Electroautotrophic Microorganisms:Uptaking Extracellular Electron and Catalyzing CO2 Fixation and Synthesis

Electroautotrophic microorganisms can uptake electrons from extracellular solid donors such as metallic iron or steel, electrodes, and symbiotic microbial cells. Fuels and commodity chemicals can be produced from CO2 in a bioelectrochemical system powered by electricity and catalyzed by electroautotrophic microorganisms since they are often able to reduce and fix CO2. Thus, this provides a new and promising strategy to cope with the word energy crisis and greenhouse effect. Metabolic properties and electron uptake abilities of electroautotrophic microorganisms have direct and significant influences on viability and productivity of electrosynthesis processes. In this review, a diversity of microbial physiologies uptaking electrons from iron or steel, electrode and microbial cell, including sulphate reduction, methanogenesis, acetogenesis and nitrate reduction, are respectively summarized in the first place. Then, research progress of electrosynthesis of methane, acetate and other chemicals catalyzed by diverse electroautotrophic microorganisms are reviewed. And strategies for improving CO2 fixation and electrosynthesis efficiency and diversifying the products are emphasized, such as defined co-culture construction, cathode material modification and so on. At last, research efforts in clarifying extracellular electron transfer mechanism, catalyzing microorganisms screening and co-culture construction, and genetic engineering of electroautotrophic microbes are proposed as future directions for researchers.