A novel bacteriocin DY4-2 produced by Lactobacillus plantarum from cutlassfish and its application as bio-preservative for the control of Pseudomonas fluorescens in fresh turbot (Scophthalmus maximus) fillets

A novel bacteriocin DY4-2 was produced by strain DY4-2 which was isolated from cutlassfish (Trichiurus lepturus) and identified as Lactobacillus plantarum. This bacteriocin reached the maximum production at stationary phase after 24 h incubation. It was purified by ethyl acetate extraction followed by ultrafiltration, Sephadex G25 chromatography and high-performance liquid chromatography. The molecular mass of bacteriocin DY4-2 was determined as 1465 Da by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. The amino acid sequence of bacteriocin DY4-2 was predicted to be HAQIGMTMNGSFR by MALDI-TOF-MS/MS. Bacteriocin DY4-2 was heat-stable (30 min at 121 °C) and kept active at the pH range of 2.5-5.5, but was sensitive to proteolytic enzymes. The mode of action of bacteriocin DY4-2 was bactericidal. It exhibited broad spectrum antimicrobial activity against fish pathogenic and spoilage bacteria, such as Pseudomonas fluorescens, P. aeruginosa, Vibrio parahaemolyticus, Aeromonas sobria and Listeria monocytogenes. The addition of partially purified bacteriocin DY4-2 in turbot fillets reduced the number of P. fluorescens by 2.7 log units at 4 °C storage for 12 days. Moreover, compared to the control, a significant decline in total viable counts and total volatile base nitrogen was observed in bacteriocin DY4-2 treated samples. Theses results suggested that bacteriocin DY4-2 had potential to act as seafood bio-preservative.