Figure 1.2: The basics compound of cellulose is cellubiose, disaccharides of two β- 1-4 bonded glucoses 2.2.2 Hemicelluloses Hemicelluloses are heterogeneous polymers of pentoses (xylose, arabinose), hexoses (mannose, glucose, galactose) and sugar acids. In hardwood hemicelluloses mostly contains xylan, whereas softwood hemicelluloses contains mostly glucomannans. Xylan of many plant materials are heteropolysaccharides with homopolymeric backbone chains of 1,4-linked units. The β-D-xylopyranose monosaccharides released upon hemicellulose hydrolysis include a large fraction of pentoses (Gunda 1970). et al., In several plants the majority of hemicelluloses is xylan which can be hydrolyzed into xylose. Particularly the hemicellulose of hardwood is rich in xylan. Consequently it is possible to obtain xylan and xylose as by-products from cellulose industry using hardwood (Gunda 1970). et al., Figure 1.3 the structure of xylan and enzymes cleavage site. The complex structure of xylan needs different enzymes to complete its hydrolysis. The main enzyme that randomly hydrolysis the main chain of xylan to produce mixture xylooligosaccharides named as endoxylanase and will liberate xylose β-xylosidase from short oligosaccharides. Moreover, the sides groups presents in xylan are liberated
Figure 1.2: The basics compound of cellulose is cellubiose, disaccharides of two β- 1-4 bonded glucoses 2.2.2 Hemicelluloses Hemicelluloses are heterogeneous polymers of pentoses (xylose, arabinose), hexoses (mannose, glucose, galactose) and sugar acids. In hardwood hemicelluloses mostly contains xylan, whereas softwood hemicelluloses contains mostly glucomannans. Xylan of many plant materials are heteropolysaccharides with homopolymeric backbone chains of 1,4-linked β-D-xylopyranose units. The monosaccharides released upon hemicellulose hydrolysis include a large fraction of pentoses (Gunda et al., 1970). In several plants the majority of hemicelluloses is xylan which can be hydrolyzed into xylose. Particularly the hemicellulose of hardwood is rich in xylan. Consequently it is possible to obtain xylan and xylose as by-products from cellulose industry using hardwood (Gunda et al., 1970). Figure 1.3 the structure of xylan and enzymes cleavage site. The complex structure of xylan needs different enzymes to complete its hydrolysis. The main enzyme that randomly hydrolysis the main chain of xylan to produce mixture xylooligosaccharides named as endoxylanase and β-xylosidase will liberate xylose from short oligosaccharides. Moreover, the sides groups presents in xylan are liberated
CD5904_MOHD_SHAHRIL_MUSTAFA.docx