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Thermostable saccharidases are required for industrial processing of starch and lignocellulosic fibers. Thermophilic microbes have not been used as sources for industrial enzymes and the molecular biochemistry of enzyme thermophilicity is not understood. We have purified and characterized thermostable (70°C) saccharidases from thermoanaerobic bacteria including: β-amylase, amylopullulanase, α-glucosidase, glucose isomerase (GI), and endoxylanase. Thermostable saccharidase synthesis was regulated in Thermoanaerobacter to produce fructose directly from starch. The GI gene from Thermoanaerobacter was cloned and sequenced and site-directed mutagenesis was employed to explain enzyme catalysis and to design an enzyme active at 70°C and pH 5.5. Endoxylanase of Thermoanaerobacter was cloned and characterized in relation to a xylanosomal cellular organization and a source for fiber modification. Future studies on these novel saccharidases will focus on the molecular basis of thermophilicity, coordination with other hydrolases and industrial uses.