Nutritional conditions affecting of selenium nanoparticles synthesized by Fusarium oxysporum (CCASU-2023-F9), and their biological activities against mycotoxin-producing fungi isolated from animal feed.

One of the most promising biologically based nanomanufacturing processes is the production of selenium nanoparticles (SeNPs) by fungi. The use of these biosynthesized nanoparticles in agricultural practices has emerged as a new approach for controlling pathogen growth and mycotoxin production. In the present study, different chemical and physical parameters were investigated for the growth of Fusarium oxysporum (CCASU-2023-F9) to increase selenite reduction and obtain the highest yield of selenium nanoparticles (SeNPs). Fusarium oxysporum (CCASU-2023-F9) exhibited tolerance to up to 1 mM sodium selenite (Na₂SeO₃), accompanied by red coloration of the medium, which suggested the reduction of selenite and the formation of selenium nanoparticles (SeNPs). Reduced selenite was quantified using inductively coupled plasma‒mass spectrometry (ICP-MS), and the results revealed that Fusarium oxysporum (CCASU-2023-F9) is able to transform 45.5% and 50.9% of selenite into elemental selenium by using fructose and urea as the best carbon and nitrogen sources, respectively. An incubation temperature of 30 °C was the best physical condition at which 67.4% of the selenite was transformed into elemental selenium. The results also indicated that pH 7 was the optimum pH, as it displayed 27.2% selenite reduction with a net dry weight of 6.8 mg/mL. Increasing the concentration of sulfate resulted in a significant increase in selenite reduction, as it reached a maximum value of 75.3% at 0.15% g/ml sulfate. The maximum reduction in sodium selenite content was 85.2% at a C/N ratio of 2:1. The biosynthesized SeNPs exhibited antifungal activity against several fungi, such as Aspergillus flavus, Aspergillus niger, and Fusarium oxysporum, that were isolated from animal and poultry feed. Elevated SeNP concentrations (10500 ppm) significantly inhibited fungal growth. SeNPs at a concentration of 5000 ppm inhibited aflatoxin production (B1, B2, G1, and G2) by A. flavus, in addition to inhibiting mycotoxin production (T2 toxin, fumonisin B1, zearaleone, fusarin C, and moniliformin) by F. oxysporum. In conclusion, the results revealed favorable nutritional conditions for the maximum production of SeNPs by Fusarium oxysporum (CCASU-2023-F9) and indicated the marked inhibitory effect of SeNPs on mycotoxins that contaminate animal feed, causing serious consequences for animal health, and that lead to improving the quality of commercially produced animal feed. The obtained results can serve as a basis for commercial applicability.