Happy End for Polystyrene

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From an environmental standpoint, polystyrene is far from a dream product. Most of it ends up in landfills, where it doesn8217;t break down over time. Recycling is not an economical option.

Scientists have long sought ways to make polystyrene more environmentally friendly. Researchers at the National University of Ireland and Hamburg University in Germany have come up with a new approach. If polystyrene itself is not biodegradable, they ask, can it be converted into something that is? Their answer, to be published in the journal Environmental Science and Technology, is yes. And they8217;ve called on bacteria to do the converting.

In the process, developed by Patrick G Ward, Kevin E O8217;Connor and colleagues, polystyrene is first converted to styrene oil by pyrolysis, heating the material to about 970 degrees Fahrenheit in the absence of oxygen. Then the oil is supplied to a strain of Pseudomonas putida bacteria as its sole source of food. The bacteria metabolids the oil and accumulate a different kind of polymer, known as PHA, that can be extracted. This plastic is biodegradable, but it also can be used in pressure-sensitive adhesives and plastic coatings. Since it breaks down, it has medical applications, as well, in materials for treating wounds or delivering drugs within the body.

The researchers point out that pyrolysis can be used to convert many petrochemical products into oil, and there are many micro-organisms capable of accumulating PHA. So the process has potential to recycle other types of plastic waste. Science Times

Frog? But that8217;s mosquito repellent
Rick Weiss
Could frog sweat be the source of the world8217;s next great mosquito repellant? After all, frogs get bitten by mosquitoes, too8212;so a few species, at least, may have evolved natural protections. That thinking led to experiments involving the skin secretions of five kinds of Australian frogs8212;at least one of which shows some promise, according to a new report.

Craig Williams of James Cook University in Cairns, Australia, and his colleagues applied mild electrical stimulation to individual frogs living in captivity. Electrical currents force muscles to contract, which causes a suite of mostly unidentified substances to be squeezed from skin glands.

In one experiment, each frog8217;s secretion was slathered over the hairless tail of a mouse that was kept in a cage with 80 bloodthirsty female Culex mosquitoes. While untreated tails were typically bitten within about 12 minutes, tails treated with secretions from Litoria caerulea Australia8217;s 8216;8216;dumpy treefrog8217;8217; stayed insect-free for more than 45 minutes, on average. In another experiment, the team found that the odour alone of that secretion and two others from other species persuaded mosquitoes to fly to an odour-free portion of a chamber, showing that the secretions can repel at a distance, the team reports in the online version of the British journal Proceedings of the Royal Society B.

LAT-WP