直投式酸奶发酵剂高密度培养工艺的研究

Study on high cell density culture conditions of DVS yogurt starter cultures

以实验室筛选获得的适于发酵生产用的直投式酸奶发酵剂菌株组合保加利亚乳杆菌L.b-23和嗜热链球菌S.t-14为材料,对其高密度培养工艺进行了研究。结果发现,按球菌:杆菌=1:1的混合培养比例,pH6.6～6.8,转速85～100r/min,42℃培养18h后,活菌数达到1.27×109cfu/mL;菌悬液经1.8%海藻糖、0.25%甘油、5.5%谷氨酸钠和0.5%吐温80保护剂处理,冷冻干燥后获得的发酵剂活菌数达到3.35×1011cfu/g。

Lactobacillus bulgaricus L.b-23 and Streptococcus thermophilus S.t-14,which had been isolated and identified in our laboratory,were used for the production of DVS yogurt starter cultures.The optimum fermentation condition was studied.For strains L.b-23：S.t-14 of 1：1,pH varied from 6.6～6.8,shaker s rotating speed 85～100r/min,42℃ for 18h,the cell population was up to 1.27×109cfu /mL.The cryoprotectants consisting of trehalose （1.8%）,glycerin （0.25%）,glutamate-Na （5.5%） and Tween 80 （0.5%） was added to the suspension, Owing to the cryoprotectants produced a very positive effect on promoting the viability of the paired strains L.b-23-S.t-14,the cells of the production were 3.35 ×10^11cfu/g after freeze-drying treatment.