Biotechnology Journal International

Background and Aim: Various feeds and food grains are contaminated with mycotoxins produced by certain fungi along with other secondary metabolites due to long term storage, storage condition, or improper handling during harvest. The economic effects attributed to mycotoxin infections are widely felt in all sectors of the production and consumption of grain products. They are considered a major factor in the spoilage of food stuffs, leading to great economic loss and have implications for food safety and public health. The study aims to isolate and characterize Aflatoxin producing fungi associated with the spoilage of some stored grains within Bauchi metropolis.

Place and Duration of Study: This study was carried out in Abubakar Tafawa University (ATBU), Bauchi, Nigeria, in a period duration of August 2024 to January 2025.

Methodology: Grain samples were obtained from various stores in markets and transported to the laboratory. Grains samples were aseptically inoculated in a set of three Petri dishes each containing of Potato Dextrose Agar (PDA) and incubated for 5 days at 30°C. Pure culture was obtained from identified isolate after Identification of the isolates morphologically and phenotypically. Pure isolates were subjected to Polymerase Chain Reaction (PCR) by extracting the DNA following the Bioneers kit manufacturers manual and gel electrophoresis was ran on the pure DNA extracted.

Aflatoxin test was done on samples using Thin Layer Chromatography (TLC). Grain samples were ground into fine powder using mortar and pestle. Extraction was done on the samples and 10µl of the extract was added to the TLC plate 1cm from the bottom edge and allowed to dry. The TLC plate was placed in the developing chamber with the solvent at the bottom, allowing the solvent to rise up by capillary action. When solvent reached the top of the plate, the plate was allowed to air-dry completely. Sulfuric acid spray was used to visualize the separated compounds and plate was observed using spectrophotometer.

Results: The findings revealed a diverse array of Aspergillus species capable of producing aflatoxins, notably Aspergillus flavus and Aspergillus parasiticus. Aspergillus was identified as the predominant fungal species, accounting for 51.47% of isolates, followed by Rhizopus (22.06%), Penicillium (19.12%), and Fusarium (7.35%). Significant aflatoxin contamination was observed across various grain types, with millet and groundnut exhibiting high contamination rates and concentrations. Molecular analysis further confirmed the presence and co-expression of aflR and aflS genes in Aspergillus flavus isolates, indicating strong aflatoxigenic potential.

Conclusion: This study highlights the prevalence and some of the genetic diversity of the aflatoxin producing fungi focussing on the aflR and aflS gene which is one of the genes that plays a crucial role in the biosynthesis of aflatoxins. The study emphasizes the need for targeted interventions to mitigate aflatoxin contamination and ensure food safety. The prevalence of aflatoxin producing fungi in this study was 65% based on the TLC result showing that 65 samples have exceeded the NAFDAC permissible limit. Aspergillus flavus and Aspergillus parasiticus were the primary aflatoxin producers observed among the fungal isolates. The relationship between the grain type and aflatoxin contamination is highly significant indicating that the effect of grain type on aflatoxin production is consistent independent of storage conditions.