AUTHOR=Zhang Weixiao , Huang Ruipin , Zhang Tao , Wang Baolong , Li Na , Sun Yan , Ma He , Zhang Qian , Zhang Junxin , Liu Ying 

TITLE=Study on the inactivation and reactivation mechanism of pathogenic bacteria in aquaculture by UVC-LED

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1139713

DOI=10.3389/fmars.2023.1139713

ISSN=2296-7745

ABSTRACT=<p>Ultraviolet disinfection is an important method for controlling the large-scale outbreaks of diseases in aquaculture. As a novel and promising light source, ultraviolet light-emitting diode (UV-LED) has the advantages of safety, high efficiency and no environmental pollution risks. However, it remains unclear whether UV-LEDs can replace traditional UV light sources for aquaculture water treatment processes. Present study aimed to investigate the efficacy of UVC-LEDs (265 nm) on pathogenic bacteria, specifically <italic>Aeromonas salmonicida</italic> and <italic>Escherichia coli</italic>. The effects of UVC-LED dose, light conditions, and temperature on bacterial reactivation were also investigated. The results showed that exposure to UVC-LED effectively inactivated both types of bacteria. To achieve 4.5-log inactivation of <italic>A. salmonicida</italic> and <italic>E. coli</italic>, 24 mJ/cm<sup>2</sup> and 28 mJ/cm<sup>2</sup> UVC-LED irradiation were required, and the inactivation rate increased with increasing UVC-LED fluence. Both <italic>A. salmonicida</italic> and <italic>E. coli</italic> were revived after UVC-LED disinfection, and photoreactivation was significantly higher than dark reactivation. Bacterial reactivation rate due to high-dose UVC-LED treatment was significantly lower than that of low-dose. After 72 h of reactivation, photoreactivation and dark reactivation rates were 1 ± 0.4% and 2.2 ± 0.2%for <italic>A. salmonicida</italic>, and 0.02% and 0% for <italic>E. coli</italic>, respectively. Besides, the photoreactivation rates for the two bacteria exhibited different correlations with temperature. The highest photoreactivation rate for <italic>A. salmonicida</italic> was 68.7 ± 4% at 20°C, while the highest photoreactivation rate for <italic>E. coli</italic> was 53.98 ± 2.9% at 15°C for 48 h. This study reveals the rapid and efficient inactivation of bacteria by UVC-LED, and elucidates the mechanism and influencing factors for inactivation and reactivation by UVC-LED. The study also highlights that adequate UVC-LED irradiation and avoidance of visible light after UVC-LED disinfection can effectively inhibit bacterial reactivation. Our findings form a reference for the design and operation of UV disinfection in aquaculture.</p>