Sunday, August 12, 2012
Columbia Hall, Terrace Level (Washington Hilton)
To date, lignocellulose deconstruction enzyme systems which best act at ≥70°C are not available. For example, most of the lignocellulosic ethanol producing companies are using enzymes which work best at ≤50°C for lignocellulose saccharification. Therefore, the focus of this study is to clone and overexpress the thermostable lignocellulose deconstruction enzymes which can perform efficiently at ≥70°C. We have isolated several thermophilic cellulose- and xylan-degrading cultures belonging to the genera Bacillus and Geobacillus using soil samples collected from the Homestake Gold Mine, SD and a local compost facility. Endoxylanase and β-xylosidase produced by one of our isolate are found to be highly thermostable as compared to the reported literature. In order to produce these enzymes in bulk, we overexpressed thermostable xylanases in a heterologous expression system. Purified endoxylanase and β-xylosidase were characterized in terms of kinetics, pH, temperature, thermostability, and molecular weight. Industrial potential of xylanases was also assessed by hydrolyzing inexpensive lignocellulosic materials to fermentable sugars. In the near future, thermostable xylanases in combination with thermostable cellulases, will be used to prepare a thermostable mixed enzyme system for efficient lignocellulose conversion.