A glycosyl hydrolase family 12 endoglucanase from Acidothermus cellulolyticus is one of the most thermostable endoglucanases known.  It has been demonstrated to have activity on a number of substrates including beta-glucan, arabinoxylan, xylan, and xyloglucan, making it an important enzyme for biomass conversion. To better understand the structural basis for its thermotolerance, the crystal structure was determined at high resolution and evaluated in regard to known parameters conferring thermotolerance.  Using CHARMM, we also conducted molecular dynamics simulations at ambient conditions to build a wild type native contact map of the protein in solution.  Melting simulations were conducted at high temperature to identify the structural features of the enzyme susceptible to thermal unfolding.  A library of mutants was then screened with these computational methods and the most promising mutants were produced experimentally for thermostability and activity measurements.  Correlations between in-silico and in-vitro results will be discussed.