Utilization of corn steep liquor for biosynthesis of pullulan, an important exopolysaccharide

Five different agricultural wastes viz. rice bran oil cake, soya bean oil cake, cotton seed oil cake, mustard seed oil cake and corn steep liquor (CSL) were evaluated for their use as nutrient along with 15% (w/v) glucose as carbon source for biosynthesis of pullulan using Aureobasidium pullulans RBF 4A3. Among the selected agricultural wastes, CSL was found to be the best and supported production of 77.92gL(-1) pullulan under un-optimized conditions. Single point optimization technique resulted in increase in 18% pullulan (88.59gL(-1)) production. The process was successfully validated in a 7-L fermenter and a process economic analysis has suggested that use of CSL as nutrient may result in 3-fold reduction of cost of raw materials for pullulan production as compared to a process where conventional nitrogen sources were used. These observations may be helpful in development of a cost effective process for pullulan production.