Dissolving the plastic bag problem
The Phage Factor
Anton By rights the world and its dog should now know the name Daniel Burd. For Daniel Burd has an eco-friendly solution for disposing of the plastic bag menace. About half a trillion plastic bags are produced globally each year, but they take up to 1000 years to decompose. In the meantime they can migrate to the oceans and be ingested by wildlife, with fatal results.
Burd's discovery is bacteria which he reckons in combination can eliminate poly(ethyl)ene bags in about three months. The judges of the 2008 Canada-Wide Science Fair in Ottawa agreed, and awarded Burd top prize. You can read the report he presented ("Plastic not fanastic") here (pdf)].
Burd started with the idea that if plastic bags are being degraded by microorganisms in nature, it should be possible to isolate them. He collected soil samples from a local landfill site, and spent three months culturing them up on a diet exclusively of ground-up polythene bag. At this stage, he reasoned, if there were bacteria of interest, there should be enough of them to make a measurable difference. And so his experiments began.
The cultured broth was introduced to weighed amounts of polythene film strips, and the two were allowed to commerce for six weeks. Measure against a control sample of boiled broth which showed no change, the active samples showed a promising 17 per cent weight loss.
Burd then grew the broth on agar and found it contained four different types of bacteria. These he worked to separate, and tested them individually and in pairs for their polythene appetites. While one type of microbe showed a marked predilection for plastic bag, he also observed that a combination was even better at eliminating polythene. An identification kit enabled him to identify these as Sphingomonas and Pseudomonas types. Pseudomonas has been cited in previous research, but his discovery of the much more ravenous Sphingomonas, and the rest of his experiment, is new.
Further research by Burd on his microbe consortium, as his paper terms it, showed that their rate of digesting polythene was affected by temperature, population density, and by the level of concentration of added sodium acetate. He eventually achieved a stonking 42 per cent elimination of polythene in six weeks. On this basis, Burd projects that a complete dispersal of polythene is possible in under three months.
You can do this at home, folks, and you don't need lab equipment, or even to chop up the plastic bags. Burd is reported as having tried five or six whole bags in a bucket of his special goo, and the process worked just as well.
"All you need is a fermenter . . . your growth medium, your microbes and your plastic bags." said Burd. He points out that little energy is required as an input, as the microbes produce heat as they work, and they generate a meagre 0.01 per cent of their body mass as waste CO2. So we are unlikely to change the climate by helping nature's little helpers dispose of plastic bags the Burd way.
An impressive array of awards garnered by this nice piece of science at the Canada-Wide Science Fair is listed here, where it may be noted that among his many talents young Daniel can also write a mean CV.
Turning a new phage
There are resonances in this story of an earlier Canadian. Felix d'Herelle was a self-taught microbiologist, later nominated for a Nobel prize for his work on phages.