Viriditoxin production by Aspergillus viridi-nutans and related species

Bioproduction of viriditoxin on various substrates by strains of the Aspergillus fumigatus group was determined under several incubation conditions. Aspergillus viridi-nutans strains NRRL 4365 and 576 produced the largest quantities of toxin, A. brevipes gave reduced yields, and there was no detectable synthesis by isolates of four related species. After 30 days in static culture at 20 C on various autoclaved agricultural commodities, optimal yields of 440 and 380 mg of toxin were observed per kilogram of sorghum and rice. Toxin levels were reduced on corn, rye, and wheat (40-200 mg/kg); yields were low on cottonseed, barley, and oats. Incubation at 10 C restricted biosynthesis of viriditoxin, and no toxin accumulated on substrates maintained at 5 C for 120 days. In a liquid, yeast extract-sucrose medium, maximal mycotoxin production developed in shake flasks; after 156 h, 10 mg of toxin accumulated per gram of mycelium. Viriditoxin produced in submerged culture was associated with the mycelium; less than 1% was detected in the filtered broth after 156 h of incubation.