Biomedical Engineering Reference
In-Depth Information
Chapter 2
Chemical Composition and Structure
of Natural Lignocellulose
Abstract
The wide variety of natural cellulosic materials has complex and uneven
components. Cellulose, hemicellulose, and lignin comprise the main composition
of cell walls of plants and are important components of natural lignocellulosic
materials. Cellulose molecules determine the cell wall framework, and pectin is
located between the cellulose microfilaments of the cell wall. In addition, cellulosic
materials contain rich cell wall protein, pigment, and ash. Understanding of the
chemical composition and structure of natural lignocellulosic materials, characteris-
tics of each component, and interrelationships between various components would
contribute to the research and development regarding natural cellulose materials.
This chapter mainly describes the chemical composition and structure of natural
cellulosic materials.
Keywords
Cellulose • Hemicellulose • Lignin • Cell wall protein • Biological
properties
2.1
Main Components of Natural Lignocellulosic Materials
Cell walls of plants consist mainly of three organic compounds: cellulose, hemicel-
lulose, and lignin. These compounds are also major components of natural ligno-
cellulosic materials. Cellulose molecules arrange regularly, gather into bundles, and
determine the framework of the cell wall. Fibers are filled with hemicellulose and
lignin. The structure of the plant cell wall is compact. There is different bonding
among cellulose, hemicellulose, and lignin. Cellulose and hemicellulose or lignin
molecules are mainly coupled by a hydrogen bond. In addition to the hydrogen
bond, there is the chemical bonding between hemicellulose and lignin, which results
in the lignin, isolated from natural lignocelluloses, always contains a small amount
of carbohydrates. The chemical bonds between the hemicellulose and lignin mainly
refer to the chemical bonds between galactose residues, arabinose residues on the
side chains of hemicellulose molecules and lignin, and carbohydrates, with this
