Occurrence, distribution, and structure of natural polysaccharides

Abstract Polysaccharides, as the name implies, are comprises of monosaccharide residues connected by glycosidic bonds. The average number of monosaccharide units in polysaccharides varies from about 10 to perhaps 10 million. Depending upon the nature of the monosaccharide unit, polysaccharides are classified as linear or branched chain polysaccharides which determine the diversity and complexity of the polysaccharides. Branches may be short saccharide units on a linear backbone or the molecule may have a branch-on-branch structure. All polysaccharides are polydisperse, i.e., are present in a range of molecular weights rather than having a single molecular weight. They are the most abundant natural biopolymer derived from multiple natural resources such as plants, animals, bacteria, fungi, algae, arthropods etc. Polysaccharides possess unique chemical, physical and biological properties. They are not only an important component of energy and structural components but also serve a variety of biological functions. Polysaccharides possess a number of reactive functional groups in their chemical structure, including hydroxyl, amino, and carboxylic acid groups, indicating the possibility for chemical modification. The aim of this chapter is to summarize the natural occurrence, distribution and the multifaceted structures of polysaccharides.