Abstract
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 39.5U/mg protein with additional hemicellulases including β-xylosidase (0.209U/mg) and arabinofuranosidase (0.230U/mg), after the bacterium was grown in xylan for 24h. Partially purified DC3 endoxylanase exhibited a molecular mass of approximately 43kDa according to zymography with an optimal pH of 7 and optimal temperature of 70°C. The kinetic constants, K m and V max, were 13.8mg/mL and 77.5μmol xylose/min·mg xylan, respectively. The endoxylanase was highly stable and maintained 70% of its original activity after 16h incubation at 70°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.
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