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Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass

BACKGROUND: Lignocellulosic biomass is a viable source of renewable energy for bioethanol production. For the efficient conversion of biomass into bioethanol, it is essential that sugars from both the cellulose and hemicellulose fractions of lignocellulose be utilised. RESULTS: We describe the devel...

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Autores principales: Kricka, William, James, Tharappel C, Fitzpatrick, James, Bond, Ursula
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417197/
https://www.ncbi.nlm.nih.gov/pubmed/25928878
http://dx.doi.org/10.1186/s12934-015-0242-4
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author Kricka, William
James, Tharappel C
Fitzpatrick, James
Bond, Ursula
author_facet Kricka, William
James, Tharappel C
Fitzpatrick, James
Bond, Ursula
author_sort Kricka, William
collection PubMed
description BACKGROUND: Lignocellulosic biomass is a viable source of renewable energy for bioethanol production. For the efficient conversion of biomass into bioethanol, it is essential that sugars from both the cellulose and hemicellulose fractions of lignocellulose be utilised. RESULTS: We describe the development of a recombinant yeast system for the fermentation of cellulose and xylose, the most abundant pentose sugar in the hemicellulose fraction of biomass. The brewer’s yeast Saccharomyces pastorianus was chosen as a host as significantly higher recombinant enzyme activities are achieved, when compared to the more commonly used S. cerevisiae. When expressed in S. pastorianus, the Trichoderma reesei xylose oxidoreductase pathway was more efficient at alcohol production from xylose than the xylose isomerase pathway. The alcohol yield was influenced by the concentration of xylose in the medium and was significantly improved by the additional expression of a gene encoding for xylulose kinase. The xylose reductase, xylitol dehydrogenase and xylulose kinase genes were co-expressed with genes encoding for the three classes of T. reesei cellulases, namely endoglucanase (EG2), cellobiohydrolysase (CBH2) and β-glucosidase (BGL1). The initial metabolism of xylose by the engineered strains facilitated production of cellulases at fermentation temperatures. The sequential metabolism of xylose and cellulose generated an alcohol yield of 82% from the available sugars. Several different types of biomass, such as the energy crop Miscanthus sinensis and the industrial waste, brewer’s spent grains, were examined as biomass sources for fermentation using the developed yeast strains. Xylose metabolism and cell growth were inhibited in fermentations carried out with acid-treated spent grain liquor, resulting in a 30% reduction in alcohol yield compared to fermentations carried out with mixed sugar substrates. CONCLUSIONS: Reconstitution of complete enzymatic pathways for cellulose hydrolysis and xylose utilisation in S. pastorianus facilitates the co-fermentation of cellulose and xylose without the need for added exogenous cellulases and provides a basis for the development of a consolidated process for co-utilisation of hemicellulose and cellulose sugars. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12934-015-0242-4) contains supplementary material, which is available to authorized users.
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spelling pubmed-44171972015-05-03 Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass Kricka, William James, Tharappel C Fitzpatrick, James Bond, Ursula Microb Cell Fact Research BACKGROUND: Lignocellulosic biomass is a viable source of renewable energy for bioethanol production. For the efficient conversion of biomass into bioethanol, it is essential that sugars from both the cellulose and hemicellulose fractions of lignocellulose be utilised. RESULTS: We describe the development of a recombinant yeast system for the fermentation of cellulose and xylose, the most abundant pentose sugar in the hemicellulose fraction of biomass. The brewer’s yeast Saccharomyces pastorianus was chosen as a host as significantly higher recombinant enzyme activities are achieved, when compared to the more commonly used S. cerevisiae. When expressed in S. pastorianus, the Trichoderma reesei xylose oxidoreductase pathway was more efficient at alcohol production from xylose than the xylose isomerase pathway. The alcohol yield was influenced by the concentration of xylose in the medium and was significantly improved by the additional expression of a gene encoding for xylulose kinase. The xylose reductase, xylitol dehydrogenase and xylulose kinase genes were co-expressed with genes encoding for the three classes of T. reesei cellulases, namely endoglucanase (EG2), cellobiohydrolysase (CBH2) and β-glucosidase (BGL1). The initial metabolism of xylose by the engineered strains facilitated production of cellulases at fermentation temperatures. The sequential metabolism of xylose and cellulose generated an alcohol yield of 82% from the available sugars. Several different types of biomass, such as the energy crop Miscanthus sinensis and the industrial waste, brewer’s spent grains, were examined as biomass sources for fermentation using the developed yeast strains. Xylose metabolism and cell growth were inhibited in fermentations carried out with acid-treated spent grain liquor, resulting in a 30% reduction in alcohol yield compared to fermentations carried out with mixed sugar substrates. CONCLUSIONS: Reconstitution of complete enzymatic pathways for cellulose hydrolysis and xylose utilisation in S. pastorianus facilitates the co-fermentation of cellulose and xylose without the need for added exogenous cellulases and provides a basis for the development of a consolidated process for co-utilisation of hemicellulose and cellulose sugars. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12934-015-0242-4) contains supplementary material, which is available to authorized users. BioMed Central 2015-04-28 /pmc/articles/PMC4417197/ /pubmed/25928878 http://dx.doi.org/10.1186/s12934-015-0242-4 Text en © Bond et al.; licensee BioMed Central. 2015 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Kricka, William
James, Tharappel C
Fitzpatrick, James
Bond, Ursula
Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title_full Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title_fullStr Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title_full_unstemmed Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title_short Engineering Saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
title_sort engineering saccharomyces pastorianus for the co-utilisation of xylose and cellulose from biomass
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417197/
https://www.ncbi.nlm.nih.gov/pubmed/25928878
http://dx.doi.org/10.1186/s12934-015-0242-4
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