Extracellular Alkaline Amylase from a Bacillus Species

Abstract

A selective medium was used to isolate a bacterium ( Bacillus species NRRL B-3881) that produced extracellular alkaline amylase in an alkaline medium ( p H 9.5). Maximal enzyme yield was obtained in an aerated medium after 21 hr at 36 C. The enzyme was purified 18-fold by ultrafiltration and ammonium sulfate precipitation. Three active isoenzymes (one major and two minor) of alkaline amylase were detected by disc electrophoresis in polyacrylamide gel. The enzyme was only 12% inactivated by 20 m m ethylenediaminetetraacetic acid after 1 hr at p H 9.2 and 32 C. The optimal temperature was 50 C at p H 9.2, and the optimal p H was 9.2 at 50 C. The enzyme was stable between p H 7.5 and 10. It had an endomechanism of substrate encounter. The products produced from amylose and amylopectin had the β-configuration. Cyclomaltoheptaose was hydrolyzed to maltotriose, maltose, and glucose. The main final product produced from amylose and amylopectin was β-maltose; the other final products were maltotriose and small quantities of glucose and maltotetraose. The predominant product at early stages of hydrolysis was maltotetraose; other products were maltose through maltonanaose.