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Binding of heterocyclic amines by lactic acid bacteria from miso, a fermented Japanese food
1Laboratory for Microbial Biochemistry, Hiroshima University, Higashi Hiroshima, Japan.
Abstract:
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.
Insights
Lactic acid bacteria in miso can bind to carcinogenic heterocyclic amines. Bacterial cell walls, particularly peptidoglycan, show the strongest binding activity, suggesting a role in reducing mutagen exposure from food.
Area of Science:
- Food Science
- Microbiology
- Toxicology
Background:
- Miso, a traditional Japanese fermented food, contains lactic acid bacteria.
- Foodborne carcinogenic heterocyclic amines are a concern for public health.
- Understanding microbial interactions with these compounds is crucial for food safety.
Purpose of the Study:
- To investigate the binding capacity of lactic acid bacteria from miso to various foodborne carcinogenic heterocyclic amines.
- To identify specific bacterial components responsible for this binding.
- To explore the influence of enzymatic and chemical modifications on binding.
Main Methods:
- Isolation and characterization of lactic acid bacteria from miso.
- Testing the binding activity of bacterial isolates and their components (cell wall, peptidoglycan, cytoplasmic contents) against eight different heterocyclic amines.
- Enzymatic and chemical treatments to elucidate binding mechanisms.
Main Results:
- All tested bacterial isolates showed significant binding to Trp-P-1, Trp-P-2, MeA alpha C, and PhIP.
- Pediococcus acidilactici isolates demonstrated varying binding strengths, with isolate 1 being a strong binder.
- Bacterial cell walls and peptidoglycan exhibited higher binding activity than whole cells or cytoplasmic contents.
Conclusions:
- Lactic acid bacteria in miso possess the ability to bind carcinogenic heterocyclic amines.
- Bacterial cell wall components, especially peptidoglycan, play a key role in this binding process.
- These findings suggest a potential role for lactic acid bacteria in mitigating exposure to foodborne mutagens.