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Christakopoulos, PaulORCID iD iconorcid.org/0000-0003-0079-5950
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Publications (10 of 246) Show all publications
Raghavendran, V., Nitsos, C., Matsakas, L., Rova, U., Christakopoulos, P. & Olsson, L. (2018). A comparative study of the enzymatic hydrolysis of batch organosolv-pretreated birch and spruce biomass. AMB Express, 8(1), Article ID 114.
Open this publication in new window or tab >>A comparative study of the enzymatic hydrolysis of batch organosolv-pretreated birch and spruce biomass
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2018 (English)In: AMB Express, ISSN 2191-0855, E-ISSN 2191-0855, Vol. 8, no 1, article id 114Article in journal (Refereed) Published
Abstract [en]

A shift towards a sustainable and green society is vital to reduce the negative effects of climate change associated with increased CO2 emissions. Lignocellulosic biomass is both renewable and abundant, but is recalcitrant to deconstruction. Among the methods of pretreatment available, organosolv (OS) delignifies cellulose efficiently, significantly improving its digestibility by enzymes. We have assessed the hydrolysability of the cellulose-rich solid fractions from OS-pretreated spruce and birch at 2% w/v loading (dry matter). Almost complete saccharification of birch was possible with 80 mg enzyme preparation/gsolids (12 FPU/gsolids), while the saccharification yield for spruce was only 70%, even when applying 60 FPU/gsolids. As the cellulose content is enriched by OS, the yield of glucose was higher than in their steam-exploded counterparts. The hydrolysate was a transparent liquid due to the absence of phenolics and was also free from inhibitors. OS pretreatment holds potential for use in a large-scale, closed-loop biorefinery producing fuels from the cellulose fraction and platform chemicals from the hemicellulose and lignin fractions respectively.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-70136 (URN)10.1186/s13568-018-0643-y (DOI)000438255300003 ()29992363 (PubMedID)2-s2.0-85049690419 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-07-19 (inah)

Available from: 2018-07-19 Created: 2018-07-19 Last updated: 2018-09-14Bibliographically approved
Matsakas, L., Nitsos, C., Raghavendran, V., Yakimenko, O., Persson, G., Olsson, E., . . . Christakopoulos, P. (2018). A novel hybrid organosolv: steam explosion method for the efficient fractionation and pretreatment of birch biomass. Biotechnology for Biofuels, 11(1), Article ID 160.
Open this publication in new window or tab >>A novel hybrid organosolv: steam explosion method for the efficient fractionation and pretreatment of birch biomass
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2018 (English)In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, no 1, article id 160Article in journal (Refereed) Published
Abstract [en]

The main role of pretreatment is to reduce the natural biomass recalcitrance and thus enhance saccharification yield. A further prerequisite for efficient utilization of all biomass components is their efficient fractionation into well-defined process streams. Currently available pretreatment methods only partially fulfill these criteria. Steam explosion, for example, excels as a pretreatment method but has limited potential for fractionation, whereas organosolv is excellent for delignification but offers poor biomass deconstruction.

Results

In this article, a hybrid method combining the cooking and fractionation of conventional organosolv pretreatment with the implementation of an explosive discharge of the cooking mixture at the end of pretreatment was developed. The effects of various pretreatment parameters (ethanol content, duration, and addition of sulfuric acid) were evaluated. Pretreatment of birch at 200 °C with 60% v/v ethanol and 1% w/wbiomass H2SO4 was proven to be the most efficient pretreatment condition yielding pretreated solids with 77.9% w/w cellulose, 8.9% w/w hemicellulose, and 7.0 w/w lignin content. Under these conditions, high delignification of 86.2% was demonstrated. The recovered lignin was of high purity, with cellulose and hemicellulose contents not exceeding 0.31 and 3.25% w/w, respectively, and ash to be < 0.17% w/w in all cases, making it suitable for various applications. The pretreated solids presented high saccharification yields, reaching 68% at low enzyme load (6 FPU/g) and complete saccharification at high enzyme load (22.5 FPU/g). Finally, simultaneous saccharification and fermentation (SSF) at 20% w/w solids yielded an ethanol titer of 80 g/L after 192 h, corresponding to 90% of the theoretical maximum.

