| In order to study the distribution and functional properties of the fine microorganism in Traditional soybean paste,the lactic acid bacteria and yeast were screened and purified from Northeast traditional soybean paste in different provinces in the northeast and and Shandong province,and then the strains with wide spectrum bacteriostasis and high enzyme activity were screened and the strains were identified.In order to provide a good theoretical basis for the research and production of fine microorganism in the fermented food industry.This experiment was mainly through plate dilution,preliminary screening and purification of the selected samples,the lactic acid strains and strains of yeast were isolated from them.The screened lactic acid strains and strains of yeast were inoculated into the culture medium of amylase,lipase,protease,cellulase,and?-glucosidase,in order to screen of different enzyme producing strains.Lactic acid bacteria were inoculated in Escherichia coli,Bacillus cereus,Streptococcus mutans,Salmonella typhimurium,and Staphylococcus aureus indicating bacteria suspension.,Using the filter paper method to screen the Bacteriostasis of lactic acid bacteria.The PCR amplification technique was used to identify the species of the representative strains by 16S rRNA gene sequence analysis and the comparative analysis of the homology of the strains.The strains of yeast were inoculated into YEPD liquid medium,using CTAB method to extract total DNA,the PCR amplification technique was used to identify the species of the representative strains by 18S rRNA gene sequence analysis and the comparative analysis of the homology of the strains.85 strains of lactic acid bacteria and 85 strains of yeast were isolated from 18 Northeast soybean paste samples which selected from three provinces in Northeast China and Shandong province.The enzymatic properties and bacteriostatic analysis of lactic acid bacteria were studied,the results on enzyme activity showed that,23 strains were screened with cellulose activity,16 strains were screened with lipase activity,1 strain was screened with amylase activity,14 strains were screened with Beta-glucosidase activity and all strains had no activity on protease.The results on inhibitory effect showed that,1 strain showed inhibitory effect on Listeria monocytogenes,;14 strains showed inhibitory effect on Escherichia coli,the bacteriostasis effect of HS5 was the best;35 strains showed inhibitory effect on Salmonella typhimurium;10 strains showed inhibitory effect on Bacillus cereus,the bacteriostasis effect of H-S-5 on Bacillus cereus was the best;7 strains had inhibitory effect on Streptococcus mutans,5 of the strains were from the samples of HJ5,and the metabolites of lactic acid bacteria in HJ5 samples had a significant effect on inhibiting the growth of Streptococcus mutans;and all strains had no inhibitory effect on staphylococcus aureus.In all the samples of soybean paste,only soy bean paste HS5 could inhibit Escherichia coli,Salmonella and Bacillus.The representative strains were identified by the analysis of 16S RNA gene sequence,Lactobacillus plantarum,Lactobacillus sporogens,and Bacillus coagulans were identified from that.Comprehensive analysis of bacteriostasis and enzyme production of 18 kinds of samples,the samples HJ7 and HS5 have the best enzyme production and bacteriostasis.The screening of yeast and the analysis of enzyme property analysis,by identifying the medium,there were 10 strains producing cellulase,25 strains producing beta-glucosidase and 34 strains producing lipase.None of the selected strains produced protease and amylase.Through the analysis of 18S rRNA gene sequence analysis,three yeast strains were identified,they were the Debaryomyces hansenii?Candida zeylanoides and Zygosaccharomyces rouxii.It is expected to be applied to the production and development of fermented food.The research on the traditional soybean paste in the northeast of China is of great significance in the food industry,and it is worth further research. |
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