Ability of probiotic Lactobacillus casei DN 114001 to bind or/and metabolise heterocyclic aromatic amines in vitro

Heterocyclic aromatic amines (HCA) are compounds with high mutagenic potential, formed when meat is cooked at high temperatures of 150-300 A degrees C. These compounds contribute to development of colon and gastric cancer. Western diet provides a lot of HCA and influences the available substrates for the intestinal microbiota which can activate HCA to direct acting mutagens. On the other hand, lactic acid bacteria existing in the colon and ingested with food including probiotics, may exert an anti-carcinogenic action, but the mechanism is still poorly understood. In the present study we determined the ability of probiotic Lactobacillus casei DN 114001 (Actimel strain) to metabolise or adsorb three HCA: IQ, MelQx and PhIP in vitro. Lactobacilli were cultivated in MRS and in a modified MRS broth with reduced concentrations of nitrogen and carbon (MRS NC), with addition of 25 mu g/ml of IQ, MelQx or PhIP. Their concentration after cultivation with L. casei DN 114001 was measured with high-performance liquid chromatography and the genotoxicity was evaluated by the alkaline comet assay. It was measured, that after 24 h cultivation in MRS (cell density was 10(9) cfu/ml), rapid decrease of IQ and PhIP (98-99%) was observed, and the peaks on chromatograms were almost completely reduced. In case of MeIQx the decrease was about 27%. In a modified MRS broth (cell density was 10(8) cfu/ml), the ability to decrease HCA concentration during prolonged cultivation (to 168 h) depended on the growth phase of bacteria, and it was about 51.5% for IQ and at about 11.2% for MeIQx. Non-growing cells (in phosphate buffer), could reduce the content of IQ and PhIP from 72 h to the end of incubation. L. casei DN 114001 reduced genotoxicity of HCA (IQ from 46 to 48%; MeIQx from 35 to 65% and PhIP from 32 to 81%), and the degree depended on the incubation time, cell growth and the medium used. It may suggest that bacteria can metabolise or adsorb HCA.