Aflatoxins: production of the toxins on rice-corn steep medium according to some cultural conditions.

Rice powder-corn steep (RC) medium proved to be the most suitable among 6 nutrient liquid media for both aflatoxin formation and mycelial growth by the Aspergillus flavus strain No. 182, isolated locally. The production of aflatoxins by the mould was studied in relation to some cultural conditions on RC medium. Highest aflatoxin yields (2527 microgram/50 ml) by A. flavus were attained using rice (5%, w/v) + corn steep (4%, w/v), at initial pH level of 4,25 degree C and 6 days incubation. The initial pH levels at either extreme of the range used (3 and 11), and temperatures of incubation below 20 degree C or above 40 degree C were inhibitory to mould growth and aflatoxin formation. The ratio of aflatoxin B1 to G1 varied with different cultural conditions. The aflatoxin content of the mycelia highly exceeded that of the culture filtrates.