Promoting of direct electron transfer of multicopper oxidase by control of enzyme molecule density on multi-walled carbon nanotube

In order to improve the performance of direct electron transfer-type electrode using multicopper oxidase (MCO), it is important to shorten the distance between the redox site of the enzyme and the electrode surface to increase electron transfer efficiency between enzyme and electrode. In this study, we focused on the mobility of the MCO from hyperthermophilic archaeon, Pyrobaculum aerophilum, immobilized onto electrode surface via an affinity tag at the MCO terminus. The mobility of the immobilized enzyme was controlled by changing the density of the immobilized enzyme on the electrode surface by altering the density of the linker for enzyme immobilization. The electrode with low density of MCO immobilized on electrode surface was improved swing ability of the enzyme. It showed 265% higher current density for electrochemical O 2 reduction than that with high density of MCO immobilized on electrode surface. Biofuel cell using a cathode with a low density of MCO immobilized on the electrode showed 160% higher power density than a biofuel cell using a cathode with a high density of MCO immobilized on the electrode.