Inhibition of Raw Starch Digestion by One Glucoamylase Preparation from Black Aspergillus at High Enzyme Concentration

Raw starch digestion by glucoamylase I (Ab. G‐I) preparation from black Aspergillus was inhibited significantly at relatively high concentration of the enzyme. The properties of this enzyme were studied together with those of another glucoamylase I (Nor. G‐I), also from black Aspergillus . The two glucoamylases do not differ so much in their physico‐chemical properties such as molecular weight, pH and thermal stability, pH and temperature optimum, substrate specificity, debranching activity, isoelectric point etc. The adsorption rate of both enzymes on raw starch increased by the increase of enzyme concentration. The raw starch digestion rate by adsorbed Ab. G‐I, however, was decreased with the increase of concentration of enzyme whereas the same was increased in case of Nor. G‐I. The inhibitory effect was weaker at 60°C or above.