Genetic mutations in plants could make it easier to break down the cellulose in biomass—corn stalks and leaves, for example—for more efficient biofuel production. Photo: Maddison Sieck, Iowa State’s Bioeconomy Institute
Genetic mutations to cellulose in plants could improve the conversion of
cellulosic biomass into biofuels, according to a research team that included
two Iowa State University
The team recently published its findings in the online early edition of the
Proceedings of the National Academy of
Sciences. Mei Hong, an Iowa State professor of chemistry and an associate of the
U.S. Department of Energy’s Ames Laboratory, and Tuo Wang, an Iowa State
graduate student in chemistry, contributed their expertise in solid-state
nuclear magnetic resonance spectroscopy to the study.
The study was led by Seth DeBolt, an associate professor of horticulture at
the University of Kentucky in Lexington.
Chris Somerville, the Philomathia Professor of Alternative Energy and director
of the Energy Biosciences Institute at the University
of California, Berkeley, is also a contributing author. The
research project was supported by grants from the National Science Foundation
and the U.S. Department of Energy.
Researchers studied Arabidopsis
thaliana, a common model plant in research studies, and its
cellulose synthase membrane complex that produces the microfibrils of cellulose
that surround all plant cells and form the basic structure of plant cell walls.
These ribbons of cellulose are made of crystallized sugars. The crystal
structure makes it difficult for enzymes to break down the cellulose to the
sugars that can be fermented into alcohol for biofuels. And so DeBolt assembled
a research team to see if genetic mutations in the plant membrane complex could
produce what the researchers have called “wounded” cellulose that’s
not as crystalline and therefore easier to break down into sugar.
Hong, who had done previous studies of plant cell walls, used her laboratory’s
solid-state nuclear magnetic resonance technology to study the cell walls
created by the mutated system. The goals were to collect as much information as
possible about the molecular structure of the cell walls to see if mutations to
the plants resulted in changes to the cellulose.
“We found that the crystalline cellulose content had decreased in the
mutant cell walls,” Hong said. “We can quantify the degree of change,
and be very specific about the type of change.”
The cellulose microfibrils in the mutant cell walls, for example, were
thinner than those found in normal plants, Hong said. The studies also found an
additional type of cellulose with an intermediate degree of crystal structure.
Hong said those findings suggest the genetic mutations did create
differences in cellulose production and formation.
The study also reports the cellulose produced by the mutated plant could be
more efficiently processed into the sugars necessary for biofuel production.
“What this work suggests, in very broad terms, is that it is possible
to modify cellulose structure by genetic methods, so that potentially one can
more easily extract cellulose from plants as energy sources,” Hong said.
The research team’s paper said
developing techniques to modify the structure of plant cellulose in crops for
better and easier conversion to fermentable sugars “could be
transformative in a bio-based economy.”