Researches On The Function Of Fermented Soymilk With Lactobacillus Acidophilus On Serum Lipid

As a probiotic bacterial, Lactobacillus acidophilus was reported with the beneficial effect on reducing cholesterol. In addtion, soymilk as a representative of Chinese traditional soybean foods contains abundant blood lipid-reducing components. In view of these, the lipid reducing function of tested strain and fermented soymilk were investigated in this study.The research evaluated the probiotic characteristics and lipid-lowering function of Lactobacillus acidophilus MF204(CGMCC No.2122) which was isolated and preserved by our lab. The results showed that the strain kept high activity after treated with artificial gastric solution in pH 3.0 and intestinal fluid in pH 6.8 for 3h successively, and the strain also could tolerate 0.45% bile salt. The antimicrobial assay showed that the strain significantly inhibited the growth of Escherichia coli, Proteus, Shigella dysenteriae, Vibrio Parahemolyticus, Staphylococcus citreus and Bacillus subtilis. Moreover, the strain assimilated 65.64% cholesterol from MRS medium, and effectively regulated serum cholesterol of rats fed on rich-fat diet at prometaphase stage of the test. It indicates that Lactobacillus acidophilus MF204 is a high quality probiotic strain with production potential.Changes of components in soymilk after fermentation were analysed, results showed partial crude protein was degraded into smaller peptides and free amino acids, partial glycosides of soybean isoflavones was transformated to bioactive aglycones during fermentation. The contents of peptides and free amino acids increased by 0.1% and 0.25% respectively, and small peptides with 27, 45, 64kDa molecular weight were produced after fermentation. The ratio of (De+Ge)/(D+G) increased by 14.4 times. Consequently, fermentation process increase bioactive substances, and improve its nutrition and function.The research evaluating the lipid-lowering function of the fermented soymilk showed that fermented soymilk could regulate blood lipids and related lipid metabolism to some extent. Compared with model group, the content of CHO, TRG, LDL-C in serum of fermented soymilk group decreased by 32%, 21%, 50%, and the content of CHO, LDL-C in liver and the liver/body coefficients of fermented soymilk group decreased by 31%, 57%, 14% respectively. Meanwhile, the lipid-lowering effect of fermented soymilk was better than the fermentation strain and soymilk, which further proved the improving on the function of soymilk by fermentation. However, the fermented soymilk fortified by soybean isoflavones and soybean peptides had much better effect than the fermented soymilk without addition, which indicated that the partial efficacious components of reducing blood lipid in fermented soymilk are soybean isoflavones and soybean peptides.Finally, the research sought the mechanism of fermented soymilk reducing blood lipids from three respects, including bile acid excretion, antioxidant level and related lipoprotein metabolic enzyme activity. The results show that the later two belong to the biological approaches on fermented soymilk reducing blood lipid. however, the function and metabolism of fermented soymilk in relation to regulation of blood lipid and lipid metabolism is not clear, and further study needs tobe addressed.