ORCID Profile
0000-0001-6769-2628
Current Organisation
University of Sydney
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Publisher: Cold Spring Harbor Laboratory
Date: 04-01-2023
DOI: 10.1101/2023.01.03.522676
Abstract: The effect of plasma activated water (PAW) generated with a dielectric barrier discharge diffusor (DBDD) system on microbial load and organoleptic quality of cucamelons was investigated and compared to the established sanitizer, sodium hypochlorite (NaOCl). Pathogenic serotypes of Escherichia coli , Salmonella enterica , and Listeria monocytogenes were inoculated onto the surface of cucamelons (6.5 log CFU g −1 ) and into the wash water (6 log CFU mL −1 ). PAW treatment involved 2 minutes in situ with water activated at 1500 Hz and 120 V, and air as the feed gas NaOCl treatment was a wash with 100 ppm total chlorine and the control treatment was a wash with tap water. PAW treatment produced a 3 log CFU g −1 reduction of pathogens on the cucamelon surface without negatively impacting quality or shelf life. NaOCl treatment reduced the pathogenic bacteria on the cucamelon surface by 3-4 log CFU g −1 , however, this treatment also reduced fruit shelf life and quality. Both systems reduced 6 log CFU ml −1 pathogens in the wash water to below detectable limits. The critical role of superoxide anion radical (·O 2 − ) in the antimicrobial power of DBDD-PAW was demonstrated through a scavenger assay, and chemistry modelling confirmed that ·O 2 − generation readily occurs in DBDD-PAW generated with the employed settings. Modelling of the physical forces produced during plasma treatment showed that bacteria likely experience strong local electric fields and polarization. We hypothesize that these physical effects synergise with reactive chemical species to produce the acute antimicrobial activity seen with the in situ PAW system. Plasma activated water (PAW) is an emerging sanitizer in the fresh food industry, where food safety must be achieved without a thermal kill step. Here we demonstrate PAW generated in situ to be a competitive sanitizer technology, providing a significant reduction of pathogenic and spoilage micro-organisms while maintaining the quality and shelf life of the produce item. Our experimental results are supported by modelling of the plasma chemistry and applied physical forces, which show that the system can generate highly reactive superoxide radicals and strong electric fields that combine to produce potent antimicrobial power. In situ PAW has promise in industrial applications as it only requires low power (12 W), tap water and air. Moreover, it does not produce toxic by-products or hazardous effluent waste, making it a sustainable solution for fresh food safety.
Publisher: Cold Spring Harbor Laboratory
Date: 27-07-2023
DOI: 10.1101/2023.07.26.550769
Abstract: Healing and treatment of chronic wounds are often complicated due to biofilm formation by pathogens. Here, the efficacy of Plasma Activated Water (PAW) as a pre-treatment strategy has been investigated prior to the application of topical antiseptics polyhexamethylene biguanide, povidone iodine, and MediHoney, which are routinely used to treat chronic wounds. The efficacy of this treatment strategy was determined against biofilms of Escherichia coli formed on a plastic substratum and on a human keratinocyte monolayer substratum used as an in vitro biofilm-skin epithelial cell model. PAW pre-treatment greatly increased the killing efficacy of all the three antiseptics to eradicate the E. coli biofilms formed on the plastic and keratinocyte substrates. However, the efficacy of the combined PAW-antiseptic treatment and single treatments using PAW or antiseptic alone was lower for biofilms formed in the in vitro biofilm-skin epithelial cell model compared to the plastic substratum. Scavenging assays demonstrated that reactive species present within the PAW were largely responsible for its anti-biofilm activity. PAW treatment resulted in significant intracellular RONS accumulation within the E. coli biofilms, while also rapidly acting on the microbial membrane leading to outer membrane permeabilisation and depolarisation. Together, these factors contribute to significant cell death, potentiating the antibacterial effect of the assessed antiseptics.
Publisher: Elsevier BV
Date: 10-2021
Publisher: Oxford University Press (OUP)
Date: 04-2022
DOI: 10.1111/JAM.15429
Abstract: This study aimed to compare the efficacy of plasma-activated water (PAW) generated by two novel plasma reactors against pathogenic foodborne illness organisms. The antimicrobial efficacy of PAW produced by a bubble spark discharge (BSD) reactor and a dielectric barrier discharge-diffuser (DBDD) reactor operating at atmospheric conditions with air, multiple discharge frequencies and Milli-Q and tap water, was investigated with model organisms Listeria innocua and Escherichia coli in situ. Optimal conditions were subsequently employed for pathogenic bacteria Listeria monocytogenes, E. coli and Salmonella enterica. DBDD-PAW reduced more than 6-log of bacteria within 1 min. The BSD-PAW, while attaining high log reduction, was less effective. Analysis of physicochemical properties revealed that BSD-PAW had a greater variety of reactive species than DBDD-PAW. Scavenger assays designed to specifically sequester reactive species demonstrated a critical role of superoxide, particularly in DBDD-PAW. DBDD-PAW demonstrated rapid antimicrobial activity against pathogenic bacteria, with superoxide the critical reactive species. This study demonstrates the potential of DBDD-PAW produced using tap water and air as a feasible and cost-effective option for antimicrobial applications, including food safety.
Publisher: American Society for Microbiology
Date: 17-08-2023
DOI: 10.1128/SPECTRUM.00034-23
Abstract: Plasma-activated water (PAW) is an emerging sanitizer in the fresh food industry, where food safety must be achieved without a thermal kill step. Here, we demonstrate PAW generated in situ to be a competitive sanitizer technology, providing a significant reduction of pathogenic and spoilage microorganisms while maintaining the quality and shelf life of the produce item.
No related grants have been discovered for Joanna Rothwell.