Statistical Optimization of Medium for Pullulan Production by Aureobasidium pullulans NCPS2016 Using Fructose and Soybean Meal Hydrolysates

Pullulan, with its excellent characteristics of film-forming, water solubility, and biodegradability, is attracting more and more attention in agricultural products preservation. However, high pullulan production cost largely restricts its widely application due to its low production. In order to improve pullulan production by Aureobasidium pullulans NCPS2016, the medium was optimized using single factor experiment and response surface methodology. Based on the single factor experiments, the contents of soybean meal hydrolysates (SMHs), (NH4)2SO4, and K2HPO4·3H2O were considered to be main factors influencing the extracellular polysaccharide (EPS) production, and were further optimized by Box–Behnken design. The optimal content of SMHs of 7.71 g/L, (NH4)2SO4 of 0.35 g/L, and K2HPO4·3H2O of 8.83 g/L were defined. Finally, EPS production of 59.8 g/L was obtained, 39% higher in comparison with the production in the basal medium. The purified EPS produced by NCPS2016 was confirmed to be pullulan. This is the first time fructose is reported to be the optimal carbon source for pullulan production by Aureobasidium pullulans, which is of great significance for the further study of the mechanism of the synthesis of pullulan by NCPS2016. Also, the results here have laid a foundation for reducing the industrial production cost of pullulan