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New yeast engineered by BESC, Mascoma could accelerate production of cellulosic ethanol

Consolidated bioprocessing technology company Mascoma LLC and the US Department of Energy’s BioEnergy Science Center (BESC) have developed a new strain of yeast that could help significantly accelerate the development of biofuels from nonfood plant matter. The new C5 FUEL yeast delivers fermentation and ethanol yields that set a new standard for conversion of biomass sugars from pretreated corn stover, converting up to 97% of the plant sugars into fuel, the researchers said.

While conventional yeast leaves more than one-third of the biomass sugars unused in the form of xylose, Mascoma’s C5 FUEL efficiently converts this xylose into ethanol, and it accomplishes this feat in less than 48 hours. The results were presented at the 31st International Fuel Ethanol Workshop this week in Minneapolis.

Although cellulosic biomass such as corn stover, wheat straw and bagasse (the fibrous remains after sugar is extracted from sugarcane or sorghum) is abundant and cheap, because of recalcitrance—a plant’s resistance to releasing sugars for conversion to alcohol—it is much more difficult to utilize than corn. However, Mascoma’s new strain of yeast, which is one of many strains Mascoma developed as part of BESC over the last two years, proved highly effective at xylose conversion.

While most processing methods simply convert cellulose to sugar, this new approach also converts hemicellulose, which significantly increases overall sugar yield and thereby increases the level of ethanol produced. The new strain of yeast simultaneously yields 97% conversion of xylose and glucose, and does so in a significantly shorter period of time than existing approaches.

The ability to partner the combined expertise at Mascoma and BESC in engineering microbes to release and convert sugars from lignocellulosic biomass has greatly accelerated the translation of basic research outcomes to a commercial product.

—BESC Director Paul Gilna

Gilna noted that this success and continued efforts through BESC could go a long way toward reducing the cost of ethanol and growing the number of commercial-level ethanol production plants. A key focus of BESC is to use basic research capabilities and expertise to validate the consolidated bioprocessing approach to improve cost competitiveness.

The scientific and technical resources that we have had access to as a member of BESC for the past six years have made possible the development of this uniquely high-performing yeast product. This is just the start of a pipeline of second-generation yeast products planned by Mascoma and Lallemand Biofuels and Distilled Spirits.

—Kevin Wenger, executive vice president of Mascoma

The next step for BESC will be to demonstrate and again validate the application of the consolidated bioprocessing approach using thermophilic, or heat-loving, bacteria to produce biofuels directly from biomass in a single process.

Mascoma offers two well-established lines of genetically modified yeast—Transferm and Transferm Yield+—for the production of first generation ethanol. Since June 2012, more than two billion gallons of fuel ethanol have been produced using Mascoma fermentation technology.

Led by Oak Ridge National Laboratory, BESC is one of three DOE Bioenergy Research Centers established by the DOE’s Office of Science in 2007. The centers support multidisciplinary, multi-institutional research teams pursuing the fundamental scientific breakthroughs needed to make production of cellulosic biofuels, or biofuels from nonfood plant fiber, cost-effective on a national scale. The three centers are coordinated at ORNL, Lawrence Berkeley National Laboratory and the University of Wisconsin-Madison in partnership with Michigan State University.

Resources

  • Allan Froehlich, Brooks Henningsen, Sean Covalla, Beth Miller and Rintze Zelle (2014) “Directed-engineering of Saccharomyces cerevisiae for xylose utilization” 2014 Symposium on Biotechnology for Fuels and Chemicals

  • Brown SD, Klingeman DM, Johnson CM, Clum A, Aerts A, Salamov A, Sharma A, Zane M, Barry K, Grigoriev IV, Davison BH, Lynd LR, Gilna P, Hau H, Hogsett DA, Froehlich AC (2013) “Genome sequences of industrially relevant Saccharomyces cerevisiae strain M3707, isolated from a sample of distillers yeast and four haploid derivatives” Genome Announc. 1(3):e00323-13. doi: 10.1128/genomeA.00323-13.

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