Ability of Intestinal Lactic Acid Bacteria to Bind and/or Metabolise Indole

Intestinal microbiota can contribute to the development of colon cancer by the production of many substances playing a role in carcinogenesis. Metabolites of protein fermentation in the colon, such as ammonia, amines, indole, phenol, skatole and their derivatives are toxic. On the other hand, lactic acid bacteria (LAB) existing in the colon may exert an anticarcinogenic action, but the mechanism is still poorly understood. In the present study, the aim is to determine the ability of intestinal lactobacilli to adsorb or metabolise indole in vitro. Lactobacillus strains were cultivated in MRS and a modified MRS broth with reduced concentrations of nitrogen and carbon. Indole concentration in the media was from 2 to 20 mg/mL. The decrease in indole concentration was from 1 to 10 mg/mL after cultivation in MRS broth, and from 4.3 to 6.7 mg/mL after cultivation in a modified MRS broth. It was shown that the higher concentration of indole in the medium, the higher reduction of its level. Killed bacteria displayed slight binding capacity. After the interaction of alive lactobacilli with 10 mg/mL of indole, it displayed a lower genotoxicity, as evaluated by the alkaline comet assay. The phenomenon did not depend on the decrease of indole concentration, but on the culture medium and the strain of LAB and ranged from 7 to 96 %.