Harvesting Cellulose and Sunlight to Power Butanol Biosynthesis: a Synthetic Biology Approach to Metabolic Engineering

The near-future "killer application" of synthetic biology may be in biofuel production. Therefore, the 2007 Virginia Genetically Engineered Machine (VGEM) Team utilized a modular, synthetic biology approach for the design and attempted construction of a novel metabolic pathway in E. coli for the production of butanol, a promising alternative liquid transportation fuel. This poster presents progress toward the implementation of a synthetic pathway that utilizes light energy in addition to chemical energy stored in cellulose to drive the biosynthesis of a chemical product such as butanol. A butanol biosynthesis system (from Clostridium acetobutylicum), a cellulase system (from Saccharophagus degradans), and the light-activated proton pump, proteorhodopsin (from marine metagenomic analysis), were used to design the synthetic pathway. The VGEM Team was successful in implementing proteorhodopsin in E. coli. Proteorhodopsin-expressing bacteria exhibited a growth advantage only when experiencing respiratory stress (that is, in the absence of oxygen). Therefore, proteorhodopsin may be valuable in increasing the efficiency and yields of bioprocesses that must occur under anaerobic conditions such as the biosynthesis of butanol.