Integrative Evaluation Of Lactobacillus For Cholesterol Removal Potential And Characterization Of BSH Activity

Ingestion of excessive cholesterol has been recognized as a major risk factor for cardiovascular disease. There has been an upsurge in finding ways to control the level of plasma cholesterol. Though largely reported, the evaluation rules for cholesterol-lowering potential strains and the removing mechanisms were not ensured.This research primarily aimed to establish a set of criteria to comprehensively evaluate in vitro cholesterol removal potential of Lactobacillus. This standard includes several indexes as tolerance to simulated gastric pH, resistance to simulated intestinal bile concentration, performances on cholesterol reducing which include assimilation and coprecipitation respectively, and also BSH activity. Using this standard to evaluate six lactobacillus strains, including a strain of L. salivarius and five strains of L. plantarum, results show that these characters were of strain specificity. Out of them, the L. plantarum Lp529 was selected as the most potential probiotic strain for hypocholesterolaemic studies in future.Lp529, together with the commercial strain LpOnlly, was further studied for characters of BSH activity. Their BSH activity had these characteristics:1) BSH activity was not activated or inhibited by the substrates or components, indicating BSH not an allosteric enzyme;2) The evolution of BSH total activity was in term of a sigmoid model that was analogous to the growth curve. The specific activity proliferated and reached the peak value within the exponential growth phase; it dropped and kept on a plateau at the stationary phase of growth;3) Short time exposure to simulated human bile caused a downward regulation of BSH specific activity, and this decrease was reversible when bile was removed;4) After the two strains were domesticated to simulated human bile over four generations, the lowest level acquired of BSH specific activity was about 60% of the original level.5) In the end, BSH dependent coprecipitation curve was involved for evaluation of cholesterol removal. Results verified that both precipitation and assimilation contributed to total cholesterol reduction. In all test strains, effect of assimilation was stronger than that of co-precipitation.