09/07/1995

AU Scientist Turning Tobacco into Biodegradable Plastic

AUBURN, Ala. - Tobacco is considered by many people to be a menace to society's health, but research underway at Auburn University has resulted in a scientific first that may help make tobacco a boon for society.

Genetic engineers working through the Alabama Agricultural Experiment Station (AAES) at AU have successfully implanted tobacco cells with a synthetic gene that causes the plants to manufacture polyesters that, in turn, can be used to make biodegradable plastics.

According to Henry Daniell, associate professor of botany and microbiology at Auburn and leader of the research team working on this project, many bacteria naturally produce protein-based polymers as a product of biosynthesis. Biosynthesis is the formation of chemicals by living organisms and occurs as part of an organism's life cycle.

"Scientists already knew that these naturally occurring polymers can be used to make a wide range of plastic products, ranging from milk cartons to medical devices," said Daniell. "Unlike plastics made from petroleum-based products, protein-based polymers are environmentally safe over their entire life cycle, from production to disposal. They can be made from renewable resources using water-based processing techniques and are biodegradable."

In contrast, petroleum-based plastics are made from exhaustible fossil fuels, require toxic and hazardous chemicals in their production and are a major problem in solid waste disposal because they do not degrade, he explained.

The biodegradable plastics made from these polymers not only break down in the environment, but can become a useful part of the environment. Daniell noted that salt water rapidly degrades these plastics, so these products can be disposed of in oceans and gulfs. As they degrade in the water, the plastics will provide nutrients important in the ocean's food chain, actually benefiting the marine ecosystem.

What's more, protein-based polymers can be used for more than plastic packaging, Daniell continued. "They are remarkably biocompatible, which means they are nontoxic and are readily accepted by the body," he said. Because of this, they are useful in many medical applications, including the prevention of post-surgical inflammations (adhesions), tissue reconstruction and programmed drug delivery. In addition, the polymers can be used in transducers, molecular machines, superabsorbents and controlled release pesticides and fertilizers.

So why aren't we already making lots of useful products from these polymers? Daniell explained that the natural production of these polymers does not occur rapidly or abundantly enough to make them viable for commercial use. Scientists have been trying to boost natural production by isolating the polymer-making gene, but they have found that the genetic structure behind this process is highly complicated. So Daniell and his research team joined forces with researchers at the University of Alabama at Birmingham to try a different approach -- they created a synthetic gene with a simpler genetic structure that also forms these polymers.

Daniell then incorporated this synthetic gene into bacteria (E. coli cells) where, sure enough, it caused the E. coli cells to produce a generous amount of polymer inclusion. In fact, an average of 65-75 percent of the genetically altered cell areas were filled with the polymers.

While this accomplishment was encouraging, harvesting the polymers from bacteria still requires complicated processing. If these protein-based polymers are ever to rival petroleum-based plastics on a commercial scale, they must be produced abundantly and inexpensively. One of the best ways to produce substances abundantly is to harvest them from plants. So Daniell introduced the synthetic gene into tobacco cells.

"We chose tobacco for a number of reason," he explained. "Tobacco is a model plant for genetic engineering because it can be genetically manipulated very easily. It was the first crop plant to be transgenically altered."

Tobacco also made sense as a trial crop for economic reasons. Increasing concerns about the dangers of cigarette smoking may limit the market for traditional tobacco products in the future. If this crop could be used for other purposes, such as the making of biodegradable plastics, then the nation's tobacco farmers would have a new market for their crop.

The genetic introduction of this polymer gene was successful and marks the first time that genetic engineers have demonstrated expression of a synthetic gene in plants. A patent now is being sought for the process, but in the meantime the scientists are taking the next step in the process -- testing to see if the synthetic genes will be transferred from the parent plants to the next generation of plants. To test this, cuttings have been taken from the genetically altered tobacco plants and Daniell's team is growing new plants from these cuttings. If the second generation of plants contains the gene, then the scientists believe a new variety of tobacco can be bred that can provide a source of polymers for biodegradable plastics.

The scientists also will test this gene in other plants, from row crops to trees. Daniell noted that poplar trees, which are fast-growing, also are being used as model plants for this research. The beauty of that idea is that the trees will have economic value from their first year of planting because producers can harvest the leaves for use in plastic production during the years that the tree is maturing. Once they are mature, their wood can be used for furniture and other wood products and the polymers may make the wood fire resistant and also give it a built-in varnish.

Daniell believes that there are myriad ways to use this gene for the benefit of society, maybe even turning such scourges as kudzu into economically useful plants.

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News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
Contact Katie Jackson, 334-844-5886 or smithcl@auburn.edu

September 7, 1995