Characteristics of acid-stable #alpha# -amylase production by aspergillus kawachii

摘要

In the production of shochu, an indigenous Japanese spirit, #alpha# -amylase produced by shochu koji mold, Aspergillus kawachii (A. kawachii) hydrolyzed starch contained in raw material. It is known that A. kawachii produces two types of #alpha# -amylases; one an acid-labile #alpha# -amylase similar to taka-amylase A (MW chemical bounds 50,000) and the other an acid-stable #alpha# -amylase (asAA, MW chemical bounds 85,000). Since the shochu moromi mash is fermented under the strongly acidic conditions (pH3.2 approx 4.3), due to the accumulation of citric acid produced by A. kawachii, the starch should be hydrolyzed mainly by asAa. The optimal pH of asAA was determined to be 5.0. The enzyme activity of asAA was stable in the pH range of 2.0 approx 6.5 in contrast with 4.5 approx 9.5 of the taka-amyasa A. asAA protein was composed of 640 amino acid residues.