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Metabolic Engineering of Xylose-Utilising Saccharomyces cerevisiae Strains. A Closer Look at Recombinant Strains Based on the Xylose Reductase-Xylitol Dehydrogenase Pathway.

Jeppsson, Marie LU (2004)
Abstract
Saccharomyces cerevisiae produces ethanol efficiently from the hexose sugars in lignocellulose hydrolysates, but it can not utilise pentose sugars such as xylose and arabinose. Stable xylose-utilising S. cerevisiae strains obtained by integration of the Pichia stipitis genes encoding xylose reductase (XR), xylitol dehydrogenase (XDH) and xylulokinase, exhibit low ethanol yields when utilising xylose, mainly because of xylitol formation. Xylitol results from a different cofactor usage in the NAD(P)H-dependent XR and the NAD+-dependent XDH reactions. By disruption of genes in the NADPH-producing oxidative pentose phosphate pathway, less NADPH becomes available for the reduction of xylose. As a result the XR utilises mainly NADH, and the... (More)
Saccharomyces cerevisiae produces ethanol efficiently from the hexose sugars in lignocellulose hydrolysates, but it can not utilise pentose sugars such as xylose and arabinose. Stable xylose-utilising S. cerevisiae strains obtained by integration of the Pichia stipitis genes encoding xylose reductase (XR), xylitol dehydrogenase (XDH) and xylulokinase, exhibit low ethanol yields when utilising xylose, mainly because of xylitol formation. Xylitol results from a different cofactor usage in the NAD(P)H-dependent XR and the NAD+-dependent XDH reactions. By disruption of genes in the NADPH-producing oxidative pentose phosphate pathway, less NADPH becomes available for the reduction of xylose. As a result the XR utilises mainly NADH, and the strains show enhanced ethanol yields and decreased xylitol yields, however, at the expense of the xylose fermentation rate. The xylose fermentation rate can be partly restored by enhancing the XR activity and/or fine-tuning the glucose-6-phosphate dehydrogenase activity. The overproduction of a transhydrogenase, capable of converting NADPH and NAD+ into NADP+ and NADH, also lowers the xylitol yield but has no positive effect on the ethanol yield. Not only the ethanol yield but also the rate of xylose utilisation must be enhanced in recombinant S. cerevisiae strains. The transport of xylose, the xylose pathway and the pentose phosphate pathway are possible bottlenecks during xylose fermentation. Increased XR activity results in enhanced xylose flux, but also in enhanced glycerol yield, which can be explained by the dihydroxyacetone phosphate-reducing activity of XR. The genomic changes responsible for enhanced growth on xylose have not yet been identified in xylose-growing S. cerevisiae mutants. However, genome-wide transcription analysis on a number of xylose-growing strains points towards enhanced expression levels of genes in galactose metabolism and in the pentose phosphate pathway. (Less)
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author
supervisor
opponent
  • Professor Porro, Danilo, University of Milano-Bicocca, Italy
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Microbiology, bacteriology, virology, mycology, Mikrobiologi, bakteriologi, virologi, mykologi, microarrays, cofactors, XK, XDH, XR, lignocellulose, xylose, ethanol, Saccharomyces cerevisiae, yeast
pages
146 pages
publisher
Applied Microbiology (LTH)
defense location
Chemical Center, Lund Institute of Technology, Room B
defense date
2004-04-22 10:30:00
language
English
LU publication?
