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Christakopoulos, PaulORCID iD iconorcid.org/0000-0003-0079-5950
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Publications (10 of 257) Show all publications
Patel, A., Matsakas, L., Rova, U. & Christakopoulos, P. (2019). A perspective on biotechnological applications of thermophilic microalgae and cyanobacteria. Bioresource Technology, 278, 424-434
Open this publication in new window or tab >>A perspective on biotechnological applications of thermophilic microalgae and cyanobacteria
2019 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 278, p. 424-434Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Thermophilic microorganisms, Microalgae, Cyanobacteria, Biotechnological applications, Biofuels, Biologically active compounds, Pigments
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-73043 (URN)10.1016/j.biortech.2019.01.063 (DOI)000457852400049 ()30685131 (PubMedID)2-s2.0-85060269950 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-02-27Bibliographically approved
Patel, A., Matsakas, L., Hruzova, K., Rova, U. & Christakopoulos, P. (2019). Biosynthesis of Nutraceutical Fatty Acids by the Oleaginous Marine Microalgae Phaeodactylum tricornutum Utilizing Hydrolysates from Organosolv-Pretreated Birch and Spruce Biomass. Marine Drugs, 17(12), Article ID 119.
Open this publication in new window or tab >>Biosynthesis of Nutraceutical Fatty Acids by the Oleaginous Marine Microalgae Phaeodactylum tricornutum Utilizing Hydrolysates from Organosolv-Pretreated Birch and Spruce Biomass
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2019 (English)In: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 17, no 12, article id 119Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
polyunsaturated fatty acids, EPA, DHA, marine algae, Phaeodactylum tricornutum, forest biomass
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-73136 (URN)10.3390/md17020119 (DOI)000460795500047 ()30781416 (PubMedID)2-s2.0-85061857091 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-07 (johcin)

Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-04-24Bibliographically approved
Cerullo, G., Varriale, S., Bozonnet, S., Antonopoulou, I., Christakopoulos, P., Rova, U., . . . Faraco, V. (2019). Directed evolution of the type C feruloyl esterase from Fusarium oxysporum FoFaeC and molecular docking analysis of its improved variants. New Biotechnology, 51, 14-20
Open this publication in new window or tab >>Directed evolution of the type C feruloyl esterase from Fusarium oxysporum FoFaeC and molecular docking analysis of its improved variants
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2019 (English)In: New Biotechnology, ISSN 1871-6784, E-ISSN 1876-4347, Vol. 51, p. 14-20Article in journal (Refereed) Published
Abstract [en]

The need to develop competitive and eco-friendly processes in the cosmetic industry leads to the search for new enzymes with improved properties for industrial bioconversions in this sector. In the present study, a complete methodology to generate, express and screen diversity for the type C feruloyl esterase from Fusarium oxysporium FoFaeC was set up in a high-throughput fashion. A library of around 30,000 random mutants of FoFaeC was generated by error prone PCR of fofaec cDNA and expressed in Yarrowia lipolytica. Screening for enzymatic activity towards the substrates 5-bromo-4-chloroindol-3-yl and 4-nitrocatechol-1-yl ferulates allowed the selection of 96 enzyme variants endowed with improved enzymatic activity that were then characterized for thermo- and solvent- tolerance. The five best mutants in terms of higher activity, thermo- and solvent- tolerance were selected for analysis of substrate specificity. Variant L432I was shown to be able to hydrolyze all the tested substrates, except methyl sinapate, with higher activity than wild type FoFaeC towards methyl p-coumarate, methyl ferulate and methyl caffeate. Moreover, the E455D variant was found to maintain completely its hydrolytic activity after two hour incubation at 55 °C, whereas the L284Q/V405I variant showed both higher thermo- and solvent- tolerance than wild type FoFaeC. Small molecule docking simulations were applied to the five novel selected variants in order to examine the binding pattern of substrates used for enzyme characterization of wild type FoFaeC and the evolved variants.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Directed evolution, Feruloyl esterase, Fusarium oxysporum, High-throughput screening, Library
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-72926 (URN)10.1016/j.nbt.2019.01.008 (DOI)000461362500003 ()2-s2.0-85061183564 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-18 (svasva)

Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-04-12Bibliographically approved
Matsakas, L., Raghavendran, V., Yakimenko, O., Persson, G., Olsson, E., Rova, U., . . . Christakopoulos, P. (2019). Lignin-first biomass fractionation using a hybrid organosolv: Steam explosion pretreatment technology improves the saccharification and fermentability of spruce biomass. Bioresource Technology, 273, 521-528
Open this publication in new window or tab >>Lignin-first biomass fractionation using a hybrid organosolv: Steam explosion pretreatment technology improves the saccharification and fermentability of spruce biomass
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2019 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 273, p. 521-528Article in journal (Refereed) Published
Abstract [en]

