Sublethal Non-Thermal Plasma Exposure Alters Mycotoxin Profiles of Aspergillus niger in Solid-State Cultivation

Aspergillus niger is widely used in industrial biotechnology but can also occur as a contaminant in food and feed. Certain strains produce mycotoxins, including fumonisins and ochratoxins, posing a potential risk to food safety. Non-thermal plasma (NTP) has emerged as a promising decontamination technology; however, most studies have focused on fungal spore inactivation, while its impact on mycotoxin production by growing mycelium remains poorly understood. The aim of this study was to evaluate the effect of sublethal NTP treatment on A. niger cultures and to assess the subsequent production of fumonisin B2 (FB2), ochratoxin A (OTA), and ochratoxin B (OTB). Cultures were exposed to NTP at different developmental stages and analyzed at multiple time points. Mycotoxin amounts per unit surface area were determined using UPLC–MS/MS. No mycotoxins were detected in cultures incubated for 24 h, regardless of plasma treatment or sampling time. In contrast, cultures incubated for 48 h or longer produced measurable amounts of FB2, OTA, and OTB. Untreated 72-h and 96-h control cultures exhibited substantially higher OTB concentrations compared with plasma-treated variants. Correlation and multivariate analyses confirmed an association between cultivation time and OTA/OTB levels and identified long-term untreated cultures as a distinct cluster characterized by elevated OTB production. These results demonstrate that the response of A. niger mycotoxin production to NTP strongly depends on the developmental stage of the culture. Sublethal plasma treatment applied to actively growing mycelium can modulate toxin profiles rather than merely inactivate fungal cells, highlighting an important safety aspect of plasma-based decontamination technologies.