Application of microbial α-amylase in industry - A review

Abstract

Amylases are one of the main enzymes used in industry. Such enzymes hydrolyze the starch molecules into polymers composed of glucose units. Amylases have potential application in a wide number of industrial processes such as food, fermentation and pharmaceutical industries. α-Amylases can be obtained from plants, animals and microorganisms. However, enzymes from fungal and bacterial sources have dominated applications in industrial sectors. The production of α-amylase is essential for conversion of starches into oligosaccharides. Starch is an important constituent of the human diet and is a major storage product of many economically important crops such as wheat, rice, maize, tapioca, and potato. Starch-converting enzymes are used in the production of maltodextrin, modified starches, or glucose and fructose syrups. A large number of microbial α-amylases has applications in different industrial sectors such as food, textile, paper and detergent industries. The production of α-amylases has generally been carried out using submerged fermentation, but solid state fermentation systems appear as a promising technology. The properties of each α-amylase such as thermostability, pH profile, pH stability, and Ca-independency are important in the development of fermentation process. This review focuses on the production of bacterial and fungal α-amylases, their distribution, structural-functional aspects, physical and chemical parameters, and the use of these enzymes in industrial applications.

Keywords: bacterial and fungal amylase; enzyme production; starch; α-Amylases.

Figure 1

Structure α-amylase. Domain A is shown in red, domain B in yellow and domain C in purple. In the catalytic center, the calcium ion is shown in the blue sphere and the chloride ion in the yellow sphere. The green structures are bound to the active site and to the surface binding sites (62).

Figure 2

Two types of glucose polymers are present in starch: amylose (A) is a linear polymer consisting of up to 6000 glucose units with α-1,4 glycosidic bonds (56) and amylopectin (B) consists of short α-1,4 linked to linear chains of 10–60 glucose units and α-1,6 linked to side chains with 15–45 glucose units (56).