Cellobiose dehydrogenase - an electrifying enzyme: biochemical and electrochemical characterisation of cellobiose dehydrogenase for its application in biosensors and biofuel cells

The flavocytochrome cellobiose dehydrogenase (CDH) was studied in respect to biochemical applications. The production, purification and characterisation of CDH from the lignolytic basidiomycete Ceriporiopsis subvermispora and the ascomycetes Myriococcum thermophilum, Chaetomium atrobrunneum, Corynascus thermophilus, Dichomera saubinetii, Hypoxylon haematostroma, Neurospora crassa and Stachybotrys bisbyi, which were identified during a screening of 42 ascomycete strains, is described. The molecular properties and steady-state kinetics of these CDHs and in case of M. thermophilum CDH also the separated flavin domain were investigated using IEF, SDS-PAGE and UV-Vis spectroscopy. In regard to their substrate specificity, pH profiles, interdomain electron transfer efficiencies, cellulose binding as well as their sequence, distinct differences were found depending on the origin of the CDH. The catalytic properties and the interdomain electron transfer of the ascomycete CDHs was determined on graphite and on thiol-modified gold electrodes using flow-injection amperometry, cyclic voltammetry and UV-Vis spectroelectrochemistry. Two membrane-less glucose/oxygen biofuels based on a D. saubinetii CDH-anode or a C. thermophilus CDH-anode were fabricated with a maximum power density of 5 μW cm-2 and 4 μW cm-2 , respectively. In presence of carbon nanotubes and Os-redoxpolymers the maximum power-density of M. thermophilum CDH and Phanerochaete sordida CDH anodes was raised up to 157 and 300 μW cm-2 , respectively. A combined bioanode based on glucose oxidising redox enzymes with a different regioselectivity like CDH and pyranose dehydrogenase was fabricated and characterized with an increased coulombic efficiency. These pioneered potential applications of CDH in bioelectrochemistry promise a bright future for this electrifying enzyme. (author)