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Difference between revisions of "Enzymatic processes"
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=== Origin and composition === | === Origin and composition === | ||
Lignocellulosic biomass (LCB) can be collected as a waste material from forest residues, agricultural, and industrial activities. LCB is mainly characterized by the presence of two carbohydrate polymers, namely cellulose and hemicellulose, as well as an aromatic polymer called lignin. Other components in LCB, found in smaller amounts, are ash, pectin, and proteins. The percentage content of celluloce, hemicelllulose, and lignin are varied among different lignocellulosic materials. In general, the content of cellulose, hemicellulose, and lignin in LCB is in the range of 30-60%, 20-40%, and 15-25%, respectively.<ref>{{Cite journal|author=Sawatdeenarunat, C., Surendra, K., Takara, D., Oechsner, H., Khanal, S.K.|year=2015|title=Anaerobic digestion of lignocellulosic biomass: challenges and opportunities|journal=Bioresour. Technol.|volume=178|page=178-186|doi=10.1016/j.biortech.2014.09.103}}</ref> | Lignocellulosic biomass (LCB) can be collected as a waste material from forest residues, agricultural, and industrial activities. LCB is mainly characterized by the presence of two carbohydrate polymers, namely cellulose and hemicellulose, as well as an aromatic polymer called lignin. Other components in LCB, found in smaller amounts, are ash, pectin, and proteins. The percentage content of celluloce, hemicelllulose, and lignin are varied among different lignocellulosic materials. In general, the content of cellulose, hemicellulose, and lignin in LCB is in the range of 30-60%, 20-40%, and 15-25%, respectively.<ref>{{Cite journal|author=Sawatdeenarunat, C., Surendra, K., Takara, D., Oechsner, H., Khanal, S.K.|year=2015|title=Anaerobic digestion of lignocellulosic biomass: challenges and opportunities|journal=Bioresour. Technol.|volume=178|page=178-186|doi=10.1016/j.biortech.2014.09.103}}</ref> | ||
[[File:Composition-of-the-plant-cell-wall.png|thumb|Composition of the plant cell wall]] | |||
==== Structural features ==== | ==== Structural features LCB: ==== | ||
===== Cellulose ===== | ===== Cellulose ===== | ||
Cellulose is a polysaccharide polymer of glucose disaccharide units, cellobiose, linked tightly by ß-1,4-glycoside bonds. Cellulose molecules are linked by hdyrogen bonds and have different orientations resulting in different levels of crystallinity. Its crystallinity plays a crucial role in the biodegradation of cellulose and in general the higher crystallinity level makes it harder to biodegrade the cellulose. | |||
===== Hemicellulose ===== | ===== Hemicellulose ===== | ||
Hemicellulose is a random and branched heterogeneous polymer of different polysaccharides including pentoses (xylose and arabinose), hexoses (glucose, galactose, and mannose) and sugar acids. The branched nature of the hemicellulose allows it to form strong bonds with cellulose (through hydrogen bonds) and lignin (through covalent bonds). | |||
===== Lignin ===== | ===== Lignin ===== | ||
Lignin is a complex and large compound made out of phenylpropane units linked in a three-dimensional structure. The main monomers of lignin are p-hydroxyphenyl alcohol, coniferyl alcohol, and sinapyl alcohol. Lignin acts as a cementing material that links celluose and hemicellulose to from the rigid three-dimensional structure of the plant cell wall. | |||
=== Pre-treatment === | === Pre-treatment === | ||