Enhanced Microbial Protein Production from CO and Air by a MoS Catalyzed Bioelectrochemical System.

Carbon dioxide can be relatively easily reduced to organic matter in a bioelectrochemical system (BES). However, due to insufficient reduction force from in-situ hydrogen evolution, it is difficult for nitrogen reduction. In this study, MoS was firstly used as an electrocatalyst for the simultaneous reduction of CO and N to produce microbial protein (MP) in a BES. Cell dry weight (CDW) could reach 0.81±0.04 g/L after 14 d operation at -0.7 V (vs. RHE), which was 108±3 % higher than that from non-catalyst control group (0.39±0.01 g/L). The produced protein had a better amino acid profile in the BES than that in a direct hydrogen system (DHS), particularly for proline (Pro). Besides, MoS promoted the growth of bacterial cell on an electrode and improved the biofilm extracellular electron transfer (EET) by microscopic observation and electrochemical characterization of MoS biocathode. The composition of the microbial community and the relative abundance of functional enzymes revealed that MoS as an electrocatalyst was beneficial for enriching Xanthobacter and enhancing CO and N reduction by electrical energy. These results demonstrated that an efficient strategy to improve MP production of BES is to use MoS as an electrocatalyst to shift amino acid profile and microbial community.