Purification and enzymatic identification of an acid stable and thermostableα-amylase from Rhizopus microsporus

Abstract

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 thermostableα-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. © 2012 The Institute of Brewing & Distilling.