Purification and enzymatic identification of an acid stable and thermostable α‐amylase from Rhizopus microsporus

Rhizopus microsporus, recently isolated from a solid culture of Heng‐Shui Lao‐Bai‐Gan (HSLBG, a famous distilled liquor in Northern China) was found to produce a novel extracellular acid stable and thermostable α‐amylase. This fungal α‐amylase was purified using ammonium precipitation, Sephadex G‐25 desalination and DEAE‐52 cellulose chromatography. Its molecular weight was estimated to be 75 kDa by SDS–PAGE. The optimum pH and temperature of this enzyme was pH 5.0 and 70°C respectively. Thermostability and kinetic analysis through the Arrhenius and Michaelis–Menten equations revealed that this enzyme showed an exceptional activity at low pH and high temperature. A combination of this thermostability and acid stability could be a valuable trait for the efficient hydrolysis of amylose to glucose in large‐scale biotechnology applications. Copyright © 2012 The Institute of Brewing & Distilling