TY - JOUR
T1 - Reduced oxidative pentose phosphate pathway flux in recombinant xylose-utilizing Saccharomyces cerevisiae strains improves the ethanol yield from xylose.
AU - Jeppsson, Marie
AU - Johansson, Björn
AU - Hahn-Hägerdal, Bärbel
AU - Gorwa-Grauslund, Marie-Francoise
PY - 2002
Y1 - 2002
N2 - 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.
AB - 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.
KW - Ethanol : metabolism
KW - Fungal Proteins : genetics
KW - Fungal Proteins : metabolism
KW - Genetic Engineering : methods
KW - Oxidation-Reduction
KW - Pentosephosphate Pathway : genetics
KW - Pentosephosphate Pathway : physiology
KW - Recombination
KW - Genetic
KW - Saccharomyces cerevisiae : enzymology
KW - Support
KW - Saccharomyces cerevisiae : genetics
KW - Fermentation
KW - Non-U.S. Gov't
KW - Xylose : genetics
KW - Xylose : metabolism
U2 - 10.1128/AEM.68.4.1604-1609.2002
DO - 10.1128/AEM.68.4.1604-1609.2002
M3 - Article
VL - 68
SP - 1604
EP - 1609
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
SN - 0099-2240
IS - 4
ER -