2018 Volume 67 Issue 2 Pages 80-87
Lowering of deoxycholic acid (DCA, categorized as a secondary bile acid) concentrations is important to preventing the DCA-induced diseases to extend and improve the quality of life. We examined DCA-lowering activity of two probiotic bacteria, Bifidobacterium longum SBT2928 and Lactobacillus gasseri SBT2055, in vitro. The two strains significantly removed DCA in a distinctive manner, although they removed only a trace amount of cholic acid, a precursor of DCA. B. longum SBT2928 required saccharides for this activity, with about 50% of 1 mM DCA substrate removed when 0.65％ lactose was added. The amount of removed DCA when lactose was added was more than those when glucose or galactose were added. We postulated that the mechanism of action was incorporation of DCA into cells, which was promoted by the addition of saccharides as a driving force. Further examinations showed that the rate of DCA reduction was dependent on the concentration of lactose and this reduction activity was effective even when raffinose or lactulose, which are accessible in the colon, were added as oligosaccharides. L. gasseri SBT2055 removed about 25％ of 1 mM DCA substrate, independently of saccharides. We postulated that the mechanism of action was adhesion to cell surfaces. LiCl treatment did not affect DCA-lowering activity, whereas heat treatment reduced it. We expect that these strains contribute to the protection against various DCA-induced diseases.
