Partial characterization of bacteriocins produced by environmental strain Enterococcus faecium EK13

摘要

Aims: The partial characterization of bacteriocins produced by an environmental strain Enterococcus faecium EK13, isolated from cattle dung water. Methods and Results: A bacteriocin was partially purified by ammonium sulphate precipitation, followed by a SP-Sepharose column, reverse-phase chromatography and N-terminal region sequenced. The anti-microbial substance produced was found to be a heat-stable polypeptide with molecular mass 4.83 kDa, which was determined by N-terminal amino acid sequencing to be enterocin A. A second substance was specified by PCR as enterocin P. Bacteriocins were stable at 4 and -20℃ for long storage periods. The optimum of bacteriocin production was observed in the range of pH 5.0-6.5 at 30 and 37℃. The most active substances are produced by strain EK13 in logarithmic growth phase and bacteriocins are produced after 1 h of fermentation. The highest activity detected in fermentation experiments was 51 200 AU ml~(-1) and the most sensitive indicator strain was found to be Listeria innocua LMG 13568. Differences in bacteriocin activity against two indicators could be explained by more than one type of enterocin production by strain EK13, or with different mode of action or in different sensitivity of strains. Conclusion: Enterococcus faecium strain EK13 isolated from cattle dung water produces two bacteriocins, enterocin A and P, with an inhibitory effect against the strain of the genera Enterococcus, Leuconostoc, Lactobacillus, Streptococcus, Staphylococcus, Bacillus and Listeria (in different origin). Significance and Impact of the Study: Enterococcus faecium EK13 environmental strain is a new producer of enterocin A and P. The E. faecium EK13, isolated from cattle dung water, is presented with the further aim to utilize it for waste treatment by biotechnological processes.