Interaction between certain moulds and aflatoxin B1 producer Aspergillus flavus NRRL 3251

The objective of this study was to evaluate biotic interaction between some mould species and active producer of aflatoxin B1 Aspergillus flavus NRRL 3251, co-cultured in yeast-extract sucrose (YES) broth. Twenty-five mould strains of Alternaria spp., Cladosporium spp., Mucor spp., A. flavus and A. niger, used as biocompetitive agents, were isolated from outdoor and indoor airborne fungi, scrapings of mouldy household walls, and from stored and post-harvest maize. Aflatoxin B1 was extracted from mould biomasses with chloroform and detected using the multitoxin TLC method. The results confirm antagonistic interaction between all strains tested. With Alternaria spp. and Cladosporium spp., aflatoxin B1 production decreased 100%, compared to detection in a single culture of A. flavus NRRL 3251 (Cmean=18.7 microg mL-1). In mixed cultures with Mucor spp., aflatoxin B1 levels dropped to (5.6-9.3) microg mL-1, and the inhibition was from 50% to 70%. Four of five aflatoxin non-producing strains of A. flavus interfered with aflatoxin production in mixed culture, and reduced AFB1 productivity by 100%. One strain showed a lower efficacy in inhibiting AFB1 production (80%) with a detectable amount of AFB1 3.7 microg mL-1 when compared to control. A decrease in toxin production was also observed in dual cultivation with A. niger strains. It resulted in 100% reduction in three strains), 90% reduction in one strain (Cmean=1.9 microg mL-1) and 80% reduction in one strain (Cmean=3.7 microg mL-1) inhibition.