Investigating the impact of organic matter on Vibrio parahaemolyticus inactivation in aquaculture water by UV-LED system

Abstract

Ultraviolet (UV) irradiation becomes a promising technology in inactivating pathogenic microbes, but the compositional change of organics and its consequence of inactivation need further study in raw water during UV light-emitting diode (UV-LED) irradiation. Herein, the bench-scale study aimed at evaluating the effect of organic fractions isolated from shrimp-farming water on the inactivation efficiency of Vibrio parahaemolyticus using UV-LED process at wavelengths of 265 nm, 280 nm, and combined wavelengths. The lowest required UV fluence (4.06 mJ/cm2) for 3-log inactivation was attained with UV-LED 280 nm. After UV irradiation the changes in elemental compositions of organic compounds, based on H/C and O/C ratios, were small. This is probably due to low UV exposure and UV resistant structure of organic constituents, predominantly lipid-like compounds. Contrarily, fluorescent spectroscopic analysis that showed degradation of protein-like substances by UV irradiation. In addition, the significant declines in the number of chemical formulas in organic compounds were identified through non-target screening using orbitrap mass spectrometry, suggesting degradation and amalgamation into new compounds. The presence of organic compounds did not profoundly affect inactivation efficiency at applying a minimum required fluence or greater. This study highlights the potential of UV-LED irradiation, particularly at 280 nm, for efficient inactivation of V. parahaemolyticus and subsequent molecular structure alteration of organic matter after UV irradiation.