yes
additional info
Article: Marie Jeppsson, Karin Träff, Björn Johansson, Bärbel Hahn-Hägerdal and Marie F. Gorwa-Grauslund. 2003. Effect of Enhanced Xylose Reductase Activity on Xylose Consumption and Product Distribution in Xylose-Fermenting Recombinant Saccharomyces cerevisiae. FEMS Yeast Res. 3 (2):167-175. Article: Marie Jeppsson, Björn Johansson, Bärbel Hahn-Hägerdal and Marie F. Gorwa-Grauslund. 2002. Reduced Oxidative Pentose Phosphate Pathway Flux in Recombinant Xylose-Utilizing Saccharomyces cerevisiae Strains Improves the Ethanol Yield from Xylose. Appl. Environ. Microbiol. 68 (4): 1604-1609. Article: Marie Jeppsson, Björn Johansson, Peter Ruhdal-Jensen, Bärbel Hahn-Hägerdal and Marie F. Gorwa-Grauslund. 2003. The Level of Glucose-6-Phosphate Dehydrogenase Activity Strongly Influences Xylose Fermentation and Inhibitor Sensitivity in Recombinant Saccharomyces cerevisiae Strains. Yeast 20 (15): 1263-1272. Article: Marie Jeppsson, Katja Franke, Bärbel Hahn-Hägerdal and Marie F. Gorwa-Grauslund. 2004. Reduced Affinity of Pichia stipitis Xylose Reductase for NADPH Increases Ethanol Production from Xylose in Recombinant Saccharomyces cerevisiae. Submitted. Article: Marie Jeppsson, Marco Sonderegger, Uwe Sauer, Bärbel Hahn-Hägerdal and Marie-F. Gorwa-Grauslund. 2004. Identification of Common Traits in Recombinant Xylose-Growing Saccharomyces cerevisiae Strains Using Genome-Wide Transcription Analysis. Manuscript.
id
9f38b9e8-d730-4034-ad66-01b066fd68ea (old id 466832)
date added to LUP
2016-04-04 10:12:40
date last changed
2018-11-21 20:57:27
@phdthesis{9f38b9e8-d730-4034-ad66-01b066fd68ea,
  abstract     = {{Saccharomyces cerevisiae produces ethanol efficiently from the hexose sugars in lignocellulose hydrolysates, but it can not utilise pentose sugars such as xylose and arabinose. Stable xylose-utilising S. cerevisiae strains obtained by integration of the Pichia stipitis genes encoding xylose reductase (XR), xylitol dehydrogenase (XDH) and xylulokinase, exhibit low ethanol yields when utilising xylose, mainly because of xylitol formation. Xylitol results from a different cofactor usage in the NAD(P)H-dependent XR and the NAD+-dependent XDH reactions. By disruption of genes in the NADPH-producing oxidative pentose phosphate pathway, less NADPH becomes available for the reduction of xylose. As a result the XR utilises mainly NADH, and the strains show enhanced ethanol yields and decreased xylitol yields, however, at the expense of the xylose fermentation rate. The xylose fermentation rate can be partly restored by enhancing the XR activity and/or fine-tuning the glucose-6-phosphate dehydrogenase activity. The overproduction of a transhydrogenase, capable of converting NADPH and NAD+ into NADP+ and NADH, also lowers the xylitol yield but has no positive effect on the ethanol yield. Not only the ethanol yield but also the rate of xylose utilisation must be enhanced in recombinant S. cerevisiae strains. The transport of xylose, the xylose pathway and the pentose phosphate pathway are possible bottlenecks during xylose fermentation. Increased XR activity results in enhanced xylose flux, but also in enhanced glycerol yield, which can be explained by the dihydroxyacetone phosphate-reducing activity of XR. The genomic changes responsible for enhanced growth on xylose have not yet been identified in xylose-growing S. cerevisiae mutants. However, genome-wide transcription analysis on a number of xylose-growing strains points towards enhanced expression levels of genes in galactose metabolism and in the pentose phosphate pathway.}},
  author       = {{Jeppsson, Marie}},
  keywords     = {{Microbiology; bacteriology; virology; mycology; Mikrobiologi; bakteriologi; virologi; mykologi; microarrays; cofactors; XK; XDH; XR; lignocellulose; xylose; ethanol; Saccharomyces cerevisiae; yeast}},
  language     = {{eng}},
  publisher    = {{Applied Microbiology (LTH)}},
  school       = {{Lund University}},
  title        = {{Metabolic Engineering of Xylose-Utilising Saccharomyces cerevisiae Strains. A Closer Look at Recombinant Strains Based on the Xylose Reductase-Xylitol Dehydrogenase Pathway.}},
  year         = {{2004}},
}