Boosting Microbial Electrocatalytic Kinetics for High Power Density: Insights into Synthetic Biology and Advanced Nanoscience

Abstract

Microbial electrochemical systems are able to harvest electricity or synthesize valuable chemicals from organic matters while simultaneously cleaning environmentally hazardous wastes. The sluggish extracellular electron transfer (EET) between “non- or poor-conductive” microbes and electrode involves both bio- and electrocatalytic processes but is one of the main impediments to fast microbial electrode kinetics. To boost EET, researches have been focused on engineering electrochemically active microbes, constructing a unique nanostructured electrode endowed with a large amount loading of microbes and enhancing biotic–abiotic interactions for rapid electrode kinetics. After surveys of fundamentals of microbial electrocatalysis, particularly the diverse EET mechanisms with discussions on scientific insights, this review summarizes and discusses the recent advances in bioengineering highly active biocatalytic microbes and nanoengineering unique electrode nanostructures for significantly improved microbial EET processes. In particular, this review associated with our researches analyzes in more detail the EET pathways, which contain direct and mediated electron transfer. The confusion between the energy efficiency and electron transfer rate is clarified and the approaches to elevate the EET rate are further discussed. These discussions shed both theoretical and practical lights on further research and development of more high-performance microbial catalysts by using synthetic biology coupled with nanoengineering approach for high energy conversion efficiency while achieving high power density for practical applications. The challenges and perspectives are presented. It is believed that a next wave of research of microbial electrochemical systems will produce a new generation of sustainable green energy technologies and demonstrate great promise in their broad applications and industrializations.