June 3, 2014 — New research from the University of Georgia and the Department of Energy’s Oak Ridge National Laboratory has overcome a major hurdle to cost-effective biofuel production by enabling the direct conversion of switchgrass to fuel.
The study, published in the Proceedings of the National Academy of Sciences, documents the direct conversion of biomass to biofuel without pre-treatment, using the engineered bacterium Caldicellulosiruptor bescii.
Pre-treatment of the biomass feedstock—non-food crops such as switchgrass and miscanthus—is the step of breaking down plant cell walls before fermentation into ethanol. This pre-treatment step has long been the economic bottleneck hindering fuel production from lignocellulosic biomass feedstocks.
Led by UGA’s Janet Westpheling and ORNL’s Adam Guss, the research team succeeded in genetically engineering the organism C. bescii to deconstruct un-pretreated plant biomass. The researchers are all members of the Department of Energy’s BioEnergy Science Center (BESC), which is headquartered at ORNL.
“Now, without any pretreatment, we can simply take switchgrass, grind it up, add a low-cost, minimal salts medium and get ethanol out the other end. This is the first step towards an industrial process that is economically feasible,” said Westpheling, who spent two and a half years developing genetic methods for manipulating the C. bescii bacterium to make the current work possible.
The research group engineered a synthetic pathway into the organism, introducing genes from another anaerobic ethanol-producing bacterium, Clostridium thermocellum, and constructed a pathway in the organism to produce ethanol directly.
“The use of bacteria that grow on plant biomass at high temperatures, such as Caldicellulosiruptor, has the potential to revolutionize how we make renewable fuels,” said Guss, whose expertise in bacterial genetics and metabolic engineering was instrumental in designing and implementing the synthetic pathway. “By understanding how these organisms work, we were able to engineer C. bescii to make ethanol directly from plant material.”
The recalcitrance of plant biomass for the production of fuels, a resistance to microbial degradation evolved in plants over millions of years, results from their rigid cell walls that have been the key to their survival and the major impediment to biofuel production. Understanding the scientific basis of and ultimately eliminating recalcitrance as a barrier has been the core mission of BESC.
“To take a virtually unknown and uncharacterized organism and engineer it to produce a biofuel of choice within the space of a few years is a towering scientific achievement for Dr. Westpheling’s group and for BESC,” said Paul Gilna, director of BESC. “It is a true reflection of the highly collaborative research we have built within BESC, which, in turn, has led to accelerated accomplishments such as this.”
Read more in the full UGA press release.
Coauthors on the PNAS paper include UGA’s Daehwan Chung and Minseok Cha.
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.
ORNL is managed by UT-Battelle for the Department of Energy's Office of Science.
