From petrochemical to biochemical

Modifying baker’s yeast to produce a synthetic form of the natural chemical limonene may provide a much-needed future alternative to fossil fuels.

“Limonene is a volatile chemical that is best known for contributing to the smell of citrus fruits,” explained Dr Claudia Vickers from the Australian Institute for Bioengineering and Nanotechnology at the University of Queensland.

“It might sound unlikely, but limonene one day could be a renewable, clean source of aviation fuel,” she said, adding that the environmental benefits of using limonene as a fuel were particularly exciting.

“50% of a 747’s weight on take-off is its fuel. If you consider all the planes flying around in the world, that’s a lot of fuel - and non-sustainable fossil resource carbon - being emitted in the atmosphere.”

Limonene extracted from citrus peel had been used successfully as a jet fuel component in demonstration flights in the past but large-scale limonene production from citrus peel is not a feasible option.

“Producing it in yeast should provide a route to much greater yields of limonene which are easier to extract,” Dr Vickers said.

Limonene yields from the modified yeast are not yet high enough to be commercially viable, but Dr Vickers plans to further modify the yeast to improve yields.

The same technology could be used to make a variety of other sustainable products from limonene, including rubbers, plastics and paints.