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One method of pretreatment is to soak the wood with diluted acids (with concentrations around 4%). This converts the hemicellulose into monosaccharides. When pretreatment is done with bases (for instance sodium or potassium hydroxide) this destroys the structure of the lignin. [20] This changes the structure from crystalline to amorphous.
Hemicelluloses (a heterogeneous group of polysaccharides) cross-link glycans interlocking the cellulose fibers and form a mesh like structure to deposit other polysaccharides. Xylan (/ ˈ z aɪ l æ n /; [3] / ˈ z aɪ l ən / [4]) (CAS number: 9014-63-5) is a type of hemicellulose, a polysaccharide consisting mainly of xylose residues.
The major constituents of natural fibers (lignocelluloses) are cellulose, hemicellulose, lignin, pectin and ash. The percentage of each component varies for each different type of fiber, however, generally, are around 60-80% cellulose, 5–20% lignin, and 20% of moisture, besides hemicellulose and a small percent of residual chemical components.
This process changes to the chemical structures of wood's cell wall components lignin, cellulose and hemicellulose which decreases its hygroscopy and thus increases dimensional stability. [1] Low oxygen content prevents the wood from burning at these high temperatures.
Xylose is the main building block for the hemicellulose xylan, which comprises about 30% of some plants (birch for example), far less in others (spruce and pine have about 9% xylan). Xylose is otherwise pervasive, being found in the embryos of most edible plants.
It is composed of two kinds of carbohydrate polymers, cellulose and hemicellulose, and an aromatic-rich polymer called lignin. [1] Any biomass rich in cellulose, hemicelluloses, and lignin are commonly referred to as lignocellulosic biomass. [2] Each component has a distinct chemical behavior.
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Xyloglucan is a hemicellulose that occurs in the primary cell wall of all vascular plants; however, all enzymes responsible for xyloglucan metabolism are found in Charophyceae algae. [ 1 ] [ 2 ] In many dicotyledonous plants, it is the most abundant hemicellulose in the primary cell wall. [ 3 ]