Electron spin resonance study of copper biosorption by bacteria

Abstract

The biosorption of copper by bacteria was studied by using ESR spectroscopy. Among bacteria tested, Arthrobacter nicotianae has the most excellent ability to sorb copper. The biosorption of copper by Arthrobacter cells was so rapid, affected by the solution pH, and obeys the Langmuir adsorption equilibrium. The electron spin resonance (ESR) spectra of Cu(II) in bacterial cells are axial type, having a major absorption to higher field at g ⊥ and lesser absorption to lower field at g ∥ with four lines. The ESR parameters showed that Cu(II) in the cells has the tetragonally distorted octahedral structure with nitrogen and oxygen as ligand atoms, which suggests that most of copper in bacterial cells combined with amino acid residues in the cell surface proteins. The variation of spectral patterns among bacteria could explain as the change of ligand circumstances caused by the pH of the cell surface.