Raw Starch Digestion Inhibitory Factor in One Glucoamylase Preparation of Black Aspergillus

Abstract

The inhibitory factor (IF) of raw starch digestion by one glucoamylase preparation of black Aspergillus at high enzyme concentration was isolated from the crude enzyme preparation by heat treatment at pH 7.2, adjustment of the pH to 3.4 and centrifugation. The crude IF was almost completely adsorbed onto raw starch. With an increase of IF concentration, inhibition of raw starch digestion by a normal glucoamylase preparation increased but with an increase of raw starch or enzyme concentration, the inhibition decreased. The IF was then purified by DEAE-Sephadex A-25 column chromatography, gel filtration on Sephadex G-50 and G-100, and rechromatography on DEAE-Sephadex A-25. The IF thus purified was found to be homogeneous on polyacrylamide gel electrophoresis and was a glycoprotein. It contained about 25% carbohydrate and had a molecular weight of about 12,000.