DOE Oak Ridge Scientists
Find Ethanol Gene
Ateam of researchers at the Department of Energy’s BioEnergy Science Center (BESC) have pinpointed the exact, single gene that controls etha- nol production capacity in the bacterium Clostridium thermocellum. The
organism has long been studied for its ability to digest cellulose into ethanol.
One limiting factor is that C. thermocellum also makes the waste byproducts
acetate, formate and lactate. Another is that it can’t live when its own ethanol
production pollutes its environmental soup.
now a multidisciplinary team has created a strain of C. thermocellum with a
mutated bifunctional acetaldehyde-CoA/alcohol dehydrogenase gene (adhE).
This gene has been shown to confer ethanol tolerance, and it opens the door to
using the bacterium as an efficient converter of high-cellulose feedstocks, such
as switchgrass and corn stover, for ethanol production. It may also be possible
to insert the gene into more voracious bugs. These tailor-made bacteria could
break down lignin walls to get at a plant’s sugars, and ferment them, in a single
step, without the use of expensive enzymes to “pre-digest” the feedstock.
BESC is a multidisciplinary coalition led by Oak Ridge national Laboratory
(ORnL). The team’s results were published in the Proceedings of the National
Academy of Sciences, in a paper titled “Mutant alcohol dehydrogenase leads to
improved ethanol tolerance in Clostridium thermocellum,” by Steven D. Brown,
Adam M. Guss, Tatiana V. Karpinets, Jerry M. Parks, nikolai Smolin, Shihui Yang,
Miriam L. Land, Dawn M. Klingeman, Miguel Rodriguez Jr., Babu Raman, Jonathan
R. Mielenz, Jeremy C. Smith and Martin Keller of ORnL, and Ashwini Bhandiwad,
Xiongjun Shao and Lee R. Lynd of Dartmouth College. —Se Th MaSia
Nanocatalyst Points to
Recent work by a team at Berkeley’s Laser Thermal Lab suggests that solar-powered
rooftop systems can generate hydrogen for
fuel-cell use on an economic scale.
A paper by Nico Hotz, Heng Pan and
Costas Grigoropoulos at Berkeley, with
Seung-Hwan Ko of the Korea Advanced
Institute of Science and Technology, pointed
to solar conversion efficiencies of up to 28. 5
n ICO HOTz, DuKE unIVERSIT Y
percent in summer weather, storing hydrogen
for power production at night, or as a trans-portable fuel.
Now Hotz has joined the faculty at Duke
University, where he plans to construct a rooftop prototype of the system.
The technology uses glass vacuum tubes to
heat methanol in a matrix of zinc oxide and aluminum oxide, doped with a copper catalyst. At
230°C to 250°C (446°F to 482°F) in this environment, methanol reformulates into hydrogen and carbon monoxide. Efficiency improves
with smaller catalyst particles because of their
higher surface-to-volume ratio, so the team
developed a nanocolloidal matrix with particles smaller than 200 nanometers.
A paper on the Berkeley work won honors at the Energy Sustainability section of the
ASME 2011 Energy Sustainability and Fuel
Cell Conference in August.— Se Th MaSia
