Image caption The oil that the bacteria produced had a near-identical composition and chemical properties to conventional diesel

A strain of bacteria has been created that can produce fuel, scientists say.

Researchers genetically modified E. coli bacteria to convert sugar into an oil that is almost identical to conventional diesel.

If the process could be scaled up, this synthetic fuel could be a viable alternative to the fossil fuel, the team said.

The study is published in the Proceedings of the National Academy of Sciences.

Professor John Love, a synthetic biologist from the University of Exeter, said: "Rather than making a replacement fuel like some biofuels, we have made a substitute fossil fuel.

"The idea is that car manufacturers, consumers and fuel retailers wouldn't even notice the difference - it would just become another part of the fuel production chain."

Fuel factories

There is a push to increase the use of biofuels around the world.

In the European Union, a 10% target for the use of these crop-based fuels in the transport sector has been set for 2020.

But most forms of biodiesel and bioethanol that are currently used are not fully compatible with modern engines. Fractions of the substances (between 5-10%) need to be blended with petroleum before they can be used in most engines.

However, the fuel produced by the modified E. coli bacteria is different.

Our challenge is to increase the yield before we can go into any form of industrial production Prof John Love, University of Exeter

Prof Love explained: "What we've done is produced fuels that are exactly the chain length required for the modern engine and exactly the composition that is required.

"They are bio-fossil-fuels if you like."

To create the fuel, the researchers, who were funded by the oil company Shell and the Biotechnology and Biological Sciences Research Council, used a strain of E. coli that usually takes in sugar and then turns it into fat.

Using synthetic biology, the team altered the bacteria's cell mechanisms so that the sugar was converted to synthetic fuel molecules instead.

By altering the bacteria's genes, they were able to transform the bugs into fuel-producing factories. However, the E. coli did not make much of the alkane fuel.

Professor Love said it would take about 100 litres of bacteria to produce a single teaspoon of the fuel.

"Our challenge is to increase the yield before we can go into any form of industrial production," he said.

"We've got a timeframe of about three to five years to do that and see if it is worth going ahead with it."

The team is also looking to see if the bacteria can convert any other products into fuel, such as human or animal waste.

Magic bullet?

Biofuels are considered to be a greener alternative to fossil fuels.

Image caption The European Union has set a target that 10% of transport fuel should be made from biofuels by 2020.

While petrol and diesel release carbon dioxide that has been stored deep within the Earth, biofuels are said to be carbon neutral because they release as much CO2 into the atmosphere as the plants they are made from absorbed.

However, the energy it takes to grow and process the crops needed for biofuels also should be taken into account, as this adds to their "carbon footprint".

A recent report by Chatham House said biofuels were expensive and worse for the climate than fossil fuels.

According to Geraint Evans, a biofuel consultant at the NNFCC (formerly known as the National Non-Food Crops Centre), these issues would need to be taken into account for a bacteria-produced fuel too.

"It widens the potential sources you can use to make diesel," he said.

"But we still need to consider that this is coming from the land and the sustainability needs to be carefully considered.

It's not a magic bullet - but it is another tool in the toolbox."