Bioelectrocatalysis of oxygen reduction reaction by laccase on gold electrodes

Direct electron transfer (DET) reaction of oxygen electroreduction catalyzed by enzyme laccase on monolayer modified gold electrodes was studied. Three different monolayers were investigated, from which 4-aminothiophenol was found to be optimal for the direct electron transfer to take place. The electrocatalytic reduction of the oxygen at the electrode surface was found to depend significantly on the method of immobilization. Fungal laccase from Coriolus hirsitus modified with sodium-periodate demonstrated more anodic onset potential for oxygen reduction than the tree laccase from Rhus vernicifera. Physical immobilization of enzyme did not result in any manifestation of bioelectrocatalytic activity. A maximum anodic shift in reduction potential of 300 mV was observed for fungal laccase covalently coupled on the electrode surface.