SBIR Phase II: Xylose Isomerase from Marine Bacteria for Cellulosic Ethanol

This Small Business Innovation Research (SBIR) Phase II project will develop the xylose isomerase (XI) enzyme from a marine bacterium as part of a process to convert biomass to ethanol. Xylose isomerase converts xylose, the second most common sugar in biomass, into xylulose. Xylose is not fermented to ethanol by brewing yeast, but xylulose is. Previous XI enzymes are unable to work in conjunction with fermentation due to incompatibilities in pH and inhibiting compounds. The successful Phase 1 proposal identified this marine XI as capable of performing Simultaneous Isomerization and Fermentation (SIF) of xylose to ethanol. High efficiency conversion of xylose to ethanol can improve overall process yield by 20-40%. The Phase II project will optimize the production of the enzyme in native and high-productivity heterologous hosts leading to a low cost source of the new enzyme. The optimized enzyme will be further characterized and then produced in a 200 liter bioreactor to demonstrate scalability leading to commercialization. The broader impact/commercial potential of this project is to enable the cost-effective commercial production of cellulosic ethanol. Ethanol from local cellulosic biomass is a sustainable transportation fuel that reduces greenhouse gas emissions by an average of 87% according to the Argonne National Lab?s GREET model. The toxicity of tailpipe emissions are also reduced relative to petroleum-based fuels. As a domestic source of fuel, cellulosic ethanol adds to U.S. energy security and strengthens our economy. By creating jobs and recycling dollars into the U.S. economy, cellulosic ethanol improves the trade deficit and lessens the dependence on foreign petroleum. By developing a low-cost enzyme that is added directly to the fermentation, difficulties with genetically modified fermentation organisms are avoided. This not only simplifies the ethanol production process, but also reduces the GMO content of co-products that may enter the food chain.