Sandia National Labs Developing Optimized Enzymes from Extremeophile for Production of Cellulosic Ethanol
12 June 2007
Researchers at Sandia National Laboratories are using an extremeophile—a microorganism that lives in extreme environmental conditions—as the basis for developing optimized enzymes to pre-process cellulosic biomass cheaply and efficiently for the production of cellulosic ethanol.
Sandia’s current biological object of interest is Sulfolobus solfataricus, a thermoacidophilic (heat- and acid-loving) archaeon whose extreme enzymes were isolated and discovered in 1980 by the German researcher Georg Lipps. Sulfolobus lives in and around volcanic springs (sulfurous caldrons) and metabolizes sulfur to sulfuric acid.
Sulfolobus expresses three cellulase-type enzymes that efficiently break down cellulose into sugars. Sandia’s target is an endoglucanase (SSO 1949).
Pre-processing of cellulosic biomass to breakup the lignocellulosic material into easily converted polymers is one of the current barriers to the cost effective production of cellulosic ethanol.
[Biomass] production is not a concern. More than a billion tons of biomass is estimated to be created each year in the timber and agricultural industries, as well as a variety of grasses and potential energy crops. Unfortunately, you can’t just take a tree trunk, stick it into an enzymatic reactor, and ferment the sugar produced into ethanol with any kind of efficiency. The process of turning certain lignocellulosic materials into ethanol is very difficult and costly.—Blake Simmons, Sandia National Laboratory
Correspondingly, the search for better pre-processing techniques and enzymes is one of the major areas of concentration in R&D for cellulosic ethanol. One of the challenges is the acidity and temperature of the bioreactor production environment.
Instead of trying to create an extremozyme from sources that live in rather benign environmental conditions, why not just manipulate a real one isolated from its natural state?—Blake Simmons
Sandia is applying a technique called “site-directed mutagenesis” to manipulate and optimize the Sulfolobus sequence that expresses the cellulase enzymes in hopes of improving performance. These mutations are identified using computational modeling techniques at Sandia that compare the structure and sequence of the extremozymes with their more benign counterparts to identify key genetic sequences of interest.
The ultimate dream—and it’s only a dream right now—would be to take a poplar tree, put it into a tank, let it sit for three days, then come back and watch as the ethanol comes pouring out of the spigot. Though we’re probably decades away from that, this project aims to consolidate the pretreatment steps and get us one step closer to realizing that vision.—Blake Simmons
Simmons’ team has demonstrated increased enzyme activity of a recombinant SSO 1949 enzyme under thermoacidophilic conditions (pH 1.8 at 80°C) as compared to established enzymes. The computational tools the team developed will help identify candidate modifications to the genetic sequence to improve performance.
Next steps are to increase the purification and activity analysis of SSO 1949 mutants, analyze mutants for increased activity and then develop techniques for the directed evolution of SSO 1949.
The team will also expand its work to include other enzymes, and develop other expression systems for the enzymes.
Simmons presented his team’s preliminary findings from the extremeophile project recently at the 4th World Congress on Industrial Biotechnology & Bioprocessing. The team hopes to publish more advanced findings soon and is finalizing several proposals that could lead to further funding. The lab would be open, Simmons said, to conducting collaborative R&D with other commercial partners or research entities, or to licensing its research capabilities.
This and other efforts at Sandia National Laboratories are expected to be a component of the Joint Bio-Energy Institute (JBEI), a multi-lab/university effort to bring a Department of Energy-funded bio-research facility to the San Francisco Bay Area.
“Development of Novel Endoglucanases Isolated from Thermoacidophiles” (presentation at 4th Annual World Congress on Industrial Biotechnology and Bioprocessing)
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