METHYLOTROPHIC MICROBIAL COMMUNITIES FOR THE BIOSYNTHESIS OF NOBLE METAL NANOPARTICLES.

The biosynthesis of noble metal nanoparticles using microorganisms (“green synthesis of nanoparticles”) has recently become widespread for medical applications. The characteristics of the resulting nanoparticles depend on the microorganisms used and the process conditions. Screening of a number of methylotrophic bacterial communities of a practical biotechnological value was carried out to determine those ones, which were able to synthesize silver and palladium nanoparticles at high rate and efficiency. In several studied natural communities containing bacteria of the genera Methylobacterium, Methylococcus, Methylobacter and from 2 to 5 related cultures, silver or palladium nanoparticles are formed from salts. The yield and parameters of silver and palladium nanoparticles are affected by the concentration of exopolysaccharides and components of the cytoplasm of cells, which are realized in the culture liquid during the lysis of microorganisms that produce them. It was found that the ratio of microorganisms in the community significantly affects the size of the synthesized metal nanoparticles and their organic shell. The characteristic range of sizes of nanoparticles is unique and corresponds to a certain composition of the community, all other things being equal. A number of studied communities of microorganisms withstand several times more concentrated initial solutions of silver and palladium salts in comparison with monocultures belonging to the communities under study. Optimization of conditions for controlled cultivation of methylotrophic bacterial communities for the synthesis of nanoparticles (medium composition, contact time with salts, growth phase, pH, illumination, etc.) using extremely simple media with methanol as the sole carbon source allows obtaining samples of silver or palladium nanoparticles from 3 nm up to 130 nm with the dominance of a certain fraction. The optimum conditions of biosynthesis providing maximum nanosilver and nano-palladium yields have been selected. [ABSTRACT FROM AUTHOR]