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Spring 2001

Our new oil fields
By Steve Tally


Image: Clint Chapple
Purdue biochemist Clint Chapple discovered a gene while working with Arabadopsis (the plant in the growth chamber) that may make using plants for manufacturing plastic a reality. (Photo by Tom Campbell).

The shorter the chain of carbons, the more explosive the fuel is, and the more power it offers an engine. On the other hand, the longer a hydrocarbon chain is, the more structure it has.

Chemists have known for decades how to alter the hydrocarbon chains in petroleum through processes known as cracking and reforming. Shortened hydrocarbon chains are used as solvent bases for paints and chemicals. Longer chains--as many as 200 hydrocarbons--are known as plastics. But these products also can be made from plants.

In fact, green plants have an advantage over black crude when it comes to making new plastics. Hydrocarbon molecules can have other chemical chains attatched, forming unique links in the chains. Scientists call these chains polymers, and the individual molecules that form the chain are called monomers.

Clint Chapple, professor of biochemistry and recipient of the 2001 Purdue Agricultural Research Award, says that one reason scientists are interested in making plastics from plants is that plants produce an amazing array of compounds that could be used for monomers in plastics.

"Historically, we have been limited by the number of polymers that we can make from petroleum," he says. "Plants are really amazing chemical factories that produce a mind-boggling number of interesting chemicals. We can exploit that ability by using genomics to identify the genes required to make those compounds and by using biotechnology to insert the genes into crop plants."

Plastics from Plants

Before World War II, most paints, coatings and adhesives were made from vegetable oils or other plant products, so basing products on materials other than petroleum isn't a new idea. In fact, Henry Ford famously made everything from clothing to automobile bumpers from vegetable oils just to show that it could be done.

However, Chapple says, the problem with using crops to produce the starting materials for new plastics is trying to get plants to make enough of these substances for the whole process to be economically viable.

"Although crude oil supplies are finite, petroleum is still an inexpensive source for plastic monomers," Chapple says. However, that could soon change. Chapple and Knut Meyer of DuPont and Co. have cloned a gene from the common laboratory plant Arabadopsis that will allow the possibility to produce plastics in crops without damaging the plant's health. A patent application in which both Purdue and DuPont have rights has been filed on the use of the gene for the production of monomers.

 

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