For a transition to a sustainable society, fuels, chemicals, and materials should be produced from renewable resources. Lignocellulosic biomass constitutes an abundant and renewable feedstock; however, its successful application in a biorefinery requires efficient fractionation into its components; cellulose, hemicellulose and lignin. Here, we demonstrate that a newly established hybrid organosolv – steam explosion pretreatment can effectively fractionate spruce biomass to yield pretreated solids with high cellulose (72% w/w) and low lignin (delignification up to 79.4% w/w) content. The cellulose-rich pretreated solids present high saccharification yields (up to 61% w/w) making them ideal for subsequent bioconversion processes. Moreover, under high-gravity conditions (22% w/w) we obtained an ethanol titer of 61.7 g/L, the highest so far reported for spruce biomass. Finally, the obtained high-purity lignin is suitable for various advanced applications. In conclusion, hybrid organosolv pretreatment could offer a closed-loop biorefinery while simultaneously adding value to all biomass components.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Softwood, Organosolv explosion, High gravity fermentation, Fractionation, Biorefinery
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-71766 (URN)10.1016/j.biortech.2018.11.055 (DOI)000453742100064 ()30471644 (PubMedID)2-s2.0-85056772752 (Scopus ID)
Funder
Swedish Energy Agency, 2015-006989
Note

Validerad;2018;Nivå 2;2018-11-27 (johcin)

Available from: 2018-11-27 Created: 2018-11-27 Last updated: 2019-03-27Bibliographically approved
Krige, A., Sjöblom, M., Ramser, K., Christakopoulos, P. & Rova, U. (2019). On-line Raman spectroscopic study of cytochromes’ redox state of biofilms in microbial fuel cells. Molecules, 24(3), Article ID 646.
Open this publication in new window or tab >>On-line Raman spectroscopic study of cytochromes’ redox state of biofilms in microbial fuel cells
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2019 (English)In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 24, no 3, article id 646Article in journal (Refereed) Published
Abstract [en]

Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as modifying microorganisms for enhanced electricity production. Geobacter are well known for their ability to form thick biofilms and transfer electrons to the surfaces of electrodes. Currently, there are not many “on-line” systems for monitoring the activity of the biofilm and the electron transfer process without harming the biofilm. Raman microscopy was shown to be capable of providing biochemical information, i.e., the redox state of C-type cytochromes, which is integral to external electron transfer, without harming the biofilm. In the current study, a custom 3D printed flow-through cuvette was used in order to analyze the oxidation state of the C-type cytochromes of suspended cultures of three Geobacter sulfurreducens strains (PCA, KN400 and ∆pilA). It was found that the oxidation state is a good indicator of the metabolic state of the cells. Furthermore, an anaerobic fluidic system enabling in situ Raman measurements was designed and applied successfully to monitor and characterize G. sulfurreducens biofilms during electricity generation, for both a wild strain, PCA, and a mutant, ∆S. The cytochrome redox state, monitored by the Raman peak areas, could be modulated by applying different poise voltages to the electrodes. This also correlated with the modulation of current transferred from the cytochromes to the electrode. The Raman peak area changed in a predictable and reversible manner, indicating that the system could be used for analyzing the oxidation state of the proteins responsible for the electron transfer process and the kinetics thereof in-situ. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Cytochrome-C, Geobacter sulfurreducens, Microbial fuel cell, Omc, Raman spectroscopy
National Category
Bioprocess Technology Applied Mechanics
Research subject
Biochemical Process Engineering; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-73003 (URN)10.3390/molecules24030646 (DOI)000458934000270 ()30759821 (PubMedID)2-s2.0-85061525740 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-26 (svasva)

Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2019-02-27Bibliographically approved
Antonopoulou, I., Iancu, L., Jütten, P., Piechot, A., Rova, U. & Christakopoulos, P. (2019). Screening of novel feruloyl esterases from Talaromyces wortmannii for the development of efficient and sustainable syntheses of feruloyl derivatives. Enzyme and microbial technology, 120, 124-135
Open this publication in new window or tab >>Screening of novel feruloyl esterases from Talaromyces wortmannii for the development of efficient and sustainable syntheses of feruloyl derivatives
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2019 (English)In: Enzyme and microbial technology, ISSN 0141-0229, E-ISSN 1879-0909, Vol. 120, p. 124-135Article in journal (Refereed) Published
Abstract [en]

