An 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.

Ginger is a condiment vegetable and widely cultivated in many countries for its important role as spice and medicinal herb in international trade. However, the quality of fresh ginger will reduce after harvest and during storage. In the present study, edible coatings were developed based on konjac glucomannan (KGM) and sodium alginate (SA), incorporating with allicin and in situ SiOx. The coatings were characterized, and the effects of the coatings on the quality of ginger were evaluated. The results demonstrate that the addition of allicin improve the compatibility of KGM and SA in film, and the addition of allicin and in situ SiOx promote more hydrogen bond formation in the film. The physicochemical properties of KGM/SA film are improved due to modification, and allicin coating is optimal for mechanical properties, while allicin‐SiOx film is optimal both for mechanical properties and gas barrier. The KGM/SA coatings especially KGM/SA‐allicin‐SiOx significantly inhibited the total phenol, flavonoid, total soluble sugars content, enzyme activities such as peroxidase (POD), polyphenol oxidase (PPO), and cellulase of gingers during storage. In addition, KGM/SA coatings effectively preserved the ascorbic acid (AsA), and titratable acidity (TA). Over all, KGA/SA coatings, especially with allicin and in situ SiOx, exhibited more significant and positive effects on quality of gingers during storage. Therefore, the KGM/SA coatings are promising in gingers preservation.

Pseudomonas fluorescens is a specific spoilage microorganism of refrigerated marine fish, which possesses strong adaptability to low temperature. Cold shock proteins (CSPs) play an important role in bacterial cold adaptation. In this study, the CSP genes were obtained from the genome of P. fluorescens PF08 by search the conserved domain of CSPs through HMMER software, and their physicochemical property, structure and function were analyzed by bioinformatics. A total of five typical CSPs are identified in P. fluorescens PF08 genome (PfCSPs). The results showed that the five PfCSPs are all small hydrophilic acidic proteins with molecular weight around 7.4 kDa. They are located in the cytoplasm and are non-secretory and non-transmembrane proteins. Multiple sequence alignment analysis indicated the CSPs were highly conserved between different species, especially in DNA-binding sites and RNA-binding motifs that can bind to single-stranded DNA and RNA. The five PfCSPs were clustered together with CspD from Escherichia coli and Salmonella typhimurium , which suggested that a close homology and high functional similarity among the five PfCSPs and CspD. The secondary and tertiary structures of the PfCSPs are accordance with the characteristics of the CSPs family and ligand binding sites with higher likelihood were found in PfCSPs. The five PfCSPs were predicted to interact with some of the same proteins that involved in virulence, stress responses (including low temperature), cell growth, ribosome assembly and RNA degradation. The results provides references for further elucidation of the function of CSPs in the process of low temperature adaptation of P. fluorescens .