Bergdale Terran E, Hughes Stephen R, Bang Sookie S
Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, 501 East Saint Joseph Street, Rapid City, SD, 57701, USA.
Appl Biochem Biotechnol. 2014 Apr;172(7):3488-501. doi: 10.1007/s12010-014-0784-7. Epub 2014 Feb 19.
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.
从南达科他州利德市原霍姆斯特克金矿1.5千米深处分离出了一株嗜热菌株——嗜热栖热放线菌（Geobacillus sp.）DC3，它能够产生半纤维素分解酶。在木聚糖中培养24小时后，DC3菌株表达出高水平的细胞外内切木聚糖酶，酶活为39.5 U/mg蛋白，还产生了包括β-木糖苷酶（0.209 U/mg）和阿拉伯呋喃糖苷酶（0.230 U/mg）在内的其他半纤维素酶。根据酶谱分析，部分纯化的DC3内切木聚糖酶的分子量约为43 kDa，最适pH为7，最适温度为70℃。动力学常数K m和V max分别为13.8 mg/mL和77.5 μmol木糖/分钟·mg木聚糖。该内切木聚糖酶高度稳定，在70℃孵育16小时后仍保持其原始活性的70%。嗜热栖热放线菌DC3菌株的热稳定特性和三种不同半纤维素酶的存在，支持了其在木质纤维素等可再生生物质工业水解中的潜在应用。
