Inhibitory effect of Vibrio parahaemolyticus phage-functionalized PCL films on the host bacterium

An environmentally stable Vibrio parahaemolyticus phage 475s1 was isolated. • Phage 475s1 was stably immobilized onto biodegradable PCL films. • The films displayed strong antibacterial efficacy in vitro and in salmon. Vibrio parahaemolyticus ( V. parahaemolyticus ) is recognized as a major foodborne pathogen with global prevalence. The overuse of traditional antibiotics has not only induced the emergence of drug-resistant strains, but also posed a potential threat to human health through the food chain. Therefore, the development of green and precisely targeted antibacterial agents is urgent. In this study, a V. parahaemolyticus phage 475s1 was isolated and exhibited remarkable stability over a broad temperature range (0-70 °C), pH range (4–11) and ultraviolet (UV) irradiation durations (0-60 min). It was capable of lysing 12 out of 23 tested V. parahaemolyticus strains, with a burst size of 110 plaque-forming units (PFU) per infected cell. The phage 475s1 was immobilized onto the surface of biodegradable polycaprolactone (PCL) films. The results showed that the binding density of phage on the PCL films reached 0.04 phages/μm 2 , while the host-capturing density was approximately 0.05 cells/μm 2 . After ultrasonic treatment for 20 min, 35% of the phages remained stably adsorbed on the PCL films. The phage-functionalized PCL films were further applied to artificially contaminated salmon samples. At an incubation temperature of 37 °C, the phage-functionalized PCL films exhibited significant antibacterial efficacy. Compared with the control group, the bacterial concentration decreased by 1.72 log CFU/mL at 2 h and 1.60 log CFU/mL at 3 h, respectively. Therefore, these findings indicate that the V. parahaemolyticus phage-functionalized PCL films hold great promise as a novel and effective antibacterial packaging material. This work provides a feasible green antibacterial strategy against seafood-borne V. parahaemolyticus , offering valuable theoretical support for the development of biodegradable active packaging for industrial aquatic preservation.