Mycotoxin formation by Aspergillus flavus and Fusarium graminearum irradiated maize grains in the presence of other fungi

Abstract

Production of aflatoxins B1 and G1 and zearalenone by, respectively, Aspergillus flavus and Fusarium graminearum was measured when they were cultured alone and in pairs with other filamentous fungi in irradiation-sterilized maize seeds, at three water activities (0.98, 0.95 and 0.90 a(w)) and two temperatures (25 and 16°C). A. flavus was paired with A. niger, A. oryzae, Penicillium viridicatum and F. graminearum and F. graminearum was paired only with A. flavus. Compared to pure culture, aflatoxin production in mixed fungal cultures was decreased at high water activities but was enhanced when water activity was low (0.90 a(w)). More aflatoxin was usually produced at 25 than at 16°C. Zearalenone production was markedly decreased at 16°C by the presence of A. flavus but was little affected at 25°C. Zearalenone production in pure cultures of F. graminearum changed little between 25 and 16°C at any a(w).