Using copper-tolerant fungi to biodegrade wood treated with copper-based preservatives

Within the United States, the volume of wood products that was treated with copper-based preservatives grew exponentially during the 1970 s and 1980 s and remains at a high level today. Ultimately, these materials will have to be reused, recycled, or disposed in an environmentally acceptable manner. We are exploring whether copper-tolerant fungi might have utility in bioprocessing spent, treated wood after it is withdrawn from service. In laboratory experiments, Southern Pine sapwood was treated with copper-based wood preservatives, then challenged with wood decay fungi known to be tolerant of copper. For each preservative, fungal isolates were assessed for their potential to reduce the bulk of the treated product, as observed by weight loss. Low retention levels of some preservatives stimulated decay by Wolfiporia cocos, but not Postia placenta. Isolates of the copper-tolerant fungus Wolfiporia cocos (Schw syn. Poria cocos) varied significantly in their ability to degrade wood treated with copper-bearing preservatives and to concentrate copper in the mycelium. Copper was bioaccumulated (w/w basis) in mycelium of some isolates harvested from decayed wood, but the concentration of copper in the decayed wood residue was generally similar or only slightly different from that in the wood before decay.