Ochratoxigenicity of Aspergillus ochraceus group and Penicillium verrucosum var. cyclopium strains on various media.

Production of ochratoxin A (OA) by strains of Aspergillus ochraceus group (A. ochraceus--21, A. sclerotiorum--1, A. sulphureus--1) and Penicillium verrucosum var. cyclopium strains--11, on various media was investigated. Thirteen percent of A. ochraceus strains and 18% of P. verrucosum var. cyclopium formed OA growing on sterile crushed wheat for 14 days at 25 to 27 degrees C (preliminary experiments). Toxin concentrations were 5.0 to 7.0 micrograms/kg. Five strains OA-positive on crushed wheat and four OA-negative strains were cultivated on various liquid nutritional media (YES, RM, OAT, CG and AFP). All the strains tested, including OA-negative ones, produced OA on certain liquid media. Concentrations of OA were low again (trace to 16.0 micrograms/l). The largest number of mould strains examined produced OA on YES (55.5%) and RM media (44.0%), but the highest concentration (16.0 micrograms/l) was formed on YES and CG media.