Mycosynthesized Silver Nanoparticles (AgNPs) for the Control of Foodborne Pathogenic Bacteria: Escherichia coli and Staphylococcus aureus.

This study evaluated the ability of filamentous fungi to biosynthesize silver nanoparticles (AgNPs). The nitrate reductase activity of the selected fungi, considered a key enzyme involved in AgNP biosynthesis, was assessed as a selection criterion. AgNPs were mycosynthesized using Fusarium equiseti AM-0197, F. cerealis AM-0206, F. oxysporum AM-0192, Alternaria scrophulariae AM-0187, and Aspergillus sp. (1-HSF-08 and 3-HSF-02) isolates. The synthesized AgNPs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. In all cases, spherical AgNPs were obtained, with maximum absorption peaks ranging from 400 to 420 nm. XRD analysis demonstrated a face-centered cubic crystalline structure, whereas Zeta potential measurements revealed a negative surface charge. FTIR analysis indicated the presence of organic functional groups on the nanoparticle surface acting as capping agents. The antibacterial activity of the synthesized nanomaterials was evaluated against reference strains of Escherichia coli and Staphylococcus aureus, two major foodborne pathogens, using the disk diffusion method. Inhibition zones ranged from 11.3 to 13.6 mm for E. coli ATCC 25922 and from 9.3 to 15.0 mm for S. aureus ATCC 43300. The minimum inhibitory concentration (MIC) determined by microdilution was 37.5 ppm for all AgNPs tested against E. coli, whereas MIC values against S. aureus ranged from 18.7 to 75 ppm depending on the nanoparticle evaluated. These findings demonstrate the effectiveness of mycosynthesized AgNPs as next-generation antibacterial agents for the in vitro control of foodborne bacterial pathogens.