Bioscience Division, B

Turning Fungus into Fuel

A spidery fungus T. reesei with a voracious appetite for military uniforms and canvas tents could hold the key to improvements cost effectiveness and efficiency in the production of biofuels, a team of government, academic and industry researchers announced. The fungus rose to dubious fame during World War II when military leaders discovered it was responsible for rapid deterioration of clothing and tents in the South Pacific. T. reesei was later identified as a source of industrial enzymes and a role model for the conversion of cellulose and hemicellulose—plant fibers—into simple sugars. The organism uses enzymes it creates to chemically break down human-indigestible fibers of plants into the simplest form of sugar, a monosaccharide. The fungus then digests the sugars as food.

Researchers decoded the genetic sequence of T. reesei to discover why the deep green fungus was so efficient at digesting plant cells. In a paper, “Genome Sequencing and Analysis of the Biomass-degrading Fungus Trichoderma reesei (syn. Hypocrea jecorina” published in Nature Biotechnology 26, 553-560 (2008), scientists from LANL and DOE’s Joint Genome Institute (JGI) and collaborators announced that the genetic sequence of the fungus Trichoderma reesei has uncovered important clues about how the organism breaks down plant fibers (cellulose) into simple sugars. The finding introduces possibilities for industrial processes that can more efficiently and cost effectively convert corn, switchgrass and cellulose-based municipal waste into ethanol for fuel. While the genome has a surprisingly small number of genes to code for the enzymes to break down plant fibers, the researchers believe that the genome has “clusters” of enzyme-producing genes, a strategy that may account for the organism’s efficiency at breaking down cellulose.

On an industrial scale, T. reesei could be employed to secrete enzymes to be added to cellulose pulp and other materials to produce sugar, which yeast can ferment to produce ethanol. Currently the high cost of hydrolyzing biomass polysaccharides to fermentable sugars remains a major obstacle that must be overcome before cellulosic ethanol can be effectively commercialized. Because the costs of cellulases and hemicellulases (enzymes to break down cellulose) contribute substantially to the price of bioethanol, much cheaper sources of these enzymes are needed. The scientists suggest opportunities to generate improved enzyme cocktails that may be used for the conversion of plant biomass to fermentable sugars. Because complete hydrolysis of the plant substrates requires multiple enzymes acting synergistically, development of superior enzyme blends could occur through genetic engineering of suitable industrial strains. The capacity for secreting copious amounts of extracellular enzymes, the availability of genetic tools and the straightforward, inexpensive fermentation of T. reesei make it an ideal candidate for producing enzymes useful for the conversion of biomass feedstocks to fuel ethanol and manufacturing chemicals that are currently derived from nonrenewable resources. Production of these enzymes at economically viable levels will require an increased understanding of the dynamics of cell growth and enzyme production.

Researchers include Diego Martinez (B-6 and University of New Mexico), Thomas Brettin, David Bruce, Chris Detter, Cheryl Kuske, Olga Chertkov, Melissa Jackson, Cliff Han, Monica Misra, Nina Thayer, Ravi Barbote, and Gary Xie (all in LANL-JGI); and collaborators from Novozymes, Inc.; Universités d’Aix-Marseille I & II, Joint Genome Institute - Production Genomics Facility in Walnut Creek, CA; VTT Finland; Pacific Northwest National Laboratory; U.S. Department of Agriculture’s Forest Products Laboratory; Universitat Wien, Austria; Catholic University of Chile; Oregon State University; Genencor International; University of New Mexico; AlerGenetica SL, Spain. The DOE Office of Science, Biological and Environmental Research Program and the National Institutes of Health supported the work.

Photo: a microscope image of the fungus Trichoderma reesei growth filaments. In the image, proteins in fungal cells are stained red, while chitin, a component of the cell walls, is stained blue.  Image credit: Mari Valkonen, VTT Technical Research Center, Finland

>>>More Highlights

B-6 Teams

• Applications
• Bioinformatics
• Computational Finishing
• Project Management
• Sequencing Technology

Focus on Research

Links / Resources

• Joint Genome Institute (JGI)