Bacteria engineered to pump out diesel from sugar
Genes from 2 different organisms brought together in E. coli
Diesel fuel has been produced from sugar instead of petroleum by specially engineered bacteria.
"We put in glucose and out of the other end came a range of alkanes … that mimic exactly the retail diesel that you buy at the pump," said John Love, a biosciences researcher at the University of Exeter, in an interview that airs on Quirks & Quarks Saturday.
John Love talks to Quirks & Quarks Saturday at noon on CBC Radio One.
Alkanes, such as octane, are the main type of chemical compound in fossil fuels such as gasoline and diesel.
Ethanol, biodiesel and other "biofuels" derived from living organisms such as corn have been touted as a way to reduce greenhouse gas emissions, since they absorb carbon dioxide as they grow. That potentially compensates for the carbon dioxide they release when they are burned and theoretically makes them "carbon neutral."
However, because conventional modern engines are optimized to burn alkanes, they won't function if the fuel contains more than about 20 per cent biofuel, Love said.
He and his colleagues at the University of Exeter and at the U.K. technology research centre funded by the oil company Shell decided to tackle this problem by seeing if they could make biofuels that more closely mimic fossil fuels.
The ideal case would be if they could find an organism that could naturally produce alkanes in large amounts.
"Because it doesn't exist, we decided we would take the synthetic biology approach and build it from scratch," Love said. E. coli bacteria, which feed on glucose, were a good starting point.
Excess sugar becomes fat
"Much like we do, if they have an excess of sugar, they will start to make fat," Love said.
By stringing together two biochemical processes, that fat can be converted into alkanes.
The researchers pored through gene databases and scientific papers, and managed to find what they needed — two organisms, one with each of the biochemical processes in its metabolic repertoire.
They pulled the appropriate genes from a bioluminescent bacterium call Photorhabdus luminescens and a cyanobacterium or blue-green algae called Nostoc punctiforme. Then they popped those genes into E. coli.
To their surprise, the genetically engineered E. coli didn't seem to have any trouble with their new genes — they just started pumping out diesel, which floated to the top of the watery solution they lived in and was separated out, Love said.
The researchers published their results this week in the journal Proceedings of the National Academy of Sciences.
The next step is to optimize the process to produce more diesel by turning up or down some of the genes. They also hope to add extra genes that will allow the bacteria to use certain kinds of agricultural waste or other waste materials instead of glucose.
However, Love said, the process is a long way from being efficient enough for a gas station near you.
"It's only when it becomes cost efficient that you will actually see a realization of this process to the pump."