Copper biosorption by chemically treated Micrococcus luteus cells

In order to clarify the binding states of copper in microbial cells, copper biosorption from aqueous systems using the chemically treated Micrococcus luteus IAM 1056 cells (hot water-treated, diluted NaOH-treated, chloroform–methanol-treated, and chloroform–methanol/concentrated KOH-treated cells) was examined. The intact cells of M. luteus adsorbed 527 mol of copper per g cells, and its copper adsorption was very rapid and was affected by the solution pH. The chloroform–methanol/concentrated KOH-treated cells showed higher copper biosorption capacity than the intact and the other chemically treated cells. The electron paramagnetic resonance (EPR) parameters, g and |A|, of Cu(II) ion in microbial cells indicate that Cu(II) ion in the intact and all the chemically treated cells have coordination environments with nitrogen and oxygen as donor atoms, being similar to those of type II proteins. The parameter g also indicated that the coupling between Cu(II) ion and the cell materials in the CHCl₃–MeOH/concentrated KOH-treated cells is rather more stable than those between Cu(II) ion and the cell materials in the other treated cells.