US researchers have discovered a species of fungus that can convert cellulose directly into diesel - potentially opening a new route to biofuels.

While several microorganisms are known to break down cellulose, Gliocladium roseum is the first that directly converts cellulose into a fuel, say Gary Strobel from Montana State University and colleagues. The fungus - discovered in the Patagonian rainforest - produces a diesel-like mixture of hydrocarbons, which the team dubbed myco-diesel. 

Cellulose is the most abundant organic molecule on Earth, so holds great promise as a potential source of biofuels. But the molecule is notoriously difficult to break down because it forms protective tangled microfibrils. Even the bugs known to attack cellulose produced breakdown products needing extra chemical steps to turn them into fuels - until G. roseum was discovered.

Strobel’s team grew the fungus in the lab on a cellulose-based agar under oxygen-poor conditions, and then used GC-MS to analyse the range of reduced hydrocarbons the bug produced. The compounds included many components of conventional diesel fuel, including octane, 1-octene and hexadecane.

’The direct conversion of cellulose into a fuel gives this research a bit of a wow factor,’ says James Clark, who researches cellulose conversion at the University of York, UK. ’We need to look at a wide range of technologies to use cellulose - but this is certainly an interesting option.’

Strobel says that the most valuable aspect of the discovery might be the genes that code for G. roseum’s fuel-making molecular machinery - which could potentially be transferred into a bacterium host more amenable to industrial scale production. ’My son Scott - chair of Molecular Biophysics and Biochemistry at Yale - is already at work to do the complete gene sequence of this bug,’ says Strobel.

The discovery of a fungus that produces hydrocarbons could also challenge theories on the formation of crude oil, says Strobel. Fossil fuels are believed to have formed over millions of years - but perhaps some could have been formed by fungi fermenting plant material, he suggests. Strobel plans to travel to Borneo and Patagonia before the end of the year to test the theory further.

James Mitchell Crow

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