Oxidative lesions and post-treatment viability attenuation of listeria monocytogenes triggered by atmospheric non-thermal plasma

Abstract

Aims The aim of the current study was to investigate the effect of plasma‐mediated oxidative stress on the post‐treatment viability of Listeria monocytogenes at the physiological and molecular levels. Methods and Results 107 CFU/ml L. monocytogenes in 10 ml phosphate‐buffered saline (PBS) was treated with atmospheric non‐thermal plasma for 0, 30, 60, 90 and 120 s respectively. Optical diagnostics using optical emission spectroscopy (OES) confirmed that dielectric barrier discharge (DBD) plasma was a significant source of ample exogenous reactive oxygen and nitrogen species (RONS). The development of extracellular main long‐lived species was associated with plasma exposure time, accompanied by a massive accumulation of intracellular ROS in L. monocytogenes (p < 0.01). With the exception of virulence genes (hly), most oxidation resistance genes (e.g. sigB, perR, lmo2344, lmo2770 and trxA) and DNA repair gene (recA) were upregulated significantly (p < 0.05). A visible fragmentation in genomic DNA and a decline in the secretion of extracellular proteins and haemolytic activity (p < 0.01) were noticed. The quantitate oxygen consumption rates (OCRs) and extracellular acidification rates (ECARs) confirmed the viability attenuation from the aspect of energy metabolism. Survival assay in a real food system (raw milk) further suggested not only the viability attenuation, but also the resuscitation potential and safety risk of mild plasma‐treated cells during post‐treatment storage. Conclusion DBD plasma had the potential to inactivate and attenuate the virulence of L. monocytogenes, and it was recommended that plasma exposure time longer than 120 s was more suitable for attenuating viability and avoiding the recovery possibility of L. monocytogenes in raw milk within 7 days. Significance and Impact of the Study The current results presented a strategy to inactivate and attenuate the viability of L. monocytogenes, which could serve as a theoretical basis for better application of non‐thermal plasma in food in an effort to effectively combat foodborne pathogens.

Plasma‐activated liquids for mitigating biofilms on food and food contact surfaces

“…The generation mode of PAW can be divided into three categories: direct discharge of the electrode underneath the liquid surface, discharge above the liquid, and multiphase discharge, such as liquid mist or vapor in contact with the plasma. Over the years, researchers have developed various plasma generation systems for different applications, such as plasma jets, gliding arc discharge, plasma needles, plasma pencils, dielectric barrier discharge (DBD), and surface micro‐discharge (Ali et al, 2021b; Pan et al, 2022; Scholtz et al., 2015; Wu et al, 2022). PALs have been found to be a promising antimicrobial agent that could effectively inactivate bacterial cells on various contact surfaces and food surfaces, resulting from the formation of reactive species when plasma interacts with water in the gas phase (Bourke et al., 2017; Esua et al, 2021; 2022d).…”

Correlation of plasma generated long-lived reactive species in aqueous and gas phases with different feeding gases

“…Plasma treatment was initially carried out in a direct way, where the plasma reactive species was directly in contact with the sample surface to complete the treatment [20][21][22][23][24]. In recent decades, indirect plasma approaches were applied by some researchers, where plasma is first discharged in or close proximity to water (or solutions) to create plasma-activated water (PAW), then these nitrogen-oxide-contained acidified solutions were used to immerse samples to complete plasma treatments [10,[25][26][27][28][29].…”