Cholesterol removal mechanisms of potential probiotic Enterococcus species and bsh gene analysis

Cardiovascular diseases are among the main causes of death in many countries. One of the main factors related with coronary heart disease is considered as high serum cholesterol level. This study investigates the deconjugation activity of Taurocholic acid (TCA) and Glucocolic acid (GCA) bile salts, precipitation of cholesterol with deconjugated bile and production of exopolisaccaharide (EPS) during deconjugation and precipitation activities to determine the cholesterol inhibiting effects of 4 Enterococcus faecium and 6 Enterococcus faecalis strains which were isolated from traditional Turkish white cheeses. A prebiotic feeding medium was prepared, and its effects on deconjugation, precipitation, and EPS production by Enterococcus sp. strains were determined. bsh gene which is responsible for deconjugation was identified through polymerase chain reaction (PCR) and confirmed with sequence analysis. While none of Enterococcus sp strains were able to deconjugate TCA in a prebiotic-free medium, they were able to deconjugate GCA. It was determined that E. faecium RT94 had the highest GCA deconjugation activity (1.93 mM) and E. faecium RT122 had the lowest (0,37 mM). Cholesterol removal percentages were studied in media containing different bile concentrations and the highest cholesterol removal percentage was determined for E. faecium RT94 strain (50%) in bile-free nutrient media. EPS production of Enterococcus sp. strains were seen to increase in direct proportion with their deconjugation and precipitation activities. It was determined that TCA deconjugation of Enterococcus sp strains increased and their GCA deconjugation decreased in prebiotic containing media. As a result of this study, E. faecalis and E. faecium strains were found to have cholesterol lowering effects.