Upcycling CO2 into Long Chain Fatty Acids by Decoupled Microbial Electrochemical Systems

Abstract

The heavy reliance on fossil fuels results in excessive greenhouse emissions, exacerbating environmental change, and global warming. CO₂ electrocatalysis has been widely studied and the products are limited to C_1-2. Herein, we reported the integration of electrocatalysis and microbial catalysis for the synthesis of fatty acids from CO₂. Here, we compared two decoupled MESs for fatty acid production, electrocatalysis-purification system (System I), and direct-electrocatalysis system (System II). Firstly, an upstream electrolysis was used to reduce CO₂ to formate using KHCO₃ and medium as electrolyte, respectively, with carbon nanofiber supported bismuth (Bi@PCF) catalyst. The results indicated that KHCO₃ as electrolyte had higher formate yield and Faraday efficiency than that of medium. Subsequently, a downstream microbial catalysis composed of Cupriavidus species was employed to synthesize fatty acids from formate in System I and System II, respectively. It was demonstrated that System I with the yield of 1.006 mg L⁻¹ was more favorable for the synthesis of fatty acids than System II with the yield of 0.349 mg L⁻¹. These results suggested that decoupled electrochemical and microbial catalysis were an efficient approach for fixing CO₂, indicating the great potential of a renewable energy driving artificial photosynthesis.