Formation of Crystalline Metal Nanoparticles by Marine Isolates and Their Microbial Consortium

The present study reports that microbes from marine sediments can reduce noble metal ions (Au, Ag, and Pt) to their nanoparticles (NPs). The microbes were initially screened for the synthesis of gold (Au) NPs through bioreduction. The cell-free extracts (CFE) of the most promising strain, Photobacterium sp. (MB 8), was further subjected to the synthesis of Ag, Au, and Pt NPs. The resulting metal NPs were characterized by UV-Vis spectrophotometry and transmission electron microscopy (TEM). The TEM results revealed the presence of well-dispersed NPs in the presence of CFE. The residual concentration of metal ions was measured by inductively coupled plasma mass spectrometry (ICP-MS). X-ray diffraction (XRD) analysis of the NPs confirmed the presence of crystalline Au and AgCl NPs. However, no peaks for the presence of crystalline Pt were observed. X-ray photon spectrometry (XPS) analysis of NPs obtained from synthetic wastewater confirmed the formation of nano-sized zero-valent Au and Ag. The consortium of microbes was found to be more efficient in bioreduction of ionic metals to zero-valent form than an individual strain.