Study On Identification Of Lactic Acid Bacteria Isolated From Sani Dairy Cake In Yunnan And Its Functional Characteristics

In this study,Lactic acid bacteria was isolated from twenty-five goat milk cakes and five acid whey produced by Sani people resided in Shilin County,Yunnan Province.Genus-species identification of the forty-six bacilli and twenty-seven cocci were completed by combining traditional identification methods and modern molecular biology techniques.Besides,acid resistance,bile tolerance and antibacterial characterization of selected sixteen isolates were also studied.The results were as follows.Lactic acid bacteria were the main microorganism group in the thirty samples.The number of lactic acid bacteria reached up to 10~8cfu/g or 10~8cfu/mL,while that of yeast was mostly 10~4cfu/g or 10~4cfu/mL.The counts of lactic acid bacteria were obviously higher than those of yeast in the samples.Further,a simple,accurate,economic and semiautomatic method of plate culture count was established and dynamic variation of lactic acid bacteria number and pH value of representative samples through post-fermentation was first studied in the field of microbiological investigation on dairy products.Forty-six bacilli of seventy-three isolates consisted of strains from four genera,thirteen species.They were Lactobacillus plantarum(fourteen strains),Lactobacillus fermentum (three strains),Lactobacillus casei(two strains),Lactobacillus brevis(two strains), Lactobacillus alimentarius(one strain);Weissella confusa(eleven strains),Weissella paramesenteroides(four strains),Weissella cibaria(one strain);Bacillus cereus(three strains), Bacillus subtilis(two strains),Bacillus coagulans(one strain),Bacillus thuringiensis(one strain) and Citrobacter freundii(one strain).Among them,Lactobacillus plantarum and Weissella confuse were dominant strains.Twenty-seven cocci of seventy-three isolates consisted of strains from five different genera,nine different species.They were Pedicoccus acidilactici(seven strains),Pedicoccus pentosaceus(seven strains);Lactococcus lactis(five strains);Enterococcus faecium(two strains),Enterococcus durans(two strains);Leuconostoc lactis(one strain),Leuconostoc pseudomesenteroides(one strain) and Staphylococcus capitis (one strain),Staphylococcus simulans(one strain).Drawing of phylogenetic tree and molecular evolutionary genetics analysis of lactic acid bacteria isolated from dairy cake and acid whey were completed after sequencing.Among the screened sixteen isolates,fifteen strains were able to grow in MRS broth medium whose pH value was 2.0;only two Lactobacillus plantarum strains were able to grow in MRS broth medium whose bile salt concentration was 0.5%and all isolates were able to inhibit the growth of three pathogenic bacteria,namely E.coli,Staphylococcus aureus subsp. aureus and Listeria monocytogenes.