Magnetic Nanostructures Immobilized Microorganisms for the Development of Nano-Biofertilizers

Abstract

In this manuscript, Fe3O4 nanoparticles (NPs) were prepared by using a simple cost-effective domestic microware based chemical route. The Crystal structure of Fe3O4 nanoparticles studied using X-ray diffraction and selective area electron diffraction pattern clearly showed that Fe3O4 NPs exhibited single-phase FCC structures. The average crystallite size calculated using the XRD pattern and TEM micrographs was found to be ∼7 and ∼12 nm, respectively. The magnetic hysteresis loop measured at room temperature inferred that Fe3O4 NPs exhibited the soft ferromagnetic behavior. The nanoparticles then immobilized with Pseudomonas aeruginosa strain JS11. Bacteria have contemporaneous plant growth and biocontrol potential viz indole acetic acid (IAA) production, tri-calcium phosphate solubilization in Pikovskaya’s medium. These auxiliary activities of strain showed remarkable capability in the presence of Fe3O4 NPs at different concentrations. The IAA assay revealed the presence of Fe3O4 NPs (50 and 100 ng mL-1) increased the production of about 26.1 and 27.9 μg mL-1 of IAA, respectively, as compared to 22 μg mL-1 IAA in the medium. Phosphate solubilization also increased in the presence of Fe3O4 NPs 100 ng‘mL-1 as compared to the control. Production of siderophores and antibiotic phenazine-1-carboxylic acid (PCA) production in bacterial cell culture was determined. Thus, the increase in auxiliary biological activities viz. IAA production, phosphate solubilization, siderophores, and PCA production in the presence of Fe3O4 NP stratifies the better plant growth and biocontrol activities in agricultural soils.