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Ravening Fungus Eats Toxic Waste!!

A common woodland fungus with an amazing ability to gobble up toxic substances may be a clean, green way to solve a major environmental problem.

There are more than 8,000 sites in this country listed as having toxic chemicals in the soil -- an estimated 800 alone being the legacy of old timber mill practices. The clean-up operations are expensive, may involve more chemicals and removal of tonnes of soil to landfill sites.

But HortResearch scientists are working on a way to do the job that is environmentally friendly and cheaper, using white-rot fungus, which has an appetite for pollutants such as PCPs used in timber treatment, one of the most common groups of soil contaminants in New Zealand.

White-rot fungi, found just about everywhere there is dead wood, can degrade PCPs by using unique enzyme systems. Sites overseas have already been successfully decontaminated by adding white-rot fungus to the soil.

Monika Walter of HortResearch's Environment and Risk Management Group, is trying to identify New Zealand strains of the fungus, to avoid the uncertainties involved in introducing a foreign variety.

"These enzymes, evolved for lignin breakdown, can tackle a wide range of complex organic substrates, including persistent man-made chemicals. Very few other living organisms can do this," she says.

The fungi are incorporated into the polluted environment on a growing medium such as wood chips, sawdust, corn cobs or other agricultural wastes. The growth substrate is needed to keep them alive, as they don't occur naturally in soil.

"The fungi secrete enzymes which gobble up all the pollutants in their way, effectively clearing the environment wood of harmful substances ready for the fungi and other microorganisms to use. Once the growth substrate is depleted the fungi will die, allowing the naturally occurring soil organisms to recolonise the soil habitat," she adds.

So far 20 fungi have been laboratory tested using three different levels of soil contamination, and four particularly promising ones have been identified. Bark, sawdust, apple pomace and maize products have been used as growing media for the fungi, with moderate success. Now more work is needed to optimise the system under lab conditions and then to move the fungi "into the field".