Kinetics and spatial distribution of OTA in Aspergillus carbonarius cultures

The aim of this study was to characterize Ochratoxin A (OTA) production by Aspergillus carbonarius under different environmental conditions, and to elucidate the diffusion capacity of OTA throughout synthetic medium. One strain belonging to the species A. carbonarius isolated from vine dried fruit was single-point inoculated onto triplicate synthetic nutrient medium plates at two water activities (0.92 and 0.97) and two temperatures (20 and 30 °C). Daily radii were measured and OTA production was tested after 4, 7, 10, 14 and 18 days of incubation at four distances from the centre of colony (1–4 cm). OTA production was detected mainly at 0.97aw. Earlier production was detected at 30 °C (optimum for growth), whereas maximum OTA concentrations were found at 20 °C. OTA production was detected from mycelium that was only a few days old and attained its optimum when mycelium was 4–7 days old at 0.97aw. OTA diffusion was observed at 0.92aw and 20 °C. Thus OTA production is discernable in young A. carbonarius mycelium and diffusion of the toxin has been shown to occur in a solid substrate.