Synthesis and antibacterial activity of iron manganite (FeMnO3) particles against the environmental bacterium Bacillus subtilis

Nanocrystalline iron manganite powder was synthesized using the sol–gel combustion process, with glycine as fuel. It was further calcined at 900 °C for 8 h, resulting in the formation of a loose cubic FeMnO₃ powder with a small specific surface area, net-like structure and plate-like particles as confirmed by XRD, N₂ physisorption, FESEM and TEM analyses. The metal ion release was studied by ICP-OES and showed that less than 10 ppb of Fe or Mn ions were released by leaching in water, but 0.36 ppm Fe and 3.69 ppm Mn was found in LB (Luria–Bertani) bacterial medium. The generation of reactive oxygen species (ROS) was monitored in distilled water and bacterial medium and showed that FeMnO₃ particles do not generate O₂˙⁻ ions with or without UV irradiation, but synthesize H₂O₂ and show an antioxidative effect. Besides the higher stability of FeMnO₃ particles in aqueous solution they showed an inhibitory effect on Bacillus subtilis growth in LB medium even at low concentrations (0.01 mg ml⁻¹), but not in BHI medium even at 1 mg ml⁻¹. This study points out that the mechanism of antibacterial action of engineered metal oxides needs continued investigation and specific experimental controls.

Iron manganite (FeMnO₃) particles express antibacterial activity against Bacillus subtilis, together with H₂O₂ release and Fe, Mn-ion release in LB bacterial medium.