Using a sterile technique, make a single streak inoculation of organism to be tested into the centre of labeled plate.Peptic digest of animal tissue 5.000, Sodium chloride 5.000, Yeast extract 1.500, Beef extract 1.500 Starch, soluble 2.000 Agar 15.000 Final pH ( at 25☌) 7.4☐.2 Method Agar is the solidifying agent and starch is the carbohydrate. Beef extract and pancreatic digest of gelatin provide nitrogen, vitamins, carbon and amino acids. Starch agar is a simple nutritive medium with starch added. Since no color change occurs in the medium when organisms hydrolyze starch, iodine solution is added as an indicator to the plate after incubation. While the non-hydrolysed starch forms dark blue color with iodine, its hydrolyzed end products do not acquire such dark blue color with iodine.Ĭonsequently, transparent clear zones are formed around the colonies that hydrolyze starch while the rest of the plate show a dark blue coloration as iodine forms the colored complex with starch. If the bacteria have the ability to hydrolyze starch, it does so in the medium, particularly in the areas surrounding their growth while the rest of the area of the plate still contain non-hydrolysed starch. In the starch hydrolysis test, the test bacteria are grown on agar plates containing starch. In this manner, nutrient sources, such as starch, that are too large to be absorbed through the cell membrane can be broken down into smaller molecules and transported into the cell via diffusion. Many bacteria produce extracellular enzymes used to catalyze chemical reactions outside of the cell. To differentiate organism based on their α- amylase enzyme activity.To determine the ability of an organism to hydrolyze starch.The ability to degrade starch is used as a criterion for the determination of amylase production by a microbe.The major component of starch can be hydrolyzed by a-amylase, which is present in some bacteria while well known in case of fungi.In these molecules, shorter chains of glucose units linked by α-1,4 are also joined to each other by α-1,6 linkages. Amylopectin is a branched polysaccharide.It has 2 non-reducing ends and a reducing end. The amylose consists of D-glucose units linked in a linear fashion by α-1,4 linkages.Starch consists of 2 components-amylose and amylopectin, which are present in various amounts.Starch is a complex polysaccharide found abundantly in plants and usually deposited in the form of large granules in the cytoplasm of the cell.

Gelatin hydrolysis test