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


Abstract: 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^{-1} and a pullulan concentration of 16.7 g l^{-1} were obtained in synthetic medium whereas 35.0 g l^{-1} of polysaccharide and 16.9 g l^{-1} of pullulan were obtained in molasses medium containing 50 g l^{-1} 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^{-1} and a pullulan concentration of 6.6 g l^{-1} were obtained in a stirred tank bioreactor with synthetic medium. These concentrations were lower than those in shake flask culture.

Keywords: pullulan, beet molasses, synthetic medium, Aureobasidium pullulans

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