Binding of heterocyclic amines by lactic acid bacteria from miso, a fermented Japanese food.

Miso, a widely used Japanese fermented food was analysed for its lactic acid bacterial count on bromocresol purple agar. The binding of eight different foodborne carcinogenic heterocyclic amines to 25 bacterial isolates from miso were investigated. The heterocyclic amines used were 3-amino-1,4-dimethyl[5H]pyrido(4,3-b)indole (Trp-P-1), 3-amino-1-methyl[5H]pyrido(4,3-b)indole (Trp-P-2), 2-amino-6-methyldipyrido(1,2-a:3'2'-d)imidazole (Glu-P-1), 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), 2-amino-dimethylimidazo(4,5f)quinoline (IQ), 2-amino-3,4-dimethylimidazo(4,5-f) quinoline (MeIQ), 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx), and 2-amino-3-methyl-9H-pyrido(2,3)indole (MeA alpha C). The lyophilized cells of all of the isolates exhibited high binding activity towards Trp-P-1, Trp-P-2, MeA alpha C, and PhIP, while Glu-P-1 and IQ were not effectively bound. Of the isolates tested, the strongest and weakest binders were identified as Pediococcus acidilactici 1 and 2, respectively. Lyophilized cell wall fractions, heat-treated cells, and the cytoplasmic contents of P. acidilactici 1 and 2 were analysed for their ability to bind to different mutagens. Pure cell wall and peptidoglycan showed greater binding activity than the bacterial cells. Cytoplasmic content also showed some binding, but it was much less effective. The impact of enzymes (amylase, protease, cellulase, chitinase, muraminase, and peptidase) and acetylation of Trp-P-1 and IQ on the binding action of bacteria and cell wall material were also analysed to understand the possible processes involved in the binding of lactic acid bacteria to carcinogenic heterocyclic amines.