The electrochemistry of the ligninolytic redox enzymes, which include lignin peroxidase, manganese peroxidase and laccase and possibly also cellobiose dehydrogenase, is reviewed and discussed in conjunction with their basic biochemical characteristics. It is shown that long-range electron transfer between these enzymes and electrodes can be established and their ability to degrade lignin through a direct electron transfer mechanism is discussed.

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A membrane‐free biofuel cell (BFC) is reported based on enzymes wired to graphite electrodes by means of Os‐complex modified redox polymers. For the anode cellobiose dehydrogenase (CDH) is used as a biocatalyst whereas for the cathode a laccase was applied. This laccase is a high‐potential laccase and hence able to reduce O2 to H2O at a formal potential higher than +500 mV versus Ag/AgCl. In order to establish efficient electrochemical contact between the enzymes and graphite electrodes electrodeposition polymers containing Os‐complex with specifically designed monomer compositions and formal potentials of the coordinatively bound Os‐complex were synthesised and used to wire the enzymes to the electrodes. The newly designed CDH/Os‐redox polymer anode was characterised at different pH values and optimised with respect to the nature of the polymer and the enzyme‐to‐polymer ratio. The resulting BFC was evaluated running on β‐lactose as a fuel and air/O2 as an oxidising agent. The power output, the maximum current density and the electromotor force (Eemf) were found to be affected by the pH value, resulting in a maximum power output of 1.9 μW cm–2 reached at pH 4.3, a maximum current density of about 13 μA cm–2 at pH 3.5, and the highest Eemf approaching 600 mV at pH 4.0.

The design of polymers carrying suitable ligands for coordinating Os complexes in ligand exchange reactions against labile chloro ligands is a strategy for the synthesis of redox polymers with bound Os centers which exhibit a wide variation in their redox potential. This strategy is applied to polymers with an additional variation of the properties of the polymer backbone with respect to pH-dependent solubility, monomer composition, hydrophilicity etc. A library of Os-complex-modified electrodeposition polymers was synthesized and initially tested with respect to their electron-transfer ability in combination with enzymes such as glucose oxidase, cellobiose dehydrogenase, and PQQ-dependent glucose dehydrogenase entrapped during the pH-induced deposition process. The different polymer-bound Os complexes in a library containing 50 different redox polymers allowed the statistical evaluation of the impact of an individual ligand to the overall redox potential of an Os complex. Using a simple linear regression algorithm prediction of the redox potential of Os complexes becomes feasible. Thus, a redox polymer can now be designed to optimally interact in electron-transfer reactions with a selected enzyme.