Microbial polysaccharides and their classification: a brief study on fundamental biochemical properties

Microbial polysaccharides are typical poly-carbohydrates those are abundant in many types of microorganisms. Because of their poly-carbohydrate nature microbial polysaccharides consist of long chain polymeric carbohydrates composed of monosaccharide units joined by glycosidic linkages. These microbial polysaccharides have high molecular weight and react with water by using amylase enzymes as catalyst. However, microbial polysaccharides are water soluble biopolymers but their rheological characteristics make them act like binders, coagulants, emulsifiers, biofilms, hydrogels, lubricants, stabilizers and thickening or suspension molecules. Microbial polysaccharides are derived from different microorganisms like bacteria, yeast, fungi and algae. Some of the examples of microbial polysaccharides are Gellan gum, Xanthan gum, Scleroglucan, Pullulan, Hyaluronic acid, Fucogel, Cholanic acid, Alginic acid, Bacterial cellulose, Dextran, Curdlan, Levan polysaccharide etc. Microbial polysaccharides are non-toxic modules with diverse physical properties such as, viscosity, mechanical strength, elasticity and biocompatibility. Bacterial polysaccharides are obtained from several species of bacteria including Alcaligenes sp, Agrobacterium sp, Rhizobium sp, Bacillus sp, Cellulomonas sp, Bifidobacterium sp, Streptococcus sp, Klebsiella sp, Enterococcus sp, Staphylococcus sp, etc. Microbial polysaccharides are classified into three main categories: capsular polysaccharides (CPSs), lipopolysaccharides (LPSs) and exopolysaccharides (EPSs). According to morphological localization microbial polysaccharides can be divided as intracellular and extracellular polysaccharides. On the basis of structural formation, polysaccharides which contains only one kind of monosaccharide unit are called homo-polysaccharides. Similarly, polysaccharides consisting two or more types of mono-saccharides are called hetero-polysaccharides. Such as, cellulose, dextran and pullulan are homo-polysaccharides and xanthan and hyaluronic acid are known as hetero-polysaccharides.