Assessment of the efficacy of bacterial inactivation by combination treatment with peracetic acid and UVC light-emitting diode and elucidation of the bactericidal mechanism

Abstract

This study was conducted to investigate the bactericidal effects of combination treatment with an ultraviolet C light-emitting diode (UVC LED) and peracetic acid (PAA) on three major foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes). Pathogen-inoculated peptone water (5 ml) was treated with UVC LED and PAA individually or simultaneously. Following combination treatment, a 6.5-log inactivation was observed at 60 s for E. coli O157:H7 and 5.9-log and 3.9-log inactivation were observed at 90 s for S. Typhimurium and L. monocytogenes, respectively. The possibility of reusing the PAA-solution was evaluated to determine the effectiveness of the system in repetitive treatments, which showed that combination treatment could ensure sufficient microbial safety up to 5 treatments. The microbicidal mechanism and role of putative molecules were investigated to elucidate the synergistic of combination treatment. Using reactive oxygen species (ROS) scavengers, center dot O-2(-) was confirmed as the major ROS generated by the combination system, and enhanced cell membrane damage and inhibition of enzymatic activity were observed following combination treatment compared with individual treatments. This study demonstrated that combination treatment with UVC LED and PAA could be used as an innovative non-thermal technology for washing minimally processed fresh produce.