Elimination and detoxification of softwood extractives by white-rot fungi

The ability of several white-rot fungal strains to remove and detoxify acet one extractives (pilch or resin) in Scots pine sapwood was investigated in stationary laboratory batch assays. Fungal pretreatment provided up to 62% total pitch reduction and significant decreases in pitch toxicity. The best strains were Bjerkandera sp, strain BOS55, Stereum hirsutum and Trametes v ersicolor that eliminated over 93% of the problematic triglyceride fraction and 58-87% of other lipophilic extractive classes in only 2 weeks. Fungal removal of the wood extractives was accompanied by a 7.4-16.9-fold decrease in their inhibitory effect, as determined in the Microtox bioassay. Wood p retreatment by Bjerkandera sp. and T. versicolor caused limited losses of w oody mass (less than 4% in 4 weeks); whereas S. hirsutum led to somewhat hi gher mass losses (7% in 4 weeks). These results indicate the potential of w hite rot fungi to control pitch deposition problems in pulping and to reduc e the aquatic toxicity caused by naturally-occurring lipophilic extractives in forest industry effluents. (C) 2000 Elsevier Science B.V. All rights re served.