Identification and Characterization of Multi-Mycotoxins Recovered from Dry Corn in Selected Markets in Enugu Metropolis, Enugu State, Nigeria

Abstract

Corn is an important food crop that forms a major meal plan in Nigeria. Its high nutritious value also makes it perfect for fungi to thrive and produce its metabolites. Mycotoxin is a fungi metabolite that is toxic to both humans and animals. This study aimed at isolation of fungi from corn vended in selected markets in Enugu metropolis, identification and characterization of mycotoxin  produced from the isolates. A total of 9 corn samples were collected from 3 different markets in Enugu metropolis comprising of Emene ,Ogbete and New markets  respectively . The samples were cultured on potatoes dextrose agar for isolation, isolates were identified and characterized by cultural, biochemical and microscopic analysis of the organisms; selected isolates were further characterized by polymerase chain reaction (PCR). The isolates were subjected for mycotoxin production by culturing in potatoe dextrose broth for 14 days at 35°C after which the filtrates were assayed for the presence of mycotoxin using gas chromatography-mass spectroscopy (GC-MS) and individual aflatoxins were further characterized using high performance liquid chromatography (HPLC). From the study, Fusarium and Aspergillus flavus occurred at 66% respectively, Aspergillus niger at 55%, Mucor spp at 77%, Penicillium spp at 33%, and Aspergillus fumigates at 44%. PCR amplified products of the selected isolates showed positive amplification at 650bp for internal transcribed spacer gene. Mycotoxins identified from isolates were aflatotoxin, ochratoxin A (OTA), citrinin, patulin, citreoviridin, T-2 toxin, deoxynivalenol (DON), diacetoxyscirpenol, zearalenone (ZEN), nivalenol, Ht-2 toxin, cyclopiazonic acid with ochratoxin A, Diacetoxyscirpenol and Ht-2 toxin being above consumption limit at 2.64ug/kg,1.27ug/kg and 424.48ug/kg respectively. The isolates showed varied concentration of individual aflatoxins comprising of B1, B2, G1 and G2. These aflatoxins were produced by Aspergillus flavus strain ZMXL11, Aspergillus flavus strain AF-13, and Penicillium citrinin PEN-65 among, B1 was found to be above the maximum limit at 99% in all the isolates.Aflatoxin has been found as to be a group 1 carcinogen implicated in liver cancer. Constant consumption of mycotoxin contaminated corn could lead to varying health risk that includes liver cancer, kidney and gastrointestinal disturbances. This study showed that corn sold in selected markets in Enugu metropolis were contaminated with mycotoxigenic fungi that produced high levels of mycotoxin concentrations which is of public health concern.