Efficient production of lycopene from CO2 via microbial electrosynthesis

Abstract

Valorization of CO2 is key to establishing a carbon–neutral society. However, CO2 possesses a strong C = O with bond energy of 750 kJ/mol, which makes it difficult for electrochemical conversion. As a result, the conversion of CO2 to complex molecules remains a grand challenge and product profiles based on inorganic catalysis are only limited to a few simple chemicals, such as formate, acetate, and ethanol. Here, we employed microbial electrosynthesis to diversify the product spectrum. First, an engineered Cupriavidus necator strain was constructed to produce lycopene from H2 and CO2. Then, by coupling de novo microbial catalyzed lycopene synthesis with inorganic catalyzed water electrolysis, a microbial electrosynthesis (MES) system was developed. Lycopene, representing the most complex nonnative molecules in the MES system, was produced with CO2 as the sole carbon source and H2 derived from electrochemical water splitting as the reducing power. Moreover, the produced lycopene provided long-term cytoprotective capacity against reactive oxygen species, thereby addressing the incompatibility between microbial and inorganic catalysis. Finally, 1.73 mg/L lycopene was produced from real exhaust gas from a coal-fired power plant in the MES system. The present study opens a possible route to turn trash to cash for industrial exhaust gas.