Bactericidal effect and mechanism of high-voltage electrostatic field (HVEF) against meat-borne spoiler Pseudomonas fragi: Cell membrane damage and oxidative stress

This study aimed to investigate the antibacterial effect of high-voltage electrostatic field (HVEF) treatment (35 kV) at different times (0, 3, 6, 9, 12, 15 min) against Pseudomonas fragi (P. fragi), and the bactericidal mechanism of HVEF was evaluated through the damage of cell wall/membrane and oxidative stress. The results indicated that with the prolongation of treatment time, the mortality rate of P. fragi increased and was up to 99.91 % at 15 min, and the sublethal count firstly increased and then decreased. HVEF treatment made the accumulation of intracellular reactive oxygen species, which led to bacterial cell wall damage and cell membrane perforation, increased membrane permeability and decreased fluidity, thereby causing the leakage of intracellular components. Energy limitation also appeared under HVEF stress as seen from inactivation of ATPase on the membrane. In addition, expression levels of oxidative stress-related genes (sodA, AhpC, and KatE) of P. fragi induced by HVEF were significantly upregulated while significantly upregulated in expression levels of FabF. The decrease in Superoxide Dismutase (SOD) activity and Glutathione/Oxidized Glutathione (GSH/GSSG) ratio further demonstrated that the lipid peroxidation of cell membrane and bacterial oxidative stress contributed to the antibacterial mechanism induced by HVEF.