Microbial Composition Of Jiangshui Fermentation Seed Liquid And Research On Its Related Characteristics

Jiangshui is a traditional natural fermented food with a long history and certain regional characteristics.It has a unique flavor and is good for our body.There are no systematic studies on the microbial flora composition and dynamic changes during the procession of Jiangshui fermentation.Metagenomics is an effective method for studying the composition of microbes in complex systems.Without the need for isolation and culture of microorganisms,the microbial composition of the system can be obtained.The method was based on the whole genome of microbial flora in the system,and the abundance information,active substances and new functional genes of the sample was obtained by high-throughput sequencing.In this study,natural Jiangshui was used as the raw material,then through purification and domestication to obtain seed liquid.The fermentation broth obtained by continuous fermentation of seed liquid was taken as the research object.The stability and composition of the fermentation broth were studied by means of metagenomics,16 S strain identification,and gas chromatography-mass spectrometry(GC-MS).The Lactobacillus in the fermentation broth were separated,and the material composition of the fermentation broth was also analyzed.Besides,the other physical and chemical characteristics of the fermentation broth were studied.The main research results were as follows:(1)The microbial composition of nine samples was analyzed by 16 S rRNA metagenomics technique.The results showed that the average abundance was 61.94% of the Firmicutes and 37.15% of the Proteobacteria separately at the level of the Phylum.The average abundance of Lactobacillus was 61.87%,and the average abundance of Acetobacter was 35.93% at the level of the genus.Lactobacillus and Acetobacter were the dominant flora in the fermentation broth.The variance analysis showed that the content and composition ratio of Lactobacillus and Acetobacter were maintained during the whole fermentation.The composition of the flora remains stability should be under the conditions of that the fermentation process carried out in a laboratory environment free of mold and pathogen,and the fermentation process terminated at a fixed acidity value.In addition,composition ratio of raw materials and control of fermentation temperature is also very important;(2)The single colonies on the MRS medium were isolated by the traditional platelet separation method.The isolated single colonies were identified by physiological and biochemical methods and 16 S rRNA method respectively.The results showed that the lactic acid bacteria in the fermentation broth were mainly Lactobacillus,including Lactobacillus fermentum,Lactobacillus plantarum and Lactobacillus paracasei,and the results of physiological and biochemical identification were consistent with the results of molecular biology identification.Lactobacillus fermentum,Lactobacillus plantarum and Lactobacillus paracasei in the fermentation broth not only ensured the good flavor and oxidation resistance,but also greatly inhibited the growth of the harmful bacteria.In addition,it also provided a reliable basis for the preparation of fermentation agent.(3)The GC-MS results showed that the fermentation broth was rich in lactic acid,carbohydrate,alcohol and other substances.The results of multivariate statistical analysis of nine samples showed that there were differences in the contents of different samples,which was related to the type and proportion of Lactobacillus in the samples of fermentation broth.Although the samples of lactic acid bacteria showed stable,but the proportion of lactic acid bacteria will directly affect the content of its metabolites.In addition,the open fermentation environment and the unfixed fermentation broth material will also cause the difference in the composition of the fermentation broth.