Physicochemical Characterization of a Bacteriocin from Lactococcus lactis KLDS4.0325
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Abstract:
A bacteriocin produced by Lactococcus lactis KLDS4.0325 isolated by Xinjiang herdsmen from self-made koumiss was purified and characterized. The double-plate method was used for detection. The diameter of the inhibition zone (mm) was used as the evaluation index, and it was quantified against Escherichia coli ATCC 25922. The bacteriocin produced by this strain was extracted, purified, and subjected to physicochemical analysis. The bacteriocin crude extract was extracted from the cell-free fermentation supernatant by precipitation with 60% ammonium sulfate. This was followed by SP Sepharose FF cation exchange chromatography to obtain purified bacteriocin samples. The specific activity of the purified bacteriocin was estimated to be 51.02 IU/mg and the inhibitory activity was increased by 18 folds. The molecular mass of the purified bacteriocin was estimated using tricine-sodium dodecyl sulfate polyacrylamide gel electrophoresis and was found to be approximately 3.4 ku. Additionally, the biological characteristics of the bacteriocin were studied by sensitivity experiments of temperature, pH, and various enzymes. The results showed that the bacteriocin was heat-stable and its inhibition zone diameter showed insignificant changes when pH of incubation was increased from 2.0 to 10.0, showing good stability. The inhibitory activity of the bacteriocin was found to be sensitive to proteolytic enzymes such as pepsin, trypsin, papain, α-chymotrypsin, and proteinase K,indicating that it is a type of protein.
