When polyethylene terephthalate, or PET plastics, were invented in the 1940s, they revolutionized the manufacture of containers, and switched the world from heavy, breakable, biodegradable glass, to light-weight but sturdy, non-biodegradable plastic, and the planet was transformed. PET polymers make up nearly one-sixth of the world’s annual plastic production of 311 million tonnes. According to the World Economic Forum (WEF) only a little more than half of this is recycled, and even less is reused. 5gyres.org provides us with the first ever estimate of the amount of plastics just in the oceans: 270,000 metric tonnes. The ocean acts like a blender, breaking up the bags and bottles into smaller and smaller parts. There are chunks and bits of every size. Some are wandering solitarily, for a while, but eventually the currents whorl them into five vortices or gyres, and from space, they are recognizable as five islands of multi-coloured debris. To get a reference for just how much plastic this is, imagine stacking water bottles to the moon and back, twice! To date, very few species of fungi—but no bacteria—have been found to break down this polymer plastic.
But the journal Science has just published the research findings of a Japanese team, led by Dr. Kohei Oda from the Kyoto Institute of Technology and Dr. Kenji Miyamoto from Keio University, and their collaboration in the fields of chemistry and engineering has produced some very encouraging results. They collected 250 samples of PET debris from soil and wastewater, and screened them for bacterial candidates that depend on PET film as a primary source of carbon for their own growth. They identified Ideonella sakaiensis 201-F6, which could almost completely degrade a thin film of PET after six weeks at a temperature of 86 degrees Fahrenheit (30 degrees Celsius). In the results published by the Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Yoshida et al. show how the biodegradation of plastics by specialized bacteria could be a viable bioremediation (waste management) strategy. The team hopes the discovery will lead to new ways of breaking down plastic, using either the bacteria themselves, or the two enzymes they use for the job. It won’t cure the plastic problem, but it could be a land-and-sea change!
Publisher’s Note: Judith Stapleton is a writer in the fields of science and medicine.