- LONDON - Cloth could soon be grown by bacteria. Scientists have harnessed
genetically altered bacteria to eat sugar from corn and secrete the chemical
needed to make polyester fibers.
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- Not only is it much cheaper and better
for the environment than industrial chemical processes, the resulting
polyester has a range of superior qualities and it can also be continually
recycled.
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- DuPont scientists who have been working
with biotechnologists claim the new material they have made will soon
be used in clothing, carpets, curtains and synthetic leathers, as well
as in the production of polyurethane elastomers.
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- The polymer polytrimethylene, known as
3GT, has better properties than traditional polyester, or 2GT. But it
has been slow to come to market because of the high cost of making trimethylene
glycol, or 3G, which is one of the main constituents of 3GT.
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- At present 3G is made by expensive chemical
processes, but DuPont scientists working with Genencor International have
taken a genetic engineering route that could revolutionize the £20
billion ($30 billion) a year world polyester market.
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- It is known that some naturally occurring
yeasts convert sugar into glycerol, while other forms of bacteria can
change glycerol to 3G. But no single organism has existed until now which
can go the whole way and convert sugar into 3G.
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- DuPont and its collaborators have genetically
engineered one type of bacterium by introducing genes from two others
to make it do just that. Instead of converting sugar to ethanol (alcohol),
it is modified to convert sugar or glucose into 3G.
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- The fermentation of sugars into alcohol
by yeast or bacteria has been practiced for thousands of years, but it
is only since the arrival of genetic engineering that has it been possible
to harness biological processes for the production of other chemicals.
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- According to Ray Miller of DuPont, the
advantage of the process is that in a single step you go from a low-cost
raw material like corn starch to having a product that is normally expensive
to manufacture.
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- "The approach we are taking is to
use recombinant DNA, modify an organism using the genetic information
from two naturally occurring organisms and inserting it into a third.
You are then creating an organism that has in its body the genetic code
that allows the necessary chemistry to occur. You have an organism that
has all the enzymes needed to turn sugar into 3G. It then operates like
a winery, taking sugar and excreting what we want," he says.
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- "The sequence of genes tells the
bacteria what enzymes to produce. Once you figure out what sequence does
what chemically, you can excise that piece of the genetic code and insert
it into another organism. The new organism then has the trait that goes
with the gene you have inserted," says Miller.
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- The production process starts with ordinary
corn, which is milled to make a starch. The corn starch can then be converted
using enzymes to a sugar commonly used for sweetening colas.
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- But the same sugar can also be fermented,
and when it is mixed with the genetically modified bacteria it is ingested
and converted into 3G. The chemical is then collected and separated from
the liquor.
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- The bacteria carry on working and producing
the chemical rather than the ethanol they would normally produce.
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- The chemical is then refined and spun
to make the polymer for 3GT or improved polyester for clothing, home
furnishings, upholstery, and fabric and carpets.
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- "It is very exciting for us, and
apart from a natural material like cotton, this is the first bio material
that will be used in the textile industry in large volume," says
Miller. "The fermentation process uses no heavy metals or toxic
chemicals, and the primary material is corn starch. Rather than releasing
carbon dioxide into the atmosphere, the process captures it because the
growing corn will absorb the gas," he says.
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- The 3GT polymer is resilient and can
be molded or extruded. The fibers can be stretched by 15 percent.
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- It is also biodegradable and can be returned
to its original components. Scientists believe it will be possible to recycle
the material indefinitely.
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