Monday, July 25, 2011: 8:30 AM
Grand Chenier, 5th fl (Sheraton New Orleans)
It has been established that thermostable enzymes are important in various industrial processes including the conversion of lignocellulosic biomass into biofuels. Thermophilic bioprocessing offers several advantages including improved hydrolysis of cellulosic substrates, higher mass-transfer rates leading to better substrate solubility, lowered risk of contamination, and increased flexibility with respect to process design. 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. Our results showed that i) with an increase in temperature from 50 to 70°C, the rates of cellulose hydrolysis by cellulases produced by DUSELR13 and WSUCF1, were increased about 5 times and ii) DUSELR13 endoglucanase, b-glucosidase, and xylanase showed remarkable residual activity (>50%) after prolonged incubation (96, 76, and 116 hours, respectively) at high temperature (70°C) compared to others reported in literature. We also compared thermostability of our enzymes with commercial enzymes from Novozymes and Genencor. Further hydrolysis rates of xylan and cellulose were also studied with the crude enzyme preparations of concentrated xylanase and cellulase, and compared with commercial enzymes from Novozymes (Cellic HTec2, Cellic CTec2). In order to produce these enzymes in bulk, we expressed these thermostable enzymes extracellularly using E. coli as a heterologous host. Recombinant enzymes were characterized and compared with native and commercial enzymes. The fundamental research information obtained is currently being used to establish a novel cost-effective and more efficient form of the simultaneous saccharification and fermentation process.