The genetic make-up of heat-loving fungi could form the basis of better enzymes for use in the extraction of sugars from biomass for the next generation of biofuels.
A team of researchers from the United States and Canada have decoded the complete genetic make-up of the fungi Myceliophthora thermophila and Thielavia terrestris. These fungi are classified as rare organisms known as thermophiles which thrive at temperatures between 45 and 122 degrees Celsius - temperature thought too high to support most life forms.
A key component of these organisms' ability to survive is the fact that their enzymes - proteins that catalyze chemical reactions - can still function even under temperatures considered extreme. In contrast, human enzymes work best at 37 degrees Celsius. At temperatures above 50 degrees Celsius they cease to function.
Enzymes are used to produce biofuel from biomass by breaking down cellulose into sugar for fermentation into ethanol.
These enzymes are known as cellulases and the ones currently used in biofuel production thrive at temperatures of 20-35 degrees Celsius and, like human enzymes, don't work at 50 degrees Celsius and up.
The low temperature threshold of cellulases is considered unfortunate as studies have shown that a high-temperature environment is better for biofuel production - not only does it decrease the risk of contaminants which can reduce the final yield, but at higher temperatures, cellulose swells and makes it easier to break down.
This is where interest in the M. thermophila and the T. terrestris comes in. Thriving at temperatures above 45 degrees Celsius, their enzymes remain active at temperatures ranging from 40 degrees Celsius to 75 degrees.
"These thermophilic fungi represent excellent hosts for biorefineries where biomass is converted to biofuels as an alternative to modern oil refineries," said Igor Grigoriev of the United States Department of Energy's Joint Genome Institute.
Mr. Grigoriev is head of the institute's fungal genomics section. He studied the fungi along with collaborators Randy Berka from Novozymes and Adrian Tsang of Concordia University in Canada.
The researchers decoded the genetic make-up of the two fungi and found the codes for a multitude of enzymes that can decompose biomass materials.
They also tested the efficacy of these enzymes on a variety of biomass feedstock and found that they had effectively evolved to break down and convert biomass into simple sugars at a wide range of temperatures.
"Since these thermophiles are much more efficient than other cellulose degraders in breaking down cellulosic biomass, their enzymes are likely to be more active than known cellulases and they have developed new strategies for biomass degradation," suggested Mr. Tsang, who works with Concordia's Center for Structural and Functional Genomics.
"Our next goal is to figure out how these organisms flourish at high temperatures and what makes them so efficient in breaking down plant materials," he added.
A better understanding of the enzymes also offers the possibility of tweaking them for use in other industrial processes using biomass. For example, the enzymes could replace the use of chemicals in the manufacture of plant-based commodities such as pulp and paper.
The research was supported by the D.O.E., the Cellulosic Biofuel Network of Agriculture and Agri-Food Canada, Genome Canada and Genome Quebec.
By. Katrice R. Jalbuena