BIODEGRADABLE PLASTICS
- TRANSGENIC PLANTS PROVIDING A SOLUTION
Almost every product we buy most of the food we eat and many of the liquids we drink come encased in plastic packaging, which provides excellent protection for the product. It is cheap to manufacture and seems to last forever. Lasting forever, however, is proving to be a major environmental problem. Plastics are manufactured from numerous non-renewable resources like natural gas, coal, and oil. Plastics cannot be degraded easily in the natural environment due to their long polymer molecules which are too large and too tightly bound.
A type of sturdy and hard plastic is made with a molecule known as Bisphenol A, BPA. BPA like many other man made chemicals is now detectable in most people’s blood streams and could cause dangerous hormonal changes in children. BPA may tend to cause cancer, early puberty, obesity and even attention deficit disorder.
To overcome this problem BIODEGRADABLE PLASTICS have been developed which are made from renewable resources, such as plants. Biodegradable plastics are made with plant-based materials and result in 15% less carbon emission. Infact biodegradable plastics have not been successful in replacing the wide spread use of traditional petrochemical plastics.
The following are few items and the time required for their decomposition,
Tin cans- 50 to 100 years
Aluminum Cans- 80 to 100 years
Glass Bottles- 1 million years
Newspapers- 25 to 50 years
Polystyrene- 1000's of years
Plastic bags- 400 years
So now we know the raising alarm being caused in the environment by the use of plastics. But a solution is always there,
"Green Film" Plastic Bags and Products- 9 months to 5 years .
The plastics that are decomposed in the natural environment are known as the “biodegradable plastics”. (‘Biodegradable’ means that a substance can naturally decompose with the help of micro organisms and will not persist in the environment beyond a certain period of time). The chemical bonds of biodegradable compounds are easily destroyed by a variety of bacteria over a small period of time to facilitate their decomposition. As early as in the year 1926, Lemoigne managed to isolate the first of the polyhydroxyalkanoates – polyhydroxybutyrate (a homopolymer whose building unit is the 3-hydroxybutyric acid) from the Bacillus megaterium bacterium. At the end of the 1950s, the presence of the polyhydroxybutyrate was confirmed as an energy and carbon source and storage in many other bacteria. Many species of bacteria accumulate polyhydroxyalkonoates as energy storage compounds, some of the PHA polymers are commercially valuable as biodegradable plastics.
Polyhyroxybutyrate is a PHA produced in Ralstonia eutropha via three enzyme bio synthetic pathway consisting of ? – ketothiolase, aceto acetyl Co-A reductase, and PHB synthase. PHB synthase production in plants was first demonstrated in transgenic Arabidopsis thaliana. Polyhydroxy alkanoates (PHAs), e.g., polyhydroxybutyrate (PHB), are synthesized from acetyl-CoA used as precursor, and are used for the synthesis of biodegradable plastics with thermoplastic properties. At present, PHAs are produced by bacterial fermentation, and the cost of biodegradable plastic is substantially higher than that of synthetic plastics.
Attempts are being made to produce PHAs in transgenic plants to reduce the cost. Genes encoding the two enzymes, aceto-acetyl-CoA reductase (PhbB) and PHB synthase (phbC), involved in the PHB synthesis from the precursor acetyl-CoA have been transferred from the bacterium Alcaligenes eutrophus and expressed in Arabidopsis thaliana. When the two enzymes were targeted into the plastids, PHB accumulated in leaves. PHB production by transgenic plants provides an example of a novel compound synthesized in plants.
Standards that certify biodegradability and compostability,
Following international organizations have established standards and testing methods for compostability: American Society for Testing and Materials ASTM ASTM 6400-99
European Standardization Committee (CEN) EN13432
International Standards Organization (ISO) ISO14855 (only for biodegradation)
German Institute for Standardization (DIN) DIN V49000
The ASTM, CEN and DIN standards specify the criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable. While ISO 14855 makes no stipulations regarding disintegrations or toxins remaining.
Dealing with plastic wastes has taken on significance not far short of ultimate redemption. Developing biodegradable plastics is just one of the solutions to the existing problem. Its our responsibility to remember that by the uncontrolled use of plastics we are contributing our share to a deadly pollution whose ill effects are irreversible and capable of reaching out to numerous generation to come.
REFERENCES
1. Nature journal, Nature Biotechnology.
2.Crop science journal.
3. India Together, Science and environment and environmental plastics.
4. Australian Academy of Science.
5. Eco Greenwares.
6. abc NEWS – Health
7. Institute of science and society
Article Source: http://www.articlesbase.com/science-articles/biodegredable-plastics-transgenic-plants-providing-a-solution-602078.html
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