Preliminary Study On Microbial Diversity And Probiotic Characteristics Of Lactic Acid Bacteria In Traditional Fermented Raw Cheese(Suzme) From Northern Xinjiang

Raw cheese,as a typical characteristic food in Xinjiang,has been loved by people of all nationalities for a long time.Among them,Kazakh traditional cheese has a long history,which has exquisite practice,unique flavor and civilization.However,these dairy products with unique national characteristics are less and less valued by the impact of cheese industrialization.In the long run,it will not only cause the loss of this traditional technology,but also cause the loss of rich microbial resources contained in cheese.Therefore,it is of great significance to increase the mining and evaluation of lactic acid bacteria resources in traditional dairy products.In this study,five traditional fermented dairy products,including cheese and milk lumps,were collected from farmers’ families in Urumqi,Altay,Tacheng and other regions of Xinjiang.The microbial population structure and diversity in cheese were evaluated by high-throughput sequencing technology.Based on the analysis of traditional culture technology,the dominant strains were selected from traditional fermented dairy products,and the probiotics and tolerance test of dominant lactic acid bacteria were carried out.The main results are as follows:1.The results of High-throughput bacterial sequencing showed that there were 26 phyla,68 classes,172 orders,267 families,447 genera,640 species and 802 OTUs in the five sample bacterial communities.At the level of 16 S r RNA,Firmicutes was dominant,followed by Proteus and a small number of Bacteroides.At the genus level,streptococcus was the dominant bacteria in the samples of Fuyun County cheese a,Tacheng cheese Q and Urumqi cheese U,while lactobacillus was the dominant bacteria in the samples of Urumqi milk lump K and Harbin County cheese N.There were a large number of strains which could not be classified at the genus level in the traditional fermented cheese of Northern Xinjiang,and the OTUs accounted for 2.67%,indicating that there may be a large number of unknown populations.2.Based on ITS genus level,taxonomically,the fungal communities of the five samples involved 7 phyla,21 classes,41 orders,69 families,99 genera,141 species and179 OTUs.Geotrichum and Candida were the main species in the five samples.The richness of Urumqi cheese U and Tacheng cheese Q samples was higher than that of other samples,and the low abundance of Saccharomyces and Saccharomyces were also detected in fermented cheese Kazachstania,tausonia,Issatchenkia,etc.3.In this study,the traditional hand-made dairy raw cheese and milk lumps of herdsmen’s families in Northern Xinjiang were selected as the research objects.The culturable microorganisms in Raw cheese were isolated and identified by traditional isolation and culture methods and molecular biology methods.A total of 53 strains of bacteria were obtained from 5 samples,which were classified into 4 genera and 13 species.Among them,14 strains were Lactobacillus paracasei,12 strains of Lactobacillus gallinarum,8 strains Lactobacillus rhamnosus,2 strains were Enterococcus durans,2strains of Bacillus thuringiensis and 2 strains of Lactobacillus brevis,4 strains of Bacillus cereus,2 strains of Bacillus pumilus,1 strain of Bacillus safensis,1 strain was Bacillus subtilis,1 strain of Bacillus tropicalis,1 strain of Paenibacillus polymoya,in which Lactobacillus)The dominant bacteria were bacillus and Enterococcus.A total of27 yeasts were identified by 26 S r DNA D1 / D2 spacer sequence analysis.They were classified into 4 genera and 4 species,including 19 Pichia fermentans,6 strains were Yarrowia lipolytica,1 Kluyveromyces lactis culture and 1 geotirichum candidum.Comparing the results of this study with other studies at home and abroad,we can see that there are similarities and differences in the microbial composition of Raw cheese in different regions.4.The growth curve of 41 strains of lactic acid bacteria screened out in this study and their tolerance to low p H environment were tested.The results of acid tolerance test showed that 6 strains(QM-5,QM-27,UM-12,UM-18,NM-11,NM-14)of 41 strains of lactic acid bacteria could grow well at p H 2,2.5,3,3.5,4 respectively,The survival rate of the strain was more than 50%,and the content of lactic acid bacteria was more than 108 CFU / ml.41 strains of lactic acid bacteria isolated from cheese were cultured in simulated gastrointestinal solution and solution containing 0.3%,0.5% and 1.0% bovine bile salt.The tolerance test of artificial gastrointestinal solution and bovine bile salt was carried out.The results showed that lactic acid bacteria isolated from cheese had strong acid resistance and bile salt resistance,and could survive in gastrointestinal environment smoothly.41 strains had inhibitory effect on Escherichia coli,Staphylococcus aureus and Bacillus subtilis.Based on the results of tolerance test,acid resistance test,gastrointestinal trsimulation test,bile salt tolerance test and bacteriostasis test,we selected 3 strains as the dominant strains.