INFLUENCE OF CULTURE PH AND AERATION ON ETHANOL-PRODUCTION AND PULLULAN MOLECULAR-WEIGHT BY AUREOBASIDIUM-PULLULANS

The formation of ethanol by the polymorphic fungus Aureobasidium pullu lans was examined under a range of culture pH values and aeration cond itions. Although culture pH had a profound effect on fungal morphology , with a greatly increased proportion of the biomass in the unicellula r (yeast-like) form at pH 6.5, there appeared to be no direct link bet ween morphological form and ethanol formation. The levels of ethanol n oted may have influenced the morphology. Cessation of aeration rapidly led to a halt in growth and exopolysaccharide synthesis, while ethano l synthesis proceeded rapidly. The ethanol formed could be re-oxidised under conditions where the available carbon source was depleted. Two distinct exopolysaccharides of different molecular weights were recove red from the culture fluids. Overall, the molecular weight of both dec lined with process time.