Biodegradability of extractives in sapwood and heartwood from Scots pine by sapstain and white rot fungi

The fungal degradation of lipophilic extractives in sapwood and heartwood f rom Scots pine (Pinus sylvestris) was studied. In sapwood, the white rot fu ngi, Bjerkandera sp. and Funalia trogii, removed higher amounts of extracti ves than the sapstain strains, Ophiostoma ainoae and Ceratocystis allantosp ora. Triglycerides, long chain fatty acids, steryl esters and waxes in pine sapwood were almost completely degraded by all the fungi. Sterols and resi n acids were also extensively degraded by the white rot strains; however, t hese components were not or only poorly removed by the sapstain fungi. The removal of total extractives by all the fungal strains was higher in sapwoo d as compared to heartwood. The highly concentrated extractive fraction in pine heartwood mainly consists of resin acids. As observed in sapwood, saps tain were also poorly effective in the degradation of the resin acids prese nt in heartwood. The fungal degradation of heartwood extractives was not on ly limited by the degradative ability of the various test microorganisms, b ut also by the inhibitory effect exerted by the extractive fraction. The wh ite rot fungus F. trogii was particularly inhibited on heartwood. Bjerkande ra sp. showed a higher tolerance to toxic extractives and was the most effi cient fungus in degrading extractive constituents in both Scots pine heartw ood and sapwood. Therefore, Bjerkandera sp. strain BOS55 should be consider ed as a potential agent for pitch control in pulp and paper manufacture.