Bacterial Diversity Of Mare's Milk And Its Products In Yili Of Xinjiang

Koumiss was considered to be popular dairy products by nomadic people in Inner Mongolia,Xinjiang,Mongolia and Central Asia.Koumiss was endowed with rich microbial biodiversity,especially lactic acid bacteria by traditional processing technology and natural production environment.This work aimed to reveal the bacterial biodiversity and abundances of fresh mare's milk and koumiss,culture dependent method was performed to obtain lactic acid bacteria isolates in these samples,meanwhile single molecule real time sequencing technology was used to investigate bacterial communities.The viable counts of lactic acid bacteria were ranged between 6.00×104 CFU/mL?9.20×108 CFU/mL in this study.A total of 246 lactic acid bacteria isolates were isolated from mare's milk,which were identified as belonging to 6 genera and 20 species or subspecies.Among which,the predominant species was Lactobacillus helveticus with the proportion of 32%.In the fresh mare's milk,the dominant lactic acid bacteria isolates was coccus,accounting for 86%of total isolates in fresh mare's milk.The majority of lactic acid bacteria isolates from koumiss were Lactobacillus,accounting for 76%of total isolates in koumiss.The results of culture dependent method showed that there were significant differences of the composition of lactic acid bacteria communities between fresh mare's milk and koumiss.Based on PacBio SMRT sequencing,a total of 550 species of bacteria belong to 366 genera and 18 phyla were identified from these samples.Among them,Firmicutes was the predominant phyla,Lactobacillus,Lactococcus,Staphylococcus and Streptococcus were the predominant genera,Lactobacillus helveticus,Lactococcus lactis,Lactobacillus kefiranofaciens and Streptococcus thermophilus were the most abundant species.The results of PCoA analysis showed that the bacterial community structure was different in fresh mare's milk and koumiss(p<0.05),and the bacterial diversity in the fresh mare's milk was significantly complex than that in the koumiss.Staphylococcus aureus(3.03%)and other opportunistic pathogens also were detected in a few fresh mare's milk;however,these strains were not found in koumiss.It maybe infers that lactic acid bacteria could inhibit opportunistic pathogens growth with the progress of fermentation.Thus,we can conclude bacterial composition in fresh mare's milk has an important influence on the bacterial community structure of koumiss.This study combines culture dependent method and PacBio SMRT sequencing to analyze bacterial diversity of koumiss and fresh mare's milk,and also provide theoretical guidance for the quality improvement and industrial production of traditional koumiss.