Removing Lignin from Wood with White-Rot Fungi and Digestibility of Resulting Wood

Nine white-rot fungi were examined for their ability to remove lignin faster than they removed polysaccharides from aspen and from birch wood. One of the fungi was similarly examined with southern pine, Douglas-fir, and Sitka spruce. During decay most of the fungi decreased the lignin content of the aspen and the birch; that is, they removed a larger percentage of the lignin than of the polysaccharides. Lignin removal was always accompanied by removal of polysaccharides, but lignin removal did not correlate with removal of any particular component of the polysaccharides. During decay lignin was usually more selectively removed in the first few percentages of weight loss than were the polysaccharides. Fomes ulmarius removed lignin faster from southern pine, Sitka spruce, aspen, and birch than it did from Douglas-fir. The decayed woods with less lignin were more digestible by a mixture of polysaccharidases and by rumen fluid than were the control samples. Digestibility was inversely related to lignin content.