Efficacy of UV-A, UV-B, and UV-C irradiation on inactivation of foodborne pathogens in different neutralizing buffer solutions

In many UV sterilization studies, buffer solutions are used for investigating the inactivation mechanisms and evaluating the antimicrobial effect of UV light. The aim of this study was to investigate the effects of the type of buffer solution [phosphate-buffered saline (PBS) or peptone water (PW)] on UV inactivation of major foodborne pathogens, including Escherichia colt O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes. A mixed culture cocktail was inoculated in PBS or PW and treated with UV-A, -B, or -C irradiation. The bactericidal efficacy in PW was much lower than that in PBS during all UV treatments. In order to trace the cause of the difference, the absorption spectra of the two buffer solutions were analyzed from 190 to 360 nm. The UV absorption pattern of PW was different from those of PBS. The absorbance rate of PBS in the range of UV-A (356 nm), UV-B (307 nm), and UV-C (254 nm) lamp wavelengths was lower than that of PW. As a result, the different UV absorption levels of the two buffer solutions may affect the sterilization efficiency. These results suggest that PBS is the appropriate neutralizing buffer for ensuring reliable data in microbial research treated with UV-rays.