Smet Cindy, Govaert Marlies, Kyrylenko Alina, Easdani Md, Walsh James L, Van Impe Jan F
Optimization in Engineering Center of Excellence, KU Leuven, Ghent, Belgium.
CPMF2, Flemish Cluster Predictive Microbiology in Foods, Ghent, Belgium.
Front Microbiol. 2019 Jul 4;10:1539. doi: 10.3389/fmicb.2019.01539. eCollection 2019.
Recent research has proven the ability of cold atmospheric plasma (CAP) for assuring food safety. A more flexible and transportable alternative is the use of plasma activated liquids (PAL), which are also known to have antimicrobial properties. However, within the context of food safety, little is known on its potential regarding decontamination. This research therefore focusses on identifying the impact of (i) the microbial species and its cell type (planktonic cells or biofilms), (ii) the CAP settings (i.e., gas composition and generation time) and (iii) PAL related factors (treatment time and PAL age) on the technologies efficacy. Cell densities were monitored using the plate counting technique for which the results were analyzed by means of predictive inactivation models. Moreover, the pH and the concentrations of long-lived species (i.e., hydrogen peroxide, nitrite, and nitrate) were measured to characterize the PAL solutions. The results indicated that although the type of pathogen impacted the efficacy of the treatment, mainly the cell mode had an important effect. The presence of oxygen in the operating gas ensured the generation of PAL solutions with a higher antimicrobial activity. Moreover, to ensure a good microbial inactivation, PAL generation times needed to be sufficiently long. Both CAP related factors resulted in a higher amount of long-lived species, enhancing the inactivation. For 30 min. PAL generation using O, this resulted in log reductions up to 3.9 for biofilms or 5.8 for planktonic cells. However, loss of the PAL activity for stored solutions, together with the frequent appearance of a tailing phase in the inactivation kinetics, hinted at the importance of the short-lived species generated. Different factors, related to (i) the pathogen and its cell mode, (ii) the CAP settings and (iii) PAL related factors, proved to impact the antimicrobial efficacy of the solutions and should be considered with respect to future applications of the PAL technology.
最近的研究已经证实了冷大气等离子体（CAP）确保食品安全的能力。一种更灵活、便于运输的替代方法是使用等离子体活化液体（PAL），众所周知，这种液体也具有抗菌特性。然而，在食品安全背景下，人们对其去污潜力知之甚少。因此，本研究着重于确定（i）微生物种类及其细胞类型（浮游细胞或生物膜）、（ii）CAP设置（即气体成分和产生时间）以及（iii）与PAL相关的因素（处理时间和PAL存放时间）对这些技术效果的影响。使用平板计数技术监测细胞密度，并通过预测失活模型对结果进行分析。此外，还测量了pH值以及长寿命物质（即过氧化氢、亚硝酸盐和硝酸盐）的浓度，以表征PAL溶液。结果表明，尽管病原体类型会影响处理效果，但主要是细胞模式产生重要影响。操作气体中氧气的存在确保了具有更高抗菌活性的PAL溶液的产生。此外，为确保良好的微生物失活，PAL的产生时间需要足够长。这两个与CAP相关的因素都会导致产生更多的长寿命物质，从而增强失活效果。对于使用氧气产生30分钟的PAL，生物膜的对数减少量可达3.9，浮游细胞的对数减少量可达5.8。然而，存放溶液的PAL活性丧失，以及失活动力学中频繁出现拖尾阶段，都表明了所产生的短寿命物质的重要性。与（i）病原体及其细胞模式、（ii）CAP设置和（iii）PAL相关因素有关的不同因素，都被证明会影响溶液的抗菌效果，在考虑PAL技术的未来应用时应予以考虑。
