Shewanella oneidensis MR-1 coupled with biomass-derived carbon dots for promoted bioelectrochemical CO2 reduction: Mechanism elucidation of intensified energy metabolism

Abstract

Bioelectrochemical CO2 reduction reaction (CO2RR) has been touted as one of the promising strategies to convert CO2 to high-value chemicals via the efficient microbial electrosynthesis (MES). However, the sluggish electron transfer efficiency between microbes and cathodes hampers the CO2 reduction efficiency. Herein, biomass-derived carbon dots (CDs) with high electrical conductivity were coupled with Shewanella oneidensis (S. oneidensis) MR-1 to construct a nanomaterial-bacterial biohybrid system to promote CO2-to-formate formation. Specifically, the corncob-derived CDs (cc-CDs) were highly-biocompatible with S. oneidensis MR-1, with such a constructed biohybrid system showing a marked formate titer of 0.50 mmol/L. Upon doping with Fe element, the resultant Fe-cc-CDs exhibited a considerably boosted formate titer of 1.22 mmol/L, which was 7.7 times higher than the pure S. oneidensis MR-1 system. Such significant CO2-to-formate conversion enhancement was contributed by the internalized CDs in S. oneidensis MR-1 stimulating extracellular electron transfer efficiency, therefore accelerating energy metabolism for formate bioelectrosynthesis. The intensified energy metabolism in S. oneidensis MR-1 was corroborated by the increased concentrations of ATP, NADH and overexpression of energy-related genes. This work demonstrates an intensified energy metabolism exemplification for CO2 reduction, which can be expanded to a host of different nanomaterials-internalized MES systems for bioelectrochemical implications.