Relationship between bile salt hydrolase activity, changes in the internal pH and tolerance to bile acids in lactic acid bacteria.

摘要

The effect of conjugated bile acid (BA) on microbial internal pH (pHin) values in lactic acid bacteria with and without the ability to hydrolyze bile salts (BSH[+] and BSH[--] strains, respectively) was evaluated. BSH(+) strains showed a gradual increase in the pHin following the addition of conjugated BA; this behavior was more pronounced with GDCA than with TDCA may be due to the higher affinity of BSH for the glyco-conjugates acids. Conversely, the BSH(--) strains showed a decrease in internal pH probably as a consequence of weak acid accumulation. As expected, a decrease in the cytoplasmic pH affected the cell survival in this last group of strains, while the BSH(+) strains were more resistant to the toxic effect of BA. To evaluate bile salt hydrolase activities, changes in the internal pH and cell survival to bile acids in lactic acid bacteria were measured to establish the relationship between these parameters