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University of Georgia, Oak Ridge National Laboratory

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Proc. Natl. Acad. Sci. USA, published ahead of print June 2, 2014 | doi:10.1073/pnas.1402210111 Direct conversion of plant biomass to ethanol by engineered Caldicellulosiruptor bescii

Abstract

Daehwan Chung^a,b,1, Minseok Cha^a,b,1, Adam M. Guss^b,c, and Janet Westpheling^a,b,2

^aDepartment of Genetics, University of Georgia, Athens, GA 30602; and
^bThe BioEnergy Science Center and
^cBiosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831

Abstract
Ethanol is the most widely used renewable transportation biofuel in the United States, with the production of 13.3 billion gallons in 2012 [John UM (2013) Contribution of the Ethanol Industry to the Economy of the United States]. Despite considerable effort to produce fuels from lignocellulosic biomass, chemical pretreatment and the addition of saccharolytic enzymes before microbial bioconversion remain economic barriers to industrial deployment [Lynd LR, et al. (2008) Nat Biotechnol 26(2):169?172]. We began with the thermophilic, anaerobic, cellulolytic bacterium Caldicellulosiruptor bescii, which efficiently uses unpretreated biomass, and engineered it to produce ethanol. Here we report the direct conversion of switchgrass, a nonfood, renewable feedstock, to ethanol without conventional pretreatment of the biomass. This process was accomplished by deletion of lactate dehydrogenase and heterologous expression of a Clostridium thermocellum bifunctional acetaldehyde/alcohol dehydrogenase. Whereas wild-type C. bescii lacks the ability to make ethanol, 70% of the fermentation products in the engineered strain were ethanol [12.8 mM ethanol directly from 2% (wt/vol) switchgrass, a real-world substrate] with decreased production of acetate by 38% compared with wild-type. Direct conversion of biomass to ethanol represents a new paradigm for consolidated bioprocessing, offering the potential for carbon neutral, cost-effective, sustainable fuel production.

metabolic engineering bioenergy and thermophiles

¹ D.C. and M.C. contributed equally to this work.
² To whom correspondence should be addressed.

Author contributions: D.C., M.C., and J.W. designed research; D.C. and M.C. performed research; D.C., M.C., and J.W. contributed new reagents/analytic tools; D.C., M.C., A.M.G., and J.W. analyzed data; and D.C., M.C., A.M.G., and J.W. wrote the paper.

논문정보

형식Research article
게재일2014년 06월 (BRIC 등록일 2014-06-10)
연구진국외 연구진
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