Abstract:

This experimental work was primarily on the fermentation techniques of lactic acid，trying to enhance the production of lactic acid by mutation of the strain and optimization of the culture medium. The final concentration of L-lactic acid in the broth was 18.5 g/L using the basic medium with the original strain，and the conversion rate based on glucose was 50.27%. A high-yield strain was screened out by laser mutation from original strain，which was named DBLB28. The culture medium was optimized after screening out the high-yield strain. Several factors that had important effects on lactic acid fermentation were chosen by orthogonal experiment design. Then they were optimized by response surface methodology（RSM），and the regression equation was proved to be effective after analysis of variance. Finally，the optimized condition was as follows：glucose concentration 68.6 g/L，beef extract concentration 22.4 g/L，peptone concentration 23.2 g/L. The concentration of lactic acid production was 29.0 g/L from the regression equation，and the data from experiment was 29.4 g/L.

摘要：

本实验在选育高产菌株及优化培养基的基础上，通过探索德氏乳杆菌的发酵工艺提高其乳酸产量。用初始菌株在基础发酵培养基上进行乳酸（DL-乳酸）发酵，其中L-乳酸的产量为18.5 g/L，对葡萄糖的转化率为50.27%。对原始菌株进行了激光诱变，选育出一株高产菌株DBLB28，对其培养基进行了进一步优化。先用正交实验设计法选出了主要的影响因子，然后再利用响应面法对所选因子进行优化，最优的条件为：葡萄糖浓度68.6 g/L；牛肉膏浓度22.4 g/L；蛋白胨浓度3.2 g/L，从回归方程预计乳酸的最大产量为29.0 g/L。在以上优化条件下进行发酵实验，测得乳酸产量为29.4 g/L，与预计值吻合较好。