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

Abstract:

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.

Key words:L. casei Zhang, High cell density culture, Cultural condition