Thermostable Hemicellulases of a Bacterium,Geobacillus sp. DC3, Isolated from the Former Homestake Gold Mine in Lead,South Dakota |
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Authors: | Terran E Bergdale Stephen R Hughes Sookie S Bang |
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Institution: | 1. Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, 501 East Saint Joseph Street, Rapid City, SD, 57701, USA 2. Renewable Product Technology Research Unit, National Center for Agricultural Utilization Research (NCAUR), Agricultural Research Service (ARS), United States Department of Agriculture (USDA), 1815 North University Street, Peoria, IL, 61604, USA
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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 39.5 U/mg protein with additional hemicellulases including β-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 °C. The kinetic constants, K m and V max, were 13.8 mg/mL and 77.5 μmol xylose/min·mg xylan, respectively. The endoxylanase was highly stable and maintained 70 % of its original activity after 16 h 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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