Strain-Dependent Variability in Ochratoxin A Production by Aspergillus spp. Under Different In Vitro Cultivation...

The aim of this study was to investigate differences in the dynamics of ochratoxin A (OTA) production by various Aspergillus isolates under different cultivation conditions. Nine strains representing A. westerdijkiae, A. ochraceus, A. sulphureus, A. carbonarius, and A. albertensis were tested on malt extract agar (MEA), Czapek yeast extract agar (CYA), potato dextrose agar (PDA), and yeast extract sucrose agar (YES). Cultivations were performed at 18 °C, 22 °C, 25 °C, and 30 °C, and OTA production was monitored on the 6th, 10th, 14th, 21st, and 30th days using HPLC analysis. OTA yields strongly depended on the producing strain, with significant variability even among isolates of the same species. The most productive strain was A. ochraceus from cereals with a maximum concentration of 848 µg g^-1 OTA, followed by two isolates of A. westerdijkiae from grapes of Slovak origin (591 and 479 µg g^-1), and A. sulphureus from soil (546 µg g^-1). In contrast, A. carbonarius strains showed the weakest OTA production. Across media, YES supported the highest toxin levels, whereas the most favourable cultivation temperatures were 18 °C and 25 °C. Each strain reached its production maximum at different time points, highlighting the strain-specific nature of OTA biosynthesis.