SUBSTRATE REGULATION AND SPECIFICITY OF AMYLASES FROM AUREOBASIDIUM STRAIN NRRL Y-12,974

Pullulan is an industrial biopolymer produced by the yeast-like fungus Aureobasidium, usually by direct fermentation of starch. Despite evidence that autogenous amylases produced during these fermentations are detrimental to the final molecular mass of the product, fundamental studies of these enzymes have not been reported. Total extracellular amylases were studied from the promising production strain NRRL Y-12,974. Growth rates and yields were equivalent in cultures grown on glucose, maltose, soluble starch, or cornstarch. Total amylase levels were low and varied only three-fold, from 0.01 IU ml-1 in glucose-grown cultures to 0.03 IU ml-1 in soluble-starch-grown cultures. All cultures showed both alpha-amylase activity and activity against pullulan. Synthetic oligosaccharide substrates were apparently attacked by an alpha-glucosidase, produced in highest levels by maltose-grown cultures.