Isolation and Properties of Lactococcuslactis Strain from Kefir Grains
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Abstract:
In order to select probiotic, lactic acid bacteria, a predominant strain, named HUCM 201, was isolated from Kefir grains, which is used as a starter culture for traditional fermented dairy products. This bacterial strain was identified as Lactococcuslactis subsp. Lactis based on its morphologic properties, 16S rDNA sequences, as well as physiological and biochemical characteristics. The strain showed a certain degree of tolerance to acid and bile. After 3 h in a simulated gastric fluid, viable counts for the strain were maintained up to 105 CFU/mL. HUCM 201 strain exposed to MRS broth supplemented with 1% oxgall for 4 h showed a slight decrease in cell viability. Meanwhile, Caco-2 cells, a model forintestinal epithelial cells, were used to measure bacterial adhesive ability. HUCM 201 strain exhibited adherence to Caco-2 cells with an adhesion ratio of1.93%. The minimum inhibitory concentration was used to evaluate antibiotic susceptibility of the isolate. This strain was found to be susceptible to ampicillin, vancomycin, erythromycin, chloramphenicol, and penicillin. Thus Lactococcuslactis subsp. lactisstrain HUCM 201 is a good candidate for further investigation.
