Inhibition Of Mutagenic/Aarcinogenic Agents By Lactobacillus Pentosus Strains

Some hetero-bacteria from the intestinal tract often transform aromatic amino acids to phenolic and Indolic compounds,i.e.genotoxic,mutagenic or carcinogenic agents which easily Induce the development of colon cancer due to over-accumulation in the colon.Lactic bacteria have been claimed to have a role in removing pre-carcinogenic substances from the intestinal environments.Therefore,the objectives were to investigate the effects of Lactobacillus pentosus strains Ind1 and Ind3,isolated from a traditional Chinese cheese product called as Naigeda collected from Xinjiang region of China,on reducing the concentrations of phenol,p-cresol and indole potentially existing in the intestinal tract.The following are main results:A concentration of 5 to 50μg/mL phenol,p-cresol and indole had no influence on the growth and survival of the 2 strains,but the 3 chemical compounds whose concentration was higher than 150μg/mL produced slightly an inhibition against the bacterial growth.The viability of the tested lactobacilli strains was 10~6cfu/mL after 144h-incubation at 37℃.Simulation of the host intestinal environment proved that L.pentosus Ind1 and Ind3 challenged greatly the presence of phenols with different concentrations,and their live cells were maintained at a level of 10~6cfu/mL after 144h at 37℃under anaerobic conditions.HPLC was used to analyze the degradation of these potential cancer-causing agents directly by L. pentosus strains grown MRS media.When the tested lactobacilli bacteria were grown in MRS media containing the concentration of 5 to 50μg/mL phenol or p-cresol at 37℃,L.pentosus strains Ind1 and Ind3 reduced the amount of the phenol to 0.95μg/mL after 24h and 1.93μg/mL after 144h,respectively. The lowered amount of the p-cresol was 1.14μg/mL after 24h-incubation and 0.45μg/mL after 144h, respectively.The viability of the tested lactic bacteria was reduced from 10~9cfu/mL to 10~6cfu/mL.In addition,cells of the tested bacteria were proved to bind the three pre-carcinogenic substances.The surface-binding levels of L.pentosus Ind1 and Ind3 cells varied between 0.42μg/mL and 1.47μg/mL for phenol,and from 0.90μg/mL to 1.28μg/mL for p-cresol.Pre-carcinogenic agents bound by cells depended greatly the growth of the tested bacteria,since the lower the live cells existing in MRS media the lower the amounts of the mutagenic agents reduced.It was seen that the ability of L.pentosus to remove mutagenic agents from the intestinal environments was strain-dependant.Strain Ind3 showed a better effect on degrading the three mutagenic comunds than strain Ind1 did.