Cholesterol-lowering probiotics: in vitro selection and in vivo testing of bifidobacteria

Thirty-four strains of bifidobacteria belonging to Bifidobacterium adolescentis, Bifidobacterium animalis, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium longum, and Bifidobacterium pseudocatenulatum were assayed in vitro for the ability to assimilate cholesterol and for bile salt hydrolase (BSH) against glycocholic and taurodeoxycholic acids (GCA and TDCA). Cholesterol assimilation was peculiar characteristic of two strains belonging to the species B. bifidum (B. bifidumMB107 and B. bifidumMB 109), which removed 81 and 50 mg of cholesterol per gram of biomass, being the median of specific cholesterol absorption by bifidobacteria 19 mg/g. Significant differences in BSH activities were not established among bifidobacterial species. However, the screening resulted in the selection of promising strains able to efficiently deconjugate GCA and TDCA. No relationship was recognized between BSH phenotype and the extent of cholesterol assimilation. On the basis of cholesterol assimilation or BSHGCA and BSHTDCA activities, B. bifidum MB 109 (DSMZ 23731), B. breve MB 113 (DSMZ 23732), and B. animalis subsp. lactis MB 2409 (DSMZ 23733) were combined in a probiotic mixture to be fed to hypercholesterolemic rats. The administration of this probiotic formulation resulted in a significant reduction of total cholesterol and low-density cholesterol (LDL-C), whereas it did not affect high-density cholesterol (HDL-C) and HDL-C/LDL-C ratio.