(602bj) Enhanced Lignocellulose Conversion to Biofuels with Thermophilic Bacteria and Thermostable Enzymes

Aditya Bhalla¹, Dr. Kenneth Bischoff² and Rajesh Sani¹*

1. Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD.
2. Renewable Product Technology Research Unit, Agricultural Research Service, National Center for Agricultural Utilization Research, U.S. Department of Agriculture, Peoria, IL 61604

Second generation feedstock, especially nonfood lignocellulosic biomass, has been seen as a potential source for biofuel production.  Lignocellulose conversion technologies, which are carried out at ≤50°C, have several limitations.  Therefore, this study focuses on the importance of thermophiles and thermostable enzymes to overcome the limitations of existing lignocellulosic biomass conversion processes.  We have isolated several thermophilic cellulose- and xylan-degrading pure cultures belonging to the genera Bacillus and Geobacillus using soil samples collected from the Homestake Gold Mine, SD and a local compost facility.  Xylanases produced by one of our isolate are found to be highly thermostable as compared to the reported literature.  Greater hydrolysis rates of xylan were observed with xylanase from our isolate as compared to commercially available xylanases at high temperatures.  In order to produce these enzymes in bulk, we overexpressed thermostable xylanases in a heterologous expression system.  Purified xylanase was characterized in terms of pH, temperature, thermostability, and molecular weight.  The purified thermostable recombinant enzymes, in the near future, will be used to prepare a thermostable mixed enzyme system for lignocellulose hydrolysis to fermentable sugars.