Occhino L A, Morris H A, Savaiano D A
J Dairy Sci. 1986 Oct;69(10):2583-8. doi: 10.3168/jds.S0022-0302(86)80704-4.
Six Streptococcus thermophilus strains were examined for growth, acid production, and beta-galactosidase activity per milligram protein (specific activity), so that strain comparisons could be made. A wide range in activity was observed. Activity depended on growth time in M17 broth and, for most strains, continued to increase after cells had reached stationary phase. Maximum activity was at 16 h and ranged from 0 to 58 units/mg protein. Strain ST exhibited no beta-galactosidase activity but had trace phospho-beta-galactosidase activity (.8 units/mg protein after 2 h of growth). Strains 3641 and TS2B exhibited slower growth rates and lower beta-galactosidase activities in milk as compared to M17 broth. Further, strain 3641 exhibited 10 times the activity of strain TS2B (2.86 vs. .24 units) after 4 h of growth in milk.
检测了六株嗜热链球菌的生长、产酸以及每毫克蛋白质的β-半乳糖苷酶活性（比活性），以便进行菌株比较。观察到活性范围很广。活性取决于在M17肉汤中的生长时间，并且对于大多数菌株来说，在细胞达到稳定期后仍继续增加。最大活性出现在16小时，范围为0至58单位/毫克蛋白质。菌株ST没有β-半乳糖苷酶活性，但有微量的磷酸-β-半乳糖苷酶活性（生长2小时后为0.8单位/毫克蛋白质）。与M17肉汤相比，菌株3641和TS2B在牛奶中的生长速率较慢，β-半乳糖苷酶活性较低。此外，在牛奶中生长4小时后，菌株3641的活性是菌株TS2B的10倍（2.86对0.24单位）。
