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Growing plastics on
farms DRIVING his tractor along a dusty road in Punjab, Ranjitsingh, a farmer gazes towards the horizon at rows of tall, leafy corn plants shuddering in the breeze as far as the eye can see. Not only are kernels of corn growing in the ears, but also granules of plastic are sprouting in the stalks and leaves. This is not a dream. The day this will become a reality is not far away. Clint Chapple, professor of biochemistry at Purdue University, USA, and Dr Kunt Meyer of DuPont, a household name in plastics and fibre industry, have cloned a gene from the common laboratory plant Arabadopsis Thaliana that will produce plastics in crops like maize and soyabean, without damaging the plant’s health. They have found the gene that allows plants to make plastics and store them in their stalks and leaves - a discovery that may one day, open the door to producing new types of plastics from plants. As of today, plastics
are produced by making chains of organic compounds derived from crude
oil and its product petroleum. Scientists call these chains polymers,
viz polyethylene or polythene and the individual molecules that form
the chain viz ethylene are called monomers. |
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Scientists are interested in making plastics from plants, because plants produce an amazing array of compounds that could be used as monomers in making plastics. Plants also produce a wide variety of natural products. Plants also are much more versatile than petroleum. Plants are amazing chemical factories that produce an overwhelming number of interesting chemical compounds. The scientists planned to identify the genes required to make those compounds and then to use genetic engineering to insert those genes into plants. Until now, however, the problem has been trying to get plants to make enough of these substances for the whole process to be economically viable. Fortunately, plants already have methods for making and storing large amounts of compounds that help protect them from insects, disease and ultraviolet radiation in sunlight. The plants do this by combining the molecules with other molecules to produce stable, soluble forms of the compound that are stored in small structures, called vacuoles, within their cells. The vacuoles isolate the compound from the rest of the biochemical processes going on in the plant. They have now cloned a gene that produces an enzyme that is in involved in combining these compounds in plants. DuPont is investigating the use of genetically modified microbes as well as plants to produce monomers. For example, DuPont has a project near completion that uses the bacterium E coli to produce the monomer for a type of plastic that is used in making fibre used in making carpets. However, plants are more attractive chemical factories than microbes because they may be cheaper. The inherent advantage with plants is that they get their nutrients - the carbon dioxide and sunlight - for free.Manufacturing plastics with microbes involves a high capital investment because factories have to be built to produce and feed them. According to Chapple, new plastics that are not even being currently considered might soon be possible. In the future, we may be able to develop plastics with such special properties that we find new uses for them. They may be the right one for use in synthetic heart valves or in parts for jet aircraft. The scientists at Monsanto in the US
have also produced plastics from plants using genetic engineering. They
have done this by inserting four genes from the bacteria into varieties
of mustard. This turns the plants into biological factories making
plastic that can then be extracted from the plant. Plants take carbon
directly from the air and so the plastic from the crops is likely to be
relatively cheap. The plastic produced in the plant factories is not
only biodegradable, it is also suitable for widespread commercial use. |
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