干酪乳杆菌浓缩发酵剂乳清增菌培养基的优化

Optimization of whey medium for cell growth of Lactobacillus casei as concentrated starter

利用乳清为基本培养基原料培养干酪乳杆菌(Lactobacillus casei STL3102),用于生产浓缩发酵剂。采用Plackett-Burman设计对影响L.casei STL3102菌体生长的培养基成分进行了评价,从7个相关的培养基营养因子中筛选,确定了乳清、牛肉膏和酵母粉为关键影响因子。采用响应曲面法对影响菌体增殖的关键因子最佳水平进行了优化。通过建立的二次模型方程得到最优培养基组成为,乳清59.43g/L、牛肉膏8.44g/L、酵母粉8.85g/L,初始pH值为7.0。通过验证试验证实了模型的预测值与实际值之间吻合较好。不同缓冲盐对菌体增殖影响的实验结果表明,磷酸氢二钾对菌体的增殖较好,确立了培养基缓冲盐成分为磷酸氢二钾3.48g/L。采用优化后的乳清培养基,3%接种量,35℃培养16h,活菌数达3.31×109cfu/mL。

Whey was used as the basic medium for strain Lactobacillus casei STL3102 inoculation for production of concentrated starter. Effect of 7 nutrional factors in whey medium on growth of L. casei STL3102 was evaluated by Plackett-Burman design. It is showed that whey, beef extract and yeast extract were key factors. The optimum levels of three key factors were determined by response surface methodology design. Based on quadratic regression equation, the optimum medium is 59.43 g/L whey, 8.44 g/L beef extract, and 8.85 g/L yeast extract with initial pH at 7.0. Effect of different buffer salts on cell growth indicated that K2HPO4 was the best, and the optimum concentration is 3.48 g/L. The viable cells concentration of strata L. casei could reach 3.31 × 10^9 cfu/ml with the optimized medium when cultivated under 35℃ for 16h at 3% inoculation.