Isolation and characterization of anti-listerial and amylase sensitive enterocin producing Enterococcus faecium DB1 from Gajami-sikhae, a fermented flat fish in Korea

Bacteriocinogenic Enterococcus faecium DB1 was isolated from Korean gajami-sikhae, a lactic fermented flat fish. The antimicrobial spectrum of E. faecium DB1 was limited to Listeria monocytogenes, Lactobacillus curvatus, and Pediococcus acidilactici in agar well diffusion assay; while it was expanded to other Grampositive and negative bacteria by direct and deferred assays. Induction of enterocin DB1 by co-culturing with sensitive indicators was not detected. Inactivation of bacteriocin activity was observed after treatment of crude enterocin DB1 with proteolytic enzymes and alpha-amylase, but not with catalase, sodium dodecyl sulfate, Tween 20 and 80. The bacteriocin activity was retained in pH between 2.0 and 10.0, and after treatment at 121A degrees C for15 min. Maximum activity (1,280 AU/mL) against L. monocytogenes KCTC 3569 was observed in MRS broth and remained for at least 16 hr. The molecular weight of partially purified enterocin DB1 was approximately 16.5 kDa, and mode of action is bactericidal. Enterocin DB1 production trait is linked to a chromosomal DNA.