Going Small to Better Make Biodegradable Polymers

The NIST microreactor plate for studying enzyme catalyzed polymerization.
The NIST microreactor plate for enzyme-catalyzed polymerization.

Think big but go small. That’s what a team of researchers from the National Institute of Standards and Technology (NIST) and the Polytechnic Institute of New York University were thinking when they developed an improved and “greener” method for producing biodegradable polymers.

The team led by NIST materials scientist Kathryn Beers created a microscale reactor that let them track continuous polymerization using enzymes. The enzymes are a “greener” approach to making polymers on an industrial scale in the future.

The microreactor consists of an aluminium plate that’s 90 mm long and 40 mm wide with a zig-zag channel etched in it. The channel is about a millimeter deep and stuffed with hundreds of tiny beads. The beads hold the enzymes in place so they do their job.

In a paper they recently published, the group studied the synthesis of polycaprolactone (PCL) with the microreactor. PCL is a biodegradable polyester used in a variety of applications ranging from medical devices to disposable tableware. It’s typically synthesized using an organic tin-based catalyst to connect the building blocks together into the long polymer chains. The catalyst is highly toxic and troublesome to dispose.

But as public affairs specialist Michael Baum describes in his NIST Tech Beat article:

Modern biochemistry has found a more environmentally friendly substitute in an enzyme produced by the yeast strain Candida antartica, Beers says, but standard batch processes—in which the raw material is dumped into a vat, along with tiny beads that carry the enzyme, and stirred—is too inefficient to be commercially competitive. It also has problems with enzyme residue contaminating and degrading the product.

By contrast, Beers explains, the microreactor is a continuous flow process. The feedstock chemical flows through the narrow channel, around the enzyme-coated beads, and, polymerized, out the other end. The arrangement allows precise control of temperature and reaction time, so that detailed data on the chemical kinetics of the process can be recorded to develop an accurate model to scale the process.

Source: “Microreactors: Small Scale Chemistry Could Lead to Big Improvements for Biodegradable Polymers,” NIST Tech Beat, 03/30/11
Source: “Continuous Flow Enzyme-Catalyzed Polymerization in a Microreactor, Journal of the American Chemical Society, 03/25/11
Image provided by Kundu, NIST. No restrictions apply.

Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.

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