Screening of zearalenone-producing Fusarium species in Egypt and chemically defined medium for production of the toxin.

296 isolates of Fusarium spp. from 100 samples of ccereal grains were examined for their ability to produce zearalenone on liquid culture medium. Thin layer chromatographic analysis revealed that the mycotoxin was detected from 45 isolates, (F. oxysporum), 36; F. moniliforme, 8; and F. equiseti, one isolate). A suitable liquid medium and some optimal conditions for the biosynthesis of zearalenone were reported. Glutamine and riboflavin stimulated the production of the toxin. The maximum amount of zearalenone appeared at pH 7, after 12 days of incubation at 20 degrees C.