Studies on the macromolecular components of nonwood available in Bangladesh

The structural feature of macromolecular component of dhaincha, cotton stalks, jute fiber, rice straw and wheat straw, which are commonly used in paper pulp production in forest deficient countries, was thoroughly studied. Lignin was isolated by classical Bjorkman method and characterized by elemental and methoxyl analysis, alkaline nitrobenzene oxidation, FTIR and H-1 NMR spectroscopy. The C-9 formulas for cotton stalks, jute fiber, dhaincha, rice straw and wheat straw were C9H8.95O3.53(OCH3)(1.00),C9H8.12O4.03(OCH3)(1.65), C9H8.10O4.65(OCH3)(1.32), C9H8.58O3.74(OCH3)(1.23) and C9H8.31O3.54(OCH3)(1.23), respectively. The alkaline nitrobenzene oxidation products showed that syringyl to vanilin ratio of these nonwood varied from 1.1 to 2.9. Jute fiber showed the highest syringyl to vanilin ratio that are consistent with C-9 formula. The beta-O-4 units in these nonwood lignins had predominately erythro stereochemistry type. The crystalline structure of these nonwood cellulose was also studied using X-ray diffraction and FTIR spectroscopy. The proportions of crystallinity, crystal size were varied from plant to plant. jute fiber showed the highest proportion of crystallinity (73.4%) and crystal size (4.2 nm). The degree of polymerization of these nonwoods cellulose has also been studied. Degree of polymerization of jute cellulose was also the highest (3875). FTIR spectroscopy showed that these nonwoods cellulose was monoclinic unit cell structure (I-beta). Carbohydrate analysis showed that the main sugar component in the hydrolyzates of these nonwoods were xylose apart from glucose. (C) 2009 Elsevier B.V. All rights reserved.