High Aflatoxin Production on a Chemically Defined Medium

Aspergillus parasiticus ATCC 15517 produced 28 to 30 mg of aflatoxin per 100 ml of a medium containing sucrose, asparagine, and salts in stationary and shaken cultures. In the absence of asparagine in the medium, the toxin yields fell drastically, and the thin-layer chromatograms of the chloroform extracts of the cultures indicated the total absence of aflatoxin G₁ and the presence of new intense blue and green fluorescent bands having R_F values lower than aflatoxins. Initial pH was critical and had to be around 4.5 for good growth and high toxin production on this medium. Optimum concentrations of KH₂PO₄ and MgSO₄·7H₂O in the medium were much lower than those normally used in fungal growth media.