Native production of pediocin PA-1 by Enterococcus faecium E16 isolated from goats' cheese

Enterococcus faecium E16, a strain isolated from goats' cheese made from unpasteurized milk, showed antibacterial activity, in particular against Listeria monocytogenes strains. The active compound was produced at high amounts in de Man Rogosa and Sharpe broth at 37 degrees C. It was purified to homogenity from culture supernatant by using a simple method consisting of cation-exchange and reversed-phase chromatographies. Mass spectrometry showed that the antibacterial activity was due to a 4621.32 Da peptide. Its amino acid sequence was analysed using Edman degradation an it showed that the peptide consisted of 44 unmodified amino acids with two disulphide bonds linking cysteine residues at positions 9, 14 and at positions 24, 44. This structure was shown to be identical to pediocin PA-1, a class Ha bacteriocin. The antimicrobial activity of the produced pediocin PA-1 covered a range of bacteria, with strong activity against many species of Gram-positive bacteria, especially the food-borne pathogen Listeria monocytogenes, but no activity against Gram-negative bacteria. This study represents the first reported case of natural pediocin PA-1 production by an Enterococcus species.