Understanding the mechanisms of action of atmospheric cold plasma towards the mitigation of the stress induced in molds: The case of Aspergillus chevalieri

Aspergillus chevalieri is a xerophilic/xerotolerant fungi affecting dried food products. In this study the ability of non-thermal cold atmospheric plasma (CAP) at high power density (NO_x) to affect biological process inducing the stress responses of A. chevalieri species exposed for 5 min (5’CAP-NO_x) and 30 min (30’CAP-NO_x) were analysed at 0, 1, 6, 12 and 48-h post treatment (hpt). At 48 hpt with 30’CAP-NOx, 84% of fungal growth reduction was observed. The membrane integrity estimated by confocal investigation after carboxyfluorescein diacetate/propidium iodide staining showed the dead surface mycelium layers exposed to the treatments. Reverse transcription-quantitative real-time PCR revealed an early downregulation, at 0 hpt, followed by upregulation or recovery starting to 1 hpt, of selected key genes involved in fungal stress responses. The cellular response to stress was confirmed by mycelial glutathione accumulation in the early phase after both CAP-NO_x treatments, at 0 and 1 hpt, followed by the strong glutathione reduction at 12 and 48 hpt using 30’CAP-NOx treatment. The ability of A. chevalieri to modulate metabolic profile according to treatments was underlined by volatilome investigation, which mainly involved lipid metabolism. This work highlighted the adaptative response mechanisms of A. chevalieri to overcome the CAP-NOx treatment.

Industrial relevance

The application of cold atmospheric plasma (CAP) technology to avoid microbial growth in foods is considered of high interest. Utilization of CAP technology, a nonthermal technique, is encouraged because of its efficiency in maintaining natural aroma and flavor and product shelf-life. Regarding the management of Aspergillus chevalieri, the developments in mechanistic insights indicated that cold plasma affected several targets in fungal cells and was a successful tactic when employed to stop the selection of resistant fungal strains.