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Converting Cellulose to Sugars

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Cellulases include a mix of enzymes that break down cellulose into simple sugars that can be fermented by microorganisms to ethanol. Three general classes of cellulases—endoglucanases, exoglucanases, and cellobiases—work together in a coordinated fashion to hydrolyze cellulose. Endoglucanases internally cleave a cellulose chain, and exoglucanases bind the cleaved ends of the cellulose chain and feed the chain into its active site where it is broken down into double glucose molecules called cellobiose. Cellobiases split cellobiose to yield two glucose molecules. The cellulase pictured is an exoglucanase whose binding domain on the right extracts a cellulose chain. At the active site in the larger catalytic domain on the left, the cellulose chain is hydrolyzed to yield cellobiose subunits. [Image from M. Himmel et al., Cellulase Animation, run time 11 min., National Renewable Energy Laboratory (2000).] Citation : Genomics:GTL Roadmap, U.S. Department of Energy Office of Science, August 2005,

Credit or Source: M. Himmel, National Renewable Energy Laboratory "Genomics:GTL Roadmap," U.S. Department of Energy Office of Science, August 2005,


US DOE. 2005. Genomics:GTL Roadmap, DOE/SC-0090, U.S. Department of Energy Office of Science. (p. 100) (website)

Prepared by the Biological and Environmental Research Information System, Oak Ridge National Laboratory, and