Preparation of a bilayer edible film incorporated with lysozyme and its effect on fish spoilage bacteria

Abstract

AbstractAn edible bilayer film incorporated with lysozyme based on chitosan and sodium alginate was prepared via the layer‐by‐layer method. The film was characterized and its effects against the fish spoilage bacteria Pseudomonas fluorescens and Shewanella putrefaciens were investigated and compared to the monolayer films. The results suggest that electrostatic interactions such as hydrogen bonds occurred between the two layers of the bilayer film. Compared with monolayer films, the mechanical and gas barrier properties of the bilayer film were improved and higher inhibitory activity against both bacteria was exhibited. After treatment with the bilayer film, scanning electron microscopy revealed the serious damage to the bacterial cell surface, and cell membrane permeability and nucleic acid leakage increased. The bilayer film also affected the activity of alkaline phosphatase and adenosine triphosphatase. SDS‐PAGE of bacterial total protein revealed that the protein concentration n decreased, which may be due to the leakage of proteins from the damaged bacterial cell. All the results indicate that the bilayer film possesses good physicochemical properties and can destroy the bacterial cell membrane. Such superior antibacterial properties against fish spoilage bacteria indicate a good potential application of bilayer films in fish preservation.