(Invited) Carbon Electrode-Based Electron Transference Enhance Platform Chemical Productions of Live Cell

Bacteria is dynamic biocatalyst which is self-regenerating and sustainable in a bioprocess. The respiration and redox state of bacteria are mainly regulated by various external electron acceptors, and significantly influence to the yield/titer of many biosynthesis and biorefinery processes. The cellular redox state is one of the most important factors to control metabolic fluxes and pathways in bioconversion. Conventional strategies for changing the redox state (e.g., the NAD+/NADH ratio) need to provide external oxidants/reductants, such as oxygen, or chemical reductases/oxidases, and carbon source and hydrogen, which are non-sustainable and frequently produce toxic/inhibitory byproducts. In this respect, electrode-based regulation using bioelectrochemical system (BES), has been highlighted for sustainable bioelectricity generation, and in-situ control of bioconversion of substrates such as glycerol, C1 gases etc. The bioelectrochemical regulation of central metabolic fluxes may also trigger gene and enzyme expression. In this study, the increased productivity of the platform chemicals such as 3-hydroxypropionic acid and 1,3-propanediol by using recombinant Klebsiella pneumoniae and E. coli in BES, will be presented as well as recent progress of BES-based bioconversion. The suggested strategy for bacterial redox state regulation not only improves the productivity and yield/titer, but also provides the opportunity for overcoming thermodynamic imbalances in most of bioprocesses. These results could contribute to further improvements in bioprocesses, and could lead to industrial applications for the biorefinery process.