A Thermophilic and Unusually Acidophilic Amylase Produced by a Thermophilic Acidophilic Bacillus sp.

Abstract

Bacillus sp. 11-1S, a thermophilic acidophilic bacterial strain, produced an extracellular amylase with unusual characteristics. The enzyme was purified 40-fold by SE-Sephadex column chromatography. The pH optimum for activity was 2.0, and substantial activity was noted in the pH range of 1.5 ~ 3.5. The optimal temperature was 70°C, but the activity decreased markedly in lower reaction temperatures. Arrhenius plots of the reaction showed two straight lines intersecting at about 50°C. The activity or stability of the enzyme was not likely to depend on Ca^{2 +}. The molecular weight of the enzyme was 54,000 calculated from the electrophoretic mobility. The enzyme behaved like an oc-amylase (1,4-α-D-glucan gmcanohydrolase, E.C. 3.2.1.1). About 34% of glucosidic linkages of soluble starch was hydrolyzed at 65°C and pH 2.0, in 24 hr, and the major products were maltotriose and maltose.