Reduced oxidative pentose phosphate pathway flux in recombinant xylose-utilizing Saccharomyces cerevisiae strains improves the ethanol yield from xylose.

Marie Jeppsson, Björn Johansson, Bärbel Hahn-Hägerdal, Marie-Francoise Gorwa-Grauslund

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Abstract

In recombinant, xylose-fermenting Saccharomyces cerevisiae, about 30% of the consumed xylose is converted to xylitol. Xylitol production results from a cofactor imbalance, since xylose reductase uses both NADPH and NADH, while xylitol dehydrogenase uses only NAD(+). In this study we increased the ethanol yield and decreased the xylitol yield by lowering the flux through the NADPH-producing pentose phosphate pathway. The pentose phosphate pathway was blocked either by disruption of the GND1 gene, one of the isogenes of 6-phosphogluconate dehydrogenase, or by disruption of the ZWF1 gene, which encodes glucose 6-phosphate dehydrogenase. Decreasing the phosphoglucose isomerase activity by 90% also lowered the pentose phosphate pathway flux. These modifications all resulted in lower xylitol yield and higher ethanol yield than in the control strains. TMB3255, carrying a disruption of ZWF1, gave the highest ethanol yield (0.41 g g(-1)) and the lowest xylitol yield (0.05 g g(-1)) reported for a xylose-fermenting recombinant S. cerevisiae strain, but also an 84% lower xylose consumption rate. The low xylose fermentation rate is probably due to limited NADPH-mediated xylose reduction. Metabolic flux modeling of TMB3255 confirmed that the NADPH-producing pentose phosphate pathway was blocked and that xylose reduction was mediated only by NADH, leading to a lower rate of xylose consumption. These results indicate that xylitol production is strongly connected to the flux through the oxidative part of the pentose phosphate pathway.
Original languageEnglish
Pages (from-to)1604-1609
JournalApplied and Environmental Microbiology
Volume68
Issue number4
DOIs
Publication statusPublished - 2002

Subject classification (UKÄ)

  • Industrial Biotechnology

Keywords

  • Ethanol : metabolism
  • Fungal Proteins : genetics
  • Fungal Proteins : metabolism
  • Genetic Engineering : methods
  • Oxidation-Reduction
  • Pentosephosphate Pathway : genetics
  • Pentosephosphate Pathway : physiology
  • Recombination
  • Genetic
  • Saccharomyces cerevisiae : enzymology
  • Support
  • Saccharomyces cerevisiae : genetics
  • Fermentation
  • Non-U.S. Gov't
  • Xylose : genetics
  • Xylose : metabolism

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