Biosynthesis of Silver Nanoparticles Using the Shewanella oneidensis MR-1 Strain. Technological Approaches to Increasing the Production and Creating of Preparative Forms of Biogenic Nanomaterial

The results of the microbial synthesis of extracellular silver nanoparticles (Ag NPs) in a liquid medium using the metal-reducing Shewanella oneidensis MR-1 strain and silver-nitrate salts are presented. The shape of the Ag NPs is determined by scanning transmission electron microscopy as close to spherical; more than 50% of Ag NPs have dimensions from 10 to 15 nm. The spectra of energy-dispersive X-ray microanalysis show the presence of Ag peaks in all samples of biogenic Ag NPs. The interplanar distances in the crystals of Ag NPs are 2.71 Å. Fourier-transform infrared (IR) spectroscopy confirms the presence of nitrogen-containing organic compounds of protein nature on the surface of the nanomaterial. The values of the hydrodynamic diameter, zeta-potential, and optical parameters of Ag NPs are determined by dynamic light scattering and spectrofluorimetry. It is shown that a large amount of Ag NPs is present on the surface of S. oneidensis MR-1 cells during biosynthesis. A technological approach is proposed to increase the yield of nanomaterial using the ultrasound treatment of cells, followed by the isolation of Ag NPs. It is shown that the compositions of the protein corona in Ag NPs obtained by the standard method and isolated from the cell surface after ultrasound treatment, as well as the size of Ag NPs, have some differences. A technological method for producing powdered preparations of nanomaterial by lyophilization (freeze drying) of aqueous suspensions of Ag NPs and cellular biomass containing Ag NPs is developed. The possibility of restoring preparations in the form of aqueous suspensions without the agglomeration and sedimentation of nanoparticles is shown. A high biocidal activity of all forms of the nanomaterial as antimicrobial agents of a wide spectrum of activity against gram-positive and gram-negative bacteria and microscopic fungi, including yeasts and phytopathogenic mold fungi, is established, which can be used to create polymer nanocomposites of varying nature with antibacterial properties.