D-XYLOSE METABOLISM IN AUREOBASIDIUM-PULLULANS - EFFECTS OF AERATION AND VITAMINS

The yeast-like organism Aureobasidium pullulans efficiently converted D-xylose to cell mass (Y(X/S) = 0.45 g . g-1) with negligible production of polyols (Y(P/S) = 0.003 g . g-1) under aerobic conditions. A. pullulans grown semiaerobically exhibited different fermentation capacities in seven basal (vitaminless) medium and medium containing a mixture of seven vitamins. It was found that under semiaerobic conditions a mixture of vitamins significantly enhanced production of ethanol from D-xylose, resulting in a 15-fold higher yield coefficient of ethanol (Y(E/S) = 0.22 g . g-1) as compared to that achieved in vitaminless medium. This increase in ethanol production was accomplished at the expense of cell mass. A. pullulans produced extremely low amounts of polyols throughout all aerobic and semiaerobic experiments. A. pullulans displayed strictly NADPH-linked xylose reductase and NAD+-linked xylitol dehydrogenase activities.