Engineered E. coli turns fatty acids into propane

By engineering a protein found in the gut, researchers have generated renewable propane and taken a step towards producing a commercially-viable alternative to traditional fossil fuels. Using a new variant of the enzyme thioesterase and engineered Escherichia coli as a host organism, researchers interrupted the biological process that turns fatty acids into cell membranes. The enzyme specifically targets fatty acids and releases them from the natural process; by stopping the process at an early stage, researchers were able to remove butyric acid, an essential precursor to propane production. A second bacterial enzyme called CAR converts the butyric acid to butyraldehyde before aldehyde-deformylating oxygenase (ADO) – a recently discovered enzyme which naturally creates hydrocarbons – forms propane. Researchers at Imperial College London discovered that stimulating ADO with electron substantially enhanced the catalytic capabilities of ADO, ultimately producing propane. "Although this research is at a very early stage, our proof of concept study provides a method for renewable production of a fuel that previously was only accessible from fossil reserves,” said Dr Patrik Jones, from the Department of Life Sciences. “Although we have only produced tiny amounts so far, the fuel we have produced is ready to be used in an engine straight away. This opens up possibilities for future sustainable production of renewable fuels that at first could complement, and thereafter replace fossil fuels like diesel, petrol, natural gas and jet fuel." The scientists – which also included Dr Kalim Akhtar from the University of Turku in Finland – chose to target propane because easily escapes the cell as a gas, but needs little energy to transform it into a liquid that is easy to transport, store and use.  Their ultimate goal is to insert this engineered system into photosynthetic bacteria, so as to one day directly convert solar energy into chemical fuel. “This study is yet another prime example of how we’re moving very swiftly from biological discovery to translations research,” said Aktar, now at University College London. “It highlights how fundamental biological processes can be utilised to develop potentially benign technologies, ones that could be used to benefit both humankind and the environment.” The research, funded by a grant from the European Research Council, is published in Nature Communications. An engineered pathway for the biosynthesis of renewable propane