Optimization of γ-PGA fermentation condition with Bacillus subtilis by response surface methodology

The fermentation condition of γ-poly(glutamic acid)(γ-PGA) by Bacillus subtilis was optimized.Using single factorial experiments,sources of carbon,nitrogen and inorganic ions were determined as corn flour saccharification liquor,peptone,glutamate,KH2PO4,MgCl2,MnCl2,and NaCl.Three significant factors,peptone,glutamate and NaCl,were screened by Plackett-Burman design.The optimal region of γ-PGA production was found by steepest ascent approach.The optimal combined concentration for maximum γ-PGA production was determined by response surface methodology as: 0.54% Peptone,8.13% Glutamate and 0.96% NaCl.The production level was increase to 14.10 g/L.