Scientists modified bacteria E. coli to make it produce natural propane

Gut bacteria turned biofuel producer

An international research team has engineered a harmless type of bacteria living in human intestines to make it produce renewable propane.

The discovery could one day lead to a revolution in alternative fuel production.

In a study, published in the latest issue of the journal Nature Communications, the authors describe how they used the bacteria Escherichia coli to interrupt the biological process that turns fatty acids into cell membranes. The researchers used enzymes to channel the fatty acids along a different biological pathway, so that the bacteria made engine-ready renewable propane instead of the cell membranes.

“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, from the Department of Life Sciences at Imperial College London who worked on the project together with scientists from the University of Turku in Finland.

“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 ultimate goal is to insert the engineered bacteria system into photosynthetic bacteria, so as to one day directly convert solar energy into chemical fuel.

Propane is an appealing source of cleaner fuel because it has an existing global market. It is already produced as a by-product during natural gas processing and petroleum refining, but both are limited resources. In its current form it makes up the bulk of LPG (liquid petroleum gas), which is used in many applications, from central heating to camping stoves and conventional motor vehicles.

Among the advantages of targeting propane is its ability to easily escape the cell in the form of gas and low energy requirements to transform the gas into a liquid, which is more suitable for transportation.

“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,” Jones said. “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.”

The amount of propane produced using the method is currently rather insignificant. To make the technology commercially viable, the production efficiency would have to be increased at least one thousand times.

“At the moment, we don’t have a full grasp of exactly how the fuel molecules are made, so we are now trying to find out exactly how this process unfolds,” Jones explained. “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.”

This research was funded by a grant from the European Research Council. 

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