响应面法优化枯草芽孢杆菌产γ-聚谷氨酸发酵工艺

以1 株谷氨酸依赖型γ-聚谷氨酸（poly-γ-glutamic acid，γ-PGA）产生菌Bacillus subtilis GXA-28为研究对象，利用响应面法系统优化其γ-聚谷氨酸发酵培养基成分。通过单因素试验、Plackett-Burman试验、最陡爬坡试验以及Box-Behnken试验构建响应方程，利用该方程预测得到最优培养基：蔗糖33.65 g/L、酵母膏0.4 g/L、NH4Cl 1.6 g/L、谷氨酸钠15 g/L、 KH2PO4 0.4 g/L、K2HPO4·3H2O 1.68 g/L、MgSO4·7 H2O 0.1 g/L、MnSO4·H2O 0.04 g/L。利用优化培养基，在40.2 ℃、160 r/min条件下摇瓶发酵22 h，γ-PGA产量达到16.63 g/L，底物谷氨酸钠转化率比优化前提高了20%，达到100%。

Optimization of Medium Composition and Fermentation Conditions by Response Surface Methodology for theProduction of Poly-γ-Glutamic Acid by Bacillus subtilis

Poly-γ-glutamic acid, as a high molecular polymer produced by microorganism, is widely used in industry,
agriculture, food, medicine and cosmetics. This study aimed to use response surface methodology for a systematic
optimization of fermentation medium composition for the production of poly-γ-glutamic acid by a glutamic aciddependent
strain of Bacillus subtilis GXA-28. A response surface regression equation was established based on the
results of one-factor-at-a-time, Plackett-Burman, steepest ascent and Box-Behnken experimental designs. The optimal
medium formulation, as predicted from the equation, consisted of 33.65 g/L sucrose, 0.4 g/L yeast extract, 1.6 g/L
NH4Cl, 15 g/L monosodium glutamate, 0.4 g/L KH2PO4, 1.68 g/L K2HPO4·3H2O, 0.1 g/L MgSO4·7H2O and 0.04 g/L
MnSO4·H2O. The yield of poly-γ-glutamic acid reached 16.63 g/L, which was 20% higher than before the optimization,
and the conversion rate of the substrate glutamate reached 100% by using the optimized medium at 40.2 ℃ with shaking at
a speed of 160 r/min for 22 h.