Bacteria may produce high-energy missile fuel

In a path-breaking discovery, researchers have engineered a bacterium to synthesise pinene - a hydrocarbon produced by trees that could potentially replace high-energy fuels in missiles and other aerospace applications.

With improvements in process efficiency, the biofuel could supplement limited supplies of petroleum-based high-energy fuel like 'JP-10' and might also facilitate development of a new generation of more powerful engines.

"We have made a sustainable precursor to a tactical fuel with a high energy density," said Peralta-Yahya, an assistant professor in the school of chemistry and biochemistry at the Georgia Institute of Technology.

"We are concentrating on making a 'drop-in' fuel that looks just like what is being produced from petroleum and can fit into existing distribution systems," he added.

By inserting enzymes from trees into the bacterium, Peralta-Yahya and Georgia Tech graduate student Stephen Sarria boosted pinene production six-fold over earlier bioengineering efforts.

To begin with, they settled on two classes of enzymes - three pinene synthases (PS) and three geranyl diphosphate synthases (GPPS).

They placed the two enzymes adjacent to one another in the E coli bacterium cells, ensuring that molecules produced by one enzyme would immediately contact the other.

That boosted their production to 32 milligrams per litre - much better than earlier efforts.

Though a more dramatic improvement would be needed before pinene dimers can compete with petroleum-based JP-10, the scientists believe they have identified the major obstacles that must be overcome to reach that goal.

To be competitive, the researchers would have to boost their production of pinene 26-fold.

According to them, that is within the range of possibilities for bioengineering the E coli.

"If you are trying to make an alternative to gasoline, you are competing against $3 (Rs.180) per gallon. That requires a long optimisation process. Our process would be competitive with $25 (Rs.1500) per gallon in a much shorter time," Peralta-Yahya explained.

Theoretically, it may be possible to produce pinene at a cost lower than that of petroleum-based sources.

If that can be done - and if the resulting bio-fuel operates well in these applications - that could open the door for lighter and more powerful engines fueled by increased supplies of high-energy fuels.

While much research has gone into producing ethanol and bio-diesel fuels, comparatively little work has been done on replacements for the high-energy JP-10, said the study published in "ACS Synthetic Biology".