Production and purification of ochratoxin A: effects of media, light, and fungal strain variety

Ochratoxin A (OTA) is a mycotoxin produced by fungal species from the Aspergillus and Penicillium genera, frequently contaminating food products such as cereals, coffee, and dried fruits. OTA’s nephrotoxic, immunosuppressive, and potentially carcinogenic properties pose significant risks to food safety and public health. Efficient and reproducible protocols for OTA production and purification are essential to facilitate downstream applications, particularly in toxicological studies where high-purity OTA is required. This study investigated the effects of growth media, light conditions, and fungal strain variability on OTA production. Six different liquid media were first evaluated using five fungal strains to determine the optimal medium for OTA biosynthesis. The two highest-yielding strains from this screening were subsequently tested under different light conditions and time points to optimise production parameters. These optimised conditions were then applied to a large-scale screening of 53 fungal strains to assess their OTA production capabilities. Results showed that Czapek yeast autolysate medium yielded the highest OTA concentrations, with strains of Aspergillus westerdijkiae and Aspergillus steynii emerging as the highest-yielding producers. Continuous darkness significantly enhanced OTA production, with peak yields observed between days 14 and 17. The purification protocol achieved a near 100% purity level with a final recovery efficiency of 75%, ensuring a reproducible method for obtaining high-purity OTA. The optimised conditions are compatible with future isotope labelling applications, where defined media are essential. These findings contribute to standardising OTA production and purification for toxicological studies, metabolomics, and use as analytical standards.