(409a) Thermophiles for Biofuels Production

Christopher, L. P. - Presenter, South Dakota School of Mines & Technology

Environmentally friendly alternatives for sustainable biofuels production are presented through utilization of renewable lignocellulosic biomass such as switchgrass and biomass waste including agri-waste (corn stover, prairie grasses, etc.). Switchgrass is viewed as one of the most promising energy crops for the U.S. conditions and its production is predicted to significantly increase within the next ten years. Production of biofuels from biomass would reduce dependence on fossil fuels, enhance energy security, contribute to the effort of preventing global warming, and alleviate the acute and growing pollution problem in broad perspectives. To date, enzymatic hydrolysis of cellulose presents one of the major technological challenges to the economics of biofuels production due to the relatively high enzyme costs, slow reaction rates, low specific activity, end-product inhibition, time- and temperature-dependant loss of activity, etc. From this perspective, the search for and the discovery of novel thermostable enzymes with unique properties and enhanced capabilities for cellulose degradation could lead to significant improvements in the bioethanol process. The advantages of employing thermostable enzymes in lignocellulose bioprocessing to bioethanol at elevated temperatures are multi-fold: 1) Increased reaction/conversion rates due to improved mass transfer rates and improved substrate accessibility allowing the use of lower enzyme dosages and resulting in higher yields of fermentable sugars; 2) Improved substrate solubility and reduced viscosity of feedstock allowing the use of higher solids loadings; 3) Decreased risk of contamination resulting in increased robustness of process; 4) Decreased cost of energy for cooling when thermal pretreatment of feedstock is desirable; 5) Improved yields due to reduced ethanol intolerance of fermenting strains; 6) Improved integration, heat recovery and flexibility in process configuration. The use of higher solids loadings and temperatures during enzymatic hydrolysis prove beneficial for the significant reduction of hydrolysis times and enzyme loadings with important implications for reduced capital and operating costs of ethanol production. Thermophiles isolated from unique environments such as Yellowstone National Park (WY, USA) and Homestake Mine (SD, USA) and their thermostable enzymes have been employed for production of bioethanol, biohydrogen and biodiesel. Results on biofuels production utilizing new thermophilic isolates will be presented and potential benefits discussed.