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