Brown-rot fungus findings may help biofuels

By Ryan C. Christiansen
Web exclusive posted Feb. 12, 2009, at 4:48 p.m. CST

More than 50 scientists led by a team of researchers at the U.S. DOE Joint Genome Institute in Walnut Creek, Calif., and the USDA Forest Service Forest Products Laboratory in Madison, Wis., have translated the genetic code of Postia placenta, more commonly known as the brown-rot fungus, an organism that efficiently colonizes and decays wood.

According to the JGI, the findings explain the biochemistry that makes the thread-like fungi uniquely destructive to wood and provide a detailed inventory of biomass-degrading enzymes that can be leveraged to pretreat biomass for the production of biofuels, such as ethanol.

The scientists say the brown-rot fungus is unique in the way it breaks down biomass. "P. placenta has, over its evolution, shed the conventional enzymatic machinery for attacking plant material," said Dan Cullen, a scientist at the Forest Products Laboratory. "Instead, the evidence suggests that it utilizes an arsenal of small oxidizing agents that blast through plant cell walls to de-polymerize the cellulose. This biological process opens a door to more effective, less-energy intensive and more environmentally-sound strategies for more lignocellulose deconstruction," he said.

The DOE and USDA laboratories previously sequenced the genome of white-rot fungi, which simultaneously degrades lignin and cellulose, according to JGI. Brown-rot fungi are different because they rapidly de-polymerize the cellulose in wood without removing the lignin.

"For the first time we have been able to compare the genetic blueprints of brown-rot, white-rot and soft-rot fungi, which play a major role in the carbon cycle of our planet," said Randy Berka, director of Integrative Biology at Novozymes Inc. of Davis, Calif., a participant in the study. "Such comparisons will increase our understanding of the diverse mechanisms and chemistries involved in lignocellulose degradation.

"This type of information may empower industrial biotechnologists to devise new strategies to enhance efficiencies and reduce costs associated with biomass conversion for renewable fuels and chemical intermediates," Berka said.