Electron paramagnetic resonance study of retention of chromium(III), chromate or dichromate(VI) and copper(II) ions by thermotolerant Hansenula polymorpha

We report on CrIII and CrVI interaction with Hansenula polymorpha, a thermotolerant yeast, studied by means of EPR spectroscopy at room temperature. CrIII retention results in a reduced mobility of the ion, probably due to the formation of complexes immobilized on a polymeric matrix of cell. CrVI interaction produces stable, mobile CrV species, which can eventually partially decay to CrIII species. Different reducing agents in the cell may be responsible for this behaviour, especially on cell wall components or on cytoplasmic space. A comparison with a previous study on CuII ion retention is also made.