Fungal molecular identification and total aflatoxin assessment in stored peanut seeds in Kwara State, Nigeria

Article Information

Title: Fungal molecular identification and total aflatoxin assessment in stored peanut seeds in Kwara State, Nigeria

Authors: Ibrahim Ajadi, Ganiyu Shittu Olahan

Journal: Mycopath

HEC Recognition History

Category	From	To
Y	2024-10-01	2025-12-31

Publisher: University of the Punjab, Lahore

Country: Pakistan

Year: 2024

Volume: 22

Issue: 1

Language: English

Abstract

One kilogram each of peanut ( Arachis hypogaea L.) seeds were collected from each of six popular markets with high patronage in Kwara State, North-Central Nigeria, namely Alapa, Ganmo, Ipata, Kaiama, Share and Tsaragi markets. There is lack of reliable information on the fungal species and level of TAF in the peanut seeds sold in these markets. The fungal species associated with the samples were isolated using serial dilution method and pour plating method, and then identified morphologically and molecularly, after which the total aflatoxins (TAF) in each sample were evaluated using the direct competitive enzyme-linked immunosorbent assay method (ELISA). A total of five fungal species Aspergillus flavus, A. oryzae, Mucor indicus, Rhizopus oryzae and Rhizopus arrhizus were isolated from the collected samples . Aflatoxins were present in 66% of the examined peanut seeds at varying values. The highest TAF content viz. 2.5 part per billion (ppb) was recorded in the peanut seeds from Share market, while the lowest TAF content (0.9 ppb) was recorded in the seeds from Alapa market. The TAF content values obtained in this study were within the permissible limits (20 ppb) approved by the National Agency for Food and Drug Administration and Control (NAFDAC), as well as the 10 ppb approved by the Codex Alimentarius Commission (CAC) for Peanut seeds in Nigeria. However, prolonged and consistent consumption of peanut seeds with these doses of TAF may result in accumulation of aflatoxins in the body, thereby posing a potential health challenge over time.

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Research Objective

To assess the fungal species and the level of total aflatoxins (TAF) in peanut seeds sold in popular markets in Kwara State, Nigeria.

Methodology

Peanut seeds were collected from six markets in Kwara State. Fungal species were isolated using serial dilution and pour plating methods, identified morphologically and molecularly. Total aflatoxins (TAF) were quantified using the direct competitive enzyme-linked immunosorbent assay (ELISA) method. DNA was extracted using a Zymo Research DNA kit, and the Internal Transcribed Spacer (ITS) region was amplified and sequenced. Phylogenetic trees were constructed using MEGA version 11.0. Aflatoxin extraction followed the protocol by Amai et al. (2021), and detection/quantification used a total aflatoxin ELISA kit.

Methodology Flowchart

                        graph TD
    A[Collect Peanut Seeds from Markets] --> B[Divide into Batches];
    B --> C[Batch A: Fungal Isolation];
    B --> D[Batch B: Aflatoxin Analysis];
    C --> E[Culture Media Preparation];
    E --> F[Serial Dilution & Pour Plating];
    F --> G[Fungal Colony Counting & Sub-culturing];
    G --> H[Morphological Identification];
    H --> I[Molecular Identification];
    D --> J[Aflatoxin Extraction];
    J --> K[ELISA for Aflatoxin Detection & Quantification];
    I --> L[Data Analysis & Phylogenetic Analysis];
    K --> L;
    L --> M[Results Interpretation];
    M --> N[Discussion & Conclusion];

Discussion

The study identified fungal contamination and aflatoxin presence in stored peanut seeds from Kwara State. While the aflatoxin levels were within regulatory limits, prolonged consumption could lead to accumulation and potential health risks. Differences in fungal counts across markets might be due to varying storage conditions. The prevalence of Aspergillus flavus aligns with previous studies in Nigeria.

Key Findings

Five fungal species were isolated: Aspergillus flavus, A. oryzae, Mucor indicus, Rhizopus oryzae, and R. arrhizus. Aflatoxins were present in 66% of the examined peanut seeds. The highest TAF content was 2.5 ppb (Share market), and the lowest was 0.9 ppb (Alapa market). All TAF levels were within the permissible limits set by NAFDAC (20 ppb) and Codex Alimentarius Commission (10 ppb). Aspergillus flavus was the most prevalent fungal species (56%).

Conclusion

Peanut seeds in the investigated markets are contaminated with mycoflora and total aflatoxins, although at levels below regulatory thresholds. Proper storage practices are recommended to mitigate contamination risks.

Fact Check

* Fungal Species Identified: Five fungal species were isolated: Aspergillus flavus, A. oryzae, Mucor indicus, Rhizopus oryzae, and R. arrhizus. (Confirmed)
* Aflatoxin Presence: Aflatoxins were found in 66% of the examined peanut seeds. (Confirmed)
* Highest TAF Content: The highest TAF content recorded was 2.5 ppb in peanut seeds from Share market. (Confirmed)

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