Getting E. coli to make propane

Apparently some scientists have made propane in a lab with little more than the bacteria in our guts: E.coli.

This is interesting for a number of reasons. It would make propane produced in this way a renewable fuel. You don’t hear the words renewable and propane together in a sentence very often! It’s also a synthetically produced fuel that does not compete with food in the way crop-based biofuels do.

It works like this: E.coli produces fatty acids to make cell membranes. If a special enzyme called thioesterase is introduced during this process of cell membrane synthesis, these fatty acids will produce butyric acid instead. Butyric acid — aside from smelling like vomit — is also a precursor for propane.

What’s not clear to me is whether propane produced in this way is carbon-neutral. Presumably carbon is absorbed during this process and then released again when it is burnt. If inputs = outputs then I guess it is carbon-neutral but I’m really not sure. If anyone knows the answer to this then please let me know.

Here’s the media release from Imperial College –
http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_2-9-2014-16-0-8

The paper is available here –
http://www.nature.com/ncomms/2014/140902/ncomms5731/full/ncomms5731.html