|Colorized environmental scanning electron microscope photo of Gliocladium roseum, an endophytic fungus that produces myco-diesel hydrocarbons. (Photo courtesy of Gary Strobel.) Click to enlarge.|
A team led by Montana State University professor Gary Strobel has found an endophytic fungus, Gliocladium roseum (NRRL 50072), that naturally produces a large range of 55 different volatile hydrocarbons and hydrocarbon derivatives—a number of which are normally associated with diesel fuel. Accordingly, the researchers have termed the fungus’s output “myco-diesel”.
Extraction of liquid cultures of the fungus also revealed the presence of numerous fatty acids and other lipids. All of these findings have implications in energy production and utilization, the researchers concluded. A paper on the discovery appears in the November issue of the journal Microbiology.
Strobel characterized the find as bigger than his 1993 discovery of the fungus that contained the anticancer drug taxol. “These are the first organisms that have been found that make many of the ingredients of diesel,” Strobel said. “This is a major discovery.” While there are a number of known organisms that produce hydrocarbons, G. roseum appears to be the first identified that produces such a diversity of medium-chain hydrocarbons. Another promising aspect of the fungus is that it can grow in cellulose.
As an example, this organism produced an extensive series of the acetic acid esters of straight-chained alkanes including those of pentyl, hexyl, heptyl, octyl, sec-octyl and decyl alcohols. Other hydrocarbons were also produced by this organism, including undecane, 2,6-dimethyl; decane, 3,3,5-trimethyl; cyclohexene, 4-methyl; decane, 3,3,6-trimethyl; and undecane, 4,4-dimethyl. Volatile hydrocarbons were also produced on a cellulose-based medium, including heptane, octane, benzene, and some branched hydrocarbons.—Strobel et al. (2008)
Strobel found the diesel-producing fungus in a Patagonia rainforest. Strobel visited the rainforest in 2002 and collected a variety of specimens, including the branches from an ancient family of trees known as “ulmo.” When he and his collaborators examined the branches, they found fungus growing inside. They continued to investigate and discovered that the fungus, G. roseum, was producing gases. Further testing showed that the fungus—under limited oxygen—was producing a number of compounds normally associated with diesel fuel.
An extract of the host plant, Eucryphia cordifolia (ulmo), supported the growth and hydrocarbon production of this fungus. Quantification of volatile organic compounds, as measured by proton transfer mass spectrometry (PTR-MS), indicated a level of organic substances in the order of 80 p.p.m.v. (parts per million by volume) in the air space above the oatmeal agar medium in an 18 day old culture. Scaling the PTR-MS profile the acetic acid heptyl ester was quantified (at 500 p.p.b.v.) and subsequently the amount of each compound in the GC/MS profile could be estimated; all yielded a total value of about 4.0 p.p.m.v.—Strobel et al. (2008)
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.
The main value of this discovery may not be the organism itself, but may be the genes responsible for the production of these gases. There are certain enzymes that are responsible for the conversion of substrates such as cellulose to myco-diesel.—Gary Strobel
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.
Gary A. Strobel, Berk Knighton, Katreena Kluck, Yuhao Ren, Tom Livinghouse, Meghan Griffin, Daniel Spakowicz and Joe Sears (2008) The production of myco-diesel hydrocarbons and their derivatives by the endophytic fungus Gliocladium roseum (NRRL 50072). Microbiology 154 , 3319-3328; doi: 10.1099/mic.0.2008/022186-0