Host Preference of Cell Wall Degrading Enzymes in Phytopathogenic Fungi

In the production of the cellulose-ethanol, "cell wall degrading enzymes" (CWDE) are usually used to break down the carbohydrate components of plant cell walls. The bulk of CWDE's are usually cellulose and xylan degraders, called cellulases and xylanases, respectively. The main target of this enzymatic step is the production of ethanol-fermenable sugars.

For many years, most of the cellulases have been sourced from fungi belonging to Trichoderma sp. In order to find potentially new and more effective CWDE's for cellulose-ethanol production, "enzyme prospecting" activities are being initiated by research institutions. Scientists from Cornell University and the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) report the CWDE potential of some plant-pathogenic and non-plant pathogenic fungi.

They found many interesting results, among which are: (1) several plant pathogens were found to have an "abundance of CWDE's" compared to Trichoderma reesei, based on genomic analysis, (2) plant pathogenic fungi were found to have higher hydrolytic activity compared to non-plant-pathogenic fungi (in majority of the test substrates), (3) "among the pathogenic fungi, greater hydrolysis was seen when they were tested on biomass and hemicelluloses derived from their host plants (commelinoid monocot or dicot)", (4) natural isolates of the test fungi had a greater activity on xylan compared to T. reesei, but T. reesei had a higher activity on cellulose. The results showed the potential of plant pathogenic fungi for producing "tailored' CWDE's for cellulose-ethanol production.

The complete paper is published in the open-access journal, Biotechnology for Biofuels (URL above).