Abstract: The optimal fermentation conditions for the genetically engineered recombinant bacterium with amylomaltase gene conserved in our laboratory were explored in this study. One-factor-at-a-time investigations showed that the optimal fermentation culture medium was composed of 0.025 g/mL molasses, 0.015 g/mL tryptone, MgSO4 ·7H2O/K2HPO4 ratio of 7:1, and 0.5 g/L FeSO4 ·7H2O. The optimal fermentation conditions determined based on gucose oxidase activity were 100 mL of medium in a 250 mL flask, shaking speed of 200 r/min, inoculum amount of 5%, initial pH of 7.0, fermentation temperature of 37 ℃, addition of the inducer IPTG at OD600nm ＝ 0.6, induction temperature of 30 ℃, induction period of 5 h and inducer concentration of 1 mmol/L. Under the optimal conditions, the amylomaltase activity was 950 U/mL, which was improved by 7 times compared with non-optimization conditions.

Key words: amylomaltase, fermentation condition, optimization