Conclusions

The novel hybrid method developed in this study allowed for the efficient fractionation of birch biomass and production of pretreated solids with high cellulose and low lignin contents. Moreover, the explosive discharge at the end of pretreatment had a positive effect on enzymatic saccharification, resulting in high hydrolyzability of the pretreated solids and elevated ethanol titers in the following high-gravity SSF. To the best of our knowledge, the ethanol concentration obtained with this method is the highest so far for birch biomass.

Place, publisher, year, edition, pages
BioMed Central, 2018
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-69455 (URN)10.1186/s13068-018-1163-3 (DOI)000434952000002 ()29930706 (PubMedID)2-s2.0-85048400180 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-13 (andbra)

Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-08-08Bibliographically approved
Matsakas, L., Hruzova, K., Rova, U. & Christakopoulos, P. (2018). Biological Production of 3-Hydroxypropionic Acid: An Update on the Current Status. Fermentation, 4(1), Article ID 13.
Open this publication in new window or tab >>Biological Production of 3-Hydroxypropionic Acid: An Update on the Current Status
2018 (English)In: Fermentation, ISSN 2311-5637, Vol. 4, no 1, article id 13Article in journal (Refereed) Published
Abstract [en]

The production of high added-value chemicals from renewable resources is a necessity inour attempts to switch to a more sustainable society. 3-Hydroxypropionic acid (3HP) is a promisingmolecule that can be used for the production of an important array of high added-value chemicals,such as 1,3-propanediol, acrylic acid, acrylamide, and bioplastics. Biological production of 3HP hasbeen studied extensively, mainly from glycerol and glucose, which are both renewable resources.To enable conversion of these carbon sources to 3HP, extensive work has been performed to identifyappropriate biochemical pathways and the enzymes that are involved in them. Novel enzymeshave also been identified and expressed in host microorganisms to improve the production yieldsof 3HP. Various process configurations have also been proposed, resulting in improved conversionyields. The intense research efforts have resulted in the production of as much as 83.8 g/L 3HP fromrenewable carbon resources, and a system whereby 3-hydroxypropionitrile was converted to 3HPthrough whole-cell catalysis which resulted in 184.7 g/L 3HP. Although there are still challengesand difficulties that need to be addressed, the research results from the past four years have been animportant step towards biological production of 3HP at the industrial level.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
3-hydroxypropionic acid; metabolic engineering; building-block chemicals; glycerol; platform chemicals; Klebsiella pneumoniae; Escherichia coli; Saccharomyces cerevisiae
National Category
Industrial Biotechnology Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-67793 (URN)10.3390/fermentation4010013 (DOI)
Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-08-29Bibliographically approved
Antonopoulou, I., Leonov, L., Jûtten, P., Cerullo, G., Faraco, V., Papadopoulou, A., . . . Christakopoulos, P. (2018). Correction to: Optimized synthesis of novel prenyl ferulate performed by feruloyl esterases from Myceliophthora thermophila in microemulsions [Letter to the editor]. Applied Microbiology and Biotechnology, 102(1), 511-511
Open this publication in new window or tab >>Correction to: Optimized synthesis of novel prenyl ferulate performed by feruloyl esterases from Myceliophthora thermophila in microemulsions
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2018 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 102, no 1, p. 511-511Article in journal, Letter (Refereed) Published
Place, publisher, year, edition, pages
Springer, 2018
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-66731 (URN)10.1007/s00253-017-8631-8 (DOI)000419119100044 ()29159584 (PubMedID)
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-09-14Bibliographically approved
Zerva, A., Antonopoulou, I., Enman, J., Iancu, L., Rova, U. & Christakopoulos, P. (2018). Cross-Linked Enzyme Aggregates of Feruloyl Esterase Preparations from Thermothelomyces thermophila and Talaromyces wortmannii. Catalysts, 8(5), Article ID 208.
Open this publication in new window or tab >>Cross-Linked Enzyme Aggregates of Feruloyl Esterase Preparations from Thermothelomyces thermophila and Talaromyces wortmannii
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2018 (English)In: Catalysts, ISSN 2073-4344, Vol. 8, no 5, article id 208Article in journal (Refereed) Published
Abstract [en]

