceutical vital compounds. Owing to the simultaneous generation of DHA and squalene, the strain is suitable for industrial-scale production of nutraceuticals.

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