Screening Of Dominant Strains In Naturally Fermented Waxy Beans And Optimizing The Ratio Of Blended Bacteria And Waxy Beans

Lobster sauce is a traditional fermented bean products in china.At present,most of the family fermented Ladou production,there are many food safety problems,So we studied the microbial community structure in the process of natural fermented Ladou,then,Screened the strains with high protease activity,We studied the fermentation mechanism of Ladou,To develop a safe,healthy and delicious fermented bean sauce.Using Ladou as raw materials which come from a company in Suqian,The samples were sampled at different time points,and the microbial community structure during fermentation were analyzed,Design of mixed bacteria experiment,The results of this experiment are as follows:In this paper,the method of 16S rDNA V3 amplification and high throughput sequencing was used to explore the growth and decline of the bacteria in the fermentation process.Oh,6h.12h,18h,and 24h were obtained 25922,26355,28535,45503,34563 high quality sequences respectively after quality filtering(QF).At the 97%confidence level,there was a certain difference in the number of OTU at different time points,and the Alpha diversity analysis showed that OTU was the most abundant in fermented soybean sauce for 18 hours.At different time points,the diversity of microbial species was also higher,and the Bacillus species played a leading role in the whole fermentation process.Secondly,there are a small number of lactic acid bacteria.In addition,the pathogenic bacteria(E.coli,Pseudomonas spp.,etc.)also existed in the fermentation process,and even the abundance was higher.And at different time points between the principal component difference is large,in addition,the two time point of the middle of fermentation is close,There is a big difference in the rest.Through the observation of morphological features,supplemented by Gram positive,catalase negative,non H2S,amine salt,nitrate and other bases,15 strains of suspected Bacillus Strains were purified and isolated strains of the natural fermented Ladou,The protease activity of these 15 strains was determined by casein plate method,10 strains with high activity were screened.The 10 strains were used in the fermentation of fermented soybean,the content of amino nitrogen in the fermentation process was determined,and obtained 6 strains,and the content of amino nitrogen in Y5 group was more than 0.9mg/g.The results of physiological and biochemical experiments,as well as 16sRNA sequencing results showed that YW4 was Bacillus subtilis.YW2 and ZZ21 were Bacillus subtilis.Y5,ZZ25 and Y3 were Bacillus subtilis.The yeast was screened and identified by the same method,and 4 strains of Saccharomyces cerevisiae were obtained.YW2,Y5 and J1 were selected as the follow-up test.Design Expert8.06 software was used to mix the 3 strains,The results showed that:compared with the natural fermentation,the The change trend of water content was the same,but the water content of the bacterial colony was not significantly lower than that of the natural fermentation.However,in the pH value of the index,the bacteria group was significantly lower than the natural fermentation group,the sixth groups of pH value was significantly lower than other groups.As the role of the extrinsic cellulase and lipase,blank group indicators were significantly higher than that of inoculation group.The protease activity and the amino nitrogen content of two indicators,inoculation group is better than the natural fermentation group,but the content of free amino acids,the blank group did not significantly lower than inoculation group,The sixth group and tenth group of flavor amino acid and sweet amino acids were higher than that in other groups.It was also consistent with the two indices of protease activity and amino nitrogen.The electronic tongue and sensory analysis,select sixth groups for the best ratio(Bacillus subtilis,Bacillus amyloliquefaciens:Saccharomyces cerevisiae 5.33:3.67:1),and the sixth groups with the production compared to the volatile categories of ck group is naturally fermented a little less,but increase the flavor OTUstanding,which esters and aromatic compounds are higher than that of natural fermentation fermented black bean group sixth,so this group can be used into the production.