Radical Formation on Laccase Treatment of Softwoods defibrated at high temperatures. II. Studies with softwood fibers

摘要

Norway spruce and Scots pine were defined at high temperatures (171-202 deg) and the resulting fibers were extracted with water. The unextracted fibers, fiber water-extracts and water-extracted fibers were treated with laccases to study the effect of defibration temperature on the formation of phenoxy radicals and to identify the reactive fiber components. The effect of laccase treartment on the unextracted and water-extracted fibers was studied by quantification of radicals on laccase-treated fibers by ESR spectrometry and by measuring the oxygen (O_2) uptake during the treatments. Radical formation on the unextracted fibers increased with an increase in defibration temperature and content of water-extractable aromatic substances, whereas the water-extracted fibers were far less reactive than the corresponding unextracted fibers. Part of the radicals on laccase-treated fibers decayed by second-order reactions on heat treatment at 100 deg. Oxygen consumtion measurements showed that the fiber water-extracts, accounting for 6-16% of the unextracted fibers, were responsible for 50-70% of the fiber oxygen consumption.