Abstract: In this study, the bactericidal effect and mechanism of plasma activated water (PAW) against Shewanella putrefaciens, a common microorganism found in aquatic products, were investigated by plate counting, fluorescence staining and scanning electron microscopy (SEM). The impact of PAW on cell morphology, cell membrane permeability, cell membrane potential and cell content leakage was examined. The results showed that the count of Shewanella putrefaciens was significantly decreased by PAW (P < 0.05). After 6.0 min of treatment with activated water from plasma discharge 120 s (PAW120), the colony count decreased by 7.44(lg (CFU/mL)), the cell morphology showed shrinkage and rupture, and the permeability of the inner and outer membranes increased by 989.31% and 474.51%, respectively. Moreover, intracellular macromolecules such as nucleic acids and proteins leaked out of the cells, and the electrical conductivity increased significantly (P < 0.05). The results of Fourier transform infrared (FTIR) spectroscopy showed that the structures of intracellular lipids and proteins were changed after PAW120 treatment. In conclusion, PAW could destroy the cell wall, and increase the permeability of the cell membrane, thereby leading to the leakage of intracellular nucleic acids and proteins and eventually cell death. This study provides a theoretical basis for the application of PAW in the preservation of aquatic products.

Key words: plasma activated water; Shewanella putrefaciens; inactivation; cell membrane