| Title |
Safety Evaluation In Vitro of Enterococcus durans from Tibetan Traditional Fermented Yak Milk |
| Author |
Jing Li1, Fazheng Ren2, Huiyong Gu1, Xiaopeng Li1, and Bozhong Gan1* |
| Address |
1College of Food Science and Technology Engineering, Gansu Agricultural University, Lanzhou 730070, P. R. China, 22Key Laboratory of Functional Dairy, Beijing Higher Institution Engineering Research Center of Animal Product, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, P. R. China |
| Bibliography |
Journal of Microbiology, 49(5),721-728, 2011,
|
| DOI |
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| Key Words |
fermented yak milk, Enterococcus durans, safety evaluation, biogenic amines, antibiotic resistance, virulence determinants |
| Abstract |
Despite its ubiquity in fermented dairy products, the safety of lactic acid enterococcal bacteria remains controversial. In this study, five Enterococcus durans strains – A1, A2, B1, B2, and C1 – were isolated from traditional fermented yak milk from Tibet. To evaluate the strains’ safety, biogenic amine production, antibiotic resistance and presence of known virulence determinants were investigated. Strain A1 can produce biogenic amines for histamine, spermine, and spermidine (mean values: 8.64, 8.31, and 0.30 mg/L, respectively). Polymerase chain reaction amplification for Strain A1 found genes involved in expression of gelatinase (gleE), cytolysin (cylA, cylB, and cylM), sex pheromones (ccf and cpd) and cell wall adhesion (efaA). Strain A2 showed sensitivity or intermediate resistance to all tested antibiotics, and no virulence determinants except gelE and ccf, but did produce tyramine at a relatively high level (912.02 mg/L). Both strains B1 and B2 could produce histamine (10.43 and 10.56 mg/L, respectively), and showed vancomycin resistance; B1 also produced tyramine (504.02 mg/L). Strain C1 could produce all five biogenic amines tested in the study – putrescine, histamine, tyramine, spermine, and spermidine; concentrations were 6.51, 9.59, 205.85, 5.55, and 5.39 mg/L, respectively. All E. durans strains found in Tibetan traditional fermented yak milk thus offer potential risk. |
