Heterogeneous electron transfer studies with ligninolytic redox enzymes and living bacteria. Applications in biosensors and biofuel cells

Abstract: The catalytic properties and the inter-domain electron transfer of cellobiose dehydrogenase (CDH) from the ascomycete fungus Myriococcum thermophilum adsorbed on graphite and thiol (SAM) modified gold electrodes were investigated using cyclic voltammetry, flow injection amperometry and UV-Vis spectroelectrochemistry. The fabrication and characterisation of a noncompartmentalised, mediator and cofactor free glucose–oxygen biofuel cell well-operating in glucose-containing buffers and human blood serum was performed. The biofuel cell was based on adsorbed enzymes exhibiting direct bioelectrocatalysis, viz. CDH from Dichomera saubinetii and Corynascus thermophilus used as anodic bioelements and laccase (Lc) from Trametes hirsuta and bilirubin oxidase (BOD) from Myrothecium verrucaria used as cathodic bioelements, respectively. Different bacterial strains of E. coli and B. subtilis were immobilised on the electrode surface and tested for electrical communication using soluble and polymeric mediators. In the case of E. coli, the introduction of cytochromes in the inner membrane facilitated the electrochemical communication when using artificial mediators, while in the case of B. subtilis, the results demonstrated that mediators did not have to pass the cytosolic membrane to bring about an efficient electronic communication between bacterial cells with a thick cell wall and electrodes.