Technology
Green Tech America, Inc. (GTA)
is in the business of developing and commercializing an innovative
yeast-based cellulosic ethanol technology that was pioneered by Dr. Nancy
Ho at Purdue University. Cellulosic biomass (corn cobs and stover, wheat
and rice straws, wood, grasses, municipal paper wastes, etc) is renewable
and abundantly available in the United States. Recently, the US Department
of Energy has re-affirmed that yeast-based technologies are the most
desirable for cellulosic ethanol production. The application of cellulosic
ethanol to transportation will help solve our Nation’s energy problems,
strengthen our economy, save our environment, and have a significant
beneficial impact on our society. GTA is dedicated to making the
production of cellulosic ethanol a reality in this country. The goal of
GTA is to establish a novel, cutting-edge company that supports and
collaborates with ethanol producers to make the production of cellulosic
ethanol a highly profitable business. Based on the Cellulosic Ethanol
Yeast Technology developed by Dr. Ho and her colleagues at Purdue
University, GTA will optimize the technical details and establish a
blueprint for cellulosic ethanol production. The “blueprint” will then be
licensed to other ethanol producers throughout the US and around the world
to establish franchises for cellulosic ethanol production.
GTA will provide cells, enzymes, chemicals, project management and
technical support to the cellulosic ethanol producers, particularly to the
numerous newly established corn-ethanol farmer-owned plants. The goal is
to transform such plants to produce both corn- and cellulosic-ethanol.
However, GTA’s main business at the present time is to help the Purdue
researchers engineer the yeast to produce important industrial products
that can be produced alone or co-produced during ethanol production. Most
importantly, the resulting yeasts can efficiently produce these
co-products during the production of ethanol using sugars from both grain
and cellulosic biomass as feedstocks.
The novel Saccharomyces co-production technology to be marketed by GTA
will make both the current grain-to-ethanol and the emergent cellulosic
ethanol process more cost effective and profitable. The first generation
of co-products that GTA plans to produce are substances important for
animal feed, for the detergent industry, for the paper and fabric
industry, as well as others. In addition, GTA will also market high valued
products and residues, such as yeast extracts, from the yeast cells. More
importantly, GTA will generate a wide range of other products produced
from renewable resources for sustainable growth. GTA will also provide the
R&D as well as the technical consultants for all small corn- or
cellulosic-ethanol producers.
Yeast Technology for
Cellulosic Ethanol
A Chronological outline of the
development of the ideal glucose/xylose
co-fermenting Saccharomyces yeast (cellulosic ethanol-producing yeast) by
Dr. Nancy Ho’s Group at Purdue University:
1985-1993
Successfully developed the technology to genetically engineer any
Saccharomyces (baker’s) yeast to effectively co-ferment glucose and xylose
to ethanol. This was accomplished by cloning three highly modified
xylose-metabolizing-genes, XR, XD and XK, cloned on a high-copy-number
plasmid, followed by transforming the yeast with the plasmid
(incorporating the plasmid into the yeast cells). A high-copy-number
plasmid is a plasmid capable of self-replicating in the host cells many
times. As a result, the host cells will contain many copies of the cloned
genes via the plasmids.
1993-1996
Successfully developed the stable engineered yeast with cloned genes
integrated into the yeast chromosome. Genetically engineered yeast
containing genes cloned on plasmids are not stable and not suitable for
large-scale industrial production of ethanol. Thus, Dr. Ho’s group had to
develop stable yeast with many copies of the same three genes integrated
(inserted) into the chromosomes of the yeast. By then, there was no
suitable method for this genetic task. As such, Dr. Ho developed a new
method for incorporating genes into the yeast chromosomes in high-copy
numbers. This new method is easy to perform and extremely reliable. It can
transform any yeast, including industrial yeasts containing two or more
sets of chromosomes, into stable engineered yeast containing numerous
copies of the cloned genes inserted into the yeast chromosomes. Their
first successful genetically engineered stable yeast was 1400(LNH-ST),
with multiple copies of the three genes XR-XD-XK integrated together as a
cassette into the chromosome of the yeast strain 1400.
1997-1999
Large-scale screening for better yeasts with no legal constraints for
converting cellulosic sugars (mixed sugars recovered from cellulosic
biomass) to ethanol. Although 1400 (LNH-ST) was already sufficiently
effective for industry to use for the production of cellulosic ethanol, it
might not be the best. Furthermore, initially the yeast 1400 strain was a
gift to Dr. Ho’s Department by a company. The yeast was subsequently sold
to another company and the new company might want to charge whoever using
Dr. Ho’s yeast for the production of cellulosic ethanol. Thus Dr. Ho
decided to screen yeast strains that were effective for converting glucose
to ethanol, make them able to ferment xylose with her technologies, and
select the best among them for industry to produce cellulosic ethanol. The
selected yeasts for screening were all free from legal constraints. Among
the yeasts tested and integrated with the XR-XD-XK genes (more than ten
yeast strains), 424A (LNH-ST) and 259A (LNH-ST) are effective for
industrial production of cellulosic ethanol. Ethanol produced by these
yeasts does not require paying any additional royalties to any group or
company, particularly to any foreign company.
2000-Present
Further genetic engineering of the best yeast, 424A (LNH-ST), to improve
its xylose fermentation and to make it ferment two other minor sugars
effectively. There are at least three separate tasks that need to be done
to improve the yeast’s production of cellulosic ethanol. The further
improved yeast should be able to ferment xylose and other minor sugars 30
to 75% faster.
2002-Present
Successful engineering of yeast
capable of producing high-value co-products during ethanol production. One
drawback to the production of ethanol, including grain ethanol, is that
the profit margin is very narrow. In the overall strategy for the
development of recombinant yeast for the efficient conversion of
cellulosic biomass to ethanol, Dr. Ho planned to make the yeast capable of
producing high-value co-products with ethanol production. This will allow
ethanol production to be far more cost-effective and profitable. In the
past two years, the Ho group at Purdue University has made their
recombinant glucose/xylose co-fermenting yeasts produce two important
industrial products as co-products for either grain-ethanol or
cellulosic-ethanol production. Production of co-products with the
production of ethanol can improve the profit for ethanol producers by 25
to 50%. The current most urgent task of the Ho group at Purdue University
is to secure funding and quickly engineer additional co-products into
their yeast so that ethanol producers (including current grain-ethanol
producers) can generate different co-products for extra profit and further
lower the ethanol price. Producing co-products with ethanol production
would not only aid the ethanol industry, farmers, and the public, but it
would also benefit other industries that need such products to thrive. The
detergent, pulp and paper, and animal feed industries will all benefit
from the first generation of co-products that the Ho yeasts are made to
produce.
Additional features:
Dr. Ho’s recombinant
glucose/xylose co-fermenting yeasts contain several additional unique
features. The engineered yeasts are robust industrial yeast, not
laboratory strains. These recombinant yeasts were made industrial-user
friendly, and can be used immediately without further development.
The engineered yeast was made
environmentally friendly as well; it does not require the use of toxic and
expensive chemicals such as antibiotics to maintain the plasmids
containing the cloned genes in the yeast.
These were all accomplished through careful and ingenious design, driven
by the desire to provide our country (as well as the world) with an ideal
means to convert our largest renewable resource, cellulosic biomass, to
ethanol fuel or other green chemicals.
Dr. Ho has led the world in this
field since 1993. Her work has been appreciated worldwide, which is
evidenced by the international awards bestowed on Dr. Ho (see
Awards
and
Industrial endorsements).
Her work was also widely reported by newspapers and magazines in the US
and around world.
(c) 2007 Green Tech America,
All Rights Reserved