ISOLATION AND IDENTIFICATION OF FUNGI ASSOCIATED WITH IRVINGIA SPECIES KERNELS FROM SOME MARKETS WITHIN ZARIA METROPOLIS AND THEIR AFLATOXIN CONTENT
ISOLATION AND IDENTIFICATION OF FUNGI ASSOCIATED WITH IRVINGIA SPECIES KERNELS FROM SOME MARKETS WITHIN ZARIA METROPOLIS AND THEIR AFLATOXIN CONTENT
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Date
2016-10
Authors
ONUOHA, Goddy Chibueze
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Abstract
This study was carried out, in order to isolate, identify the various fungi associated with Irvingia kernels and to ascertain whether or not there was significant aflatoxin content in Irvingiakernels sold in five markets in Zaria. The two species of Irvingiastudied were Irvingiagabonensisand Irvingiawombolu. Commercially available Potato Dextrose Agar (PDA) served as the general purpose culture mediaandSabouraud Dextrose Agar (SDA) served as the selective media, which was used in the preparation of pure cultures. The cotyledons and thetesta were examined separately. Aspergillusflavus, Aspergillusfumigatus, Aspergillusniger, Penicilliumspecies and Rhizopusstolonifer were isolated from both Irvingiagabonensisand Irvingiawombolutesta and cotyledons. Four fungal species, namely, Absidiacorymbifera, Aspergillusversicolor, Mucor species and Phomaherbarum were only isolated from Irvingiawombolu cotyledons and testa.More A.flavus, A .nigerand Penicillium sp. were isolated from the testa of both I. gabonensis and I. wombolu,than from the cotyledons. Rhizopusstolonifer had the highest percentage occurrence in the cotyledons of both I.gabonensis (69.44%) andI.wombolu (47.43%). Aspergillusnigerhad the highest percentage occurrence (37.59 %) of all the fungi isolated, and was closely followed by R.stolonifer(33.81 %).Similarly, A. nigerhad the highest percentage occurrence in the testa of both I.gabonensis (45.71%) andI.wombolu (42.94 %). Also, I.gabonensis samples from SabonGari market had the highest mean number of fungal species (12), while Dan Magaji/Wusasa market had the least (2). Similarly, I.wombolu samples from A.B.U Community, Dan Magaji/Wusasa and Tudun Wada markets all had the highest mean number of fungal colonies (24), while Samaru market had the least (22). Enzyme-Linked Immunosorbent Assay (ELISA) of the kernels showed that,I.gabonensis and I.wombolu kernels from SabonGari market had the highest aflatoxin concentrations (108.36 and 95.60g/kg) respectively. Similarly, I.wombolu kernels from Dan Magaji/Wusasa market had the least
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(70.28g/kg) aflatoxin concentration, while I.gabonensis kernels from Samaru market had the least (75.02g/kg). They were all beyond the World Health Organization (WHO) standard for food samples, which is 20g/kg, hence not safe for human consumption. The study concludes that,the two Irvingia species kernels sold in some markets within Zaria metropolis were contaminated by several post-harvest fungi. One of these fungi isolated,Aspergillusflavus, had the capacity to produce aflatoxins, therefore the consumption of these kernels puts the consumers at risk.
Description
DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARDOF A MASTER OF SCIENCE DEGREE IN BOTANY
DEPARTMENT OF BIOLOGICAL SCIENCES,
FACULTY OF SCIENCE,
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA.
Keywords
ISOLATION,, IDENTIFICATION,, FUNGI ASSOCIATED,, IRVINGIA SPECIES KERNELS,, SOME MARKETS,, ZARIA METROPOLIS,, AFLATOXIN,