Aim

To study the hydrolysis of starch by microorganisms by the production of the enzyme amylase.

Introduction

Starch is a polysaccharide found abundantly in plants, and is usually deposited in the form of large granules in the cytoplasm of the cell. Starch granules can be isolated from the cell extracts by differential centrifugation. Starch consists of 2 componentsamylase and amylopectin, which are present in various amounts. The amylase consists of D-glucose units linked in a linear fashion by ?-1,4 linkages. It has 2 nonreducing ends and a reducing end. Amylopectin is a branched polysaccharide. In these molecules, shorter chains of glucose units linked by ?-1,4 are also joined to each other by ?-1,6 linkages. The major component of starch can be hydrolyzed by ?-amylase, which is present in saliva and pancreatics juice and participates in digestion of starch in the gastrointestinal tract.

Principle

Starch is a polysaccharide made of 2 components, namely amylase and amylopectin. Amylose is not truly soluble in water, but forms hydrated micelle, which produces blue color with iodine. Amylose produces a characteristic blue color with iodine, but the halide occupy a position in the interior of a helical coil of glucose units. This happens when amylase is suspended in water. Amylopectin yields a micellar which produces a violet color with iodine.

Materials

• Petri plates

• Conical flasks

• Starch agar media

• Bacterial specimen

• Iodine

Procedure