中文摘要：

为提高VC二步发酵法中糖酸转化过程的产酸量，本实验室从新鲜牛奶中筛选出一株高效促产酸菌生长和产酸的伴生菌——枯草芽孢杆菌A9。在单因素试验基础上，采用响应面法对发酵培养基成分进行优化。结果表明，三-山梨糖、玉米浆、尿素的影响比较显著，最佳培养基条件为三-山梨糖90g／L、尿素12．2g／L、玉米浆14．2g／L、CaC034．1班、MgS040．2g／L，可获得2-酮基正．古龙酸产量为69．74g／L，与理论值70．33g／L的相对误差为-0．59g／L。曲面回归方程与实验结果拟合性较好，此模型合理可靠，可用于实际预测。优化后的培养基比原培养基平均提高2-KGA产量17．4％。

英文摘要：

In order to improve 2-keto-L-gulonic acid production during the conversion process from L-sorbose to 2-keto-L- gulonic acid in the two-step fermentation of vitamin C. An efficient companion strain of Bacillus subtilis A9 that facilitates the growth of Gluconobacter oxydans and the production of acids was screened from fresh milk. Based on single factor tests, the compositions of fermentation medium were optimized by response surface methodology. The results showed that three factors including L-sorbose, corn liquor and urea revealed significant impact on the production of 2-KGA. The optimal compositions included 90 g/L L-sorbose, 14.2 g/L corn liquor, 12.2 g/L urea, 4.1 g/L CaCO3 and 0.2 g/L MgSO4. Under the optimal medium, the yield of 2-keto-L-gulonic acid was up to 69.74 g/L, which was close to the theoretical value of 70.33 g/L with the relative error of --0.59 g/L. The established regression equation for 2-KGA revealed excellent fitting. Therefore, it is credible and can be used for practical prediction.