Brashears M M, Gilliland S E
Department of Animal Science, Oklahoma State University, Stillwater 74078, USA.
J Dairy Sci. 1995 Nov;78(11):2326-35. doi: 10.3168/jds.S0022-0302(95)76859-X.
Cells of Lactobacillus acidophilus propagated in peptonized milk nutrient broth maintained at pH 5 were harvested during the late logarithmic (log) phase and at 6 h into the stationary phase of growth. Concentrated cultures were prepared from each age of cells, frozen, and stored at -196 degrees C. The concentrated cultures were assayed for numbers of total and bile-tolerant lactobacilli, beta-galactosidase activity, and ability to assimilate cholesterol before and after storage at -196 degrees C. Nonfermented acidophilus milk, prepared following 28 d of storage at -196 degrees C from each concentrated culture, was tested before and after 0, 7, 14, 21, and 28 d of storage at 7 degrees C. No decrease in numbers of total or bile-tolerant lactobacilli, beta-galactosidase activity, or amount of cholesterol assimilated was observed for any of three strains studied during storage at -196 degrees C. There were no significant differences between the two harvest times during storage at this temperature for any of the three strains. However, when the cells were suspended in milk and stored at 7 degrees C, the numbers of total and bile-tolerant lactobacilli declined over time as did the beta-galactosidase activity and the ability to assimilate cholesterol. The cells from L. acidophilus 223, harvested 6 h into the stationary phase, exhibited significantly less decrease in total numbers during extended storage at 7 degrees C than did the cells harvested in the late logarithmic phase. There was little or no difference in the decline in numbers of total lactobacilli between the two harvest times for strains 606 and 107. All strains decreased significantly in beta-galactosidase activity and the ability to assimilate cholesterol during storage in milk at 7 degrees C with no significant differences between the two harvest times.
在pH值为5的蛋白胨化牛奶营养肉汤中培养的嗜酸乳杆菌细胞，在对数生长后期和生长稳定期6小时时收获。从每个细胞生长阶段制备浓缩培养物，冷冻并储存在-196℃。在储存在-196℃之前和之后，对浓缩培养物进行总乳酸菌和耐胆汁乳酸菌数量、β-半乳糖苷酶活性以及同化胆固醇能力的测定。从每种浓缩培养物在-196℃储存28天后制备的未发酵嗜酸乳杆菌奶，在7℃储存0、7、14、21和28天之前和之后进行测试。在所研究的三株菌株中，在-196℃储存期间，未观察到总乳酸菌或耐胆汁乳酸菌数量、β-半乳糖苷酶活性或同化胆固醇量的减少。在该温度下储存期间，这三株菌株中的任何一株在两个收获时间之间均无显著差异。然而，当细胞悬浮在牛奶中并在7℃储存时，总乳酸菌和耐胆汁乳酸菌数量随时间下降，β-半乳糖苷酶活性和同化胆固醇的能力也下降。在稳定期6小时收获的嗜酸乳杆菌223细胞，在7℃长期储存期间，其总数的减少明显少于对数生长后期收获的细胞。对于菌株606和107，两个收获时间之间总乳酸菌数量的下降几乎没有差异。在7℃牛奶储存期间，所有菌株的β-半乳糖苷酶活性和同化胆固醇的能力均显著下降，两个收获时间之间无显著差异。
