(567g) Thermophiles and Their Thermostable Enzymes in Biofuel Synthesis

Sani, R. - Presenter, South Dakota School of Mines and Technology
Second-generation feedstock, especially nonfood lignocellulosic biomass, is a potential source for biofuel production. Cost-intensive physical, chemical, biological pretreatment operations and slow enzymatic hydrolysis carried out at â?¤50°C make the overall process of lignocellulosic conversion into biofuels less economical than available fossil fuels. Thermophiles and their enzymes can play important roles in many kinds of bioprocessing including in conversion of non-food biomass into biofuels. The Homestake gold mine (8000 ft. deep, Lead, SD) offers a unique opportunity for direct exploration of the deep biosphere environment. Using soil/biofilm samples of deep biosphere of the Homestake Gold Mine, compost facility (Rapid City, SD, USA), and Hot Springs State Park (Thermopolis WY, USA), we have isolated several thermophilic cellulose- and xylan-degrading and -fermenting pure cultures belonging to the genera Brevibacillus, Paenibacillus, Clostridium, Bacillus, and Geobacillus. Unique characteristics of lignocellulose-deconstructing enzymes produced by mine and compost thermophiles include optimum temperatures of >70°C, pH ranges from 4 - 8, and high thermostability (e.g., at 60ºC, 50% of cellulases and xylanases activities were retained in 35 and 23 days of incubation, respectively). Hot Springs State Park thermophiles can grow on various inexpensive regional carbon and energy sources (e.g., prairie cord grass and corn stover), and produce biohydrogen in a single step bioprocessing of biomass. This talk will describe the limitations in exiting lignocellulose conversion technologies and possible ways to overcome those limitations using thermophiles and their enzymes. The influence of high temperatures on various existing lignocellulose conversion processes and those that are under development, including separate hydrolysis and fermentation, simultaneous saccharification and fermentation, and extremophilic consolidated bioprocess will discussed. Integrated decentralized thermophilic biofuel production employing cellulolytic- and fermentative-thermophiles in a single step consolidated process will also be discussed.