Conifer-Rotting Fungus Offers Potential New Strategy for Lignocellulose Degradation
Due to its abundance and high cellulose content, wood has great potential as raw material for the production of biofuels. However, wood also contains lignin, a hard-to-degrade polymer that poses a major obstacle to converting its cellulose into liquid fuels. White rot fungi have evolved mechanisms to digest lignin and cellulose, and scientists are trying to take advantage of these capabilities. Now, new research using genome sequencing and comparative analysis of the brown rot fungus Serpula lacrymans has discovered a different strategy used by this boreal forest fungus to extract the energy-rich cellulose from conifer wood. A comparison of the gene content in white and brown rot fungi indicates that the enzymatic machinery to degrade lignin has been eliminated in brown rot fungi, enabling it to specifically target cellulose, separating it from the recalcitrant lignin. The researchers also discovered that in the presence of wood, S. lacrymans produces variegatic acid, a phenolate compound that helps in reducing iron ions to Fe+2, which are required for the initial non-enzymatic steps in cellulose degradation upon wood colonization by the fungus. These insights provide researchers with new strategies to potentially bypass the problem of eliminating lignin from renewable woody feedstocks for transportation fuel production. The research has just been published in Science and was carried out by an international consortium including researchers at DOE’s Joint Genome Institute in Walnut Creek, CA, and its partners HudsonAlpha Institute for Biotechnology (Huntsville, AL) and Pacific Northwest National Lab (Richland, WA).
D. C. Eastwood, et al. 2011. “The Plant Cell Wall-Decomposing Machinery Underlies the Functional Diversity of Forest Fungi”, Science, 333, 762-65. DOI:10.1126/science.1205411.