Spectroscopic Characterization On Interaction Of Gold (Au3+) Biosorption By Bacillus Megaterium D01

Biosorptive interaction of gold with resting cell of Bacillus megatherium D01 biomass has been characterized by spectroscopic techniques. The effects of pH, time and temperature on the correlation parameters of chemical kinetics and thermodynamics of the binding reaction has been investigated through the determination of the gold ion binding to the biomass using atomic absorption spectrophotometry (AAS). The analysis for sulfur content in dry powder of the D01 biomass by energy dispersive X-ray (EDX) shows that cysteine and methionine being capable of reducing Au3+ to Au-0 is very small, whereas the glucose content in hydrolysates of the biomass analyzed by ultraviolet-visible spectrophotometry (UV-vis) indicates that the amount of the reducing sugars in the biomass is much larger than 3.33%. The Fourier transform infrared (FTIR) spectroscopy on blank and gold-loaded biomass demonstrates that the active groups such as the hydroxyl group of saccharides and the ionized carboxyl group of amino acid residues on the cell wall seem to be the sites for Au3+ binding, and the free aldehyde group of the hemiacetalic hydroxyl group from reducing sugars, i. e. the hydrolysates of the polysaccharides, serving as the electron donor, in situ reduces the Au3+ to Au-0. X-ray powder diffractometry (XRD) and FTIR spectroscopic characterizations of the interaction of Au3+ with glucose confirm that the reduction of Au3+ to Au-0 can directly occur in the aldehyde group of the reducing sugars.