Usefulness of pulsed electric field application as an inactivation technology for plant pathogenic bacteria in hydroponic nutrient solutions

When a pulsed electric field (PEF) is applied to microorganisms, the cells are destroyed by irreversible electroporation, leading to microbial cell death. We focus on the PEF application as a disinfection technology suitable for preventing contamination of nutrient solutions by plant pathogens in closed-hydroponic systems. This study aimed to determine the electric field distribution in our newly-designed PEF disinfection chamber and to evaluate the inactivation efficacy of plant pathogenic bacteria in hydroponic nutrient solution by PEF, utilizing the new chamber. The newly-designed chamber consisted of a wire electrode as the inner anode and a cylindrical electrode as the outer cathode, bonded to insulator silicon rubber supports. Electric field simulation analysis demonstrated that by applying a pulsed voltage of 10 kV to the chamber, the maximum electric field strength in the low-impedance liquid could reach 4.5 MV/m. Simulation results were validated by conducting PEF applying disinfection experiments using the new chamber that showed Escherichia coli and Ralstonia solanacearum in the nutrient solution could be reduced by more than 4 log. It was noteworthy that our chamber with the pulsed voltage application could successfully provide an electric field at a sufficient strength to inactivate bacteria in a low-impedance nutrient solution, where application of high electric fields are difficult. The Weibull and Gompertz models effectively described the correlation between log reduction value and duration time (R 2 > 0.98). Therefore, PEF application was shown to be a potentially available new option as a disinfection technology for nutrient solutions in closed-hydroponic systems. • A coaxial cylindrical PEF disinfection chamber was newly designed and constructed. • The maximum electric field strength in the nutrient solution reached 4.5 MV/m. • PEF applying disinfection reduced plant pathogens by more than 4 log. • PEF can be a promising new disinfection option for closed-hydroponic systems.