Optimization of mineral salts in medium for enhanced production of pullulan by Aureobasidium pullulans HP-2001 using an orthogonal array method

Abstract

Based on intuitive analyses and statistical calculations using data from orthogonal array experiments, the optimal concentrations of K2HPO4, NaCl, MgSO4·7H2O, and (NH4)2SO4 in cell growth medium of Aureobasidium pullulans HP-2001 were measured as 7.5, 1.0, 0.1, and 2.4 g/L, respectively, whereas those for the production of pullulan were 2.5, 0.25, 0.8, and 0.3 g/L, respectively. The most important factor for cell growth and production of pullulan by A. pullulans HP-2001 was identified as K2HPO4. Optimal concentrations of glucose and yeast extract, along with the initial pH of the cell growth medium of A. pullulans HP-2001 containing optimized salt concentrations, were found to be 100.0, 10.0, and 6.0 g/L, respectively, whereas those for the production of pullulan were 100.0, 2.5, and 6.0 g/L, respectively. Conversion rates of pullulan from 10.0, 25.0, 50.0, 75.0, and 100.0 g/L of glucose in the presence of optimized salt concentrations were 26.0, 25.2, 22.4, 17.9, and 14.1%, respectively, whereas those in the presence of previously reported salt concentrations were 26.6, 25.2, 19.9, 14.3, and 11.7%, respectively. Optimal salt concentrations for the production of pullulan by A. pullulans HP-2001 varied according to the concentrations of the carbon and nitrogen sources, especially at higher concentrations.