Yeast: the new green fuel

Scientists are using yeast to synthesise a biofuel without taking up swathes of land.

Microorganisms engineered to produce a new type of biofuel, bisabolane, have the potential to produce transport fuels without putting large swathes of land under energy crops.

Common liquid biofuels such as bioethanol compete with food production and are energy intensive to produce. But scientists at the Joint BioEnergy Institute, a US Department of Energy research centre, believe the new technique could provide an environmentally benign solution which could be used in existing diesel engines as part of a fuel mix, in the same way that bioethanol is commonly mixed with petrol.

Bisabolane is a terpene, a class of chemicals traditionally used as fragrances and flavours. Plants are the natural source of terpenes, but Dr Teak Soon Lee and his team are using yeast as an efficient way to produce bisabolene, a closely related compound to bisabolane.

The bisabolene must then be chemically converted to bisabolane so it can be used in a normal diesel engine, and this is currently a sticking point. The ultimate goal is the complete microbial production of the fuel, reducing the environmental impact of the production process and driving down the costs.

Microbes such as yeast need a food source, and currently sugarcane and corn are used – which means there are still the same issues of land use as with conventional biofuels. But Dr Lee anticipates that eventually cellulosic biomass – which can be sourced from crop and forest residues – could serve as the feedstock instead.

While the technology is some way from commercial viability, it holds out the long-term prospect of harvesting surplus biomass to produce a cost-efficient, relatively environmentally benign fuel. – Rebecca Nesbit

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