A D-xylose reductase mutant of Pachysolen tannophilus was isolated on the basis of its poor growth on D-xylose but normal growth on xylitol and D-glucose. Fractionation of cell extracts indicated that the mutant was deficient in D-xylose reductase activity that used NADPH exclusively as a cofactor, but not in activity that used both NADH and NADPH. Mutant cultures grown on D-xylose as the sole carbon source exhibited some properties that would be desired in improved strains. Growth rate, growth

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... yield, and D-xylose consumption rate of the mutant were less sensitive than those of the wild type to changes in aeration rate. D-Xylose was utilized more efficiently in that less of a by-product, xylitol, was produced. In addition, under low aeration conditions, more ethanol was produced. A disadvantage was a relatively slow rate of D-xylose utilization.