Chou L S, Weimer B
Department of Nutrition and Food Sciences, Utah State University, Logan 84322-8700, USA.
J Dairy Sci. 1999 Jan;82(1):23-31. doi: 10.3168/jds.S0022-0302(99)75204-5.
Lactic acid bacteria have been reported to be useful as a health adjunct and are commonly added to food as the delivery mechanism. The literature contains many conflicting observations for their proposed benefits, and the mechanism of action is undefined. One source of variation is the large number of strains used without proper controls supplemented. Additionally, many of the organisms are not characterized for their acid shock response or the acid-tolerance response, which are known to vary among bacterial species. Our objective was to isolate acid-resistant and bile-resistant variants of Lactobacillus acidophilus and to determine the phenotypic changes. The acid- and bile-tolerant isolates were obtained using natural selection techniques after sequential exposure to hydrochloric acid (pH 3.5 to 7.0) and mixed bile salts. The acid- and bile-tolerant isolates retained their ability to grow at pH 3.5 with 0.3% bile after the selective pressure was removed and reapplied. Isolates varied from their parents for stability in freezing, lactose utilization, protease activity, aminopeptidase activity, plasmid profile, and cell-wall fatty acid profile. These data suggest that the isolated acid- and bile-tolerant isolates possess growth advantages over that of the parents under stress conditions and may be considered as candidates for probiotic strains after further characterization with animal models.
据报道，乳酸菌作为一种健康辅助物质很有用，并且通常作为递送机制添加到食品中。文献中关于其假定益处有许多相互矛盾的观察结果，且作用机制尚不明确。变异的一个来源是使用了大量未经适当对照补充的菌株。此外，许多生物体未对其酸休克反应或耐酸反应进行表征，而这些反应已知在细菌物种之间存在差异。我们的目标是分离嗜酸乳杆菌的耐酸和耐胆变体，并确定其表型变化。在依次暴露于盐酸（pH 3.5至7.0）和混合胆盐后，使用自然选择技术获得了耐酸和耐胆的分离株。在去除并重新施加选择压力后，耐酸和耐胆的分离株在pH 3.5和0.3%胆盐存在的情况下仍保持生长能力。分离株在冷冻稳定性、乳糖利用、蛋白酶活性、氨肽酶活性、质粒图谱和细胞壁脂肪酸图谱方面与其亲本不同。这些数据表明，分离得到的耐酸和耐胆分离株在应激条件下比亲本具有生长优势，经过动物模型进一步表征后可被视为益生菌菌株的候选者。
