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A polyphasic method for the identification of aflatoxigenic Aspergilla from cashew nuts

  • Modupeade C. AdetunjiEmail author
  • Lubanza Ngoma
  • Olusegun O. Atanda
  • Mulunda Mwanza
Original Paper
  • 108 Downloads

Abstract

The invasion of food by toxigenic fungi is a threat to public health. This study aimed at enumerating the microbial profile, detection of aflatoxin producing genes and quantification of the levels of aflatoxin contamination of cashew nuts meant for human consumption. A polyphasic method of analysis using newly formulated β-Cyclodextrin Neutral Red Desiccated coconut agar (β-CDNRDCA) and Yeast Extract Sucrose agar (YES) with Thin Layer Chromatography (TLC), Polymerase Chain Reaction (PCR) and High Performance Liquid Chromatographic (HPLC) method was adopted in determining the aflatoxigenic potential of the isolates, the presence of aflatoxin biosynthetic gene (aflM, aflD, aflR, aflJ omt-A) and estimation of the total aflatoxin content of the nuts. The fungal counts ranged from 2.0 to 2.4 log10cfu/g and sixty-three fungal isolates belonging to 18 genera and 34 species were isolated. The Aspergillus spp. were the most frequently isolated (50.79%) while Trichoderma spp. (1.59%) were the least. and fluorescence production was enhanced on the newly formulated β-CDNRDCA by the aflatoxigenic species. The aflD gene was amplified in all the isolates while aflM, aflR and aflJ gene were each amplified in 77.77% of the isolates and omt-A gene in 70.37%. The aflatoxin content of the nuts ranged from 0.03 to 0.77 µg/kg and were below the 4 µg/kg EU recommended limit for total aflatoxins. The present work confirms that a single method of analysis may not be sufficient to screen for the presence of aflatoxins in foods, as with a combination of different methods.

Graphical abstract

Keywords

Cashew nut Aspergillus Aflatoxin Biosynthetic gene Aflatoxigenic fungi Polymerase chain reaction Polyphasic 

Notes

Acknowledgements

M. C. is grateful to National Research Foundation (NRF), South Africa and Food Safety Niche Area, North West University, Mafikeng Campus for financing this project. We also acknowledge the technical team of Animal Health Department, North West University for the technical assistance.

Funding

This work was supported by the National Research Foundation South Africa (Grant No.: 105882).

Compliance with ethical standards

Conflict of interest

The authors declare no conflict of interest.

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© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Department of Animal Health, School of Agriculture, Faculty of Natural and Agricultural SciencesNorth-West University, Mafikeng CampusMmabathoSouth Africa
  2. 2.Department of Biological SciencesMcPherson UniversityAbeokutaNigeria
  3. 3.Food Security and Food Safety Niche AreaNorth-West UniversityMmabathoSouth Africa

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