Aerobic fermentation of D-xylose to ethanol by Clavispora sp.

Abstract

Eleven strains of an undescribed species of Clavispora fermented D-xylose directly to ethanol under aerobic conditions. Strain UWO(PS)83-877-1 was grown in a medium containing 2% D-xylose and 0.5% yeast extract, and the following results were obtained: ethanol yield coefficient (ethanol/D-xylose), 0.29 g g-1 (57.4% of theoretical); cell yield coefficient (dry biomass/D-xylose), 0.25 g g-1; maximum ethanol concentration, 5.9 g liter-1; maximum volumetric ethanol productivity, 0.11 g liter-1 h-1. With initial D-xylose concentrations of 40, 60, and 80 g liter-1, maximum ethanol concentrations of 8.8, 10.9, and 9.8 g liter-1 were obtained, respectively (57.2, 57.1, and 48.3% of theoretical). Ethanol was found to inhibit the fermentation of D-xylose (K(p) = 0.58 g liter-1) more than the fermentation of glucose (K(p) = 6.5 g liter-1). The performance of this yeast compared favorably with that reported for some other D-xylose-fermenting yeasts.