Dynamics Of Microbial Community During Soy Sauce Fermentation And Functional Analysis Strains Isolated From Moromi

Soy sauce is a traditional condiment produced by fermentation.Production of soy sauce involves in a complex microorganism fermentation process,and the lacking knowledge of microbial community and their metabolism in the system restrains the quality improvement of soy sauce,as well as the development of soy sauce industry.It is of great significance to study the diversity of microorganisms during soy sauce fermentation and functions of key microbe.In this study,the dynamics of microbial community during the fermentation process of high salt diluted state soy sauce was investigated,and the correlation between the formation of essential flavor substances with functional microorganism was analyzed.The main results are as follows:(1)It is found that the diversity of bacteria and fungi communities was rich during the soy sauce fermentation process,using microbial diversity sequencing to analysis the dynamic changes of microbial communities in the fermentation of soy sauce.The dominant bacteria in the moromi was detected belonging to genera of Weissella,Staphylococcus,Pediococcus,Lactobacillus and Bacillus.The abundance of Weissella strains had little changes in the soy sauce fermentation,and the abundance of Pediococcus and Staphylococcus increased gradually,but the abundance of Lactobacillus and Bacillus strains reduced gradually.Fungi is mainly composed of Aspergillus oryzae and Zygosaccharomyces rouxii,the abundance of Zygosaccharomyces rouxii was peaked(about 90%)at 53 th day of fermentation,and Candida began to appear and became the dominant microbe in the late fermentation.The quantitative analysis results showed that the quantity of Aspergillus oryzae and the total amount of bacteria during fermentation process reduced gradually;yeast began to increase rapidly at 25 th day and achieved its maximal level of 108 CFU?g-1 at the 53 th day,and then decreased gradually in the late period of the fermentation.(2)Analysis of the correlation between dynamics of microbial community and formation of the main flavor substances in the process of soy sauce fermentation revealed that: ? the brine fermentation could be divided into three stages,including the lactic acid fermentation stage(0-25 d),the ethanol fermentation stage(25-53 d)and the aging stage(53-120 d);? the consumption of reducing sugar and the synthesis of ethanol was correlated in yeast active stage,suggesting the production of ethanol by Zygosaccharomyces rouxii;? the kinds and content of volatile substances in soy sauce moromi increased significantly after strengthening Zygosaccharomyces rouxii.(3)Nine bacterial strains were isolated from the soy sauce moromi with the potential capability in promoting hydrolysis and improving soy sauce aroma,and five strains of which(Weissella paramesenteroides CQ03,Pediococcus acidilactici JY07,Pediococcus pentosaceus JY08,Staphylococcus sp.JY09 and Tetragenococcus halophilus MRS1)are tolerant to salt.Under the condition of high salt culture,Bacillus amyloliquefaciens B2 exhibited stronger capability in secretion of protease and glucoamylase,W.paramesenteroides CQ03 produced more umami tasting amino acids than other isolates.Both T.halophilus MRS1 and S.sp.JY09 retained high activities in synthesis and accumulation of volatile compounds.The potential capability in organic acids production by T.halophilus MRS1 was also detected.