PRODUCTION OF THE FUNGAL EXOPOLYSACCHARIDE PULLULAN BY BATCH-WISE ANDCONTINUOUS FERMENTATION

A mutant strain of the deuteromycete Aureobasidium pullulans deficient in melanin synthesis was used to investigate the production of the ex opolysaccharide pullulan and biomass, respectively. Shake-flask experi ments with different carbon sources showed significant differences in pullulan elaboration. Sucrose was most suitable for pullulan synthesis among the carbon sources examined. Fermentations were carried out bot h batch-wise and continuously in a stirred vessel fermentor. In batch fermentations about 45% of the glucose offered was converted into pull ulan at maximum formation rates of 0. 16 g/l per hour using standard m edium. The yield of polysaccharide could be maintained at 45% in conti nuous fermentations. At a dilution rate of 0.05 1/h, the formation rat e of polysaccharide increased up to 0.35 g/l per hour. Alterations in the nitrogen content of the feed significantly affected the consumptio n rate of glucose and the production rate of polysaccharide, but final concentrations of biomass were hardly affected.