Toward Solar-Powered Growth of Autotrophic <i>Escherichia coli</i> Using Photoelectrochemistry

Integrated coupling of renewable energy sources with microbial CO2 fixation remains a major challenge in carbon-neutral biomanufacturing. Here, a biohybrid design is presented that combines a semiartificial leaf for solar-powered conversion of CO2 into formate with an autotrophic Escherichia coli (E. coli) that is engineered to use formate as an energy source to produce biomass. First, adaptive laboratory evolution was employed to enhance formate consumption and overcome slow autotrophic growth. Second, electrode-microbe compatibility was established, showing that the adapted strain can grow directly using formate electrochemically generated from CO2 by an enzyme-modified cathode. Third, the electrical energy source was replaced with simulated sunlight, developing a biophotoelectrochemical device to support E. coli growth. Finally, an integrated platform consisting of a semiartificial leaf and autotrophic E. coli was designed, which couples solar CO2-to-biomass conversion and O2 evolution, replicating natural photosynthesis.