Production of xylitol and ethanol and activity of the key enzymes of D-xylose consumption in Pachysolen tannophilus mutant strains

Production of xylitol and ethanol, as well as activities of the key enzymes of D-xylose consumption, were studied in Pachysolen tannophilus mutants with altered growth on D-xylose, xylitol, ethanol, or D-glucose as sole carbon sources. Suppressed activity of xylose reductase with preferential affinity for NADPH and of xylitol dehydrogenase to 4.40 and 4.80 μmol mg−1 min−1, respectively, resulted in accumulation of xylitol (0.25 g per 1 g D-xylose consumed). The highest levels of NADH/NADPH-xylose reductase and xylitol dehydrogenase (6.00–6.80 and 6.80–8.40 μmol mg−1 min−1, respectively) were found in the strains producing 0.24–0.26 g ethanol per 1 g D-xylose. Application of Pa. tannophilus mutants for analysis of the regulation of D-xylose catabolism in yeasts is discussed.