Utilización de hongos ligninolíticos para el control del pitch en la industria papelera

This research investigated the ability of two different white-rot fungi, Bjerkandera sp. and Trametes versicolor, to reduce the lipid fraction (resin or extractives) in industrial chips of Scots pine (Pinus sylvestris) as well as in the pulps and effluents obtained upon mechanical pulping of the biotreated chips. Wood lipids are known to cause pitch problems in pulp and paper manufacturing that are characterized by the formation of troublesome deposits in manufacturing equipment, and spots and other quality defects in the paper sheet. Extractive components in wood chips and mechanical pulps were obtained by Sohxlet extraction with acetone, while the lipid fraction in pulping effluents was isolated by liquid-liquid extraction with tertbutylmethylether. The lipophilic extractives were then analyzed by HPLC. Fungal treatment of the wood chips during four weeks resulted in extensive degradation 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 pulp and 84% in effluents; while their removal by Bjerkandera sp. was 83% in chips, 100% in pulp and 57% in the effluents. In addition, both strains cause substantial reduction in the level of fatty acids, that are among the pitch constituents contributing to effluent toxicity. In contrast with these results, and in spite of the high levels of resin acid degradation attained in previous studies conducted in our laboratory with pine wood meal, the reduction of these inhibitory extractives during the treatment of industrial wood chips by Bjerkandera sp. and T. versicolor was low.