Green synthesis of copper oxide nanoparticles from <i>Pleurotus ostreatus</i> extract: optimization, characterization, and application as safe antimicrobial agent

The green synthesis of copper oxide nanoparticles (CuONPs) using mushroom extracts offers a promising alternative for developing antimicrobial agents to combat drug resistance. This study investigated the synthesis of CuONPs from aqueous extract of Pleurotus ostreatus mycelia with copper nitrate as a precursor. Biosynthesis parameters were optimized using response surface methodology (RSM) based on a central composite design (CCD). The CuONPs were characterized using UV–Visible analysis with a peak at 335 nm, and X-ray diffraction (XRD) revealed the characteristic pattern. The resulting NPs had an average diameter of 45.9 nm and a zeta potential of about −10 mV, indicating good stability. The CuONPs exhibited notable antibacterial (with minimum inhibitory concentration against Escherichia coli 72 ± 1.78 mg/L, Klebsiella pneumoniae 81 ± 2.21 mg/L, Bacillus subtilis 95 ± 1.72 mg/L, and Streptomyces sp. 102 ± 0.83 mg/L) and antifungal activity (ED50 value 199.41 mg/L against Fusarium oxysporum). The antibacterial effect was further confirmed by observations of morphological alterations, compromised membrane integrity, reduced motility, and ROS production. In addition, CuONPs showed antioxidant activity, and the ED50 dose did not show any toxic effect when applied to the chili plant. Thus, CuONPs synthesized using the mushroom extract might be applied for curing bacterial and fungal diseases.