We discuss and comment on the role agriculture will play in the containment of the CO2 problem and address protocols for terraforming the planet Earth.
A model farm template is imagined as the central methodology. A broad range of timely science news and other topics of interest are commented on.
Saturday, January 12, 2013
Galactan and Biofuels
I suppose that the idea here is to increase the yield of galactan in
order to produce a viable feedstock for high quality fuel. Since the
model is some species of mustard, using canola can not be far behind.
It would be convenient to covert a ton of canola waste into a couple
hundred pounds of fuel feedstock.
Otherwise, I think that this is a long shot for the advertised
benefits and more pure research.
Then again, converting plant waste into useful feed-stocks is high on
the research agenda anyway. It allows us to jump past the oil
industry with superior green credentials.
Sugars Could Boost Biofuel Production
Galactan is a polymer
of galactose, a six-carbon sugar that can be readily fermented by
yeast into ethanol and is a target of interest for researchers in
advanced biofuels produced from cellulosic biomass. Now an
international collaboration led by scientists at the U.S. Department
of Energy (DOE)'s Joint BioEnergy Institute (JBEI) has identified
the first enzyme capable of substantially boosting the amount of
galactan in plant cell walls.
advanced biofuels synthesized from the sugars in plant cells walls
could replace gasoline, diesel and jet fuels on a gallon-for-gallon
basis and be dropped into today's engines and infrastructures with no
Also, adanced biofuels
have the potential to be carbon-neutral, meaning they could be burned
without adding excess carbon to the atmosphere. Among the key
challenges to making advanced biofuels cost competitive is finding
ways to maximize the amount of plant cell wall sugars that can be
fermented into fuels.
confirmed the identity of the GT92 enzyme as the first enzyme shown
to increase the biosynthesis of galactan," says Henrik Scheller,
vice president for JBEI's Feedstocks Division and director of its
Cell Wall Biosynthesis group. "This identification of the first
B-1,4-galactan synthase provides an important new tool for the
engineering of advanced bioenergy fuel crops."
Scheller, who also
holds an appointment with DOE's Lawrence Berkeley National Laboratory
(Berkeley Lab), is the corresponding author of a paper in the journal
Plant Cell that describes this work.
The paper is titled
"Pectin Biosynthesis: GALS1 in Arabidopsis thaliana is a
B-1,4-Galactan B-1,4-galactosyltransferase." Co-authors were
JBEI's April Liwanag, Berit Ebert, Yves Verhertbruggen, Emilie
Rennie, Carsten Rautengarten, and Ai Oikawa, plus Mathias Andersen
and Mads Clausen of the Technical University of Denmark.
polysaccharide components of pectin, the sticky sugar substance that
binds together the individual cells in plant cell walls and is used
to make jellies and jams. The B-1,4-galactan component of pectin is
especially abundant in the "tension wood" that forms in
cell walls in response to mechanical stress from wind or snowfall.
composed of hexoses, which in contrast to pentoses, are easily
utilized by fermenting microorganisms for the production of biofuels
and other compounds," Scheller says. "It would be
advantageous to develop plants with increased galactan content
instead of hemicelluloses consisting largely of pentoses."
GT92 is a family of
glycosyltransferase proteins whose genes are found in all plants that
have been genetically sequenced. An increased expression of GT92
genes has been observed in studies of tension wood.
combined with the knowledge that tension wood is rich in
B-1,4-galactan led Scheller and his colleagues to investigate the
function of GT92 proteins in Arabidopsis thaliana, a small flowering
relative of mustard that serves as a model organism for plant
Arabidopsis has three
members of GT92, which Scheller and his colleagues designated as
GALACTAN SYNTHASE 1,2 and 3 (GALS1, GALS2 and GALS3). While
loss-of-function mutants in all three genes were found to be galactan
deficient, Scheller and his colleague isolated and tested GALS1.
of GALS1 resulted in plants with 50-percent higher B-1,4-galactan
content and no adverse phenotype," Scheller says. "We
expect that the results for GALS2 and GALS3 overexpressors will be
similar though we have yet to test them."
Given that all three
Arabidopsis GALS genes showed overlapping but not identical
expression, Scheller and his colleagues are now combining mutations
of GALS genes to better understand the role of B-1,4-galactan in
They're also carrying
out basic studies on these enzymes, including crystallization and
structural analysis. In addition, they're overexpressing the GALS
proteins in different combinations to determine if even higher
production of B-1,4-galactan results.
B-1,4-galactan is an ancient invention, the function of GT92 as a
galactan synthase in Arabidopsis should also be applicable to
switchgrass, Miscanthus, poplar and other plants being considered as
crops for advanced biofuels," Scheller says. "We do not
anticipate any difficulty in being able to overexpress GT92 genes in
This research was
funded by the DOE Office of Science, and by the Danish Strategic