Microbial Evaluation and Identification of Aflatoxin- Producing Fungi in Dried Stored Maize Samples Sold in Open Markets in Benin City, Nigeria

Abstract

Maize (Zea mays) is an annual monoecious crop and the most important cereal in the world after wheat and rice with regard to cultivation areas and total production. Despite the various improvements in the drying and storage of maize, the growth of moulds is usually a common occurrence in stored grains. The grain is vulnerable to biodeterioration by mycotoxigenic fungi which include Aspergillus, Fusarium and Penicillium. In this study, the microbial load of dried stored maize samples from three different open markets in Benin City was evaluated, and the aflatoxin-producing Aspergillus specie identified. The pH and moisture contents of samples were also determined. Five fungal species; Aspergillus niger, Rhizopus sp. Fusarium sp. Aspergillus flavus, and Penicillium sp., as well as three bacterial species; Staphylococcus aureus, Bacillus sp. and Pseudomonas sp. were isolated and identified using standard cultural and morphological techniques. The mean total bacterial count ranged from 3.8±0.20×10  (Oba market) to 5.2±0.20×10  (New Benin market), while the mean total fungal count ranged from 3.7±0.29×10  (Oba market) to 6.47±0.38×10  (New Benin market). The mean pH ranged from 5.9 (Oba market) to 6.7 (New Benin market) while the mean moisture content ranged from 16.1% (Oba market) to 18.2% (New Benin market).  Aspergillus flavus was identified as the potential aflatoxin-producing specie, and it had 100% occurrence in all samples. The study showed that stored maize samples had higher fungal load than bacteria, and were contaminated with Aspergillus flavus; a potential aflatoxin-producing fungus. It is then necessary to observe strict pre and postharvest practices in order to reduce microbial contamination of stored grains of the unsuitability of the culture medium in the preliminary recovery of this unique group of herbicide degrading bacteria.