Microbial Synthesis of Silver Nanoparticles by Streptomyces glaucus and Spirulina platensis

摘要

Microbial synthesis of nanoparticles has a potential to develop simple, cost-effective and eco-friendly methods for production of technologically important materials. In this study, for the first time a novel actinomycete strain Streptomyces glaucus 71 MD isolated from a soy rhizosphere in Georgia is for the first time extensively characterized and utilized for the synthesis of silver nanoparticles. Transmission Electron Microscopy (TEM) images revealed that most of the particles produced by this microorganism from AgNO_3 are spherical in shape with an average size of 13 nm. Scanning Electron Microscopy (SEM) allowed observing extracellular synthesis of nanoparticles, which has many advantages from the point of view of applications. Production of silver nanoparticles proceeded extracellularly with the participation of another microorganism, blue-green microalgae Spirulina platensis (S. platensis). In this study it is shown that the production rate of the nanoparticles depends not only on the initial concentration of AgNO_3 but also varies with time in a nonmonotonic way. SEM study of silver nanoparticles remaining on the surface of microalgae revealed that after 1 day of exposure to 1 mM AgNO_3 nanoparticles were arranged as long aggregates along S. platensis cells strongly damaged by silver ions. However, after 5 days of exposure to silver S. platensis cells looked completely recovered and the nanoparticles were distributed more uniformly on the surface of the cells.