Nonmigrating Active Antibacterial Packaging: Antimicrobial Mechanism against Staphylococcus Aureus and Its Application in Large Yellow Croaker

In this study, chitosan (CS) was grafted onto the surface of polylactic acid (PLA) film by covalent immobilization to prepare four kinds of CS-grafted PLA (CS-g-PLA) films with different molecular weights. The properties of the films were characterized, and their antibacterial effect and mechanism of action against Staphylococcus aureus (S. aureus) were explored. After being treated with CS-g-PLA films, the cell morphology was destroyed, the permeability of the cell membrane changed, and malate dehydrogenase (MDH) activity decreased. Furthermore, the large yellow croaker fillets were packaged by the films mentioned above and stored at 4 °C, the physicochemical changes and microbial counts were measured. The results showed that the CS-g-PLA films could effectively delay the decay of fish fillets for 1–4 days. Overall, this study demonstrated that grafted films showed great application potential in aquatic product packaging and preservation.