CHANGE OF RICE STRAW LIGNIN WITH NAOH OXY GEN PULPING .6. CARBOHYDRATES IN LIGNIN FRACTIONS OXIDIZED WITH NAOH OXYGEN

NaOH-oxygen pulping of rice straw and NaOH-oxygen oxidations of milled lignins from rice straw (MRL), Japanese beech (Fagus crenata B1.) (MJ L) and Yezo spruce (Picea jezoensis Carr.) (MYL) were conducted in a s eries of studies. Fractions containing carbohydrates were isolated fro m the oxidized samples to study their characteristics. For the NaOH-ox ygen pulping of rice straw, it is likely that the carbohydrates in the lignin recovered from soaking spent liquor had a greater arabinoglucu ronoxylan portion, and those in the lignin from pulping spent liquor h ad a relatively larger hexose portion. For the non-stirred NaOH-oxygen oxidation of the milled lignins, the fractions from MRL and MJL conta ined much arabinoxylan with long sugar chains. In contrast, sugar chai ns from MYL were short. For the stirred NaOH-oxygen oxidation of the m illed lignins, the carbohydrate portions in them were oxidized and dec omposed into mono- and oligo-glycosyl residues. The fraction from MRL contained an overwhelming majority of xylose residue.