Bacterial and Archaeal α-Amylases: Diversity and Amelioration of the Desirable Characteristics for Industrial Applications

Deepika Mehta,Tulasi Satyanarayana

doi:10.3389/fmicb.2016.01129

Abstract

Industrial enzyme market has been projected to reach US$ 6.2 billion by 2020. Major reasons for continuous rise in the global sales of microbial enzymes are because of increase in the demand for consumer goods and biofuels. Among major industrial enzymes that find applications in baking, alcohol, detergent, and textile industries are α-amylases. These are produced by a variety of microbes, which randomly cleave α-1,4-glycosidic linkages in starch leading to the formation of limit dextrins. α-Amylases from different microbial sources vary in their properties, thus, suit specific applications. This review focuses on the native and recombinant α-amylases from bacteria and archaea, their production and the advancements in the molecular biology, protein engineering and structural studies, which aid in ameliorating their properties to suit the targeted industrial applications.

Highlights

Starch is a glucose polymer, which is synthesized by a wide array of plant species
Amylose is a linear water insoluble polymer of glucose joined by α-1, 4 glycosidic bonds (99%), while amylopectin is branched water soluble polysaccharide with short α-1, 4 linked linear chains of 10–60 glucose units and α-1, 6 linked side chains with 15–45 glucose units that form the volume of starch molecule (Buleon et al, 1998; Tester et al, 2004)
The enzyme was active in acidic conditions with an optimal pH of 5.0, and was extremely thermostable with a temperature optimum of 100◦C and a melting temperature of 109◦C; both these favored starch conversion process (Li et al, 2010)

Summary

Introduction

Starch is a glucose polymer, which is synthesized by a wide array of plant species. Starch granules contain of two types of α-glucans, amylose and amylopectin, overall representing 98–99% of its total dry weight. A thermostable α-amylase gene of 1203 bp encoding a 401-amino acid protein of Thermococcus profundus, was cloned and expressed in E. coli. SMMA consisted of 696 amino acids with a predicted molecular weight of 82.5 kDa. The enzyme was active in acidic conditions (pH 3.5–5.0) with an optimal pH of 5.0, and was extremely thermostable with a temperature optimum of 100◦C and a melting temperature of 109◦C; both these favored starch conversion process (Li et al, 2010).

Results

Conclusion