Biosynthesis, Characterization and Antibacterial Properties of CuO Nanoparticles of Psychrotrophic Bacteria

Copper oxide nanoparticles have many applications in industry and medicine. Nevertheless, few studies have been conducted in relation to the biological production of these nanoparticles. In the present study, the ability of isolated Psychrotrophic (cold-resistant) prokaryotes from the Zagros highlands located in Lorestan province of Iran and some isolated Streptomyces strains from the Oman Sea has been evaluated in the synthesis of copper oxide nanoparticles. The maximum lethal concentration of copper salts was determined for the strains and the strains with the highest level of resistance were selected. The biosynthesis of copper oxide nanoparticles was done extracellularly by inoculating Psychrotrophic and Streptomyces strains in liquid TSB culture medium containing 0.01 M copper sulfate salt and keeping the culture medium in a shaker incubator at 20 °C at 150 rpm. The production of copper oxide nanoparticles was evaluated by changing the color of the reaction solution from light blue to dark green. From the 44 cold-resistant strains and the investigated Streptomyces strains, all strains were able to tolerate concentrations higher than 5 mM. Of these, the strain OSNP13 belonging to the genus Microbacterium liquefaciens (X77444) has been able to synthesize the highest amount of copper oxide nanoparticles. The optical absorption of the solution containing synthesized nanoparticles was determined in the range of 250-350 nm by UV-vis spectrophotometer, which had a specific peak at 288 nm. And the copper oxide nanoparticles have an average size of 63.21 nm based on DLS analysis. The crystallographic characteristics of copper oxide nanoparticles were also determined by using XRD analysis, which showed that the prepared nanoparticles had a hexagonal crystal structure with a size of 31.29 nanometers. Then, the antibacterial activity of produced nanoparticles was evaluated. The MIC values ​​of copper oxide nanoparticles for E. coli and S. aureus bacteria were calculated as 125 and 250 micrograms per milliliter, respectively. The produced copper oxide nanoparticles have shown a good antimicrobial properties and can be suitable candidates for use as antimicrobial agents.