Characterization Of Hemicellulose Structures That Affect Biomass Degradation In Energy Plants

Hemicelluloses constitute nearly a third of the biomass, only slightly less than cellulose. The composition of hemicelluloses varies from one cell type to another and among plant species. According to the cell wall models that are created to illustrate how wall polymers are organized in higher-order structures, cellulose microfibrils were coated with several sheaths, with the hemicelluloses and lignin forming the most tightly bound sheath. When considering wall materials for the production of biofuels, one should be aware that the pretreatments for hemicelluloses are quite critical. In order to find out the crucial factors that determine the wall polysaccharides'degradation, I analyzed the structure and composition of hemicelluloses extracted from rice and Miscanthus,Analysis of KOH-soluble and KOH-insoluble hemicelluloses:These results suggested that 4.0mol/L KOH can only extract 80% of the total hemicelluloses. The rest are closely associated with the components in the residues. The composition of hemicelluloses varies between rice and Miscanthus, the KOH-soluble hemicelluloses in rice is about two-thirds of that in Miscanthus. The structure of hemicelluloses is also different between KOH-soluble and KOH-insoluble hemicelluloses. In terms of the KOH-soluble hemicelluloses, the percentage composition of xylose is 85%, while it is only 70% in KOH-insoluble ones, indicating that KOH-soluble hemicelluloses have less side chains than KOH-insoluble hemicelluloses.Fermentation of 4.0mol/L KOH treated residues:These results implied that, after 4.0mol/L KOH treatment, the residue fermentation ratio decreased as the percentage composition of xylose increased. It suggests that the side chains of KOH-insoluble hemicelluloses affect residues'fermentation.Test of cellulose crystallinity:The crystallinity of cellulose was determined by X-ray diffraction. The results indicate that, the crystallinity of cellulose was decreased with the increasing in xylose's percentage composition. It may also suggested that the side chains of hemicellulose were tightly associated with the microfibrils.Determination of lignin composition:Composition of lignin was determined using HPLC. Three monomers G, S. H have a remarkable difference in different samples. There is no significant correlation between fermentation ratio and lignin composition.