A novel bacteriocin from Lacticaseibacillus rhamnosus with potent anti-Vibrio activity: Purification, characterization and application in shrimp preservation

The increasing prevalence of antibiotic-resistant pathogens, particularly in seafood, necessitates the discovery of novel biopreservatives. This study reports the isolation of a Lacticaseibacillus rhamnosus SLG21 strain from fermented fish sauce, which exhibits exceptional tolerance to high selenite concentrations (5 mM) and potent antagonistic activity against foodborne pathogens. A novel bacteriocin, designated SLG21, was purified and identified as a 16-residue cationic peptide (KYGNGGLSRIFSALLK, 1554.15 Da). Bacteriocin SLG21 demonstrated broad-spectrum bactericidal activity, with minimum inhibitory concentrations (MICs) of 4–16 μg/mL against Gram-positive pathogens and, crucially, 16–128 μg/mL against Gram-negative pathogens. Mechanistic studies revealed that the bacteriocin SLG21 overcomes the Gram-negative outer membrane barrier through high-affinity binding to LPS, leading to outer membrane permeabilization and subsequent inner membrane depolarization. Toxicology assessments confirmed its biosafety at preservative-relevant concentrations. In a shrimp model inoculated with Vibrio parahaemolyticus, bacteriocin SLG21 (1× MIC) rapidly inhibited bacterial growth and delayed chemical spoilage (as measured by total volatile basic nitrogen). Although its recoverable activity decreased to 28.5% by day 8, the initial bactericidal action may suggest potential application in Pacific white shrimp against V.parahaemolyticus.