Modification of antimicrobial, antioxidant and catalase activities in cell free supernatant of some Bacillus strains induced by iron oxide nanoparticles

Abstract

Iron oxide nanoparticles (Fe3O4) are extensively studied for their interactions with microorganisms, and they have promising applications in biotechnology and medicine. Bacillus spp. can synthesize a variety of structurally and functionally diverse secondary metabolites, including antibiotic peptides such as gramicidins, bacitracins and tyrocidines, which exhibit strong antimicrobial activity. It was investigated the effects of iron (II, III) oxide nanoparticles on the antimicrobial, antioxidant, and catalase activities of the cell-free supernatant obtained from the cultivation of some Bacillus strains. Rising nanoparticle concentrations up to 10.0 mg/L increased antimicrobial activity, which was strain-dependent. In most cases, a concentration of 10.0 mg/L exhibited a greater antimicrobial effect, with increases ranging from 17% to 36% compared to the control. The presence of iron oxide nanoparticles decreased the protein content of the cell-free supernatant, accompanied by a significant increase in catalase activity, that revealing a strong correlation with a coefficient of determination R2=0.943. Antioxidant activity, assessed via the ABTS assay, showed lower values than the control, indicating an inhibitory effect of the nanoparticles on this parameter. The results highlight the potential of iron oxide nanoparticles to modulate microbial metabolism by stimulating antimicrobial activity and optimize the production of bioactive compounds, underscoring their potential for applications in microbial biotechnology.