RESUMEN
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 concen-tration 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 anae-robic condition was kept by sparged with nitrogen periodically;The temperature was set at 37?C and cul-tured 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.