Purification and Characterization of an α-Amylase of Pichia burtonii Isolated from the Traditional Starter “Murcha” in Nepal

Abstract

Among more than 20 yeast strains isolated from the traditional starter “murcha” in Nepal, we characterized a yeast that might be involved in saccharification. This strain, identified as Pichia burtonii, produced an extracellular amylolytic enzyme when cultured in the presence of starch in the medium. Since no amylase secreted by P. burtonii has yet been reported, we purified the enzyme and determined its N-terminal amino acid sequence. Together with the results of a hydrolyzing activity assay toward various substrates, it was found to be an α-amylase. The purified enzyme, named Pichia burtonii α-amylase (PBA), was a glycoprotein with an apparent molecular mass of 51 kDa. Enzyme activity was optimal at pH 5.0 at 40 °C. The enzyme retained 80% of its original activity after incubation under the optimal pH condition at 50 °C for 30 min. The activity was inhibited by metal ions such as Cd²⁺, Cu²⁺, Hg²⁺, Al³⁺, and Zn²⁺.