Preparation And Research Of Chitosan/Poly (L-lactic Acid) Antibacterial Film

Antimicrobial coating packaging is a kind of active packaging, which has been paid attention because of its safety, economy and high efficiency. The papers focus on the antimicrobial coating film research, preparation of nisin and Sodium L-lactate loaded chitosan (CS)/polylactic acid (PLLA) film. The film mechanical properties, barrier properties and antibacterial behavior were researched.(1) Films were prepared with chitosan, poly (L-lactic acid). The results of Fourier infrared spectroscopy (FTIR), and thermogravimetric analysis (TG) showed that the existence of hydrogen between CS and PLLA improved the thermal stability of films. 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 significantly decrease in tensile strength and elongation at break were present when the CS/PLLA ratio was below 1:1. The films of gas transmission rate (carbon dioxide, oxygen, water vapor) and transmission were also different since the difference of content of CS and PLLA led to different degrees of crystallization of films.(2) Nisin-CS/PLLA films were prepared with chitosan, poly (L-lactic acid) and nisin. The antibacterial behavior of nisin-CS/PLLA against S. aureus was assessed. The diffusion behaviors of nisin from films were evaluated by diffusion kinetics and thermodynamics, and the diffusion efficiency was investigated as a function of pH and ionic strength. The thermodynamic parameters(ΔH °, ΔS° and ΔG°) 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.(3) Sodium L-lactate-CS/PLLA films were prepared with chitosan, poly (L-lactic acid) and Sodium L-lactate. The antibacterial behavior of Sodium L-lactate -CS/PLLA against E. colid was assessed. Sodium L-lactate-CS/PLLA films revealed well controlled release and better antimicrobial activity against E. colid. From diffusion results, the kinetic diffusion agrees well with the Fick’s second law. The thermodynamic parameters (ΔH°, ΔS°and ΔG°) indicated that the diffusion process of Sodium L-lactate from film was spontaneous and endothermic.