FRACTIONAL EXTRACTION AND PHYSICOCHEMICAL CHARACTERIZATION OF HEMICELLULOSES AND CELLULOSE FROM SUGAR-BEET PULP

Four hemicelluloses and cellulose fractions were extracted with 10% KO H or 7.5% NaOH at 15 degrees C for 16 h and with 24% KOH or 17.5% NaOH at 15 degrees C for 2 h from defatted, protein and pectin free, ligni fied or delignified sugar beet pulp (SBP). There was no significant di fference in the yield and sugar composition of isolated hemicelluloses and cellulose obtained from four different procedures. 7.5% NaOH extr action at 15 degrees C for 16 h from lignified SEP gave a slightly hig her yield of hemicelluloses (10.96%), while 24% KOH extraction at 15 d egrees C for 2 h from delignified SEP produced the highest yield of ce llulose (18.35%). Molecular-average weights ranged from 88 850 to 91 3 30 Da for the hemicelluloses obtained from lignified SEP, and 21620-21 990 Da for the hemicelluloses isolated from delignified SBP. The neutr al sugar composition of the hemicelluloses consisted of glucose, arabi nose, galactose, xylose, and minor quantities of rhamnose and mannose. The infrared spectra showed an absorption band at 900 cm(-1), indicat ing some amounts of beta-linked polysaccharides. Besides ferulic and p -coumaric acids, six other phenolics were also identified in the mixtu re of alkaline nitrobenzene oxidation of associated lignin in the isol ated hemicelluloses and cellulose fractions. (C) 1998 Elsevier Science Ltd. All rights reserved.