¹³ C-Labeling the carbon-fixation pathway of a highly efficient artificial photosynthetic system

Interfacing the CO ₂ -fixing microorganism, Ralstonia eutropha , to the energy derived from hydrogen produced by water splitting is a viable approach to achieving renewable CO ₂ reduction at high efficiencies. We employ ¹³ C-labeling to report on the nature of CO ₂ reduction in the inorganic water splitting| R. eutropha hybrid system. Accumulated biomass in a reactor under a ¹³ C-enriched CO ₂ atmosphere may be sampled at different time points during CO ₂ reduction. Converting the sampled biomass into gaseous CO ₂ allows the ¹³ C/ ¹² C ratio to be determined by gas chromatography-mass spectrometry. After 2 hours of inoculation and the initiation of water splitting, the microbes adapted and began to convert CO ₂ into biomass. The observed time evolution of the ¹³ C/ ¹² C ratio in accumulated biomass is consistent with a Monod model for carbon fixation. Carbon dioxide produced by catabolism was found to be minimal. This rapid response of the bacteria to a hydrogen input and to subsequent CO ₂ reduction at high efficiency are beneficial to achieving artificial photosynthesis for the storage of renewable energy.