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Plastic + Time=Water? Sure! Remarkable Bacteria Can Make Biodegradeable Plastic and Even Eat Toxic Waste
Photo by Michael Zide
Sheila Browne, Pamela Maynard, Anastasia Dimitropoulou, Tiffaney Burford
Chemist Sheila Browne (far right) involves seniors (left to right) Pamela Maynard, Anastasia Dimitropoulou, and Tiffaney Burford in her pioneering work creating biodegradable plastics.

Americans buy more than sixty billion pounds of plastic goods a year. Even with recycling, about one-third of the nation's soda bottles, six-pack rings, shrink-wrap, diapers, garbage bags, and other plastic waste gets landfilled and stays intact virtually forever. An additional 450,000 plastic containers are dumped into the world's oceans every day, and one million marine animals are killed by plastic waste each year. But chemistry professor Sheila Browne says there's a way to protect the environment even without changing our throwaway society. The answer is biodegradable plastics.

It sounds too good to be true, but Browne is making such plastics right now, right here on campus. "You can stick a bottle made of biodegradable polymer [plastic] in a pile of leaves or mulch, and it will become water and carbon dioxide within six months," Browne explains. These polymers will decompose in many different environments, from fresh water and garden soil to salt water and sewage sludge. All they need is moisture and fungi or bacteria. Luckily, more than 600 types of bacteria can do the job.

Bacteria actually produce the polymer inside their microscopic bodies, much as humans make and store fat. Normally, the bacteria use the polymer for their own energy needs. But if bacteria are "harvested" before using the polymer they've stored, it can be used by people instead.

"You grow bacteria in vats, using the same fermentation process that creates beer," Browne explains. "You feed them sugar, starch, oils, or even gasoline, wait a few days, then harvest the polymer grown inside the bacteria. Then you can melt the polymer and re-form it into any shape." She has invented a way, using a nuclear magnetic resonance spectrometer, to determine the best harvest time and to measure how much and what kind of polymer the bacteria create. (The bacteria's diet determines the characteristics of the polymer they produce.)

Although Browne didn't discover polymer-making bacteria, she is one of a handful of international researchers working on a new "generation" of biodegradable polymers. In this field, she's a rarity both as a woman and as a professor at a liberal arts college. "Usually polymer science is taught on the graduate or postdoctoral level, so having our undergraduates learn it and help with my research gives them a very special experience," Browne says. Consequently, her student assistants are sought after as interns by industry giants such as Cyanamid, Kodak, and 3M. Browne herself has been invited to deliver lectures at major international conferences, and recently published an article in Polymers, naming MHC students as coauthors.

The new polymers aren't only good for career building; Browne's collaborations with scientists as close as the University of Massachusetts at Amherst and as far-flung as Italy and France reveal many very practical uses for polymers. Most obviously, they can be made into a wide variety of biodegradable plastic consumer goods including disposable diapers, razors, feminine hygiene products, fishing nets, product packaging, and shopping bags.

"Biodegradable plastics are already widely used in Europe and Japan, because people there are much more environmentally conscious," Browne says. And, although these polymers are more expensive than traditional plastics, it's not price that's keeping them from the American market. A law requiring companies to prove their products decompose in any environment in which they might be left "has made it virtually impossible to market biodegradable products in this country," Browne says. "You'd have to spend millions of dollars to prove it will decompose not only in a Minneapolis landfill but also in a New York dump. And you still couldn't prove it would decompose on an Alaskan parking lot."

Browne is also exploring the use of polymers for medical treatment and environmental cleanup. Some polymers can be formed into artificial tendons; others deliver time-release drugs inside the body, then disintegrate. "You make little polymer beads, put drugs inside, and place the beads exactly where you want the drug to be released," she explains. "And you can create a polymer that breaks down in six weeks, eight months; whatever you want."

Most amazing of all, some bacteria can even convert oil spills and toxic waste into harmless, biodegradable polymer. "I'm working with American Home Products on a Superfund site in New Jersey, and we're feeding this poisonous stuff to the bacteria. They eat it, and turn it into a nontoxic, biodegradable plastic," Browne says.

Imagine the possibilities if this technology were used to its fullest extent worldwide. Sheila Browne has imagined it ... and is helping to make it happen. Chemist Sheila Browne (far right) involves seniors (left to right) Pamela Maynard, Anastasia Dimitropoulou, and Tiffaney Burford in her pioneering work creating biodegradable plastics.

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