Identification of an acidic α-amylase from Alicyclobacillus sp. A4 and assessment of its application in the starch industry

An acidic α-amylase was purified from thermoacidophilic Alicyclobacillus sp. A4 by ion exchange chromatography with 22% recovery, and showed a molecular mass of 64 kDa by SDS–PAGE. Its amino acid sequence was determined by sequencing three internal peptides and the complete genome of strain A4, and shared highest identity (64%) with Alicyclobacillus acidocaldarius α-amylase. Compared with other reported α-amylases, the purified enzyme had some distinct characteristics. The optimal activity was found to occur at 75 °C and pH 4.2, similar to the glucamylase widely used in the starch industry. The enzyme was Ca2+ independent, and had strong ability to digest raw starch (96.71%) with commercial glucamylase in one step. These properties of the purified enzyme make up the deficiency of the commercial α-amylases currently used and avoid repeated adjustment of pH and temperature in double-enzymatic sugar-making process. The purified enzyme will be commercially valuable in the starch industry.