Metabolism Of Toxic Ammonia Compounds By Pediococcus Acidilactici BBE1120 In Soy Sauce

Soy sauce is a traditional fermented condiment generally used in people’s daily life. For safety reason, soy sauce free of toxic compounds is important. Toxic or carcinogenic ammoniac compounds(i.e. ethyl carbamate and biogenic amines) can be produced from microbial nitrogen metabolism during soy sauce fermentation, which may lead to the unsafety of soy sauce, risking human’s health.It was demonstrated that Pediococcus acidilactici was the major microorganism responsible for the accumulation of citrulline, the main ethyl carbamate precursor in soy sauce. This study focused on effects of growth and environmental factors on citrulline accumulation by Pediococcus acidilactici. Meanwhile, the ability of Pediococcus acidilactici to produce and degrade biogenic amines was also studied.(1) P. acidilactici BBE 1120, a strain isolated from koji was used for citrulline accumulation analysis under different conditions. It was demonstrated that high concentration of Na Cl was the key factor contributing to citrulline accumulation by P. acidilactici BBE 1120. Carbon sources also influenced citrulline accumulation of this strain.(2) The citrulline conversion rates from arginine of six P. acidilactici strains from different origins(including P. acidilactici BBE 1120) in presence of 18% salt were analyzed. Strains with higher salt tolerance showed a relatively lower citrulline conversion rate from arginine.(3) A Tetragenococcus halophilus R23 strain with a high ornithine conversion rate from arginine was co-cultured with P. acidilactici BBE 1120 to reduce EC precursor in soy sauce. A significant reduction of citrulline in the broth was observed. The citrulline conversion rate from arginine was dramatically decreased.(4) The ability of Pediococcus acidilactici BBE 1120 to produce biogenic amines was qualitatively and quantitatively analyzed. None of the detected biogenic amines was produced by P. acidilactici BBE 1120. Moreover, P. acidilactici BBE 1120 was confirmed to be able to degrade biogenic amines, even in the presence of 18% salt.