microorganisms synthesize polysaccharide by the polymerization reaction of monosaccharide repeating unit as shown in figure 9 . The constiuent monosaccharide unit are joined by alfar or bata glucosidic linkges with loss of molecule of water (Mcllrol, 1967) .polysaccharide and their derivatives are collectively celled "gum" act as energy reserver and as structural materals in cell walls and in extracellular capsules or slime