Antimicrobial mechanism of Larimichthys crocea whey acidic protein-derived peptide (LCWAP) against Staphylococcus aureus and its application in milk.

Antimicrobial peptides are being explored for use as food preservatives to prevent foodborne diseases. In this study, bioinformatics tools were used to screen potential antimicrobial amino acid sequences from the whey acidic protein (WAP) of large yellow croaker (Larimichthys crocea). A novel antimicrobial peptide, designated as LCWAP, was identified and its antimicrobial effect and mechanism of action on Staphylococcus aureus was explored. The minimal inhibitory concentration (MIC) of LCWAP on S. aureus was 15.6 μg/mL. Transmission electron microscopy and laser confocal microscopy revealed that LCWAP kills bacteria by aggregating on the cell surface, destroying the integrity of bacterial cell membrane and resulting in the leakage of intracellular solutes. Moreover, peptide LCWAP inhibit biofilm formation, at concentrations of 1-1/16 × MIC, with biofilm formation found to decrease by 94.3%-13.7% upon LCWAP treatment. The ability of peptide LCWAP to bind bacteria DNA was revealed using electrophoresis analysis and ultraviolet absorption spectroscopy, with peptide LCWAP/DNA weight ratios of 125/1, and 17.3% decrease in the absorption peak of LCWAP. Furthermore, LCWAP had no cytotoxic effects on normal human hepatocytes, although it had strong inhibitory effect on S. aureus growth in milk.