Synthesis and Antibacterial Activity of Silver Nanoparticles Stabilized by Lipopeptides and Glycolipids Produced by Bacillus amyloliquefaciens and Pseudomonas fluorescens

The colloidal chemical and antibacterial properties of aqueous dispersions of silver nanoparticles stabilized by surfactin and rhamnolipids isolated from B. amyloliquefaciens and P. fluorescens were studied. The isolated biosurfactants were identified by thin layer chromatography and Fourier transform infrared spectrometry. Using the methods of UV-visible spectrophotometry, transmission electron microscopy and dynamic light scattering, the colloidal chemical characteristics of the resulting dispersions were studied. Optimal ratios of the precursor substances were found in which the used biosurfactants perform as effective stabilizers of dispersions of silver nanoparticles and ensure their aggregative stability for at least two months. It was shown that the studied dispersions have antibacterial activity against gram-positive B. subtilis and gram-negative P. aeruginosa and E. coli. A comparative assessment of the antibacterial activity of silver nanoparticles stabilized by biosurfactants and traditional silver-containing preparations, such as a silver nitrate solution and a dispersion of silver nanoparticles stabilized by citrate, was carried out. Furthermore, dispersions stabilized with surfactin showed the highest antibacterial activity, comparable to the effect of a silver nitrate solution, which is associated with their good colloidal stability. In addition, high antibacterial activity of dispersions of silver nanoparticles stabilized with biosurfactants isolated from Bacillus and Pseudomonas bacteria against strains of the other genus was discovered. An explanation of the observed phenomenon is given and the prospects for its application in medicine are proposed.