Microbial electrosynthesis (MES) systems aim to use electroactive microorganisms (EAMs) to achieve electricity-driven CO2 fixation for biosynthesis of multicarbon chemicals. However, the low efficiencies of extracellular electron transfer (EET) and CO2 assimilation of EAMs remain the essential limiting factors that restrict performance of MES systems. Herein, we developed an electrosynthetic biohybrid system to synergistically supply electrons and CO2 to Rhodopseudomonas palustris (an EAM) for lycopene biosynthesis. Intracellular carbon and energy fluxes were redirected by strengthening the lycopene biosynthesis pathway and blocking the nitrogen-fixation pathway, resulting in 23-fold increase in lycopene yield than that of the wild-type R. palustris. To enhance extracellular transfer of CO2 and electrons to R. palustris, metal-organic frameworks (MOFs) with high CO2 adsorption capacity were assembled with polydopamine on cell membrane to construct a biohybrid MES system, which produced 3.55 mg/L lycopene in two consecutive MES cycles, the highest lycopene production from CO2. Electrochemical and transcriptomic analyses revealed that the biohybrid MES system stimulated microbial metabolism including EET, the Calvin-Benson-Bassham cycle and lycopene biosynthesis, thereby improving CO2-to-chemical conversion. This study demonstrated directional supply of electrons and CO2 to EAMs enabled high-performance MES systems, which also offered insights into the mechanisms underlying efficient CO2 fixation and carbon-negative biomanufacturing.
Xiong et al. (Fri,) studied this question.