Inactivation of Salmonella Typhimurium by Non-Thermal Plasma Bubbles: Exploring the Key Reactive Species and the Influence of Organic Matter

Abstract

The key reactive species generated by non-thermal plasma bubbles for the inactivation of Salmonella Typhimurium and the effects of organic matter on the inactivation efficacy were investigated. Plasma, which is primarily composed of ozone (O3), was generated by dielectric barrier discharge and injected into a solution (400 mL) as a bubble. The surviving population of S. Typhimurium decreased in proportion to the treatment time, resulting in a 5.29 log reduction after 5 min of treatment. Verification tests to specify key reactive species were conducted using an O3 destruction unit and reactive oxygen species scavengers. The results indicated that singlet oxygen (1O2) contributes substantially to the inactivation of S. Typhimurium, and that the presence of superoxide anion radicals (O2·−) from O3 is essential for the production of 1O2. When a S. Typhimurium suspension containing organic matter (final concentration: 0, 0.005, 0.05, 0.1, and 0.5 g/L), consisting of beef extract and peptone, was treated with plasma bubbles for 5, 10, 15, 20, 25, and 30 min, respectively, the potential of the plasma bubbles for inactivating S. Typhimurium successfully was verified with longer contact time, despite organic matter attenuating the inactivation efficiency in a dose-dependent manner.

The antimicrobial efficacy of plasma-activated water against Listeria and E. coli is modulated by reactor design and water composition

“…Tiron selectively interacts with and is oxidized by superoxide, allowing its effective removal from the solution (Peskin et al, 1998;Taiwo, 2008). The demonstration of superoxide as a major player in our novel DBDD system is supported by previous research that found superoxide anions and downstream reactive species such as singlet molecular oxygen to be significant contributors to the antimicrobial activity of PAW produced by a dialectic barrier discharge system using plasma generated above the water interface with helium as a feed gas (Xu et al, 2021) and in a bubble system using deionized water (Baek et al, 2020).…”

“…The energetic collisions of electrons with O 2 molecules (O 2 + e − →2O + e − ) account for the formation of ∙O radicals (Zhou et al, 2020) at 777.2 and 844.6 nm, which were produced by both reactors but in higher concentrations in the BSD reactor (Figure 5). Previous studies of dielectric barrier discharge PAW have similarly observed increasing concentrations of O 3 over the activation period (Zhou, Zhou, et al, 2021) and very low concentrations of NO x (Baek et al, 2020).…”

The Antimicrobial Efficacy Of Plasma Activated Water Is Modulated By Reactor Design And Water Composition

“…Trion selectively interacts with and is oxidized by superoxide, allowing its effective removal from the solution (26,27). Our finding is supported by previous research showing that superoxide anions and downstream reactive species such as singlet molecular oxygen are significant contributors to the antimicrobial activity of PAW produced by dialectic barrier discharge against yeast cells (28) and Salmonella Typhimurium (29).…”

Instant inactivation of aerosolized SARS-CoV-2 by dielectric filter discharge

“…These fine particles (≤ 1.0 μm) can evaporate within a few milliseconds, becoming virus-containing “droplet nuclei” and spreading over a wide area of air [ 2 ]. The air-passable DFD generator showed electrical characteristics ( Fig 2B ), which can be observed in the general dielectric barrier discharge [ 21 – 23 ]. The discharge remained stable even when the media aerosols passed through the discharge area.…”