Molecular Characterization of Fungi Producing Aflatoxin in Vigna subterranean (Bambara Groundnut) sold in Three Selected Markets in Enugu Metropolis

Abstract

Humans require nutritious food for a healthy diet. Bambara groundnut (Vigna subterranean) as a crop has many varieties of uses. However, toxic strains of Aspergillus species found in contaminated BG produce carcinogenic aflatoxins. Intake of food that has contamination of aflatoxin (>20 ppb) is unsafe. This study identified the fungi that produce aflatoxin in BG using a molecular approach. Samples were acquired from five different locations in Abakpa, New Main, and Ogbete Market in Enugu State, Nigeria. Streptomycin was used to inhibit bacterial growth, and the samples were directly plated on Saboraud Dextrose Agar to isolate the fungi. The plates were stored at room temperature for 48-72 hours, and pure fungus culture was obtained by repeated subculturing. BG aflatoxin quantification was carried out using an enzyme-linked immunosorbent assay. The isolates were subjected to an aflatoxigenic analysis using molecular methods. The number of isolated fungi was 77 isolates. Among the isolates, the frequency of occurrence ranged from Alternaria macrospora and Scolecosporae (1% each) to Aspergillus flavus (32%). Aflatoxin levels in the samples were higher than the permissible threshold (20 ppb), ranging from 69 ppb (Abakpa) to 80 ppb (Ogbete). All sequenced and screened isolates contain an aflatoxin regulatory gene. The study results show aflatoxin contaminated BG samples, rendering them unhealthy for human consumption.