| Coronary heart disease (CHD) is the main cause of death in many countries. A large of epidemiological and nutritional studies has shown that higher than normal serum total cholesterol or low-density lipoprotein (LDL) cholesterol increased the risk of coronary heart disease. In recent years, the probiotic activity of lactic acid bacteria been emphasized. One of the beneficial health effects related to probiotics is the ability to reduce serum cholesterol. Several reports have indicated that consumption of certain Lactobacillus strains or its dairy products resulted in reduction of serum cholesterol concentrations. However, the rules for screening of cholesterol-lowering strains and its mechanisms have not yet been sufficiently elucidated.In this study,18 strains of Lactobacilli isolated from traditionally home-made koumiss samples in Xinjiang region were assessed for potential probiotic properties. Low pH and bile tolerance, hydrophobicity, cholesterol-lowering ability of these strains were tested, respectively. According to the in vitro screening experiment, the stains of E7304 and XB4-1 were selected to study the mechanisms of cholesterol-lowering in vitro and the effect on cholesterol metabolism in vivo. Meanwhile, the strain of E7304 was identified by 16SrRNA/DNA molecular biological methods.The conclusion as follows:Although the origins and sources of lactobacilli are similar, potential probiotic properties of these strains is various. There were no correlation between the abilitys to removal cholesterol and Low pH and bile tolerance, hydrophobicity among these strains.The strains of E7304 and XB4-1 had stronger acid resistance and bile tolerance, and higher ability to removal cholesterol than other strains. Their survival rates in artificial gastrointestinal juice at pH3.0 for3h were 71.31% and 57.14%; growth rate in 0.5% bile were 79.0% and 46.7%; the amounts of cholesterol removed from growth medium were 59.7% and 37.7%, respectively. In vitro, the cholesterol-lowing mechanisms of Lactobacillus of E7304 and XB4-1 were related to co-precipitation with deconjugated ,bile of cholesterol by the cell wall and bindingmainly assimilation of cholesterol by the cells.Administration of lactobacill E7304 and XB4-1 had a great reduction (P<0.05)serum total cholesterol , triglyceride and low-density lipoprotein cholesterol, and significantly increased(P<0.05)high-density lipoprotein compared to the control group. These results indicate the probiotic effect of the strains of E7304 and XB4-1 on serum cholesterol reduction. Meanwhile, none of the diets exhibited harmful translocation of lactobacilli to liver. Results from this study clearly indicated that Lactobacillus was safe and did not translocate to other internal organs.E7304 is identified as Lactobacillus plantarum by 16SrRNA/DNA sequences homology analysis.
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