Cross-linked enzyme aggregates (CLEA®) technology is a well-established method in the current literature for the low-cost and effective immobilization of several enzymes. The main advantage of this particular method is the simplicity of the process, since it consists of only two steps. However, CLEA immobilization must be carefully designed for each desired enzyme, since the optimum conditions for enzymes can vary significantly, according to their physicochemical properties. In the present study, an investigation of the optimum CLEA immobilization conditions was carried out for eight feruloyl esterase preparations. Feruloyl esterases are a very important enzyme group in the valorization of lignocellulosic biomass, since they act in a synergistic way with other enzymes for the breakdown of plant biomass. Specifically, we investigated the type and concentration of precipitant and the crosslinker concentration, for retaining optimal activity. FAE68 was found to be the most promising enzyme for CLEA immobilization, since in this case, the maximum retained activity, over 98%, was observed. Subsequently, we examined the operational stability and the stability in organic solvents for the obtained CLEA preparations, as well as their structure. Overall, our results support that the maximum activity retaining and the stability properties of the final CLEAs can vary greatly in different FAE preparations. Nevertheless, some of the examined FAEs show a significant potential for further applications in harsh industrial conditions.

Place, publisher, year, edition, pages
MDPI, 2018
National Category
Chemical Engineering Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-68931 (URN)10.3390/catal8050208 (DOI)000435191500037 ()2-s2.0-85048056816 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-05 (rokbeg)

Available from: 2018-05-28 Created: 2018-05-28 Last updated: 2018-06-28Bibliographically approved
Muraleedharan, M. N., Zouraris, D., Karantonis, A., Topakas, E., Sandgren, M., Rova, U., . . . Karnaouri, A. C. (2018). Effect of structural properties of lignin isolated from different sources on its efficiency to serve as electron donor of fungal Lytic Polysaccharide Monooxygenases. Biotechnology for Biofuels
Open this publication in new window or tab >>Effect of structural properties of lignin isolated from different sources on its efficiency to serve as electron donor of fungal Lytic Polysaccharide Monooxygenases
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2018 (English)In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
BMC, 2018
National Category
Bioenergy Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-70690 (URN)
Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2018-08-31
Varriale, S., Cerullo, G., Antonopoulou, I., Christakopoulos, P., Rova, U., Tron, T., . . . Faraco, V. (2018). Evolution of the feruloyl esterase MtFae1a from Myceliophthora thermophila towards improved catalysts for antioxidants synthesis. Applied Microbiology and Biotechnology, 102(12), 5185-5196
Open this publication in new window or tab >>Evolution of the feruloyl esterase MtFae1a from Myceliophthora thermophila towards improved catalysts for antioxidants synthesis
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2018 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 102, no 12, p. 5185-5196Article in journal (Refereed) Published
Abstract [en]

The chemical syntheses currently employed for industrial purposes, including in the manufacture of cosmetics, present limitations such as unwanted side reactions and the need for harsh chemical reaction conditions. In order to overcome these drawbacks, novel enzymes are developed to catalyze the targeted bioconversions. In the present study, a methodology for the construction and the automated screening of evolved variants library of a Type B feruloyl esterase from Myceliophthora thermophila (MtFae1a) was developed and applied to generation of 30,000 mutants and their screening for selecting the variants with higher activity than the wild-type enzyme. The library was generated by error-prone PCR of mtfae1a cDNA and expressed in Saccharomyces cerevisiae. Screening for extracellular enzymatic activity towards 4-nitrocatechol-1-yl ferulate, a new substrate developed ad hoc for high-throughput assays of feruloyl esterases, led to the selection of 30 improved enzyme variants. The best four variants and the wild-type MtFae1a were investigated in docking experiments with hydroxycinnamic acid esters using a model of 3D structure of MtFae1a. These variants were also used as biocatalysts in transesterification reactions leading to different target products in detergentless microemulsions and showed enhanced synthetic activities, although the screening strategy had been based on improved hydrolytic activity.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-68496 (URN)10.1007/s00253-018-8995-4 (DOI)000432692300016 ()29687143 (PubMedID)2-s2.0-85045854653 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-01 (rokbeg)

Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-06-21Bibliographically approved
Karnaouri, A. C., Topakas, E., Matsakas, L., Rova, U. & Christakopoulos, P. (2018). Fine-tuned enzymatic hydrolysis of organosolv pretreated forest materials for the efficient production of cellobiose. Frontiers in Chemistry, 6, Article ID 128.
Open this publication in new window or tab >>Fine-tuned enzymatic hydrolysis of organosolv pretreated forest materials for the efficient production of cellobiose
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2018 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 6, article id 128Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
Keywords
cellobiohydrolases, hydrolysis, enzymatic cocktail, cellobiose, experimental design, thermostable enzymes, prebiotics
National Category
Engineering and Technology Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-68257 (URN)10.3389/fchem.2018.00128 (DOI)000430398300001 ()2-s2.0-85047449575 (Scopus ID)
Projects
"Food-grade prebiotic oligosaccharide production, merging marine and forest resources for moving up the cellulose value-chain (ForceUpValue)"
Funder
VINNOVA, 158526
Note

Validerad;2018;Nivå 2;2018-05-03 (andbra)

Available from: 2018-04-10 Created: 2018-04-10 Last updated: 2018-06-07Bibliographically approved
Matsakas, L., Karnaouri, A. C., Cwirzen, A., Rova, U. & Christakopoulos, P. (2018). Formation of Lignin Nanoparticles by Combining Organosolv Pretreatment of Birch Biomass and Homogenization Processes. Molecules, 23(7), Article ID 1822.
Open this publication in new window or tab >>Formation of Lignin Nanoparticles by Combining Organosolv Pretreatment of Birch Biomass and Homogenization Processes
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2018 (English)In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, no 7, article id 1822Article in journal (Refereed) Published
Abstract [en]

Valorization of lignocellulosic biomass into a biorefinery scheme requires the use of all biomass components; in this, the lignin fraction is often underutilized. Conversion of lignin to nanoparticles is an attractive solution. Here, we investigated the effect of different lignin isolation processes and a post-treatment homogenization step on particle formation. Lignin was isolated from birch chips by using two organosolv processes, traditional organosolv (OS) and hybrid organosolv-steam explosion (HOS-SE) at various ethanol contents. For post-treatment, lignin was homogenized at 500 bar using different ethanol:water ratios. Isolation of lignin with OS resulted in unshaped lignin particles, whereas after HOS-SE, lignin micro-particles were formed directly. Addition of an acidic catalyst during HOS-SE had a negative impact on the particle formation, and the optimal ethanol content was 50⁻60% v/v. Homogenization had a positive effect as it transformed initially unshaped lignin into spherical nanoparticles and reduced the size of the micro-particles isolated by HOS-SE. Ethanol content during homogenization affected the size of the particles, with the optimal results obtained at 75% v/v. We demonstrate that organosolv lignin can be used as an excellent starting material for nanoparticle preparation, with a simple method without the need for extensive chemical modification. It was also demonstrated that tuning of the operational parameters results in nanoparticles of smaller size and with better size homogeneity.

Place, publisher, year, edition, pages
MDPI, 2018
National Category
Bioprocess Technology Infrastructure Engineering
Research subject
Biochemical Process Engineering; Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-70225 (URN)10.3390/molecules23071822 (DOI)30041408 (PubMedID)2-s2.0-85052024905 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-06 (andbra)

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-09-03Bibliographically approved
Patel, A., Matsakas, L., Rova, U. & Christakopoulos, P. (2018). Heterotrophic cultivation of Auxenochlorella protothecoides using forest biomass as a feedstock for sustainable biodiesel production. Biotechnology for Biofuels, 11(1), Article ID 169.
Open this publication in new window or tab >>Heterotrophic cultivation of Auxenochlorella protothecoides using forest biomass as a feedstock for sustainable biodiesel production
2018 (English)In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, no 1, article id 169Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
BioMed Central, 2018
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-69722 (URN)10.1186/s13068-018-1173-1 (DOI)000436108000002 ()29946359 (PubMedID)2-s2.0-85049028591 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-20 (andbra)

Available from: 2018-06-20 Created: 2018-06-20 Last updated: 2018-08-06Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-0079-5950

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