Optimization of fermentation medium for γ-PGA with response surface method

Production of γ-polyglutamic acid by fermentation with screened Bacillus subtilis and optimization of fermentation medium was studied.Reference ranges of each factor were firstly determined with single factorial experiment and three major factors significantly affected production of γ-PGA,which were yeast extracts,sodium glutamate and CaCl2 were determined by Plackett-Burman design.The optimum fermentation conditions were optimized with Box-Behnken experiment and the largest regional of γ-PGA production was approach with the steepest ascent experiment.The optimum composition of medium was addition of yeast extract,sodium glutamate and CaCl2 was 4.18g/L,76.89g/L and 0.1422g/L,respectively.Under the optimum fermentation medium conditions,production of γ-PGA was 43.26g/L,increased 1.035 times to that of using initial medium.