Silver nanoparticles biosynthesised by using Bacillus megaterium IBB_Po17

The present study aimed to investigate the capability of a solvent-tolerant bacterium, Bacillus megaterium IBB_Po17, to synthesise silver nanoparticles (AgNPs) through either intracellular or extracellular activities, and to establish if their production was affected when the cells were grown in the presence of organic solvents. The intracellular and extracellular biosynthesis of AgNPs by B. megaterium IBB_Po17 was first confirmed by visual observation and UV–vis spectroscopy and further analysed by high-performance thin-layer chromatography (HPTLC) and transmission electron microscopy (TEM). The antibacterial activity of the synthesised AgNPs was investigated by the agar diffusion method. The intracellular and extracellular biosynthesis of AgNPs by B. megaterium IBB_Po17 when the cells were grown or not in the presence of organic solvents (i.e., n-decane, n-hexadecane, n-hexane, cyclohexane) was confirmed visually by the appearance of a yellowish-brown colour in the reaction mixture or a dark precipitate, as well as by using UV–vis spectroscopy (surface plasmon resonance peaks at 425–455 nm) and TEM analyses (particle with spherical shape, size ranging from 1–85 nm). The biosynthesised AgNPs showed excellent antibacterial activity against several Gram-positive and Gram-negative bacteria. Due to their characteristics, the biosynthesised AgNPs could be used as antibacterial agents, but they could have many other applications. (paper)