Isolation And Identification Of Lactic Acid Bacteria In Goat Milk And Its Bacterial Diversity

Goat milk has high nutritional value with abundant protein,fat,lactose,minerals and vitamins which is a natural medium for microbial growth and propagation of the contaminated microbes Therefore,microbial compositions in goat milk are meaningful for controlling and guaranteeing the quality of raw milk.In this research,molecular biology techniques were used to isolate and identify the lactic acid bacteria(LAB)in goat milk and study the probiotics and harmful bacteria to provide the basis for the development and utilization of goat milk.Part one:Lactic acid bacteria compositions in goat milk.LAB in 71 goat milk samples were identified by physiological biochemistry methods and 16S rRNA gene sequencing analysis.Through microbial analysis,LAB contents was relatively low,accounting for 0.39%to 9.75%of total bacterial contents.Senventy-senven strains of LAB were identified as E.hirae(80.5%),E.faecalis(10.4%),W.cibaria(3.9%),L.lactis(2.6%),E.faecium(1.3%)and L.garvieae(1.3%)by 16S rRNA gene sequencing.The results showed that E.hirae is dominant LAB in goat milk.Part two:Analysis of bacteria diversity in goat milk.The metagenomic DNA of the bacteria in 6 goat milk samples were extracted to analyze the microbial diversity.The results showed that there are 27 bacterial phyla,including Firmicutes,Bacteroidetes,Proteobacteria,etc;there are 354 bacterial genera,including Staphylococcus,Acinetobacter,Enterobacter,Stenotrophomonas,Massilia,Pseudomonas,Bacillus,there are 826 bacterial species,with more than 1%bacteria species have P.aeruginos,A.johnsonii,P.geniculata,B.anthracis.Enterobacter,Acinetobacter,Lachnoclostridium,Pseudomonas,Staphylococcus,Massilia,Bacteroides,Stenotrophomonas,Bacillus,and Bradyrhizobium are identified in all 6 samples.Microbial distribution in goat milk varied in different districts.The particular genera of Cellulosilyticum,Lutispora,Aminivibrio,Aminobacterium,Prevotella,Longilinea and Epulopiscium,etc.were identified in goat milk sampled from Yangling district;Oscillospira,Rhodovulum,Alsobacter,Mesoflavibacter,Prevotellaceae,Acetitomaculum,Halobacteriovorax,Halioglobus and Legionella,etc,were identified in Baoji district;and Bergeyella,C.Nitrosopelagicus,Anaerofustis,Neptuniibacter,Lachnoclostridium and C.Soleaferrea,etc.were identified in Weinan district.Part three:Analysis of probiotics and harmful bacteria in goat milk.Through the analysis of bacteria diversity in goat milk,probiotics and harmful were identified including probiotics of Lactococcus,S.thermophilus,Lactobacillus,Enterococcus and Weissella,bacteria species have L.lactis,L.delbrueckii,L.casei,L.intestinalis,L.reuteri,L.ruminis,W.cibaria,L.mucosae,L.iners and L.curvatus.L.lactis,L.delbrueckii,L.casei,L.intestinalis,L.reuteri,L.ruminis,W.cibaria,L.mucosae,L.iners and L.curvatus;and harmful bacteria of Enterobacter,Acinetobacter,Staphylococcus,Stenotrophomonas,Halomonas,Oligella,Ae omonas,Moraxella,Brachysp ira,Fusobacterium,Oscillosp ira,Treponema,P revotella,Serratia,Erysipelothrix,Rhodococcus,Prevotellaceae,Haemophilus and Myroides.There are thermophilic bacteria that during storage produce thermostable lipase and thermostable protease,have Pseudomonas,Alcaligenes,Psychrobacter,P.aeruginosa,P.geniculata,P.psychrotolerans,P.alimentarius,P.celer,etc.