<Original>Microwave Irradiation of Lignocellulosic Materials : VIII. Microwave Irradiation of the Neutral Fraction (C-I-M) of Pine Bjorkman LCC

Abstract

Effect of microwave irradiation on the partially acetylated galactoglucomannan bearing a small amount of lignin (C-I-M) isolated from pine Bjorkman LCC was investigated. When the native C-I-M was heated above 180℃ by microwave irradiation in the presence of water, its carbohydrate portion was hydrolyzed into oligosaccharides having d.p. of 2-5 and monosaccharides. The degree of depolymerization of carbohydrates strongly depended upon the heating temperature and did not reach a maximum below 237℃, at which the reducing sugar content attained to 45.7%. The lignin molecules precipitated during microwave irradiation and a substancial amount of their, β-0-4 linkages were splitted. The lignin-carbohydrate bondings were also splitted at the heating temperature above 230℃. The hydrolysis of the carbohydrate portion of C-I-M was found to be remarkably enhanced by addition of 0.5% acetic acid during microwave irradiation. In this case, the reducing sugar production showed a maximum (74.2%) at about 210℃. Acetic acid was an excellent reagent for enhancement of the extent of depolymerization of galactoglucomannan in C-I-M.