The antibacterial effect of chitosan-based edible coating incorporated with a lytic bacteriophage against Escherichia coli O157:H7 on the surface of tomatoes

Edible coating can be used as carriers of bacteriophages, whose release into the food surface could control bacterial growth. The aim of the study was to isolate and characterize bacteriophages against a wide range of E. coli strains. Furthermore, the efficacy of chitosan-based edible coating incorporated with a lytic bacteriophage in the biological control of E. coli on the surface of tomatoes was evaluated and discussed. Three phages were isolated from raw beef and goat stool samples, and were characterized by host range, virion structure, and DNA restriction profiles. Analysis by electron microscopy revealed that the three phages belong to the Caudovirales order. Based on the host range of the phages, they have wide infection abilities against the Enterobacteriaceae family. Phages isolated have dsDNA genomes at about 40 kbp according to restriction digest of complete phage genome. The results demonstrate that the chitosan-based edible coating can stabilize phage vB_EcoMH2W without significant loss in lytic activity of phage over a period of one week. Moreover, the results of bacterial growth analysis showed an approximately 3 log differences in microbial levels between the control and the treatment samples. Therefore, chitosan as edible coating would enhance the microbial safety of foods during storage. Practical applications The development of functional edible coatings formulations incorporated with antimicrobial agents to minimize the risk of foodborne contamination by pathogens, inactivate pathogens present in the food, and limit pathogen growth is an environmentally friendly alternative that offers substantial advantages. Several antimicrobial agents, including phages, that can be incorporated into edible coating as packaging strategy to reducing levels of pathogenic bacterial. The edible coating incorporated with lytic phages have several potential applications in the food industry as a natural method for biocontrol of food-borne pathogens, which can be released into the food slowly and steadily extending the antimicrobial activity.