Fungus Has Future in Plastics
By Ben Hardin
April 27, 2000
WASHINGTON, April 27, 2000--A
new bioengineered fungus could usher in truly biodegradable plastic milk jugs
and soda bottles that dont hang around landfills for ages. This fungus
could become a workhorse in converting grain and other renewable
agricultural resources into environmentally friendly solvents and plastics.
The research on utilization of agricultural products such as
cornstarch and fibrous crop residues bodes well for both farmers and
consumers, said Floyd P. Horn, administrator of USDA's
Agricultural Research Service.
ARS has applied for patent protection on an invention that can team microbes
with the machinery to produce more lactic acid at less cost. Lactic acid is the
building block of polylactic acid (PLA) plastic. The plastic is similar to
polyethylene terephthalate or PET used in packaging.
In research at the ARS National Center
for Agricultural Utilization Research, Peoria, Ill., microbiologist
Christopher D. Skory first isolated an enzyme called lactate dehydrogenase
(Ldh) produced by the fungus Rhizopus oryzae. The amount of
enzyme produced determines how efficiently the fungus can produce lactic acid.
After researching the isolated enzyme, Skory cloned the gene responsible for
Ldh synthesis and bioengineered the fungus to have multiple copies of the gene.
Weve developed a system thats helped us improve upon
something the fungus already did quite well, says Skory. So far,
some of our strains are producing about 30 percent more lactic acid in
considerably less time than the original strains. The new strains are
being tested for their potential through a Cooperative Research and Development
Agreement with industry.
Engineering into the new strains a more efficient route for fermenting
sugars meant less energy would be wasted on making unwanted byproducts.
Its like widening one fork of a stream to increase the flow in that
specific direction, says Skory.
Because the new microbial strains dont need a lot of added nutrients
in their diets of sugars derived from the plant material, the lactic acid they
produce during fermentations is easier to purify for making clear plastic. Even
before the new improved strains came about, the emerging PLA industry was using
R. oryzae, because it produces lactic acid with uniform quality
thats superior to a mix of lactic acids from bacterial fermentations,
Lactic acid and its derivatives have many uses other than for plastics. For
example, lactic acid is commonly used in foods ranging from soda to sausages
because it preserves, enhances flavor or imparts desired acidity. Derivatives
of lactic acid such as the solvent ethyl lactate can also be used in
manufacturing electronic products, cosmetics textiles, paints, adhesives,
de-inkers and degreasers. Environmentally friendly, chlorine-free ethyl lactate
some day could supplant most of the present 3.8 million-ton market for
petroleum- derived solvents.
Presently, some 5 to 7 percent of petroleum used in the U.S. goes into the
manufacture of plastics, according to industry estimates.
ARS is the U.S. Department of
Agricultures chief scientific research agency.
Scientific contact: Christopher D. Skory, ARS National Center for
Agricultural Utilization Research, Peoria, IL 61604; phone (309) 681-6275; fax
(309) 681-6567; firstname.lastname@example.org.