Abstract
(1) Raw starch digestion by black-koji amylase system was studied. (a) The ability of the black-koji amylase system to digest raw starch may be associated with ability to adsorb on raw starch. (b) Alpha-amylase has an extremely weak activity to digest raw starch, but glucoamylase has a strong activity to digest raw starch. (c) Alpha-amylase and glucoamylase, when used jointly, interact with each other increasing digestion of raw starch to about 3 times the sum of their separate activities . (d) Glucoamylase consists of two kinds of glucoamylases, that is, glucoamylase I and glucoamylase II. The former can adsorb on raw starch and is the principle of raw starch digestion. This enzyme also can hydrolyze β-limit dextrin from glycogen very easily. On the other hand, the latter, glucoamylase II, can not adsorb on raw starch and has an extremely weak activity to digest raw starch. This enzyme can scarcely hydrolyze β-limit dextrin from glycogen. (2) Alpha-amylase adsorption on raw starch and its relation to raw starch digestion were investigated. (a) Pancreatic a-amylase digests raw starch most strongly and is adsorbed on raw starch most easily. Fungal α-amylase digests raw starch most weakly and is adsorbed on raw starch imperceptibly. In the case of α-amylases from bacteria and malt, α-amylase adsorption curves reverse positions from those shown for digestion. (b) The adsorption of pancreatic α-amylase on raw starch is rapid and the adsorbed amylase is desorbed at a decelerating rate with time and is similar to the digestion activity curve. (c) Glucose and maltose, especially the latter, inhibit both amylase adsorption on raw starch and raw starch digestion, and so the raw starch digestion is accelerated by dialysis . (3) Pseudomonas isoamylase assists the raw starch, especially waxy starch, digestion by the black-koji glucoamylase I.