The feruloyl esterases Fae125, Fae7262 and Fae68 from Talaromyces wortmannii were screened in 10 different solvent: buffer systems in terms of residual hydrolytic activity and of the ability for the transesterification of vinyl ferulate with prenol or L-arabinose. Among the tested enzymes, the acetyl xylan-related Fae125 belonging to the phylogenetic subfamily 5 showed highest yield and selectivity for both products in alkane: buffer systems (n-hexane or n-octane). Response surface methodology, based on a 5-level and 6-factor central composite design, revealed that the substrate molar ratio and the water content were the most significant variables for the bioconversion yield and selectivity. The effect of agitation, the possibility of DMSO addition and the increase of donor concentration were investigated. After optimization, competitive transesterification yields were obtained for prenyl ferulate (87.5-92.6%) and L-arabinose ferulate (56.2-61.7%) at reduced reaction times (≤ 24 h) resulting in good productivities (> 1 g/L/h, >300 kg product/kg FAE). The enzyme could be recycled for six consecutive cycles retaining 66.6% of the synthetic activity and 100% of the selectivity.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-70723 (URN)10.1016/j.enzmictec.2018.08.007 (DOI)000452576500016 ()30396393 (PubMedID)2-s2.0-85053620494 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-08 (johcin)

Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2019-02-01Bibliographically approved
Karnaouri, A. C., Antonopoulou, I., Zerva, A., Dimarogona, M., Topakas, E., Rova, U. & Christakopoulos, P. (2019). Thermophilic enzyme systems for efficient conversion of lignocellulose to valuable products: Structural insights and future perspectives for esterases and oxidative catalysts. Bioresource Technology, 279, 362-372
Open this publication in new window or tab >>Thermophilic enzyme systems for efficient conversion of lignocellulose to valuable products: Structural insights and future perspectives for esterases and oxidative catalysts
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2019 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 279, p. 362-372Article in journal (Refereed) Published
Abstract [en]

Thermophilic enzyme systems are of major importance nowadays in all industrial processes due to their great performance at elevated temperatures. In the present review, an overview of the current knowledge on the properties of thermophilic and thermotolerant carbohydrate esterases and oxidative enzymes with great thermostability is provided, with respect to their potential use in biotechnological applications. A special focus is given to the lytic polysaccharide monooxygenases that are able to oxidatively cleave lignocellulose through the use of oxygen or hydrogen peroxide as co-substrate and a reducing agent as electron donor. Structural characteristics of the enzymes, including active site conformation and surface properties are discussed and correlated with their substrate specificity and thermostability properties.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Thermophilic enzymes, Thermostability, Esterases, Laccases, Peroxidases, LPMOs, Biotransformation, Lignocellulose valorization
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-73041 (URN)10.1016/j.biortech.2019.01.062 (DOI)000458999200043 ()30685134 (PubMedID)2-s2.0-85060269655 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-27 (johcin)

Available from: 2019-02-27 Created: 2019-02-27 Last updated: 2019-03-08Bibliographically approved
Mu, L., Wu, J., Matsakas, L., Chen, M., Rova, U., Christakopoulos, P., . . . Shi, Y. (2019). Two important factors of selecting lignin as efficient lubricating additives in poly (ethylene glycol): Hydrogen bond and molecular weight. International Journal of Biological Macromolecules, 129, 564-570
Open this publication in new window or tab >>Two important factors of selecting lignin as efficient lubricating additives in poly (ethylene glycol): Hydrogen bond and molecular weight
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2019 (English)In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 129, p. 564-570Article in journal (Refereed) Published
Abstract [en]

Lignin, one of the most abundant natural polymers, has been successfully used as an effective lubricant additive with high value. The chemical structure of lignin is very diverse and strongly affected by both the source of lignin (i.e. plant species) and the lignin extraction process. In this work, a series of lignin from different biomass sources (hard or soft wood) and extraction process (organosolv with or without acid catalyst) has been successfully incorporated into poly(ethylene glycol) (PEG) and fortified lubricating properties were achieved. The effects of different lignin on the rheological, thermal and tribological properties of the lignin/EG lubricants were systematically investigated by different characterization techniques. Lignin in PEG significantly improves the lubricating property, where a wear reduction of 93.8% was observed. The thermal and lubrication properties of the PEG lubricants filled with different kinds of lignin are tightly related to the synergistic state of hydrogen bonding and molecular weight distribution. Lignin with broader molecular weight distribution and higher hydroxyl content shows better adhesion on metal surfaces and strengthened lubricating film, which could be used as the efficient lubricating additives. This work provides a criterion for selecting appropriate lignin as the efficient lubricant additive and accelerates the application of lignin.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Lignin, Lubrication, Poly (ethylene glycol), Hydrogen bonding, Molecular weight
National Category
Bioprocess Technology Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements; Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-72899 (URN)10.1016/j.ijbiomac.2019.01.175 (DOI)2-s2.0-85061540788 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-20 (svasva)

Available from: 2019-02-14 Created: 2019-02-14 Last updated: 2019-02-26Bibliographically approved
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
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ORCID iD: ORCID iD iconorcid.org/0000-0003-0079-5950

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