Detection Of Characteristics Of Weissella Strains And Their Contents In Soy Sauce Moromi Mash During Soy Sauce Fermentation

Weissella was widely detected in fermented foods.Strains of this genera involve in fermentation and contribute to formation of volatile compounds in foods.In soy sauce moromi mash,Weissella is the dominant genera of bacteria.Thus,it is of great importance to characterize their adaption to environment,as well as properties related to soy sauce fermentation.To isolate the main species of Weissella from soy sauce moromi mash,and evaluate their function for soy sauce fermentation by analyzing the dynamic composition of each species and their adaptation to the environment.The quantitative analysis of the absolute number of strains and the comparison of their tolerance were carried out.The characteristics of synthesis of short chain fatty acids,exopolysaccharides,biogenic amines and ethyl carbamate or their precursors under high salt conditions were investigated,and the effects of Weissella on the fermentation and safety of soy sauce were studied.The main results are listed as following.?1?Strains from three speices of Weissella were isolated from the soy sauce moromi mash.They were identified belonging to Weissella confusa,Weissella paramesenteroides and Weissella cibaria.Among them,Weissella paramesenteroides could tolerate high concentrations of salt,and grow better than W.confuse and W.cibaria at lower temperature,as well as lower p H.These traits are related to their composition in the moromi mash during soy sauce fermentation.?2?By comparing the ability of polysaccharide production by Weissella from sauce mash,it was found that the ability of synthesizing short chain fatty acids of Weissella paramesenteroides is higher than that of Weissella confusa and Weissella cibaria.The yield of extracellular polysaccharides synthesized by Weissella cibaria 02 was the highest,reaching 3.34 g?L^-1 It may contribute to the synthesis of?-and?or??-type polysaccharides in soy sauce by Weissella.The three predominant Weissella species also exhibit the ability to synthesize short chain fatty acids.The ability of short chain fatty acid synthesis by Weissella paramesenteroides higher than that of Weissella confusa and Weissella cibaria.?3?The interaction between microorganisms has great influence on the growth and metabolic synthesis of flavor substances of the strain.Weissella strains from soy sauce mash inhibit the growth of a few Gram-positive bacteria,Zygosaccharomyces rouxii and Aspergillus oryzae could promote the growth of Weissella paramesenteroides,and Aspergillus oryzae could inhibit the growth of Weissella confusa and Weissella cibaria.?4?Ammonia?amine?toxic compounds present in soy sauce are mainly biogenic amines and ethyl carbamate,which are generated due to the incompleteness of utilization of nitrogen by microorganisms.It was found that most of the Weissella strains derived from the sauce mash do not produce biogenic amines,and few strains of them produce more than one type of biogenic amines.Interestly,Weissella cibaria can degrade many biogenic amines.Although Weissella strains from moromi mash can use arginine to produce trace amount of citrulline?the precursor of ethyl carbamate?,it is far less than that produced by Pediococcus acidilactici or Staphylococcus.The results further confirmed that Weissella was not the main producing strain of citrullinic acid,the precursor of carbamate in sauce mash.