Journal of Fundamentals of Renewable Energy and Applications
Open Access

The plasticity of cyanobacterial metabolism supports direct CO2 conversion to ethylene

International Congress and Expo on Biofuels & Bioenergy

August 25- 27, 2015 Valencia, Spain

Jianping Yu, Wei Xiong, John A Morgan, Justin Ungerer, Bo Wang and Pin-Ching Maness

Posters-Accepted Abstracts: J Fundam Renewable Energy Appl

Abstract :

The cyanobacterial tricarboxylic acid (TCA) cycle serves in biosynthesis and energy generation. However, it has until recently
been generally considered to be incomplete with limited flux, and few attempts were made to draw carbon from the cycle for
biotechnological purposes. We demonstrated that ethylene can be sustainably and efficiently produced from the TCA cycle of the
recombinant cyanobacterium Synechocystis 6803 expressing the Pseudomonas ethylene-forming enzyme (Efe). A new strain with
a modified ribosome-binding site in front of efe gene diverts 10% of fixed carbon to ethylene and shows increased photosynthetic
activities. The highest specific ethylene production rate reached 718±19 μL/L/h/OD730. Experimental and computational analyses
based on kinetic 13C-isotope tracer and LC-MS revealed that the TCA metabolism is activated by the ethylene forming reaction,
resulting in a predominantly cyclic architecture. The outcome significantly enhanced flux through the remodelled TCA cycle
(37% of total fixed carbon) in comparison to a complete, but bifurcated and low-flux (13% of total fixed carbon) TCA cycle in
wild type. Global carbon flux is redirected toward the engineered ethylene pathway. The remarkable metabolic network plasticity
of this cyanobacterium is manifested via the enhancement of photosynthetic activity and redistribution of carbon flux, enabling
efficient ethylene production from the TCA cycle.