Oxalic acid production and metal removal during fungal degradation of CCA-treated wood in nutrient culture

The objective of this study was to evaluate characteristics of oxalic acid (OA) production and metal removal during degradation of CCA-treated wood in nutrient culture by brown-rot fungi. Two brown-rot fungi, Crustoderma sp. and Fomitopsis palustris extensively degraded the CCA-treated wood, causing mass losses (MLs) up to 49.0% and 43.5%, respectively, while these fungi produced OA during degradation up to 21.3 mg g^-1 and 43.8 mg g^-1, respectively. Antrodia vaillantii and Polyporales sp. produced OA up to 28.9 mg g^-1 and 29.8 mg g^-1, respectively, with < 3% ML. Fomitopsis palustris with the highest OA production removed effectively 87.5% As and 86.0% Cr during degradation of the treated wood. Antrodia vaillantii and an unknown Polyporales sp. showed notable As removal rates of 90.3% and 88.9%, respectively, and 81.0-83.9% Cr removal. However, only moderate amounts of Cu (40.8%) were extracted by the fungi investigated. The conclusion is that OA production by brown-rot fungi can be partially associated with removal of Cr and As during fungal degradation of CCA-treated wood.