Diffusion and Antibacterial Properties of Nisin-Loaded Chitosan/Poly (L-Lactic Acid) Towards Development of Active Food Packaging Film

Nisin-loaded chitosan/poly (L-lactic acid) (nisin-CS/PLLA) antimicrobial films were prepared by coating method. The structure and mechanical properties of nisin carrier CS/PLLA films were investigated, and the antibacterial behavior of nisin-CS/PLLA against Staphylococcus aureus ATCC6538 was assessed. Furthermore, the diffusion behaviors of nisin from films were evaluated by diffusion kinetics and thermodynamics, and the diffusion efficiency was investigated as a function of CS/PLLA ratio, pH, and ionic strength. When CS/PLLA ratio was at 1:1 (w/w) and above, a notable enhancement was observed in the tensile strength with the increase of PLLA content, while the elongation at break was decreased slightly at the same time. However, a significant decrease in tensile strength and elongation at break were present when the CS/PLLA ratio was below 1:1. There existed intermolecular hydrogen bonds between CS and PLLA molecules. The diffusion of nisin from film was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔH ᵒ , ΔS ᵒ , and ΔG ᵒ) indicated that the diffusion process of nisin from film was spontaneous and endothermic. From diffusion and antimicrobial activity results, nisin-CS/PLLA films revealed well-controlled release and better antimicrobial activity against S. aureus, which may have potential as a novel active food packaging film.