Optimization of fermentation medium of Cytophaga sp. CX08 producing marine low-temperature raw starch glucoamylase

In order to improve the ability of strain to produce raw starch glucoamylase, the liquid fermentation was carried out with Cytophaga sp. CX08 as strain. Using the activity of raw starch glucoamylase as the response value, the compositions of fermentation medium were optimized by Plackett- Burman (PB) tests, the steepest climbing tests and Box-Behnken (BB) tests. The results showed that the optimal medium compositions for raw starch glucoamylase production were corn starch 42 g/L, NaNO₃ 4 g/L, K₂HPO₄ 3 g/L, KCl 0.4 g/L, MgSO₄·7H₂O 0.5 g/L and FeSO₄·7H₂O 0.02 g/L. Under these optimized conditions, the activity of raw starch glucoamylase produced by the strain was the highest, which was 168.31 U/ml and 1.61 times higher than that before optimization.