Isolation and Purification of Enterocin EL1, a Bacteriocin Produced by a Strain of Enterococcus faecium ^†

A meat isolate, identified as Enterococcus faecium L1, was found to produce a bacteriocin designated enterocin EL1 Enterocin EL1 was active against a narrow spectrum of microorganisms, inhibiting all tested strains of Listeria . Identification of the producer strain was determined phenotypically by biochemical and morphological tests. Enterocin EL1 was heat stable, sensitive to several proteolytic enzymes, and stable from pH 2 to 11. Adsorption of the bacteriocin to producer cells was dependent on ionic interaction of the bacteriocin and the cell surface at various pHs. By changing the pH of the extraction buffer, enterocin EL1 was extracted from E. faecium L1 cells in a concentrated form. Enterocin EL1 isolated by cell extraction was resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a protein with an approximate molecular weight of 2,300. Partially purified enterocin EL1 added to sensitive cells of Listeria ivanovii was bactericidal; however, the bacteriocin did not inhibit the producer strain L1.