EXTRACELLULAR BIO-SYNTHESIS OF GOLD NANOPARTICLES USING Escherichia coli AND DECIPHERING THE ROLE OF LACTATE-DEHYDROGENASE USING LDH KNOCK OUT E. coli

This paper is devoted to apprehend the exploitation of biological machinery and optimum biosynthesis parameters using Escherichia coli exudates for gold nanoparticle (GNP) synthesis and its modus operandi. The most influential parameters for the synthesis of GNPs were pH 7.35, 300C and 100 ppm aurochlorate salt. The results were verified using UV-Vis spectroscopy, XRD and High Resolution Transmission Electron Microscopy. HRTEM micrographs as well as the SPR peaks of UV-Vis spectra showed that the size of the GNPs ranged from 25-30 nm. The HRTEM demonstrated that at inherent pH of reactant spherical GNPs were formed whereas when pH was adjusted to 4, formation of anisotropic nanostructures occurred. The mechanism of GNP synthesis was decoded using Lactate dehydrogenase (LDH) knock out E.coli. It was found that LDH knock out bacteria was incapable of synthesizing GNP. The role of LDH was further demonstrated when its activity got reduced from 73.5umol mg-1 min-1 to 24umol mg-1min-1 in normal E.coli