Purification of the Anti‐listerial Bacteriocinlike Inhibitory Substance Produced by Enterococcus Faecium 108

Extracellular antimicrobial substances produced by certain enterococci inhibit Listeria monocytogenes. Enterococcus faecium 108, a competitive food isolate, produced a heat‐stable and protease‐sensitive anti ‐L. monocytogenes bacteriocin‐like substance (Ef108) in Listeria selective enrichment broth and other media. Ef108 activity was purified to homogeneity by a four‐step procedure including (NH 4 ) 2 SO 4 fractionation, chromatography on anion exchange QSepharose column, and two Superose 12 gel filtration columns. In activities represented by two peaks (Ef108A and Ef108B), 90% of the crude activity was due to peak B. Ef108A is believed to be a variable aggregate of the active moiety in Ef108B. All Listeria spp. and five L. monocytogenes serotypes were inhibited by Ef108B in several media including Listeria enrichment medium. The Ef108 activity may be due to a bacteriocin‐like inhibitory substance produced by E. faecium 108 that may suppress the growth and predominance of Listeria monocytogenes during selective enrichment .