Starch Hydrolysis Test- Objectives, Principle, Procedure, Results


Starch is one of the most abundant and important carbohydrates in nature. It is a major source of energy for many living organisms, including humans. However, not all organisms can utilize starch directly. Some bacteria and fungi have the ability to break down starch into simpler sugars by producing enzymes called amylases. These enzymes catalyze the hydrolysis of the glycosidic bonds that link the glucose units in starch molecules. The hydrolysis products of starch are maltose, a disaccharide, and glucose, a monosaccharide. These sugars can then be transported into the cells and metabolized for energy or other purposes.

The starch hydrolysis test is a simple and widely used method to detect the presence and activity of amylases in microorganisms. The test is based on the principle that starch forms a dark blue complex with iodine, while the hydrolysis products of starch do not. Therefore, if an organism produces amylases and hydrolyzes starch in the medium, a clear zone will appear around the colony after adding iodine solution. The size of the clear zone indicates the extent of starch hydrolysis by the organism.

The objectives of the starch hydrolysis test are:

  • To determine the ability of an organism to produce and secrete amylases that can hydrolyze starch.
  • To differentiate organisms based on their ability to hydrolyze starch with amylases.
  • To aid in the identification and classification of some bacterial and fungal genera and species that are known to produce amylases.

The starch hydrolysis test is useful for distinguishing between some members of the genera Corynebacterium, Clostridium, Bacillus, Bacteroides, Fusobacterium, and Enterococcus. It can also be used to identify some fungal species that produce amylases, such as Aspergillus and Penicillium.

The starch hydrolysis test is a simple, inexpensive, and reliable technique that can provide valuable information about the metabolic capabilities and taxonomic relationships of microorganisms. It can also be used to screen for potential industrial applications of amylases, such as in food processing, textile manufacturing, paper making, and biotechnology.