Biodegredable Plastics - Transgenic Plants Providing a Solution

BIODEGRADABLE PLASTICSpolyhydroxyalkonoates as energy storage
- TRANSGENIC PLANTS PROVIDING Acompounds, some of the PHA polymers are
SOLUTION        commercially valuable as biodegradable plastics.
                   Almost every                 Polyhyroxybutyrate is a
product we buy most of the food we eat andPHA produced in Ralstonia eutropha via three
many of the liquids we drink come encased inenzyme bio synthetic pathway consisting of ?
plastic packaging, which provides excellent– ketothiolase, aceto acetyl Co-A reductase,
protection for the product. It is cheap toand PHB synthase. PHB synthase production in
manufacture and seems to last forever. Lastingplants was first demonstrated in transgenic
forever, however, is proving to be a majorArabidopsis thaliana. Polyhydroxy alkanoates
environmental problem. Plastics are manufactured(PHAs), e.g., polyhydroxybutyrate (PHB), are
from numerous non-renewable resources likesynthesized from acetyl-CoA used as precursor,
natural gas, coal, and oil. Plastics cannot beand are used for the synthesis of biodegradable
degraded easily in the natural environment due toplastics with thermoplastic properties. At present,
their long polymer molecules which are too largePHAs are produced by bacterial fermentation, and
and too tightlythe cost of biodegradable plastic is substantially
    higher than that of synthetic plastics.
                  A type of sturdy and                  Attempts are being
hard plastic is made with a molecule known asmade to produce PHAs in transgenic plants to
Bisphenol A, BPA. BPA like many other man madereduce the cost. Genes encoding the two
chemicals is now detectable in most people’senzymes, aceto-acetyl-CoA reductase (PhbB) and
blood streams and could cause dangerousPHB synthase (phbC), involved in the PHB
hormonal changes in children. BPA may tend tosynthesis from the precursor acetyl-CoA have
cause cancer, early puberty, obesity and evenbeen transferred from the bacterium Alcaligenes
attention deficit disorder.eutrophus and expressed in Arabidopsis thaliana.
                 To overcome thisWhen the two enzymes were targeted into the
problem BIODEGRADABLE PLASTICS have beenplastids, PHB accumulated in leaves. PHB
developed which are made from renewableproduction by transgenic plants provides an
resources, such as plants. Biodegradable plasticsexample of a novel compound synthesized in
are made with plant-based materials and result inplants.
15% less carbon emission. Infact biodegradable Standards that certify biodegradability and
plastics have not been successful in replacing thecompostability,
wide spread use of traditional petrochemical Following international organizations have
plastics.established standards and testing methods for
The following are few items and the time requiredcompostability: American Society for Testing and
for their decomposition,Materials ASTM ASTM 6400-99
 Tin cans- 50 to 100 years European Standardization Committee (CEN)
Aluminum Cans- 80 to 100 yearsEN13432
Glass Bottles- 1 million yearsInternational Standards Organization (ISO)
Newspapers- 25 to 50 yearsISO14855 (only for biodegradation)
 Polystyrene- 1000's of yearsGerman Institute for Standardization (DIN) DIN
Plastic bags- 400 yearsV49000
So now we know the raising alarm being caused                The ASTM, CEN and
in the environment by the use of plastics. But aDIN standards specify the criteria for
solution is always there,biodegradation, disintegration and eco-toxicity for
 "Green Film" Plastic Bags and Products- 9a plastic to be called compostable. While ISO
months to 5 years .14855 makes no stipulations regarding
                The plastics that aredisintegrations or toxins remaining.
decomposed in the natural environment are                Dealing with plastic
known as the “biodegradable plastics”.wastes has taken on significance not far short of
(‘Biodegradable’ means that a substanceultimate redemption. Developing biodegradable
can naturally decompose with the help of microplastics is just one of the solutions to the existing
organisms and will not persist in the environmentproblem. Its our responsibility to remember that
beyond a certain period of time). The chemicalby the uncontrolled use of plastics we are
bonds of biodegradable compounds are easilycontributing our share to a deadly pollution whose
destroyed by a variety of bacteria over a smallill effects are irreversible and capable of reaching
period of time to facilitate their decomposition. Asout to numerous generation to come.
early as in the year 1926, Lemoigne managed to REFERENCES 
isolate the first of the polyhydroxyalkanoates1. Nature journal, Nature Biotechnology.
– polyhydroxybutyrate (a homopolymer2.Crop science journal. 
whose building unit is the 3-hydroxybutyric acid)3. India Together, Science and environment and
from the Bacillus megaterium bacterium. At theenvironmental plastics.
end of the 1950s, the presence of the4. Australian Academy of Science.
polyhydroxybutyrate was confirmed as an energy5. Eco Greenwares.
and carbon source and storage in many other6. abc NEWS – Health
bacteria. Many species of bacteria accumulate7.