Biosynthesis of Silver Nanoparticles via the Fungus Ophiostoma novo-ulmi: A Green Approach
Abstract
The green synthesis of metal nanoparticles using non-toxic and biodegradable chemicals represents a sustainable, eco-friendly approach that enables the synthesis of nanoparticles with enhanced stability and specific bioactive properties. The synthesis of silver nanoparticles (AgNPs) using an aqueous extract of the fungus Ophiostoma novo-ulmi and an aqueous AgNO₃ solution is reported in this study. Ophiostoma novo-ulmi is a highly virulent ascomycete responsible for Dutch elm disease (DED), a destructive vascular wilt affecting elm trees (Ulmus spp.). It produces a diverse range of bioactive metabolites, enabling efficient reduction and stabilization of nanoparticles, while also representing a novel example of transforming a phytopathogenic organism into a valuable biotechnological resource. The biosynthesized AgNPs were characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and transmission electron microscopy (TEM). The characterization results confirmed the successful synthesis of AgNPs mediated by the O. novo-ulmi extract, which acted as both the reducing and stabilizing agent, with a characteristic UV-Vis absorption maximum at ≈ 402 nm. FT-IR analysis identified key bioactive metabolites that are potentially responsible for bio-reductive activity. PXRD results revealed a crystallite size of ≈15 nm, calculated using the Scherrer equation, with a face-centered cubic (FCC) structure. Evaluation of antibacterial properties by the broth microdilution method demonstrated inhibitory effects of the biosynthesized AgNPs against both Gram-positive and Gram-negative bacteria. The synthesized AgNPs exhibited antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, with MIC values ranging from 0.01563 to 0.500 mg mL⁻¹. Overall, the findings highlight the high potential and effectiveness of O. novo-ulmi as a biological agent for fungal-mediated green synthesis of silver nanoparticles.