Magazine article Science News

Busy Little Recyclers: Chemical Process, Microbial Metabolism Transform Trash-Bound Plastics

Magazine article Science News

Busy Little Recyclers: Chemical Process, Microbial Metabolism Transform Trash-Bound Plastics

Article excerpt

A two-step approach that converts a common plastic into a biodegradable polymer could cut the number of packing peanuts and Styrofoam cups that end up in landfills, researchers suggest.

In 2003, U.S. manufacturers produced more than 2 million tons of polystyrene to make such items as food packaging, packing materials, and furniture. Nearly all of this plastic was discarded, according to the Environmental. Protection Agency. There is little demand for recycled polystyrene because it's of lower quality than the polystyrene made directly from petroleum components, notes Kevin E. O'Connor of the University College Dublin.

Last year, O'Connor's group reported that the bacterium Pseudomonas putida CA-3 could metabolize pure styrene, the precursor of polystyrene, and convert it into polyhydroxyalkanoate (PHA), a biodegradable polymer that can be made into good-quality plastic. While other members of this microbe family turn sugars and other plant-based materials into PHA, converting styrene is rare, says O'Connor.

In an upcoming Environmental Science & Technology, O'Connor and his colleagues describe adding a chemical step to the microbial process, thereby changing polystyrene into PHA.

First, they heated the polystyrene to 520[degrees]C in a closed reactor, which broke down the polymer chains and produced styrene oil containing a few other chemical compounds.

The researchers then cooled the liquid and added it to P. putida CA-3 growing in the lab. O'Connor says that he was not sure whether the microbes would tolerate the impure styrene, but "they grew well. …

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