Chemical structure, concentration, and pH are key factors influencing antimicrobial activity of conjugated bile acids against lactobacilli

Effects of chemical structure, concentration, and pH on antimicrobial activity of conjugated bile acids were investigated in 4 strains of lactobacilli. Considerable differences were observed in the antimicrobial activity between the 6 human conjugated bile acids, including glycocholic acid, taurocholic acid, glycodeoxycholic acid, taurodeoxycholic acid, glycochenodeoxycholic acid, and taurochenodeoxycholic acid. Glycodeoxycholic acid and glycochenodeoxycholic acid generally showed significantly higher antimicrobial activity against the lactobacilli, but glycocholic acid and taurocholic acid exhibited the significantly lower antimicrobial activity. Glycocheriodeoxycholic acid was selected for further analysis, and the results showed its antimicrobial activity was concentration-dependent, and there was a significantly negative linear correlation (R-2 > 0.98) between bile-antimicrobial index and logarithmic concentration of the bile acid for each strain of lactobacilli. Additionally, the antimicrobial activity of glycochenodeoxycholic acid was also observed to be pH-dependent, and it was significantly enhanced with the decreasing pH, with the result that all the strains of lactobacilli were unable to grow at pH 5.0. In conclusion, chemical structure, concentration, and pH are key factors influencing antimicrobial activity of conjugated bile acids against lactobacilli. This study provides theoretical guidance and technology support for developing a scientific method for evaluating the bile tolerance ability of potentially probiotic strains of lactobacilli.

Automated summary

This study investigated the effects of chemical structure, concentration, and pH on the antimicrobial activity of conjugated bile acids against lactobacilli. Different bile acid components showed varying antimicrobial activity, with glycodeoxycholic acid and glycochenodeoxycholic acid exhibiting higher activity. Concentration and pH were found to play key roles in determining the antimicrobial activity of bile acids, providing theoretical guidance for evaluating the bile tolerance ability of potentially probiotic lactobacilli strains.