A thermophilic strain, Geobacillus sp. DC3, capable of producing hemicellulolytic enzymes was isolated from the 1.5-km depth of the former Homestake gold mine in Lead, South Dakota. The DC3 strain expressed a high level of extracellular endoxylanase at 39.5 U/mg protein with additional hemicellulases including beta-xylosidase (0.209 U/mg) and arabinofuranosidase (0.230 U/mg), after the bacterium was grown in xylan for 24 h. Partially purified DC3 endoxylanase exhibited a molecular mass of approximately 43 kDa according to zymography with an optimal pH of 7 and optimal temperature of 70 A degrees C. The kinetic constants, K (m) and V (max), were 13.8 mg/mL and 77.5 mu mol xylose/min center dot mg xylan, respectively. The endoxylanase was highly stable and maintained 70 % of its original activity after 16 h incubation at 70 A degrees C. The thermostable properties and presence of three different hemicellulases of Geobacillus sp. DC3 strain support its potential application for industrial hydrolysis of renewable biomass such as lignocelluloses.