College of Food Science and Nutritional Engineering, China Agricultural Univ., Haidian District, Beijing 100083, People's Republic of China.
J Food Sci. 2009 Aug;74(6):M328-34. doi: 10.1111/j.1750-3841.2009.01237.x.
The tolerance of lactic acid bacteria (LAB) from kefir grains to gastrointestinal tract conditions was evaluated in vitro. The effects of pH values and bile salts on the viability of LAB were investigated. The results demonstrated that pH value showed a significant effect on the viability. The viable counts exhibited a reduction of 1.5 to 2 log cycles in 0.3% to 0.5% bile salts after 4 h. The viability of LAB exposure to sequential simulated gastric and intestinal juices was assessed by response surface model (RSM). RSM indicated that the gastric pH and gastric contact time significantly affected the viability (P < 0.05), while the effect of intestinal contact time was not significant. Moreover, RSM revealed the interactions of pH and gastric contact time, and of pH and intestinal contact time. The LAB cells, temporarily damaged by the low pH of gastric juice (pH < 2), could recover in the intestinal juice; and the longer the intestinal contact time, the higher the viability of LAB. RSM proved to be a useful and accurate method to predict the viability of LAB under certain laboratory conditions by the model validation. This study indicated that LAB from kefir grains exhibited excellent tolerance to sequential simulated gastrointestinal tract conditions, and that kefiran possessed a significant protective effect on LAB in hostile environments.
体外评估了来自克菲尔粒的乳酸菌（LAB）对胃肠道条件的耐受性。研究了 pH 值和胆汁盐对 LAB 活力的影响。结果表明，pH 值对活力有显著影响。在 0.3%至 0.5%胆汁盐作用 4 小时后，活菌数减少了 1.5 至 2 个对数周期。通过响应面模型（RSM）评估 LAB 暴露于连续模拟胃液和肠液后的活力。RSM 表明，胃 pH 值和胃接触时间显著影响活力（P < 0.05），而肠接触时间的影响不显著。此外，RSM 揭示了 pH 和胃接触时间以及 pH 和肠接触时间之间的相互作用。LAB 细胞在胃酸（pH < 2）的低 pH 值下受到暂时损伤，但可在肠液中恢复；肠接触时间越长，LAB 的活力越高。通过模型验证，RSM 证明了一种在特定实验室条件下预测 LAB 活力的有用且准确的方法。该研究表明，来自克菲尔粒的 LAB 对连续模拟胃肠道条件具有优异的耐受性，并且在恶劣环境中，青稞壳聚糖对 LAB 具有显著的保护作用。
