Rainforest Fungus Makes Diesel Compounds From Cellulose

"These are the first organisms that have been found that make many of the ingredients of diesel," said Professor Gary Strobel from Montana State University. "This is a major discovery."

The discovery may offer an alternative to fossil fuels, said Strobel, MSU professor of plant sciences and plant pathology, who travels the world looking for exotic plants that may contain beneficial microbes. The find is even bigger, he said, than his 1993 discovery of fungus that contained the anticancer drug taxol.

Strobel's paper, published in the November issue of the journal "Microbiology," is based on his discovery of the unique properties of the Patagonian fungus, called Gliocladium roseum.

Professor Gary Strobel in the Patagonian rainforest (Photos courtesy Gary Strobel)

"Gliocladium roseum lives inside the Ulmo tree in the Patagonian rainforest," Strobel begins, telling the story of how he and his team learned that they had found an entirely new source of fuel.

"We were trying to discover totally novel fungi in this tree by exposing its tissues to the volatile antibiotics of the fungus Muscodor albus," Strobel recounts. "Quite unexpectedly, G. roseum grew in the presence of these gases when almost all other fungi were killed. It was also making volatile antibiotics."

"Then when we examined the gas composition of G. roseum, we were totally surprised to learn that it was making a plethora of hydrocarbons and hydrocarbon derivatives. The results were totally unexpected and very exciting and almost every hair on my arms stood on end!"

Strobel calls the fuel produced by the fungus "myco-diesel," from the Greek-derived root word for the study of fungi - mycology.

"This is the only organism that has ever been shown to produce such an important combination of fuel substances," said Strobel. "The fungus can even make these diesel compounds from cellulose, which would make it a better source of biofuel than anything we use at the moment."

Intense research into ways of making ethanol fuel directly from cellulose now is taking place in public, private and university labs, and several companies are producing demonstration scale cellulosic ethanol from wood waste, from municipal solid waste and from agricultural residue.

Nearly 430 million tons of plant waste are produced from U.S. farmland alone every year, material that scientists are learning to convert to biofuel.

In current biofuel production, this waste is treated with enzymes called cellulases that turn the cellulose into sugar. Microbes then ferment the sugar into ethanol that can be used as a fuel.

"We were very excited to discover that G. roseum can digest cellulose," Strobel said. "Although the fungus makes less myco-diesel when it feeds on cellulose compared to sugars, new developments in fermentation technology and genetic manipulation could help improve the yield."

"When crops are used to make biofuel they have to be processed before they can be turned into useful compounds by microbes," said Strobel. "G. roseum can make myco-diesel directly from cellulose, the main compound found in plants and paper."

Culture plate of Gliocladium roseum, a fungus that produces myco-diesel hydrocarbons

In the rainforest, G. roseum produces lots of long chain hydrocarbons and other biological molecules. When the researchers grew it in the lab, it produced fuel that is even more similar to the diesel we put in our cars.

The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides carbon and hydrogen. When bonded, these elements can form seemingly limitless chains of molecules.

Professor Strobel, who travels the world looking for exotic plants that may contain beneficial microbes, says his discovery brings into question our knowledge of the way fossil fuels are made.

The accepted theory is that crude oil, which is used to make diesel, is formed from the remains of dead plants and animals that have been exposed to heat and pressure for millions of years.

Strobel speculates, "If fungi like this are producing myco-diesel all over the rainforest, they may have contributed to the formation of fossil fuels."

Strobel is the lead author of the paper published in "Microbiology." His MSU co-authors are Berk Knighton and Tom Livinghouse in the Department of Chemistry/Biochemistry, and Katreena Kluck and Yuhao Ren in the Department of Plant Sciences and Plant Pathology.

Other co-authors are Meghan Griffin and Daniel Spakowicz from Yale University and Joe Sears from the Center for Lab Services in Pasco, Washington.

Researchers in government agencies and private industry have already shown interest in the fungi. A team to conduct further research has been established between MSU's College of Engineering and researchers at Yale University.

One member of the team is Strobel's son, Scott, who is chairman of molecular biophysics and biochemistry at Yale and a Howard Hughes Medical Institute Professor. The MSU-Yale team will investigate a variety of questions, including the genetic makeup of Gliocladium roseum.

Scott Strobel said his team is already screening the fungus' genome. Besides determining the complete genetic makeup of the fungus, they will run a series of genetic and biochemical tests to identify the genes responsible for its diesel-making properties.

"The broader question is, what is responsible for the production of these compounds," Scott Strobel said. "If you can identify that, you can hopefully scale it up so you end up with better efficiency of production."

Scientists in a variety of disciplines may be able to combine their talents to optimize production and find a way to turn what is essentially a vapor into a burnable, liquid fuel.