Isolation and Purification of an Ultraviolet-Stable Bacteriocin Produced by Enterococcus Faecium Strain DSH20 against Listeria monocytogenes

Furthermore application of bacteriocins as alternates for antibiotics، they are fermented as food preservation currently. The aim of this study was isolation and purification of ultraviolet-resistant bacteriocins from enterococci strains active against Listeria monocytogenes. Different strains of enterococci bacteria were isolated and identified from various clinical specimens and bacteriocin production were evaluated against strains of Listeria monocytogenes. An isolate of enterococcus bacteria that produce significant bacteriocin against all studied strains of Listeria monocytogenes was identified based on its phenotypical and biochemical properties as well as its 16SrRNA gene sequencing. In the next stage، this bacteriocin was purified and the effects of proteolytic enzymes، pH، temperature and ultraviolet radiation (UV) on its activity were tested and its molecular weight was determined by SDS-PAGE (Sodium dodecyl sulfate polyacrylamide gel electrophoresis) method. 17 strains of enterococci were isolated and five isolates exhibited an inhibitory effect against Listeria monocytogenes strains and among them، one enterococcus had inhibitory effect against all four strains of Listeria monocytogenes. This enterococcus was identified as Enterococcus faecium strain DSH20 (access number: JX567733. 1). Using proteolytic enzymes led to the loss of antimicrobial activity; so، protein nature of it was confirmed. Bacteriocin production was resistant to UV، high temperature and pH changes. The molecular weight of the bacteriocin was at approximately 35 kilodaltons. Biochemical properties of this bacteriocin، such as thermal stability، resistance to UV radiation and pH، were significant. These properties present it as an alternative of antimicrobial agents against Listeria monocytogenes and preserving of fermented foods.