Evaluation of plasma-activated water: Efficacy, stability, physicochemical properties, and mechanism of inactivation against Escherichia coli

In this study, plasma-activated water (PAW) was prepared by discharge below the surface of sterile distilled water. In addition to physicochemical properties, the bactericidal effect and mechanism of action of PAW were studied using Escherichia coli as the target microorganism. The plasma treatment would cause an increase in the redox potential (ORP), electrical conductivity (EC), NO3− and NO2− content, and a decrease in the pH of the water. At the same time, the sterilization effect of PAW on E. coli was progressively stronger with both discharge and immersion time, up to a maximum of 4.25 log CFU/mL. In addition, the EC, NO3− and NO2− content, as well as the bactericidal efficacy of PAW decreased with increasing storage time. The properties and bactericidal effects did not change significantly after PAW thawing (p > 0.05). Finally, proteomics techniques were used to identify and classify the differential proteins before and after PAW treatment. PAW treatment induced a stress response in E. coli. Differential expression proteins of biological processes including the metabolism of phosphorus-containing compounds and the cellular response to stimuli, as well as various binding-related and membrane structure-related, were induced.