Purification and Characterization of Multiple Bacteriocins and an Inducing Peptide Produced by Enterococcus faecium NKR-5-3 from Thai Fermented Fish

Enterocins NKR-5-3A, B, C, and D were purified from the culture supernatant of Enterococcus faecium NKR-5-3 and characterized. Among the four purified peptides, enterocin NKR-5-3A (5242.3 Da) was identical to brochocin A, produced by Brochothrix campestris ATCC 43754, in mature peptides, and its putative synergistic peptide, enterocin NKR-5-3Z, was found to be encoded in ent53Z downstream of ent53A, encoding enterocin NKR-5-3A. Enterocin NKR-5-3B (6316.4 Da) showed a broad antimicrobial spectrum, and enterocin NKR-5-3C (4512.8 Da) showed high activity against Listeria. Enterocin NKR-5-3D (2843.5 Da), showing high homology to an inducing peptide produced by Lactobacillus sakei 5, induced the production of the enterocins. The enterocins showed different antimicrobial spectra and intensities. E. faecium NKR-5-3 concomitantly produced enterocins NKR-5-3A, B, C, and D which probably belong to different classes of bacteriocins. Furthermore, NKR-5-3 production was induced by enterocin NKR-5-3D.