Optimization of magnetic nano-iron production by Aspergillus flavipes MN956655.1 using response surface methodology and evaluation of their dye decolorizing and antifungal activities

Iron nanoparticles have been biosynthesized by a new Aspergillus flavipes isolate. Size of biosynthesized iron nanoparticles was in a range of 32.7 and 47.6 nm, their surface charge was − 33.5 ± 5.3 and they showed semihard ferromagnetic behavior. Salt concentration, volume of added culture filtrate and pH have been optimized using response surface methodology. A significant effect for the added culture filtrate and a mutual interaction between this factor and the pH has been detected. Model validation results showed 3.3% deviation from the statistically predicted values which reflects the accuracy of the employed model. Optimization process has increased the quantity of iron in the prepared samples and the amount of produced iron nanoparticles to a fourfold. The optimized conditions have stimulated the formation of nanoparticles in a tetrahedron shape rather than the truncated tetrahedron shape without affecting their size or surface charge. The biosynthesized iron nanoparticles have recorded a good decolorization activity for methylene blue. They showed 57 ± 4.3 decolorization percent after 6 h when tested with only 0.1 mg/ml concentration. Moreover, 50 ppm concentration has exerted a detectable antifungal activity against Alternaria solani. This study represents a new competitive green synthesis method for magnetic iron nanoparticle.