Utilization of white-rot fungi for pitch control in pulp and paper manufacturing

This research investigated the ability of two different white-rot fungi, Bj erkandera sp. and Trametes versicolor, to reduce the lipid fraction (resin or extractives) in industrial chips of Scots pine (Pinus sylvestris) as wel l as in the pulps and effluents obtained upon mechanical pulping of the bio treated chips. Wood lipids are known to cause pitch problems in pulp and pa per manufacturing that are characterized by the formation of troublesome de posits in manufacturing equipment, and spots and other quality defects in t he paper sheet. Extractive components in wood chips and mechanical pulps we re obtained by Sohxlet extraction with acetone, while the lipid fraction in pulping effluents was isolated by liquid-liquid extraction with tertbutylm ethylether. The lipophilic extractives were then analyzed by HPLC. Fungal t reatment of the wood chips during four weeks resulted in extensive degradat ion of the extractive components associated with the formation of pitch in softwoods, chiefly triglycerides and diglycerides. The total elimination of these compound classes by T. versicolor averaged 86% in chips, 100% in pul p and 84% in effluents; while their removal by Bjerkandera sp. was 83% in c hips, 100% in pulp and 57% in the effluents. In addition, both strains caus e substantial reduction in the level of fatty acids, that are among the pit ch constituents contributing to effluent toxicity. In contrast with these r esults, and in spite of the high levels of resin acid degradation attained in previous studies conducted in our laboratory with pine wood meal, the re duction of these inhibitory extractives during the treatment of industrial wood chips by Bjerkandera sp. and T. versicolor was low.