Bioelectrocatalysis is a phenomenon of acceleration of electrode reactions with biological catalysts. Most often the immobilized enzymes are used as the latter. The phenomenon of 'direct bioelectrocatalysis' presumes a possibility for direct (mediatorless) electron exchange between the electrode and the enzyme active site. In this case the electrode reaction substitutes directly one of the coupled redox reactions catalyzed by the enzyme.

The discovery of the direct bioelectrocatalysis is a proud of Russian electrochemical school. In late 70-s of the last century the enzyme electrodes active in reduction of oxygen and hydrogen peroxide made on the basis of immobilized laccase and peroxidase, correspondingly, were reported. In the beginning of 80-s a hydrogen enzyme electrode able to achieve hydrogen equilibrium potential was elaborated.

Fundamental aspects of direct bioelectrocatalysis include: (i) the investigation of the enzymes redox centers and electron transport chains, and (ii) a possibility to access enzyme catalysis, in particular to carry out redox switching of enzyme activity.

Besides fundamental aspects, the direct bioelectrocatalysis is extremely attractive concerning its applications. Among them are: (i) biosensors, (ii) biofuel cells, and (iii) systems for specific electrosynthesis. Except for the last one, the applications are rapidly developed. I will mention the biosensors for hydrogen peroxide based on peroxidase, and bioelectrocatalysis by hydrogenase and laccase used as for biofuel cells, as for analytical purposes.

Special attention will be devoted to hydrogen-oxygen fuel cells. Besides the majority of efforts are currently put on the development of platinum based fuel electrodes, there are crucial problems with platinum, which seriously limit the use of such systems in future. A valuable alternative to platinum based electrocatalysis is the bioelectrocatalysis. The advantages of the enzymes based fuel electrodes in hydrogen-oxygen fuel cells (including systems for utilization of organic wastes) will be discussed.

In addition to fuel cell applications, hydrogen enzyme electrodes can be used as hydrogen sensors, where the use of platinum is impossible due to high contamination with sulphide and other platinum poisons. A possibility for hydrogen sensing directly from microbial medium will be shown.

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