优化益生菌Lactobacillus casei Zhang高密度培养条件

为实现L. casei Zhang的高密度培养，在之前优化增殖培养基的基础上进一步寻求适宜该菌的培养条件。研究了不同中和剂、缓冲盐浓度、葡萄糖浓度、pH值控制、通气条件和补料分批培养对菌体在恒pH条件下发酵的影响，根据不同条件下菌体的比生长速率、菌体密度和活菌数情况，确定L. casei Zhang较适宜的高密度培养条件为：培养基葡萄糖浓度为80 g/L~100 g/L，以氨水为中和剂使pH保持5.9，采用间歇通氮气的方法保持环境厌氧，分批培养方式下37°C保温发酵10 h~12 h后，L. casei Zhang细胞干重达到7 g/L，活菌数3.5×1010 CFU/mL，比优化前提高7倍以上，能够满足益生菌制品生产要求的高菌体密度。

Optimization of Cultural Conditions of Probiotic Bacteria Lactobacillus casei Zhang for High Cell Density Cultivation

To get high cell density, pH-stat fermentations of L. casei Zhang were carried out in the medium optimized previously under different cultural conditions. The influences of neutralizing agents, the concentration of buffer salts and glucose in the medium, pH, aeration and fed batch fermentation on the growth of L. casei Zhang were investigated. Based on the values of maximum specific growth rate, biomass and viable cells count in different cultural conditions, the optimal growth condition was regarded as follows: Glucose level of the medium was 80 g/L ~100 g/L; The pH was kept constant at 5.9 with aqua ammonia and anaerobic condition was kept by sparged with nitrogen periodically; The temperature was set at 37°C and cultured for 10 h ~12 h. The biomass and viable cells' number of L. casei Zhang under this culture conditions were 7 g/L and 3.5×1010 CFU/mL respectively, and were 7 times as high as that before optimized, which can meet the requirements of probiotics.