To Biodegrade, Or 'rot' To Biodegrade?
Researcher Adam Gusse and his colleagues at the University of Wisconsin have found a fungus capable of rotting the previously un-rottable - compounds called phenolic resins (PRs), the plastics used in the trims on car bodies, air filter housings and other heavy-duty automotive parts. They're made by heating phenol and formaldehyde (formalin) to high temperatures in the presence of catalysts which cause the molecules to link together in a three-dimensional lattice that is hard to break. But therein lies their weakness - these compounds, which were previously thought to be non-biodegradable, closely resemble the natural substance lignin, the hard part of wood. Since lignin is a popular food source for fungi, the researchers wondered whether the cocktail of lignin-busting enzymes produced by "white-rot" fungi might also be able to break down these phenolic resins. They incubated cultures of fungi with the plastic and looked for signs of degradation. In tests on 11 fungal isolates they found one strain, called Phanerochaete chryosporium, which was capable of digesting the phenolic resins. Under an electron microscope samples of the resins showed pits where they had been eroded by the fungal digestive juices. This suggests that it might be possible to use this technology to recycle the millions of tons of phenolic resins produced each year instead of dumping them in landfills.