Screening of bile salt hydrolase-producing lactic acid bacteria and evaluation of cholesterol-lowering activity in vitro
Hypercholesterolemia is a great threat to humans. Bile salt hydrolase (BSH)-producing lactic acid bacteria (LAB) may alleviate it, but current screening methods are inadequate. This study aimed to establish a more comprehensive in vitro method to screen BSH-producing LAB with greater potential for anti-hypercholesterolemia. Forty-one LAB were initially isolated from infant feces and 37 strains could produce BSH. Strains with BSH over 2 U/mg for sodium glycodeoxycholate and sodium taurodeoxycholate were used to analyse cholesterol degradation rate, hydrophobicity, self-aggregation, gastric fluid tolerance, and intestinal fluid tolerance. Based on the results of these indicators, Lactococcus lactis Y17, L. rhamnosus Q2, and L . fermentum Q11 with the top scores were considered anti-hypercholesterolemia candidates using a principal component analysis evaluation. Antioxidant and Caco-2 adhesion assays showed that these three strains exhibited excellent antioxidant ability and Caco-2 adhesion ability. Their total antioxidant capacity was above 0.99 μmol/L, while the Caco-2 adhesion rate was higher than 8.22%. Safety assessments, via antibiotic susceptibility and hemolysis tests, confirmed their safety. In the HepG2 cells assay, the total cholesterol content of the Y17, Q2, and Q11 groups was reduced by 0.525 mmol/L, 0.426 mmol/L, and 0.581 mmol/L, which verified the potential of the three LAB in anti-hypercholesterolemia. In addition, they could enhance cholesterol uptake and bile acid synthesis in HepG2 cells by upregulating the mRNA expression of bile acid synthase ( CYP7A1 and CYP8B1 ) and cholesterol uptake receptors ( NPC1L1 and LDLR ). The results showed that the three LAB could be developed into anti-hypercholesterolemia foods with beneficial properties.
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