乳脂乳球菌CH5生长特性的研究

Growth Characteristics of Lactococcus lactis ssp. cremoris Strain CH5 in Reconstituted Skim Milk

本文以农家干酪生产使用的乳脂乳球菌(Lactococcus lactis ssp.cremoris)为研究对象,从细菌总数(CFU),pH值和滴定酸度三个指标对本实验室分离得到的乳脂乳球菌CH5在脱脂乳中的生长特性和4℃下保存过程中的活力变化进行了研究。结果表明乳脂乳球菌CH5在脱脂乳中的延滞期短,能较快进入对数生长期,6h时进入稳定期,活菌数达109CFU/ml,Tdg约为1.03h,Tda约为2.87h,这表明乳脂乳球菌CH5细胞增长速度快于产酸速率。乳脂乳球菌CH5在4℃下保存时,稳定性较好,前11d活菌数和最大产酸速率(μacid)基本保持不变,此后逐渐下降,表明CH5发酵剂在前11d的活力比较稳定,可以确定生产农家干酪的CH5母发酵剂的最佳传代时间为11d,冷却保藏第3d为最佳生产使用时间。

Using acid producing bacteria-Lactococcus lactis ssp. cremoris which is often used in cottage cheese making as research object, the growth characteristics of Lactococcus lactis ssp. cremoris strain CH5 in reconstituted skim milk (RSM) and changes of starter activity under 4℃ during storage were studied with three factors including CFU, pH and titrable acidity. The results showed that: the lag phase of strain CH5 in RSM was very short, the population of viable cell of which could reach 109CFU/ml; in the stationary phase. The doubling time for growth (Tdg) was about 1.03h and doubling time for lactic acid production (Tda) was about 2.87h, showed the efficient cell growth, not the acid production, a desirable property during bulk culture preparation. During storage under 4℃, the maximum acidification rate (μacid) appeared on 3d, and the viable cell counts and μacid did not show significant changes before 11d. It suggested that the mother culture prepared by CH5 strain could be maintained per 11d, and the optimum stage for bulk culture started from the 3rd day of cold storage.