Abstract: The aim of this study is to optimize the fermentation medium for enhancing pullulan production by Aureobasidium pullulans. Important medium components affecting pullulan production were identified by one-factor-at-a-time analysis and further optimized by response surface analysis based on a Box-Behnken design. Sucrose (carbon source) and yeast extract (nitrogen source) concentration and metal ion type had significant effects on pullulan production (P ＜ 0.05). There was a significant interaction effect between sucrose and yeast extract concentration, but no significant interaction effects were observed between metal ion type and sucrose or yeast extract concentration. The optimized fermentation medium was composed of 56.63 g/L sucrose, 3.74 g/L yeast extract and Mg2+, resulting in a pullulan yield of 60.358 g/L.

Key words: pullulan, sucrose, yeast extract, metal ion, response surface methodology