Biocontrol of Aflatoxins in Corn using Atoxigenic Aspergillus flavus: Review

Mycotoxins are low-molecular-weight natural products formed as secondary metabolites by filamentous fungi. While aflatoxins are a group of four mycotoxins (B1, B2, G1 and G2)) that are primarily produced by two closely related fungi, Aspergillus flavus and Aspergillus parasitica. Since these toxins are mutagenic and carcinogenic, over 100 countries have imposed regulations for levels of aflatoxin both in feeds and foods. Physical and biological factors affect the production of aflatoxins in both pre- and post-harvest corn. Corn is a major crop associated with high economic risks and considerable safety concerns for aflatoxin contamination yet, it is one of the most utilized cereals in the world. Several control methods of aflatoxin production in corn have been devised. However, most of these methods are expensive and not environmentally friendly. Therefore, there is interest in developing a biological control method that has been characterized as; effective, environmentally friendly, cost- effective and innovative means of reducing aflatoxins levels in crops. Utmost achievements to date in biological control of aflatoxin contamination have been attained through the use of competitive nontoxigenic strains of AspergiIlus fungi. The working principle is that when the atoxigenic AspergiIlus fungi is introduced at the right time, a shift of strain profile from toxigenic to atoxigenic will take place. Moreover, atoxigenic strains competitively exclude the toxigenic strains in the field, which gives a carryover advantage in storage. Microbiological procedures, DNA, and field-based methodologies are the powerful techniques used in selecting atoxigenic strains from the environment. Efficacy of these atoxigenic A. flavus strains (AF36, K49, NRRL 21882, La3279, F3W4 and K54 have been reported with highest reduction of aflatoxins being 99.3 %. Inoculation method, inoculum rate and Optional time for application of nontoxigenic strain are factors affecting the efficacy of atoxigenic Aspergillus flavus. Molecular studies reveal that the loss of aflatoxin production by atoxigenic Aspergillus strains is via mutation. Global climate change has being reported has a major challenge in utilizing Aspergillus flavus as a biocontrol agent in aflatoxin production in corn.