Zinc solubilizing plant growth promoting microbes produce zinc nanoparticles

Strains of Pseudomonas, Bacillus, and Azospirillum with plant growth promoting ability were checked for their zinc solubilizing ability at ICAR-CRIDA, Hyderabad, India. Efficient zinc solubilizing microorganisms were evaluated for their ability to produce nano-scale zinc particles. The nanoparticles from the cell-free culture filtrates obtained from these strains were characterized for particle size, Zeta potential and functional groups. Presence of Zn nanoparticles in the bacterial culture filtrate was confirmed by particle distribution and Scanning electron microscope (SEM) analysis. Most properties of nanoparticles are size dependent. Zinc nanoparticles were observed to be spherical in shape and size ranged from 52.0 to 106.0nm. Zeta potential of the Zn nanoparticles was estimated to understand the stability of the particles. The measured zeta potentials varied from -14.5mV to +179.10 mV indicating high stability and dispersion of the zinc nanoparticles. FTIR peaks at different wave numbers depicted the role of functional groups of proteins in the biosynthesis of Zn nanoparticles. These results demonstrate the green synthesis of zinc nanoparticles by the plant growth promoting and zinc solubilizing strains of Azospirillum, Pseudomonas and Bacillus