Diversity Of Lactic Acid Bacteria(LAB) In Raw Camel Milk In Hami Area Of Xinjiang And Screening Of Bacteriocin-Producing LAB Strains

Objective:Camel milk and its milk powder,as a characteristic dairy product in Xinjiang,is highly sought after by modern people because of its high nutritional value,low sensitivity,antagonistic effect on certain pathogens and medical and health care functions.The camel's special living environment and feeding pattern lead its milk has a unique composition of microorganisms.The microorganisms in camel's milk not only affect the nutrition of camel milk,but also have a certain impact on the consumer's health.The rich content of lactic acid bacteria in camel milk makes the milk become a unique source searching the strains which have stronger ability to produce acid.This also makes the camel's milk becoming a special source of probiotics.Thus,studying the lactic acid bacteria's composition and distribution in the milk is very meaningful for the father research and exploitation of camel's milk.Methods:In this study,lactobacillus was isolated and cultured on three kind of selective media:Lactobacillus selective medium,MRS medium and M17 medium.The lactobacillus was identified at the level of species by rep-PCR fingerprint technique and 16S rRNA sequencing technique.Then,the Oxford cup method was used to screen out the efficient and broad-spectrum antibacterial strains.Finally,the diversity of lactic acid bacteria in raw camel milk was analyzed by high throughput sequencing technology,and compared with the result of traditional culture method.Conclusion:1.In total,227 pure cultures were obtained from the raw camel milk in Hami region of Xinjiangby by traditional culture method.Then,91 lactic acid bacteria strains were screened by Gram staining and enzyme contact reaction.According to the results of 16S rRNA gene sequencing technology,all of the 91 strains belonged to 11 species or subspecies of five genera which respectively were Lactococcus,Leuconostoc,Enterococcus,Lactobacillus and Streptococcus.Among them,Leuconostoc took 36.26%which obviously was the dominant lactic acid bacteria in raw camel milk.2.The Oxford cup method was used to test the bacteriostasis ability of the selected lactobacillus strains'supernatant fermentation broth.Six pathogenic bacteria were chosen as indicator bacteria which respectively were Lister monocytoferes,Salmonella typhimurium,Salmonella enteric,Lapactic Escherichia coli,Enterotoxigenic Escherichia coli and Enterohemorrhagic Escherichia coli.Eliminating the interference of organic acid,the results showed that HMT10-38,HMT17-12,HMT53-20 and HMT61-40 had the most significant bacteriostatic effect on the six indicators.Protease hydrolysis experiments showed that bacteriocins or other antimicrobial peptides might exist in the fermentation supernatant of these four lactic acid bacteria strains.3.The result of high-throughput sequencing technology showed that was used to analyze the diversity of lactic acid bacteria in the original camel milk.There were total seven genus of lactic acid bacteria which respectively were Lactobacillus Lactococcus,Leuconostoc,Enterococcus,Lactobacillus,Streptococcus,Bacillus and Brochothrix.The relative abundance of Leuconostoc and Lactococcus was relatively high.Besides,four potential pathogens which respectively were Enterococcus,Ochrobactrum,Staphylococcus and Pseudomonas were detected.In conclusion,the result was close to the traditional separation techniques.