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Bile Salts Transformations and Cholesterol Assimilation by Enterococcus faecium L3

Summary:Bile tolerance is an essential criterion in the selection of #microbial strains for probiotic use. E. faecium L3 was grown in MRS broth #supplemented with 0.3% oxgall and 0.2% of individual bile salts. It was #shown bile salts hydrolase- and steroid 7a-dehidroxylase activities when #was grown in the presence of individual glyco- and tauroconjugated bile #salts. E. faecium L3 assimilated about 50% of the initial cholesterol #concentration when was grown in the presence of 0.3% of oxgall. #*Materials and Methods:The bile tolerance was detected by measuring the #absorbance (at 600 nm) during the growth of E. faecium in the presence of #bile salts. Bile salts transformations were determined by thin-layer #chromatography(1). Walker and Gilliland's technique was used for determination #of free cholic acid liberated from the cultures during deconjugation(2). The #concentration of free cholic acid in the supernatant was read from standard #curve. Results were expressed as micromoles of cholic acid per ml of broth. #The o-phthalaldehyde method for measuring cholesterol by Rudel and #Morris(3)was used to determine the amount of cholesterol in spent broth. #*Overview and discussion of results: If metabolic activity, multiplication, or #colonization in the small intestine are required for optimal activity of the #probiotic strains, then a bile tolerance is an essential criterion in the #selection of microbial strains. The ability of E. faecium L3 to grow in the #presence of bile salts exhibited good bile tolerance. When was grown in the #presence of glyco- and tauroconjugated bile salts, E. faecium L3 was shown #bile salts hydrolase- and steroid 7a-dehidroxylase activities. The #cholesterol assimilation by in vitro experiments were frequently used to #explain in vivo hypocholesterolemic effect. So, in the presence of oxgall, #E. faecium L3 assimilated about 50% of the initial cholesterol concentration. #The influence of individual conjugated and deconjugated bile salts on #cholesterol assimilation were also studied. Better results were obtained with #addition of conjugated than with deconjugated bile salts. #*Conclusions:E. faecium L3 was shown tolerance to bile, deconjugation of #sodium taurocholate and sodium glycodeoxycholate, and steroid #7a-dehidroxylation of cholic acid. The ability of E. faecium L3 to lover #cholesterol concentration was highest in MRS broth with 0.3% of oxgall. #*References: #(1)G.W.Tannock,M.P.Dashkevicz,S.D.Feighner,Appl.Environ.Microbiol.55(1989)1848 #(2)D.K. Walker,S.E. Gilliland, J. Dairy Sci. 76 (1993) 956-961. #(3)L.L. Rudel, M.D. Morris, J. Lipid Res. 14 (1973) 364-366.

bile salts; cholesterol assimilation; E. faecium

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