Response surface optimization of antidipteran delta-endotoxin production by Bacillus thuringiensis subsp. israelensis HD 500

Response surface optimization of Bacillus thuringiensis subsp. israelensis HD 500 fermentation for the production of its toxin proteins Cry4Ba and Cry11Aa was performed. Since the interaction of the medium components as well as cultivation conditions were expected to influence the production of the toxin proteins, an experimental chart was prepared by accepting the previously reported optimal values for the most important parameters as zero points: [Mn], 10−6 M; [K2HPO4], 50 mM; C:N ratio, 20:1 and incubation temperature; 30 °C. When the combinations of these variables at different levels were studied at 30 batch cultures and analysed for the optimum toxin protein concentrations: temperature, 28.3 °C; [Mn], 3.3 × 10−7 M; C:N ratio, 22.2 and [K2HPO4], 66.1 mM yielded the highest concentrations of both Cry4Ba and Cry11Aa toxin proteins.