Lignin Research Paper Example | Topics and Well Written Essays - 2750 words

Lignin - Research Paper Example de Candolle. His explanation about lignin was that it is a fibrous material that does not have any taste, it cannot be dissolved in water or alcohol but is soluble in weak alkaline solutions, and in order extract it from the solution an acid could be added to it which would cause its precipitation. Lignin is among the most commonly found organic polymers, and only cellulose and hemicelluloses is ahead of it regarding abundance (Shi, Xiao, Deng, & Sun, 2013). Thus, lignin forms the majority of the natural resources that man has. 30% of non-fossil organic carbon is made up of lignin while making up almost one-fourth to third of the dry mass of wood. Every species contains a unique type of lignin, the difference lying in its composition. Since lignin is a biopolymer, it attains its uniqueness owing to its heterogeneity and because it does not really have a properly defined primary structure. The most important and common function of lignin is to strengthen wood in trees, which is made from xylem cells, by providing it with support. The natural state of lignin as present within a plant is known as protolignin (Kutscha & Gray, 1970). The classification of lignins depends on their structural elements. Softwoods, hardwoods and grasses contain different lignins and the reason behind the difference between the three is the different content of guaiacyl (G), syringyl (S) and p-hydroxyphenyl (H) units. Guaiacyl lignin is present in the majority of softwoods and is mainly a polymerization product of coniferyl alcohol. Hardwoods typically contain the guaiacyl-syrinngyl lignin which is a copolymer of coniferyl and sinapyl alcohols, the ration varying from 4:1 to 1:2 for the two monomeric units (Pereira, Portugal-Nunes, Evtuguin, Serafim, & Xavier, 2013). Another type is that of compression wood that is largely made up of phenylpropane units of the p-hydroxyphenyl type along with the usual guaiacyl units. At times the term syringyl lignin and p-hydroxyphenyl lignin