A cell-free artificial anabolic pathway for direct conversion of CO2 to ethanol

Biological CO2 activation and conversion to high-value ethanol are a feasible and green strategy to close the carbon cycle. However, naturally evolved CO2 utilization pathways involve carbon loss or ATP consumption. Herein, we report a complete anabolic pathway for direct conversion of CO2 to ethanol by constructing and assembling three functional modules including CO2 activation, formaldehyde -> acetyl-CoA, and ethanol synthesis in a carbon-conserved and ATP-independent system. These artificial ethanol metabolic pathway fluxes were strengthened by screening efficient key enzymes for CO2 activation, promoting formaldehyde assimilation, and employing a two-step reaction. C-13-labeled CO2 demonstrated the feasibility of the pathway converting CO2 into ethanol in vitro by detecting the carbon flow. With this anabolic pathway, we obtained an ethanol concentration of 0.37 mM at a conversion rate of 4.33 nmol CO2 min(-1) mg(-1) enzyme and 0.5 mM R5P supply. This modularization strategy provides a new avenue in the construction of artificial metabolic pathways for ethanol synthesis from CO2.

Automated summary

This study presents a complete synthetic pathway for the direct conversion of CO2 to ethanol. The pathway consists of three functional modules and operates in a carbon-conserved and ATP-independent system. The efficiency of the pathway was enhanced by screening efficient enzymes and using a two-step reaction. The feasibility of converting CO2 to ethanol was demonstrated through experiments.