Microbial acid-stable α-amylases: Characteristics, genetic engineering and applications

• Published in: Process biochemistry (1991) 2013-02, Vol.48 (2), p.201-211
• Main Authors: Sharma, Archana, Satyanarayana, T.
• Format: Article
• Language: English
• Subjects: Acid-stable; alpha-amylase; Archaea; bacteria; baking; biocatalysts; Directed evolution; engineering; fungi; industrial applications; maltose; molecular biology; saccharification; Site directed mutagenesis; starch; Starch saccharification; temperature; textile industry; thermal stability; α-Amylase
• ISSN: 1359-5113; 1873-3298
• DOI: 10.1016/j.procbio.2012.12.018

► Acidic amylases suit starch and baking industries as native starch is acidic. ► Ca2+-independent, thermo-acid-stable α-amylases are unavailable commercially. ► The directed evolution and structural studies of acidic α-amylase are highlighted. ► There is no review available on acidic α-amylases in the published literature. Among the wide variety of amylolytic enzymes synthesized by microorganisms, α-amylases are the most widely used biocatalysts in starch saccharification, baking industries and textile desizing. These enzymes randomly cleave the α-1,4-glycosidic linkages in starch, generating maltose and malto-oligosaccharides. The commercially available α-amylases have certain limitations, such as limited activity at low pH and Ca2+-dependence, and therefore, the search for novel acid-stable and thermostable amylases from extremophilic microorganisms and the engineering of the already available enzymes have been the major areas of research in this field over the years. Several attempts have been made to find suitable microbial sources of acid-stable and thermostable α-amylases. Acid-stable α-amylases have been reported in fungi, bacteria and archaea. α-Amylases that are active at elevated temperatures have been reported in bacteria as well as in archaea. α-Amylases that possess both characteristics, to the extent required for their various applications are very scarce. The developments that have been made in molecular biology, directed evolution and structural conformation studies of α-amylases for improving their properties to suit various industrial applications are discussed in this review.