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Scientists engineer bacteria to produce renewable, engine-ready propane gas

Researchers have successfully engineered E. coli to generate renewable, engine-ready propane, which is a major sustainable fossil fuel replacement candidate.Propane has huge potential as a replacement for our rapidly dwindling fossil fuels because we already have a market for it - it's one of the main components in LPG (liquid petroleum gas), which we use in vehicles and heating. But right now it’s only produced as a byproduct of natural gas processing and petroleum refining, both of which are very unsustainable practices.

Now researchers from the Imperial College London in the UK and the University of Turku in Finland have proved that propane can be produced sustainably, by showing that the harmless gut bacteria Escherichia coli (E. coli) can be engineered to make renewable propane.

To turn the bacteria into propane-producing machines, the scientists interrupted the biological process that turns fatty acids into cell membranes. The researchers used three novel enzymes to channel the fatty acids along a different biological pathway, resulting in the bacteria producing engine-ready, renewable propane instead of cell membranes. The results are published in nature communication.

Their goal is now to insert this engineered production line into photosynthetic bacteria, which harvest energy from the sun, so that one day they’ll be able to directly convert solar energy into chemical fuel. The E. coli in this experiment were powered by sugar. The scientists also need to scale up the process - right now they’re producing 1,000 times less propane from the reaction then they would need to make the process commercially viable.

"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 Patrik Jones, a synthetic biologist and one of the authors of the paper from the Imperial College London,  in a press release.

“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 researchers chose to make the E. coli produce propane as opposed to gasoline or other fossil fuels, because propane can easily be converted from a liquid to a gas. The bacteria cells produce propane gas, but then the researchers can cheaply and easily transform this into a liquid that can be stored and transported.

"Fossil fuels are a finite resource and as our population continues to grow we are going to have to come up with new ways to meet increasing energy demands. It is a substantial challenge, however, to develop a renewable process that is low-cost and economically sustainable. At the moment algae can be used to make biodiesel, but it is not commercially viable as harvesting and processing requires a lot of energy and money. So we chose propane because it can be separated from the natural process with minimal energy and it will be compatible with the existing infrastructure for easy use,” said Jones.

The scientists are now trying to better understand what’s going on behind the scenes of the production process to make the process more efficient. "I hope that over the next 5-10 years we will be able to achieve commercially viable processes that will sustainably fuel our energy demands,” said Jones.

CULTURE OF E.COLI