Selective submerged productions of three types of glucoamylases by a black-koji mold.

Abstract

Aspergillus awamori var. kawachi produced selectively one of the three types of glucoamylases under the following different conditions in the submerged cultures at the controlled pH of 6.5 to 7.0: (1) the raw-starch digestive glucoamylase, type I, by a cultivation in the synthetic medium containing ammonium citrate as a nitrogen source, deficient in zinc and sufficient in phosphate, for a shorter period of 30 hr at 35°C; (2) one of the raw-starch indigestive glucoamylases, type I', showing the same hydrolysis curves for gelatinized starch as the type I, by a cultivation in the synthetic medium containing ammonium acetate as a nitrogen source, sufficient in zinc, for 50 hr at 30°C; (3) the other of the raw-starch indigestive glucoamylases, type II, that was less susceptible for α-1, 6 glucosidic linkages of gelatinized starch, by a cultivation in the synthetic medium containing glucose, casein-peptone and sufficient amount of inorganic elements, especially calcium and zinc, for 96 hr at 25°C.