MADISON, WI --- An international team of scientists has translated the genetic code that explains the complex biochemical machinery making brown-rot fungi uniquely destructive to wood. The mechanisms by which these fungi gain access to energy-rich sugar molecules in wood may ultimately lead to innovations for the biofuels industry, scientists said.
The research, conducted by more than 50 authors, is reported in the Feb. 4 edition of the Proceedings of the National Academy of Sciences (PNAS).
The team was led by scientists from the U.S. Department of Agriculture Forest Service, Forest Products Laboratory (FPL) and U.S. Department of Energy (DOE) Joint Genome Institute (JGI).
The paper describes analysis of the Postia placenta genome and reports a milestone in understanding lignocellulose conversions, a topic of considerable importance to the U.S. departments of Agriculture (USDA) and Energy (DOE).
Postia is representative of the brown-rot fungi, which are common inhabitants of forest ecosystems and also responsible for the destructive decay of wooden structures. The costs of replacing decayed wood and the diminishing number of environmentally friendly preservatives have spurred FPL research on brown-rot fungi for decades.
In addition to their economic importance, the degradative capacity of wood decay fungi has attracted considerable research attention. Much of this research has focused on the degradation of lignin, the "glue" that makes plant cells strong. Lignin is particularly stubborn to convert, but its removal is central to pulp and paper manufacturing. An earlier partnership between FPL, the DOE and the University of Wisconsin led to genome completion of another wood decay fungus. Published in June 2004 in Nature Biotechnology, the research focused on lignin-degrading white-rot fungus that provided fundamental insight into the degradation of lignin.
In the past five years, DOE emphasis has shifted substantially to biofuels. Solid biomass -- plants and trees -- can be converted into liquid fuels such as ethanol, methanol and biodiesel. The challenge, however, lies in efficient conversion -- creating more energy than the input required to produce it.
A particular concern to the Forest Service is that the national forests are crowded with small-diameter trees, which negatively affect the health of the forests while increasing the threat of forest fires. Therefore, the Forest Service is critically concerned with finding good use for this material. The biggest challenge to producing ethanol from woody plant matter is in learning how to cost-effectively break down lignin and to convert cellulose to small, molecular-weight compounds that can be fermented into alcohol --- a crucial part of the biofuels process. Addressing this challenge, analysis of Postia has revealed a unique mechanism for deconstructing cellulose.