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目的从实验室保存的4株乳酸菌和市售产品中分离得到的5株乳酸菌中,筛选降胆固醇能力较强菌株,并对其体外降胆固醇机制进行研究。方法对9株菌分别进行胆固醇清除试验;将降胆固醇能力最强的嗜热链球菌Strep-tococcus thermophilussBL71接种于胆固醇培养基中48h,分析培养基上清液、洗液、菌体沉淀及细胞内胆固醇含量;再转接入无胆固醇新鲜培养基中,测定发酵液中胆固醇含量;显微镜下观察菌体变化;分析灭活菌体和菌液对胆固醇清除的影响。结果9株菌中嗜热链球菌BL71对胆固醇去除率最高达到80%;镜下观察到菌体与胆固醇能结合成大的颗粒,而部分胆固醇能重新释放到新鲜培养基中;经检测分析,有部分胆固醇进入菌体细胞内部;灭活菌体和菌液都有降胆固醇的作用。结论嗜热链球菌降胆固醇是通过菌体同化作用、吸收和吸附,发酵液中代谢产物有机酸也发挥着作用。
OBJECTIVE To screen out 5 strains of lactic acid bacteria isolated from 4 strains of lactic acid bacteria and commercial products which were stored in laboratory and select the strains with strong ability of lowering cholesterol and to study the mechanism of cholesterol lowering in vitro. Methods Streptococcus thermophilus BL71, the strongest cholesterol-lowering agent, was inoculated into cholesterol medium for 48 hours. The supernatant, washings, cell pellet and intracellular Cholesterol content; then transferred to fresh cholesterol-free medium, the determination of cholesterol content in the fermentation broth; microscopic observation of bacterial changes; analysis of inactivated bacteria and bacteria on cholesterol clearance. Results The removal rate of Streptococcus thermophilus BL71 was up to 80% in 9 strains. The microscopic observation showed that the bacteria and cholesterol could be combined into large particles, and some cholesterol could be re-released into fresh medium. After the detection and analysis, Some cholesterol into the cells within the cells; inactivated bacteria and bacteria have cholesterol-lowering effect. Conclusion Streptococcus thermophilus hypocholesterolemic is through the cell assimilation, absorption and adsorption, the fermentation broth organic metabolites also play a role.