Roll your own (plastic)
By Richard P. Grant Via
5 July 2011
Oil gets everywhere. At a quick guess, about fifty percent by mass of what’s on my desk is derived from petroleum products. Yours is probably similar–and just think of all the plastics you get through in a lab. These all start out as crude oil or natural gas, and more often than not end up in landfill sites or floating around the world’s oceans, spectacularly failing to degrade. Then there’s the stuff we burn to power our cars and boats and aeroplanes.
We’re dependent on oil, and it’s running out. Even if you want to bury your head in the sand over climate change, there’s no denying that petroleum and its cousins are a limited resource–by itself an excellent reason to reduce our usage, recycle where we can, and find alternatives. Waiting a few million years for more oil and coal to be produced from dead sea creatures and plants just isn’t going to cut it, really.
So why not cut out the middle man–the natural, geochemical processes–and make some of this stuff directly? Well, we’re already doing that when it comes to fuel–biodiesel and ethanol for example (although these have problems of their own)–but what about plastics? Wouldn’t it be great if you could grow plastic?
Over the last few years, there has been significant progress in mass-producing polyhydroxyalkanoates (PHAs) by microbial fermentation. PHAs are a family of biodegradable, renewable plastics with properties that allow them to replace traditional, petroleum-derived plastics, and are found in nature as a microbial carbon storage material. Now, a group at Metabolix has successfully engineered tobacco plants to produce significant amounts of the most common bacteria-produced PHA, poly[(R)-3-hydroxybutyrate] (PHB), in their leaves.
The work is published in Plant Physiology, evaluated by Alexander Krichevsky and Vitaly Citovsky at the State University of New York at Stony Brook (free evaluation, and the article is Open Access too). What’s really cool about the work is that the transgenic plants remain fertile, and don’t appear to suffer ill effects from having heaps of plastic in their leaves. This means that it should be easy to grow and propagate such plants on an industrial scale, making grwoing plastic more likely to be economically viable (as well as being environmentally desirable, of course). There’s a also a rather neat “operon extension technique” developed by the authors which should, apparently, advance plant genetic engineering by reducing the incidence of unwanted recombination events.
I don’t recommend you smoke it, though.