383785 The Diversity of Lactic Acid Bacteria Arc Operon and Its Regulation of Arginine Metabolism in Fermented Foods
Lactic acid bacteria (LAB) are common microflora present in fermented foods. They play important roles in food mature processing and aroma components production, whereas the utilization of arginine by LAB during food fermentation generates precursors of carcinogenic compounds (ethyl carbamate, EC) or biogenic amines. Ethyl carbamate (EC), the byproduct in fermented foods and alcoholic beverages, is a group 2A carcinogen [1-2]. The formation of EC in fermented products is mainly caused by the accumulation of EC precursors (i.e. urea, ethanol, citrulline) during fermentation. In LAB, citrulline is generated from arginine metabolism through the arginine deminase pathway (ADI), which composed of three enzymes that are encoded by the arcoperon . Therefore, understanding the regulation of LAB ADI is of great importance to disclose EC accumulation mechanism in fermented foods.
Strains belonging to genera of Pediococcus, Tetragenococcus, Weissella and Staphylococcus were isolated from fermented/food products. Investigation of ADI components of these lactic acid bacteria, revealed a diverse arc genes organization. Their abilities of production of citrulline under different conditions were also investigated by analysis of arginine conversion rate. Pediococcus strain was the only one who retained the ability of accumulation citrulline in high saline. The presence of arc gene cluster encoding arginine deiminase (ADI) pathway components in Pediococcus strain was detected to be slightly different from what had been reported in other LAB. The conversion ratio from arginine to citrulline dramatically increased with the addition of salt, suggesting that, Pediococcus, a soy sauce isolate, is responsible for the accumulation of citrulline in soy sauce. These results gave a better knowledge of the citrulline accumulation mechanism, which is the fundamental for improving the safety level of fermented foods.
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