Enzymatic versus microbial bio-catalyzed electrodes in bio-electrochemical systems.

Catalyses of electrode reactions by oxidoreductases or living electroactive bacteria are compared and recent advances reviewed. The relation between the biological and nevertheless inert nature of enzymes and the living machinery of electroactive microbes is discussed. The way these biocatalysts may be electrically contacted to anodes or cathodes is considered with a focus on their immobilization at electrodes and on the issue of time stability of these assemblies. Recent improvements in power output of biofuel cells are reviewed together with applications that have appeared in the literature. This account also reviews new approaches for combining enzymes and living microbes in bioelectrochemical systems such as reproducing microbial metabolisms with enzyme cascades and expressing oxidoreductases on genetically engineered microbes. Finally, the use of surface chemistry for studying the microbe-electrode interface and bioelectrodes with cell organelles, such as mitochondria, or with higher organisms, such as yeasts, are discussed. Some perspectives for future research to extend this field are offered as conclusions.