一株仅产L-乳酸的乳酸乳球菌发酵培养基的优化

为了研究一株分离自新疆牧民家庭自制酸马奶中的乳酸乳球菌KLDS 4.0325产L-乳酸的能力，以L-/D-乳酸试剂盒验证该菌种在发酵过程中所产L-乳酸的光学纯度为100%。利用Plackett-Burman设计法对影响该菌株发酵的培养基主要组分进行筛选，确定影响L-乳酸产量的主要因素为蔗糖、酵母粉、K2HPO4。在此基础上，采用响应面法优化发酵培养基的组成，结果表明：当蔗糖添加量为102.9 g/L、酵母粉添加量为2.5 g/L、K2HPO4添加量为7.9 g/L时，L-乳酸产量最大，可达86.6 g/L，在最优发酵条件下获得的实测值与模型预测值（86.3 g/L）吻合，说明所建立的模型是切实可行的。

Optimization of Fermentation Medium of Lactococcus lactis for Only L-Lactate Production

Lactococcus lactis KLDS 4.0325, a strain isolated from home-made koumiss in Xinjiang, China, was studied for
L-lactic acid production. The optical purity of the produced lactic acid was estimated to be 100% L-lactic acid using L/D-lactic
acid enzymatic test kit. The Plackett-Burman design was used to evaluate the effects of medium components on lactate
production. On the basis of statistical regression analysis, yeast extract, sucrose and K2HPO4 were found to be the most
important factors. Subsequently, response surface methodology was employed to determine the maximum lactate production
at the optimum concentrations of key factors. The lactate production was found to correlate to the three parameters. The
optimal levels of medium components were determined as 2.5 g/L yeast extract, 102.9 g/L srucose and 7.9 g/L K2HPO4. The
predicted yield of lactate using the optimized medium was 86.3 g/L, and the actual experimental result was 86.6 g/L.