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Poster Presentation 2-22
Exploring the Metabolic Network for Xylose Fermentation in Recombinant Saccharomyces cerevisiae Expressing PsXYL1, PsXYL2, and PsXYL3
Yong-Su Jin1, and Thomas W. Jeffries1,2,3 1Department of Food Science, University of Wisconsin-Madison 1605 Linden Drive, Madison, WI 53706, USA
2Department of Bacteriology, University of Wisconsin-Madison 1550 Linden Drive, Madison, WI 53706, USA
3USDA Forest Service, Forest Products Laboratory One Gifford Pinchot Dr., Madison, WI 53705, USA
Telephone: (608) 231-9453; Fax: (608) 231-9262; E-mail: twjeffries@fs.fed.us
Pathway engineering has been applied to xylose metabolism in S. cerevisiae. Most research has focused simply on introducing genes for the initial xylose assimilation steps from Pichia stipitis, a xylose fermenting yeast, into S. cerevisiae, a yeast traditionally used in ethanol production from hexose. However, the resulting recombinant S. cerevisiae expressing PsXYL1, PsXYL2, and PsXYL3 utilized xylose in an oxidative manner. By contrast, when recombinant S. cerevisiae uses glucose, it does so fermentatively. To understand the differences in network properties that cells employ during glucose and xylose metabolism, we employed a metabolic network for S. cerevisiae that describes the biochemistry of cell growth. Feasible domains of metabolic fluxes constrained by stoichiometry were explored using different cellular parameters including P/O ratio, maintenance energy, and aeration. We compared phenotypes of recombinant S. cerevisiae during xylose metabolism with in silico phenotypes defined by extreme pathways underlying a given metabolic network. Three phases of metabolic phenotype were predicted with respect to oxygen availability from anaerobic to aerobic conditions. The metabolic phenotypes based on calculated flux distributions from stoichiometric models were in accordance with corresponding experimental data sets.
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