The major target for cellulosic ethanol production is cellulose, a highly homogenous polymer of glucose joined together in beta-1,4-glycosidic linkages. In complex with cellulose, and constituting the next highest component of plant cell wall is the more heterogenous component hemicellulose. The most common components of hemicelluloses or xylans, especially from bioenergy feedstocks such as switchgrass, are xylose and arabinose. Hemicelluloses such as xylan are, therefore, composed of a beta-1,4-linked xylose backbone with side chains of arabinofuranosyl, acetyl, and 4-O-methyl glucuronyl groups, and their complete hydrolysis, therefore, requires a complex set of enzymes. To assemble an enzyme mixture that can deconstruct xylan, we demonstrated that the bacterium Prevotella bryantii B₁4 grows rapidly on hemicellulosic substrates. The sequencing of the P. bryantii genome then allowed identification of genes likely to encode products for deconstruction of wheat arabinoxylan and other hemicellulosic substrates. Several of these genes, including endoxylanases, arabinofuranosidases, acetyl xylan esterases, and an alpha-glucuronidase, were expressed as recombinant proteins in Escherichia coli. Interestingly, four glycoside hydrolase (GH) family 3 enzymes were found in this bacterium, and each was originally auto-annotated as a beta-glucosidase. Gene expression and biochemical analysis, however, demonstrated that these polypeptides elaborate different enzymatic activities. Experiments that aimed at examining the synergistic activities of the P. bryantii enzymes have led us to reconstitute an enzyme complex that completely degrades wheat arabinoxylan into its component sugars. This enzyme mixture is a very promising product in the current effort to deconstruct fiber-based feedstocks for fermentation to biofuels.