|
Topic Name: A viable method for large-scale production of ethanol from plant matter
Category: Agricultural
Research persons: Meijuan Zeng,Michael Ladisch,Nathan Mosier,
Location: 225 South University Street,,West Lafayette, IN 47907-2093, United States
Details
Tiny pores within plant cells may hold
promise for green fuels. Researchers have discovered that particles from
cornstalks undergo previously unknown structural changes when processed to
produce ethanol, an insight they said will help establish a viable method for
large-scale production of ethanol from plant matter. Their research demonstrates
that retreating corn plant tissue with hot water - an accepted practice
that increases ethanol yields 3 to 4 times - works by exposing minute pores
of the plant's cell walls, thus increasing surface area for additional reactions
that help break down the cell wall." This brings together the tools that link
the processing technology to the plant tissue physiology," said Nathan
Mosier, an assistant professor of agricultural and biological engineering at
Purdue University. "It helps us understand, on a fundamental level, what
the processing is doing and how we can improve it."Mosier said that
research, further described in a study published Thursday (April 26) in the
journal Biotechnology and Bioengineering, applies to cellulosic ethanol,
or ethanol produced from cellulose, which is a key component of plant's cell
walls.
Using high-resolution imaging and
chemical analyses, the researchers determined that pretreatment opens reactive
areas within the cells of the corn stover - another name for postharvest
corn remnants, like leaves and stalks - that were previously overlooked. In
the next step of processing, these enlarged pores are more easily attacked by
enzymes that convert cellulose into glucose, which is in turn fermented into
ethanol by yeast, Mosier said.
Producing ethanol from cellulose would
be advantageous over existing industrial processes in several ways, said Michael
Ladisch, the study's co-author and a professor of agricultural and biological
engineering.
Currently, almost all industrial
ethanol derives from either starch found in corn grain or from sugar cane. This
limits U.S. ethanol production, which is almost entirely from corn grain, to a
grain supply that already is in demand for a variety of uses.
"Cellulosic ethanol would allow
industry to expand beyond the limits brought about by corn's other uses, like
sweetener production, animal feed and grain exports," Ladisch said.
For these reasons, he said, cellulosic
ethanol also would likely put less pressure on food prices.
The new process has the potential to
become more efficient, with a larger potential supply of plants that can be
grown more economically than traditional row crops. What's more, research in
plant science has yielded ? and will likely continue to yield - new types
of energy crops with larger pools of usable cellulose.
However, the catch is that cellulose is
not easily freed from the cell wall's complex, rigid structure, and, to date,
cellulosic ethanol has not been commercially viable. Ladisch said this study
should help change that.
"This study will help us translate
science from the lab to an industrial setting and will help produce cellulosic
ethanol economically," he said.
Plant's cell walls are rigid structures
made up of a variety of polymers, including cellulose and hemicellulose, which
can be converted into sugars that are then made into ethanol. However, cellulose
and hemicellulose are held in place by a variety of compounds like lignin, a
strong cellular glue that resists treatment and protects cellulose from being
broken down. Mosier and Ladisch found that after pretreatment opens corn's tiny
pores, enzymes not only removed more cellulose and hemicellulose from the cell
wall, but also removed it at a faster rate.
Cellulosic ethanol comes from plant
biomass, another term for the tissue of recently dead plants, or plants that
grow and die annually. This distinguishes the current supply of plant biomass -
to be used for cellulosic ethanol - from plant matter that died eons ago
and through time created our current supply of carbon fuels, namely coal and
oil. This is why plant biomass is often labeled as renewable, since it can be
grown each year, and why petroleum is referred to as non-renewable ? once it's
gone, it cannot be replaced.
Mosier and Ladisch are currently at
work on a variety of projects related to ethanol production, such as how to best
scale up from laboratory operations.
They have conducted research in this
area for years. The hot liquid water pretreatment process used in this study was
originally developed in the Laboratory of Renewable Resources Engineering at
Purdue, which Ladisch directs.
Ladisch's graduate student, Meijuan
Zeng, was the paper's first author.
ABSTRACT:
Particle size associated with
accessible surface area has a significant impact on the saccharification of
plant cell walls by cellulolytic enzymes. Small particle sizes of untreated
cellulosic substrate are more readily hydrolyzed than large ones because of
higher specific surface area. Pretreatment enlarges accessible and susceptible
surface area leading to enhanced cellulose hydrolysis. These hypotheses were
tested using ground corn stover in the size ranges of 425-710 and 53-75
micrometers. Ultrastructural changes in these particles were imaged after
treatment with cellulolytic enzymes before and after liquid hot water
pretreatment. The smaller 53-75 micrometer corn stover particles are 1.5X more
susceptible to hydrolysis than 425-710 micrometer corn stover particles. This
difference between the two particle size ranges is eliminated when the stover is
pretreated with liquid hot water pretreatment at 190 degrees C for 15 min, at pH
between 4.3 and 6.2. This pretreatment causes ultrastructural changes and
formation of micron-sized pores that make the cellulose more accessible to
hydrolytic enzymes.
About Researchers:
Nathan Mosier,
Mailing Address:
Purdue University
Department of Agricultural & Biological Engineering
225 South University Street
West Lafayette, IN 47907-2093
Office: ABE 211
Phone: (765) 496-2044
Fax: (765) 496-1115
E-mail: mosiern@purdue.edu
Laboratory
of Renewable Resources Engineering
Research
- Kinetic
Studies of Xylose Degradation for the Creation of a Corn Stover Cellulase Enzyme
Mimetic
- Enzyme
Mimicking Catalysts for Sugar Production From Agricultural Residues
Michael Ladisch,
Mailing Address:
Purdue University
Laboratory of Renewable Resources Engineering
Purdue University
Potter Engineering Center, Room 216
500 Central Drive
West Lafayette, Indiana 47907-2022
Office: POTR 1295
Phone: (765) 494-7022
Fax: (765) 494-7023
E-mail: ladisch@purdue.edu
Laboratory
of Renewable Resources Engineering
Research
- Bio-Based
Batteries
- Molecular
and Process Scale Discovery, Innovation, and Economics for Replacement of Fossil
Fuel Derived Products
Meijuan Zeng
Ladisch's graduate student
PhD - Biotechnology Bioprocess Engineering
POTR B8
49-46695
mzeng@purdue.edu
Funded:
This study was funded by the U.S.
Department of Energy, U.S. Department of
Agriculture and Purdue
Agriculture
|
