Production of Pullulan From Beet Molasses and Synthetic Medium by Aureobasidium pullulans

The production of pullulan from molasses and synthetic medium by Aureobasidium pullulans P56 in batch culture was investigated. Among the pretreatments of molasses used to increase polysaccharide production, sulfuric acid + activated carbon treatment gave better results with regard to polysaccharide concentration, polysaccharide yield and sugar utilization. A maximum polysaccharide concentration of 21.4 g l and a pullulan concentration of 16.7 g l were obtained in synthetic medium whereas 35.0 g l of polysaccharide and 16.9 g l of pullulan were obtained in molasses medium containing 50 g l of initial sugar at pH 7.5. The highest pullulan contents of the crude polysaccharide were 85.3 and 48.3% for synthetic medium and molasses medium, respectively and this showed that A. pullulans produced a mixture of pullulan and other polysaccharides in molasses medium. The experiments performed with synthetic medium showed that higher initial sugar concentrations led to a significant decrease in pullulan yield. A polysaccharide concentration of 20.4 g l and a pullulan concentration of 6.6 g l were obtained in a stirred tank bioreactor with synthetic medium. These concentrations were lower than those in shake flask culture.