Biodiversity Analysis In Hainan Yucha And Isolation And Determination Of Fermentative Bacteria

In this paper,Hainan traditional Yucha was studied in different fermentation stages,and its microbial diversity was explored by high-throughput sequencing.The changes of free amino acids and biogenic amines in samples at different fermentation stages were detected,and the bacteria related to the formation of free amino acids and biogenic amines were speculated through association analysis with high-throughput sequencing results.The volatile flavor substances in Yucha were analyzed by GC-MS.Traditional microbiological methods were used to separate and purify the lactobacillus and yeast in the sample,and one strain of lactobacillus and yeast with better fermentation performance was selected for Yucha fermentation.The purpose of this paper is to find the dominant strains through the combination of microbial diversity and other indicators in the traditional Yucha fermentation process,and examine its fermentation performance through simple fermentation experiments,providing a basis for the breeding of fish tea fermentation strains and the standardized production of Yucha.The results of high-throughput sequencing showed that the dominant bacteria in the traditional fermentation process of Yucha were lactobacillus and lactobacillus in the early stage of fermentation and lactobacillus rapidly proliferated to produce acid,effectively controlling the growth of miscellaneous bacteria.Lactococcus proliferates obviously in the anaphase of Yucha fermentation.The relative abundance of lactic acid bacteria in finished Yucha is more than 90%,which occupies an absolute advantage.The yeast is mainly involved in the fermentation of traditional fish tea in the early stage,and the yeast in the second half of the fermentation enters the dying stage.In the traditional fermentation process of Yucha,the bacteria contamination was found,which was mainly manifested as increased relative abundance of Vibrio Acinetobacter and Enterococcus.Through the determination of free amino acids and biogenic amines,13 free amino acids were found in the fermentation process of Yucha.In addition to histidine,the detection of 12 other free amino acids in finished Yucha showed an increasing trend;7 biogenic amines were detected,and the amount of biogenic amines increased with fermentation.According to the analysis results of volatile flavor substances,the main volatile flavor substances in traditional Yucha are alcohols,three of which are produced by yeast fermentation,which also indicates that yeast plays an important role in the fermentation process of Yucha.In this experiment,40 strains of lactic acid bacteria and 32 strains of yeast were isolated and purified by traditional microbiological methods.Through screening,lactic acid bacteria L111 and yeast Y16 were selected for Yucha fermentation experiments.After sterilization of raw materials,two strains of 1:1 were mixed into raw materials for anaerobic fermentation for 15 days.Compared with the traditional Yucha,the acidity of the self-made Yucha was higher than that of the traditional Yucha.The change rule of yeast viable bacteria in the fermentation process was the same as that of the traditional Yucha.The change of lactic acid bacteria viable bacteria was slightly different from that of the traditional Yucha.The kinds of free amino acids and biogenic amines detected in the self-made Yucha were less than that of the traditional Yucha.However,the detection of biogenic amines in self-made Yucha samples was significantly lower than that in traditional Yucha samples,indicating that the potential risk of biogenic amines poisoning in self-made Yucha was lower than that in traditional Yucha.