Abstract:

A cost-effective culture medium for shake flask fermentation of Bacillus amyloliquefaciens subsp. plantarum BGP20
was developed by optimizing the medium components using response surface methodology. First, based on the results of
univariate analysis and Plackett-Burman design experiments, defatted soy flour and cornstarch were identified as two key medium
components. Then a central composite design was applied to fit the relationship between these two components and optimal levels
of BGP20 cell growth. The results showed that the regression model had a high fitting degree. The optimal medium components
were 16.03 g/L defatted soy flour, 6.30 g/L cornstarch, 0.75 g/L MgSO4·7H2O, 1.25 g/L NaCl, 0.75 g/L KH2PO4 and 15 mL/L trace
elements. The maximum predicted value from the regression model was 1.985 × 109 CFU/mL, and the actual value observed in
validation experiments was 93.72% as compared to the predicted value. These results demonstrate that the regression model is of
great guiding significance for commercial fermentation of BGP20.

Key words: Bacillus amyloliquefaciens subsp. plantarum, fermentation medium, cell concentration, response surface methodology, regression model