Ochratoxin A (OTA) is a toxic secondary metabolite produced by the Aspergillus species which can contaminate various food products. This study analysed the transcriptome of the Aspergillus westerdijkiae fc-1 strain under NaCl concentrations of 0, 20, and 100 g/L using RNA-Seq technology to examine gene transcriptional changes linked to osmotic stress and OTA production. Significant changes were observed in metabolic-pathways associated with carbohydrates, cellular communication, and hydrolase activity under 20 g/L NaCl. The HOG1 gene, associated with osmotic pressure regulation was down-regulated by 78.06%. In contrast, OTA biosynthesis genes otaA, otaB, and otaC were up-regulated by 3.26 fold, 1.99 fold, and 2.06 fold, respectively. Conversely, the otaD gene was down-regulated by 43.50%. At 100 g/L NaCl, pathways related to ion transport, peptide metabolism, ribosomal function, and transmembrane transporter protein activities were significantly up-regulated. The HOG1 gene was up-regulated by 28.32% and OTA biosynthesis genes otaA, otaB, otaC, and otaD showed up-regulation of 27.06%, 36.80%, 19.59%, and 5.72 fold, respectively. The study highlights the role of metabolic pathways in osmotic stress regulation and the correlations between HOG1 expression and OTA biosynthesis genes, providing insights for developing strategies to prevent OTA contamination in food.

Aspergillus westerdijkiae is a major producer of ochratoxin A (OTA), a highly toxic and carcinogenic mycotoxin found in various food and feed products. A. westerdijkiae produces excessive amount of OTA under various water activity (a_w) conditions that occur during food and feed storage. The biosynthetic gene clusters associated with OTA production include OTAbZIP, which plays a key role in controlling mycotoxin production in response to environmental conditions. This study explored the regulation of OTA biosynthesis in A. westerdijkiae fc-1, focusing on the OTAbZIP gene’s influence under a_w stress. The mycelium growth of A. westerdijkiae fc-1 wild type and OTAbZIP mutant strains increased by 40.7% and 50.5% under high water activity (0.96 a_w) respectively, at 6 days post-inoculation (dpi), indicating a stress on A. westerdijkiae fc-1. While OTAbZIP mutant did not produce OTA under both high and moderate a_W conditions. The wild type produced OTA and OTA biosynthetic gene expression levels were downregulated under high (0.96 a_w) and moderate (0.91 a_w) water activity. The expression level of hog1 gene in OTAbZIP mutant was significantly lower than in the wild type. Pathogenicity tests revealed that deletion of OTAbZIP did not significantly affect disease infection. This study shows that deleting OTAbZIP gene greatly reduces OTA production, affecting the strain’s adaptability to water activity stress.

Application of atoxigenic strains of Aspergillus flavusto soils is the most successful aflatoxin biological control approach. The objective of this study was to evaluate the efficacies of native non-aflatoxin producing (atoxigenic) strains as a biocontrol agent in peanut field in China. The competitive atoxigenic A. flavus strains (JS4, SI1and SXN) isolated from different crops, in China were used for field evaluation. The strains applied during the growing season (June – October, 2016) in the field at rate of 25 kg inoculum/hectare. The colonization of these biocontrol agents has been investigated and the population of A. flavus communities in soil were determined. The incidences of toxin producing (toxigenic) A. flavus strains and aflatoxin contamination in peanuts were also determined. Treated plots produced significant reductions in the incidence of toxigenic isolates of A. flavus in soil. However, the total fungal densities were not significantly different (p > 0.05) after treatments. Large percentage of aflatoxin reductions, ranging from 82.8% (SXN) up to 87.2% (JS4) were recorded in treated plots. Generally, the results suggest that the strategy can be used to control aflatoxin contamination and continuous evaluation should be done.

Mycotoxin contamination of food and feed is a major concern in sub-Sahara African countries, particularly Nigeria. It represents a significant limit to health of human, livestock as well as the international trade. Aflatoxins, fumonisins, ochratoxin, zearalenone, deoxynivalenol and beauvericin are the major mycotoxins recognised in the aetiology of food safety challenges that precipitated countless number of diseases. In Nigeria, aflatoxins and fumonisin found in nearly all crops are the most common mycotoxins of economic and health importance such as sorghum, maize and groundnuts. Thus, consumption of food contaminated with mycotoxins are inevitable, hence the need for adequate regulation is necessary in these frontier economies as done in many developed economies to ensure food safety for human and animals. In low and middle-income countries, especially Nigeria, there is lack of awareness and sufficient information on the risk associated with consequent of mycotoxin contamination on wellbeing of human, animals health and the economy. It is based on the foregoing that this paper summarized the status of mycotoxin present in Nigerian food and feeds relative to the global regulatory standards. This aimed at preventing consuming mycotoxin contaminated food stuff while confronting its associated challenges. Suggestions on some possible control strategies to mitigate vending mycotoxin food and feeds were made.