College of Food Science and Engineering, Northwest A&F University, Yangling, 712100, China.
Appl Microbiol Biotechnol. 2018 Feb;102(4):1903-1910. doi: 10.1007/s00253-018-8742-x. Epub 2018 Jan 12.
A new in vitro method was developed to determine the bile tolerance of potentially probiotic lactobacilli. The overnight culture of various lactobacilli strains was inoculated into sterile, half-strength MRS broth supplemented with and without 0.3% (wt/vol) oxgall, buffered with 0.1 M sodium phosphate buffer at a final pH of 7.3, and incubated at 37 °C for 12 h under anaerobic conditions. The bile tolerance ability of the lactobacilli strains was expressed as the percentage of the propagation generations of the bacterial cells in the presence of oxgall to those in the absence of oxgall. The bile tolerance ability of 11 strains of 8 Lactobacillus species, including 3 bile salt hydrolase (BSH)-negative strains and 8 BSH-positive strains, was analyzed using the newly developed method and two traditional methods. The results showed that bile tolerance ability of the strains was considerably different depending on the analysis method used. The newly developed method mimics the physiological environment of the human small intestine, and avoids changes in pH and bile salt composition during the incubation period, which are drawbacks of the traditional bile tolerance test methods. Therefore, the analysis method developed in this study is more suitable to screen or compare the bile tolerance ability of lactobacilli strains.
一种新的体外方法被开发出来，用于测定潜在益生菌乳杆菌的耐胆汁能力。将各种乳杆菌菌株的 overnight culture 接种到无菌、半强度 MRS 肉汤中，加入和不加入 0.3%（wt/vol）牛胆盐，用 0.1 M 磷酸钠缓冲液缓冲，最终 pH 为 7.3，并在 37°C 下在厌氧条件下孵育 12 h。乳杆菌菌株的耐胆汁能力表示为在牛胆盐存在下细菌细胞的繁殖代与不存在牛胆盐下的繁殖代的百分比。使用新开发的方法和两种传统方法分析了 8 种乳杆菌属的 11 株乳杆菌，包括 3 株胆盐水解酶 (BSH) 阴性菌株和 8 株 BSH 阳性菌株。结果表明，菌株的耐胆汁能力因所使用的分析方法而异。新开发的方法模拟了人体小肠的生理环境，并且避免了孵育期间 pH 和胆盐组成的变化，这是传统耐胆汁试验方法的缺点。因此，本研究中开发的分析方法更适合筛选或比较乳杆菌菌株的耐胆汁能力。
