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Idealized structure of lignin from a softwood. Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. [1] Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily.
Lignin confers structural integrity to plants. Lignin is so heterogeneous and so recalcitrant that its value is almost exclusively measured as a fuel. hemicellulose is composed of branched polysaccharides. A particular problem is that hemicellulose is covalently linked to lignin, usually through ferulic acid component of the
Biopolymers can be sustainable, carbon neutral and are always renewable, because they are made from plant or animal materials which can be grown indefinitely. Since these materials come from agricultural crops , their use could create a sustainable industry.
The lignin is converted to lignosulfonates, which are soluble and can be separated from the cellulose fibers. For the production of cellulose, the sulfite process competes with the Kraft process which produces stronger fibers and is less environmentally costly. idealized scheme for lignin depolymerization by the Sulfite process.
The term "lignin characterization" (or "lignin analysis") refers to a group of activities within lignin research aiming at describing the characteristics of a lignin by determination of its most important properties. [1] Most often, this term is used to describe the characterization of technical lignins by means of chemical or thermo-chemical ...
Factors controlling the rate of degradation include percent crystallinity, molecular weight, and hydrophobicity. The degradation rate depends on the location in the body, which influences the environment surrounding the polymer such as pH, enzymes concentration, and amount of water, among others. These are rapidly decomposed. [8]
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.
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.
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