Introduction: Nanoparticles have attracted a lot of scientific attention as they serve as a bridge between bulk materials and atomic or molecular structures with multiple applications. Several approaches have been employed for the synthesis of nanoparticles including physical, chemical, biological, and hybrid methods. In comparison with other approaches, biosynthesis of nanoparticles is a reliable, nontoxic, and eco-friendly method, specifically when microorganisms are used to produce sufficient amount of nanoparticles with biomedical applications. In this regard, the goal of present study was to synthesis copper oxide nanoparticles (CuONPs) by a Gram negative psychrotrophic bacterium, Stentrophomonas sp. Methods: The UV-visible, FTIR and XRD were used to determine the purity and size of the nanoparticle. Antibacterial activity was tested against two types pathogenic of bacteria, Escherichia coli ATCC25922 and Staphylococcus aureus ATCC25923. These bacteria were exposed to different concentrations of biosynthesized nanoparticles in Muller Hinton broth medium and incubated at of 37 °C for 24 hours. Results and conclusion: UV–Visible spectral analysis of the solution revealed a maximum peak at 310 nm for CuONPs and. CuO nanoparticle have a minimum inhibitory concentration (MIC) of 500 µg/mL and 250 µg/mL for E.coli and S.aureus, respectively. This eco-friendly method could be an alternative method for synthesis of green nanoparticle and thus has a potential to use in biomedical applications. Accordingly, Stentrophomonas sp. could be considered as a suitable biological system for production of well dispersed and stable CuONPs.

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