Isolation and characterization of enterocin SE-K4 produced by thermophilicenterococci, Enterococcus faecalis K-4

Enterococcus sp. K-4, with a bacteriocin-like activity against E. faecium, was isolated from grass silage in Thailand. Morphological, physiological, a nd phylogenetic studies clearly identified strain K-4 as a strain of E. fae calis. Strain K-4 produced a maximal amount of bacteriocin at 43-45 degrees C. We purified, for the first time, the bacteriocin produced at high temper ature by E. faecalis to homogeneity, using adsorption on cells of the produ cer strain and reversed-phase liquid chromatography. The bacteriocin, desig nated enterocin SEK4, is a peptide of about 5 kDa as measured by SDS-PAGE, and Mass spectrometry analysis found the molecular mass of 5356.2, which is in good agreement. The amino acid sequencing of the N-terminal end of ente rocin SE-K4 showed apparent sequence similarity to class IIa bacteriocins. Enterocin SE-K4 was active against E. faecium, E. faecalis, Bacillus subtil is, Clostridium beijerinckii, and Listeria monocytogenes. Enterocin SE-KLL is very heat stable.