Bacteriocin-like inhibitory substance (BLIS) produced by Enterococcus faecium MA115 and its potential use as a seafood biopreservative

Introduction: Listeria monocytogenes is an opportunistic foodborne pathogen that can cause death to infected humans. The bacterial pathogen was frequently associated with food-borne origins including seafood. Thus, the present study aimed at screening anti-listeria-producing lactic acid bacteria (AL-LAB) isolated from the intestinal tracts of wild gilt-head seabream (Sparus aurata).

Materials and Methods: Lactic acid bacteria (LAB) were isolated from the intestinal tracts of 15 wild gilt-head seabreams and screened for antimicrobial activity against Listeria monocytogenes. LAB isolated with the strongest anti-listerial activity was identified and further characterized for its anti-listerial compounds, followed by testing its protecting capacity on experimentally contaminated salmon fillets.

Results:Three out of 52 LAB showed antagonistic activities against the foodborne pathogen. Of these 3, an isolate with the strongest inhibitory activity was obtained from strain MA115 (>400 AU). Based on its 16S rDNA sequence, strain MA115 had 99% similarity to Enterococcus faecium (Acc. Nb: MG461637.1). Further in vitro assays showed that the anti-listerial compound was very sensitive to proteinase K which suggested that it is a bacteriocin-like inhibitory substance (BLIS). In addition, the BLIS was resistant to a wide range of pH (2–10), and low (4 to −20°C) as well as high temperatures (30−121°C). In addition, the BLIS showed bactericidal activity on L. monocytogenes in artificially contaminated Salmon fillets stored at 0°C.

Conclusion: The BLIS produced by Enterococcus faecium strain MA115 has the potential for application to improve food safety, although further studies are still required to specifically identify the BLIS, for biopreservation purposes.