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Illumination magazine.
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New & Now: Spring 2009

New View of ALS

Strong Start

God and Coal

Plastics Plant

Joint Genetics

Incentives Support

 

Plastics Plant

With a Little Bioengineering, Plastics Could Get a Whole Lot Greener

We live on a planet awash in discarded plastics, an Earth littered with petroleum-wasting polymers. Consider the humble grocery bag. The environmental lobby group Worldwatch Institute estimates the world’s shoppers each year take home between 5 and 6 trillion single-use, high-density polyethylene totes; a.k.a., the “plastic” in the  “paper or plastic?” Only a tiny fraction of these are ever recycled. Most end up in landfills or as litter, where they blight the landscape and endanger wildlife.

And bags aren’t the only problem. Thirsty U.S. consumers annually discard some 2 million tons of polyethylene terephthalate, or PET, a plastic often found in the form of water and soda bottles. While recycled more often than bags, the vast majority of bottles also end up in the global waste bin.

One way to stem the tide of plastic waste is to tax its consumption, a strategy that has significantly reduced bag and bottle waste in plastic-choked nations such as Ireland, Kenya and Taiwan. A more novel approach, a “green alternative” being pursued by researchers with MU’s Interdisciplinary Plant Group, promises an even better outcome, one that could eventually allow the world’s consumers to have their plastic and discard it too.  The idea is to engineer plants that would grow organic alternatives to polyethylene polymers. If successful, the strategy could stem waste, reduce plastics’ carbon footprint and provide a new cash crop for farmers.

"Making plastics from plants is not a new idea," says Brian Mooney, research assistant professor of biochemistry and associate director of the Charles Gehrke Proteomics Center in MU's Christopher S. Bond Life Sciences Center. "Plastics made from plant starch and soy protein have been used as an alternative to petroleum-based plastics for a while. What is relatively new - and exciting - is the idea of using plants to actually grow plastics."

While such an outcome will likely take some time to fully realize, an investigation using the model plant Arabidopsis thaliana has shown promise. There are three bacterial enzymes that, when combined with two enzymes naturally occurring in Arabadopsis, can produce an organic polymer. This polymer, a tongue-twister known as polyhdroxybutyrate-co-polyhydroxyvalerate or, more conveniently, PHBV, is a flexible, moldable plastic used in a wide range of products, among them bags, soda bottles, disposable razors, flatware and, yes, grocery bags. When discarded, bacteria in the soil break it down into water and carbon dioxide.

"Of the two plant enzymes that supply the chemical precursors for PHBV, one is produced in the mitochondria. Recently, we’ve successfully modified plants so that this enzyme is diverted to the chloroplast, which has been defined as the best place in the plant to produce PHBV," says Mooney. “We also confirmed that a stable, functional complex is formed.”

The next step, Mooney says, is to see if the technique works in 'real' plants, such as switchgrass. Mooney, along with Douglas Randall, professor of biochemistry at MU, have initiated conversations with scientists at the Donald Danforth Plant Science Center in St. Louis, and the Cambridge, Mass.- based environmental tech company Metabolix Inc.

Metabolix and the Danforth Center were recently awarded a $1.14 million grant from the Missouri Technology Corporation to prodce a "double-crop" that would produce both a bioplastic and an oil for biodiesel refineries. Metabolix has already successfully produced one form of biodegradable plastic in switchgrass, but yield are low. MU researchers hope their advances will lead to higher amounts of a more usable plastic.

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Published by the Office of Research.

©2009 Curators of the University of Missouri. Click here to contact the editor.

 

Illumination home. Spring 2009 Table of Contents.