Extracellular electron transfer in acetogenic bacteria and its application for conversion of carbon dioxide into...

Acetogenic bacteria (i.e., acetogens) produce acetate from CO₂ during anaerobic chemoautotrophic growth. Because acetogens fix CO₂ with high energy efficiency, they have been investigated as biocatalysts of CO₂ conversion into valuable chemicals. Recent studies revealed that some acetogens are capable of extracellular electron transfer (EET), which enables electron exchange between microbial cells and extracellular solid materials. Thus, acetogens are promising candidates as biocatalysts in recently developed bioelectrochemical technologies, including microbial electrosynthesis (MES), in which useful chemicals are biologically produced from CO₂ using electricity as the energy source. In microbial photoelectrosynthesis, a variant of MES technology, the conversion of CO₂ into organic compounds is achieved using light as the sole energy source without an external power supply. In this mini-review, we introduce the general features of bioproduction and EET of acetogens and describe recent progress and future prospects of MES technologies based on the EET capability of acetogens.