Synergistic effects of ultrasound and plasma-activated water against Listeria innocua in crayfish disinfection by metabolomics analysis

Abstract

The synergistic mechanisms of ultrasound combined plasma-activated water (US-PAW) against Listeria innocua were investigated with the intention of crayfish disinfection. US and PAW showed a significantly synergistic effect against L. innocua at 7 min. Specifically, no significant change was observed in the CK (sterile water) and US treatment groups as the duration of treatment increased. At 7 min, the reduction of L. innocua achieved by US-PAW treatment was 4.49 Log CFU/mL, which was significantly higher (p < 0.05) than the reduction for PAW treatment (2.46 Log CFU/mL). Furthermore, the Weibull model demonstrated superior efficacy in fitting the kinetic inactivation curves of L. innocua throughout the US, PAW, and US-PAW treatments. In addition, PAW disrupted the morphology of L. innocua and increased the electrical conductivity of the bacterial suspension, accelerated leakage of proteins and nucleic acids from cells and increased the intracellular reactive oxygen species content, which was further promoted by US-PAW. The molecular mechanisms underlying these phenotypic changes were investigated using untargeted metabolomics. The results indicated that US exacerbated the destruction of PAW on the nucleotide, glycerolipid, peptidoglycan and amino acids metabolism, further affecting the metabolism of various substances and energy in cells, ultimately leading to cell death. Besides, US-PAW showed significant antibacterial effects on L. innocua in crayfish with minor effects on the sensory characteristics. These findings provided theoretical support for the application of US-PAW in crayfish disinfection.