Elevation of glucose 6-phosphate dehydrogenase activity increases xylitol production in recombinant Saccharomyces cerevisiae

To increase the NAD(P)H-dependent xylitol production in recombinant Saccharomyces cerevisiae harboring the xylose reductase gene from Pichia stipitis, the activity of glucose 6-phosphate dehydrogenase (G6PDH) encoded by the ZWF1 gene was amplified to increase the metabolic flux toward the pentose phosphate pathway and NADPH regeneration. Compared with the control strain, the specific G6PDH activity was enhanced approximately 6.0-fold by overexpression of the ZWF1 gene. Amplification in the G6PDH activity clearly improved the NAD(P)H-dependent xylitol production in the recombinant S. cerevisiae strain. With the aid of an elevated G6PDH level, maximum xylitol concentration of 86 g/l was achieved with productivity of 2.0 g/l h in the glucose-limited fed-batch cultivation, corresponding to 25% improvement in volumetric xylitol productivity compared with the recombinant S. cerevisiae strain containing the xylose reductase gene only.