Gessesse, Amare (PhD)Gashaw, Metages2021-04-012023-11-082021-04-012023-11-082008-08-06http://etd.aau.edu.et/handle/123456789/25883Starch is a major reserve carbohydrate of all higher plants. In some cases it accounts 70% of the wet weight of plant material. It occurs in the form of water insoluble granules. The size and shape of the granules are often characteristic of the plant species from which they are extracted. When heated in water the hydrogen bonds holding the granules together begin to weaken and this permits them to swell and gelatinize. Ultimately they form paste or dispersion, depending on the concentration of polysaccharide (Prasanna, 2005). Starches are produced commercially from the seeds of plants, such as corn, wheat, sorghum or rice; from the tubers and roots of plants such as cassava, potato, arrowroot and the pith of sago palm. The major commercial source of starch is corn from which it is extracted by a wet milling process (Crab, et al., 1997). Starch is a heterogeneous polysaccharide composed of two high molecular weight entities called amylose and amylopectin which are differ in structures and physical properties. The insoluble amylose, composed of linear chains of α-1, 4 linked D-glucose residues can be separated from soluble amylopectin fraction by addition of a polar solvent, e.g. n-butanol. Even if amylose has a degree of polymerization of several thousands of glucose units, because of the molecular shape and structure, it is not stable in aqueous solution and retrogrades (precipitates spontaneously) this is because linear chains align themselves by hydrogen bonding and thus forms aggregates. Due to its molecular shape amylose has also considerable viscosity in alkaline solutions and forms complex with iodine to form intense blue color and this forms the basis of a method for quantitative determination of amylose. Amylopectin accounts for 75 to 85% of most starches. It has molecular weight of 107 – 108 and has a branched structure composed of chains of about 20 – 25 α-1,4 linked D-glucose residues. Amylopectin which is branched by α-1,6 linkages may contain 4 to 5% α-1,6-D-glucosidic bonds. In aqueous solutions, amylopectins are relatively stable due to branched molecules and are not able to form compact aggregates (Fogarty and Kelly, 1990).enIdentificationCharacterization of Raw StarchDegrading Β-AmylaseEndophyticBacillusSpeciesThesis