Redox Mediators in Microbial Electrochemical Systems.

Redox mediators are commonly used in microbial electrochemical systems to enable or enhance the electron transfer between microorganisms and electrodes. In recent studies, new insights into the mechanism of mediated extracellular electron transfer were gained, but some questions remain unanswered. In this review, some of the most outstanding research questions regarding the use of redox mediators in microbial electrochemical systems were discussed. These included the recycling of artificial and natural redox mediators, limitations in electron transfer rates by mediator turnover, metabolic burden, membrane permeability, and the putative interaction sites between commonly used redox mediators and the proteins of the electron transport chain of diverse electroactive microorganisms. To simplify the planning of mediator‐based bioelectrochemical systems, these molecular interaction sites were defined by their redox potential and are assigned to redox mediators, known or hypothesized to be able to transfer electrons from or to the specific interaction site. Furthermore, we addressed the kinetics of mediator transfer through the membrane and the potential rate‐limiting step in mediator‐based processes. [ABSTRACT FROM AUTHOR]