Combined Effects of Long-Living Chemical Species during Microbial Inactivation Using Atmospheric Plasma-Treated Water

Abstract

Electrical discharges in humid air at atmospheric pressure (nonthermal quenched plasma) generate longlived chemical species in water that are efficient for microbial decontamination. The major role of nitrites was evidenced together with a synergistic effect of nitrates and H 2 O 2 and matching acidification. Other possible active compounds are considered, e.g., peroxynitrous acid.Nonthermal plasma gases are currently under study as potential alternatives to conventional sterilization techniques in numerous settings (the food industry, hospitals). Atmospheric nonthermal plasmas of the gliding-arc type (Glidarc) (9, 25) were found to be efficient against microorganisms for treatments performed under burning discharge (12,13,22,26), and the inactivation of cells in water could continue after the discharge had been switched off (13). Microbial cells were also killed by contact with water that had first been activated by discharges (and so-called plasma-activated water [PAW]) without being themselves subjected to the plasma plume (14, 15). Studies performed hitherto using Glidarc in the context of microbial decontamination have aimed to test the influence of biological (i.e., population level, planktonic or adherent state [14]) and physical parameters on decontamination efficiency. Little is known of the mechanisms of action, especially when PAW is used.UV radiation, charged particles, and temperature are some of the principal factors governing microbial inactivation under plasma technology (20), but they are not relevant for PAW decontamination because the burning discharge is switched off during treatment. It is likely that reactive-nitrogen-and -oxygen-based species play an important role in the lethal effect of nonequilibrium atmospheric air-based plasma (10,20). DNA, RNA, proteins, and lipids are the principal targets of these oxidants (4, 8). The main radical species present in the Glidarc plasma plume have been identified as ⅐ OH and NO ⅐ when humid air is the working gas (1). These radicals are precursors of other active species in water, such as nitrates, nitrites, and hydrogen peroxide (3), which endow the medium with high and sustainable reactivity. The efficiency of these long-lived chemical species in removing chemical pollutants was yet evidenced (24), but their implication in microbial inactivation by PAW was demonstrated for the first time here. Chemical species are also responsible for acidification (2) which role in the antimicrobial activity was also considered during the present study.PAW was produced by application of Glidarc (5 min) over 20 ml of sterile distilled water. The design of the device and the procedure for gas discharge have been described previously (23) , and 1.6 Ϯ 0.2 mmol liter Ϫ1 nitrites (Griess reagent; VWR, Fontenay-sous-Bois, France). Its pH value was 3.0 Ϯ 0.1. No major change in PAW characteristics was detected 30 min after the treatment (corresponding to the maximum period of disinfection). The contributions of nitrites, nitrates, and H 2 O 2 to the lethal effect of PAW w...

Gliding arc discharge-assisted biodegradation of crystal violet in solution with Aeromonas hydrophila strain

“…This %COD %bleaching Fig. 5 Evolution of residual concentration, bleaching, and COD removal of CV during direct exposure of CV to discharge method was used by Naïtali et al (2010) to stop the lethal effect of the glidarc plasma on the microorganisms in TPDR conditions and can be used in this work in order to demonstrate the effectiveness of the second step of coupling.…”

“…The plasma-pre-treated dye solution was used for the biological treatment with the A. hydrophila strain. Before this second step of coupling, the lethal effect of plasma (TPDR effects) was neutralized by adjusting the pH of the plasma-pre-treated solution at pH 6 with NaOH solution (Naïtali et al 2010).…”

UV–vis spectroscopy study of plasma-activated water: Dependence of the chemical composition on plasma exposure time and treatment distance

“…RONS combined with an increased acidity of PAW are thought to act in synergy, providing a strong oxidative attack against bacteria. 15) The reported high sensitivity of bacteria cells to PAW might arise from the higher surface area-to-volume ratio of these prokaryotic cells than of eukaryotic cells, which increases the RONS concentrations in these cells. 22) Within bacteria, RONS can destroy the cell through increased oxidative stress 5) or DNA damage.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Its proposed high level of effectiveness in killing bacteria has earned it the nickname "water of death". 10) PAL has a good shelf-life with a reported retention of its antibacterial activity from days to weeks 7,15) to even years. 16) Apart from water, plasma-treated aqueous buffer and cell culture media are being investigated for cancer therapy.…”

Translation of plasma technology from the lab to the food industry

“…The exposure of aqueous solutions to atmospheric plasmas results in the generation of relatively long-lived secondary products such as hydrogen peroxide, nitrates and nitrites which may react to form further cell toxic compounds such as peroxynitrous acid. [21,22] -9 -Conventional methods of decontamination and cleaning of fresh produce such as vegetables are based on rinsing with water containing concentrations of chlorine, chlorine dioxide or ozone.…”