Isolation of hemicelluloses from sugarcane bagasse at different temperatures: Structure and properties

Seven hemicellulosic fractions were extracted with 10% KOH from delignified sugarcane bagasse for 10 h at 20, 25, 30, 35, 40, 45, and 50 degrees C, respectively. Chemical composition and structural features of all the fractions were investigated by a combination of HPAEC, GPC, FT-IR, 1D (H-1, C-13) and 2D (HSQC) NMR spectra, and TGA-DTA. Notable differences in the molecular weights were observed that the fractions extracted at 20 degrees C, 25 degrees C, and 30 degrees C showed relatively lower molecular weights (68, 400-76, 900 g mol(-1)) and the extraction at elevated temperatures from 35 to 50 degrees C yielded the hemicellulosic populations of somewhat higher M-W (80, 400-93, 300 g mol(-1)). However, the differences in the yield, chemical composition, structural features and thermal stability were much less pronounced in this study. The results also suggested that all the hemicellulosic polymers had a backbone of (1 -> 4)-beta-D-xylan and mainly substituted with (1 -> 2) and (1 -> 3)-linked arabinofuranosyl residues, and also with 4-O-methyl-D-glucuronic acid linked to O-2 of the backbone. (c) 2012 Elsevier Ltd. All rights reserved.