Biosynthesis and characterization of iron oxide nanoparticles fabricated using cell-free supernatant of Pseudomonas fluorescens for antibacterial, antifungal, antioxidant, and photocatalytic applications.

This study investigates the biosynthesis of iron oxide nanoparticles (FeONPs) using the cell-free supernatant of Pseudomonas fluorescens. The synthesized FeONPs were characterized through UV-VIS, XRD, FTIR, FESEM, EDX, TEM, BET, and VSM analyses. The XRD results confirmed that FeONPs were successfully synthesized and EDX analysis indicated that iron accounted for 89.5% of the sample composition. Imaging via SEM and TEM revealed average diameters of 20.43 ± 5.38 nm and 24.32 ± 5.03 nm, respectively. The antimicrobial effects of FeONPs were assessed against four bacterial strains and four fungal species. Inhibition zones of 8.35 ± 0.103 mm and 8.31 ± 0.128 mm were observed for Pseudomonas syringae and Staphylococcus aureus at a concentration of 400 μg mL of FeONPs. Antifungal efficacy showed growth rate reductions of 90.4% for Aspergillus niger, 71.1% for Monilinia fructigena, 68.8% for Botrytis cinerea, and 84.2% for Penicillium expansum, compared to controls. The nanoparticles demonstrated photocatalytic degradation efficiencies of 89.93%, 84.81%, and 79.71% for methyl violet, methyl orange, and methylene blue, respectively. Also FeONPs exhibited significant DPPH free radical scavenger activity with an IC value of 8.45 ± 0.59 μg mL. The study's findings underscored the significant potential of FeONPs in addressing environmental pollution and combating pathogenic microorganisms.