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There are two methods being researched and used to produce plastics from plants. The first uses fermentation and the second relies on the plant – to become the factory for plastic production. These two methods are outlined below:
Method # 1. Fermentation:
Fermentation, used for hundreds of years by humans, is even more powerful when coupled with new biotechnology techniques. Fermentation is the use of microorganisms to break down organic substances in the absence of oxygen.
Today, fermentation can be carried out with genetically engineered microorganisms, specially designed for the conditions under which fermentation takes place, and for the specific substance that is being broken down by the microorganism.
There are two ways fermentation can be used to create biopolymers and bio-plastics:
Bacterial Polyester Fermentation:
Bacteria are one group of microorganisms that can be used in the fermentation process. Fermentation, in fact, is the process by which bacteria can be used to create polyesters. Bacteria called Ralstonia eutropha are used to do this. The bacteria use the sugar of harvested plants, such as corn, to fuel their cellular processes. The by-product of these cellular processes is the polymer. The polymers are then separated from the bacterial cells.
Lactic Acid Fermentation:
Lactic acid is fermented from sugar, much like the process used to directly manufacture polymers by bacteria. However, in this fermentation process, the final product of fermentation is lactic acid, rather than a polymer. After the lactic acid is produced, it is converted to polylactic acid using traditional polymerisation processes.
Method # 2. Plastics in Plants:
Plants are becoming factories for the production of plastics. Researchers created a Arabidopis thaliana plant through genetic engineering. The plant contains the enzymes used by bacteria to create plastics. Bacteria create the plastic through the conversion of sunlight into energy.
The researchers have transferred the gene that codes for this enzyme into the plant; as a result the plant produces plastic through its cellular processes. The plant is harvested and the plastic is extracted from it using a solvent. The liquid resulting from this process is distilled to separate the solvent from the plastic.
Biotechnology is driving the production of new bio-plastics. Biotechnology techniques used to produce bio-plastics include fermentation, and genetic engineering.
For example, fermentation is used to release the cellulose from plants, so the cellulose can be used to create plastics. Also, genetic engineering can be used to create plants, such as soybean, specifically designed to be used as a raw material for the production of bio-plastics.
Improving efficiency is a major concern for the production of plastics and bio-plastics. Currently, fossil fuel is still used as an energy source during the production process. This has raised questions by some regarding how much fossil fuel is actually saved by manufacturing bio-plastics.
Only a few processes have emerged that actually use less energy in the production process. Therefore, researchers are still working on refining the processes used in order to make bio-plastics viable alternatives to petrochemical plastics. Energy use is not the only concern when it comes to biopolymers and bio-plastics.
There are also concerns about how to balance the need to grow plants for food, and the need to grow plants for use as raw materials. Agricultural space needs to be shared. Researchers are looking into creating a plant that can be used for food, but also as feedstock for plastic production. One group is attempting to genetically engineer corn to contain the bacterial enzyme responsible for plastic production.
Eventually, they are hoping to create the plant in a way which would restrict the plastic production to the stem, and leaves of the plant. This would leave the edible part of the corn plastic free. The edible part of the corn would be used as food, or as livestock feed. The plastic would be removed from the remaining part of the corn plant.
Biopolymers and bio-plastics are the main components in creating a sustainable plastics industry. These products reduce the dependence on non-renewable fossil fuels, and are easily biodegradable.
Together, this greatly limits the environmental impacts of plastic use and manufacture. Also, characteristics such as being biodegradable make plastics more acceptable for long term use by society. It is likely that in the long term, these products will mean plastics will remain affordable, even as fossil fuel reserves diminish.