An external magnetic field for efficient acetate production from inorganic carbon in Serratia marcescens catalyzed cathode of microbial electrosynthesis system

Abstract External magnetic field with simple, rapid, standardized and controllable characters can improve electricity harvesting in bioelectrochemical systems. Herein, the fabrication of external magnetic field with microbial electrosynthesis system (MES), in which electrotrophic Serratia marcescens Q1 catalyzed acetate production from bicarbonate, is attempted for improved system performance. An acetate production of 550 ± 22 mg/L with a coulombic efficiency (CEacetate) of 57 ± 2 % and an acetate conversion efficiency (βacetate) of 84 ± 2 % at bicarbonate consumption of 1832 ± 24 mg/L was achieved, 2.2 (acetate production), 1.8 (bicarbonate consumption), 1.2 (CEacetate) and 1.2 (βacetate) times as those in the absence of magnetic field. This was ascribed to the decrease in charge transfer resistance, confirming the magnetic field in developing the electrotrophic catalysis activity for reduction of bicarbonate. While the external magnetic field and the circuital current had synergistic stimulating effects on the release of extracellular polymeric substances (EPS), and additive effects on the electrotrophic growth, the circuital current was more influential than the magnetic field on the amount of EPS with a compositional diversity. This study provides the first experimental indication for an alternative approach to rapidly fabricate controllable MES for efficient acetate production from inorganic carbon.