Carbon dioxide (CO2) fixation by photosynthetic organisms provides
virtually all organic matter for life on earth. The majority of CO2 is
fixed through RubisCO, the key enzyme in the Calvin Benson Bassham
cycle. RubisCO discriminates between CO2 and O2 poorly; the product
formed from the reaction with oxygen is toxic and must be detoxified and
recycled. This requires additional energy and results in the release of
fixed CO2, ultimately decreasing carbon capture efficiency. After the
discovery of Enoyl-CoA reductive carboxylases, that are more efficient
and specific than RubisCO, we designed and established a synthetic
CO2-fixation pathway called the Crotonyl–coenzyme A
(CoA)/Ethylmalonyl-CoA/Hydroxybutyryl-CoA (CETCH) cycle in vitro .
Transplanting this artificial CO2 fixation cycle in vivo would allow the
bypassing of RubisCO entirely, mitigating the deleterious effects of
photorespiration and ultimately enhancing carbon fixation.
Working towards the implementation of the CETCH cycle in vivo, we coupled our artificial CO2 fixation pathway with photosynthetically active membranes. Our system utilizes light energy to generate the reducing and energy equivalents (i.e. NADPH and ATP) necessary to sustain the cycle. Here we demonstrate the successful creation of a light-driven, artificial photosynthetic system that fixes CO2 through a synthetic cycle in vitro. This system of reduced complexity allows us to study and fine tune the entire light powered synthetic CO2-fixing cycle for its introduction into a complex in vivo system.
 T. Schwander, L. Schada von Borzyskowski, S. Burgener, N. Socorro Cortina, T.J. Erb, A synthetic pathway for the fixation of carbon dioxide in vitro Science Vol. 354, Issue 6314, pp. 900-904 (2016)