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

Abstract

Interfacing the CO-fixing microorganism, Ralstonia eutropha, to the energy derived from hydrogen produced by water splitting is a viable approach to achieving renewable CO reduction at high efficiencies. We employ C-labeling to report on the nature of CO reduction in the inorganic water splitting|R. eutropha hybrid system. Accumulated biomass in a reactor under a C-enriched CO atmosphere may be sampled at different time points during CO reduction. Converting the sampled biomass into gaseous CO allows the C/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 into biomass. The observed time evolution of the C/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 reduction at high efficiency are beneficial to achieving artificial photosynthesis for the storage of renewable energy.

Proton-Coupled Electron Transfer: The Engine of Energy Conversion and Storage

“…Here, the only “food” source for the bioorganism to grow or make liquid fuels is hydrogen, which it metabolized to NADPH via hydrogenases (Figure B). The NADPH/H + offers the reductant for the fixation of carbon dioxide from air, which has been established by 13 CO 2 isotopic labeling studies . In the implementation of the Bionic Leaf-C, the interface between inorganic materials and biology must be properly designed to attain high energy efficiencies.…”

Artificial Photosynthesis at Efficiencies Greatly Exceeding That of Natural Photosynthesis

“…The model predicts a linear correlation between biomass and charge passed after an induction period of low population density of bacteria and high H 2 concentration, which is consistent with the data shown in Figure B where the induction period is too short to be observed. 13 C-Enriched CO 2 atmospheres establish that accumulated biomass uses CO 2 as its sole electron carbon source . Converting the sampled biomass from the reactor at different time points during CO 2 reduction allows the 13 C/ 12 C ratio to be determined by gas chromatography–mass spectrometry analysis and shows that catabolism is minimal.…”

“…Photosystems II and I harness solar photons and combine electron and proton equivalents to produce hydrogen in the form of NADPH/H + , and then CO 2 is reduced with NADPH/H + in a dark cycle within the chloroplast. This processing path of photosynthesis may be recapitulated functionally by interfacing CO 2 -fixing microorganisms to hydrogen produced by solar water splitting ,, The coupling of solar energy via hydrogen to power cellular biosynthesis may be achieved by installing hydrogenases into the bioorganism. Indeed, owing to the work described here, it is now realized that most systems attempting to perform direct injection or redox equivalents via nanowires likely does not occur .…”

Surface Strategies for Particulate Photocatalysts toward Artificial Photosynthesis

“…(2) To determine whether reductive products are derived from CO 2 and not from introduced carbon impurity intermediates, it is essential to perform isotope labeling experiments with 13 CO 2 as a reactant. 138,170 In addition, blank tests and different control experiments are strongly recommended for all future studies. (3) Owing to variations in experimental illumination conditions, it is necessary to use a unified solar energy conversion efficiency measured by a series of standard procedures to enable comparison of the reaction rates of photocatalysts reported by different groups.…”