Community Structure of Aflatoxin Producing Fungi in Cassava Products from Nigerian Geo-political Zones

Abstract

One of the internationally recognized household food and feed safety challenge is the global contamination of agricultural commodities with aflatoxins. Fungal growth and aflatoxin contamination are the consequence of interactions among the fungus and the host crop when interplayed with favorable changes in environment/climate. Population distribution of fungi, particularly Aspergillus in substrate such as cassava products, as well as their aflatoxin contamination levels, were investigated across the six geo-political zones of Nigeria. Standard mycological methods were used to isolate and identify the fungi while Enzyme-Linked Immunosorbent Assay (ELISA) was utilized in the analysis of aflatoxins. According to results, mean fungal count ranged from 1.2x103cfu/g to 1.1x107cfu/g, with no significant difference (p>0.05) across the zones in the pellets, industrial cassava flour and Garri, except for Local Cassava flour where a highly significant difference (p<0.01). Species of fungi identified include; Aspergillus Sect.Flavi, Aspergillus niger, A. nidulans, A. tereus, A. fumigatus, Penicillium italicum, P. oxalicum, P. sp,. Mucor mucedo, M. sp., Neospora sp., Choanophora sp., Cladosporium sp., Rhizopus sp., Rhodotorula sp., Saccharomyces cerevisiae, Fusarium oxysporium, Botrydoplodia theobromae, Helminthosporium sp. and Trichoderma sp. A. niger had highest incidence of 9.8%, A. Sect. Flavi 8.5% and Trichoderma sp occurring least. Aflatoxin levels was highest in local cassava flour from Benue (83.54ppb±2.95). Only 10% of the cassava products met EU standard limit while 75% met US/Nigerian standard. Cassava acts as a good substrate for fungal growth and aflatoxin production, thus should be given adequate intervention attention like maize and groundnuts.
Key words: Bacteriological, Physicochemical, Irvingia spp, Benin