UVA-LED365 nm and UVC-LED275 nm combined irradiation effectively inactivates Vibrio parahaemolyticus and controls photoreactivation by regulating illumination

Ultraviolet disinfection is a common disinfection method for controlling large-scale disease outbreaks in aquaculture. This study investigated Vibrio parahaemolyticus, a common pathogen in aquaculture, to elucidate the differences in inactivation efficacy between UVA-LED (365 nm) and UVC-LED (275 nm) irradiation, both individually and in sequence. Additionally, it examined the effects and underlying mechanisms of various light conditions on the photoreactivation of V. parahaemolyticus following ultraviolet disinfection. The results demonstrated that UVC-LED achieved superior inactivation efficacy against V. parahaemolyticus, with a 3.9 log reduction at 12 mJ/cm². However, UVA pretreatment did not enhance the subsequent UVC-LED inactivation. Additionally, the bacterial growth rate of photoreactivation reaching 106.96 % under a white light at the intensity of 110 μmol/m²/s, which was significantly higher than that at 50 and 170 μmol/m²/s. Compared to other wavelengths, short wavelengths resulted in a relatively higher bacterial growth rate, with blue light achieving a rate of 143.48 % and significant expression of photolyase genes. In contrast, red and green light significantly inhibited the photoreactivation effect. Correlation analysis demonstrated that the bacterial growth rate was positively correlated with recovery time and light intensity during photoreactivation, while it was negatively correlated with spectral wavelength. This study clarified differences in inactivation efficiency between UVA-LED and UVC-LED, as well as the factors affecting photoreactivation of V. parahaemolyticus. To mitigate photoreactivation, increased light intensity and the avoidance of short-wavelength irradiation during the post-treatment phase provided valuable insights for UV-LED water disinfection systems.