Starch Digestion with Microbial Enzymes

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 the ability to adsorb on raw starch. b) Alpha-amylase had an extremely weak activity to digest raw starch, but glucoamylase had a strong activity to digest raw starch. c) Alpha-amylase and glucoamylase, when used jointly, interacted with each other increasing digestion of raw starch to about 3 times the sum of their separate activities. d) Glucoamylase consisted of two kinds of glucoamylase, that is, glucoamylase I and glucoamylase II. The raw waxy corn starch digestion by glucoamylase I was accelerated by adding a-amylase or isoamylase. The raw non waxy corn starch digestion by glucoamylase I was accelerated by a-amylase but not so much by isoamylase as by a-amylase. The raw waxy corn starch digestion by glucoamylase II was very weak, but was accelerated extremely by adding isoamylase, but not by a-amylase. (2) Alpha amylase adsorption on raw starch and its relation to raw starch digestion were investigated. a) Pancreatic a-amylase digested raw starch most strongly and was adsorbed on raw starch most easily. In the case of a-amylases from bacteria and malt, α-amylase adsorption curves reversed positions from those shown for digestion. b) Glucose and maltose, especially the latter, inhibite both amylase adsorption and raw starch digestion, and so the raw starch digestion was accelerated by dialysis . (3) Raw starch digestion by Rhizopus amylase system was studied. a) The glucoamylase system of Rhizopus sp. was fractionated into two kinds of glucoamylase, that is, glucoamylase I and II. b) Glucoamylase I could be adsorbed on raw starch and was highly active in raw starch digestion. The raw waxy corn starch digestion by glucoamylase I was accelerated by adding α-amylase or pullulanase. c) Glucoamylase II could not be adsorbed on raw starch. The raw waxy corn starch digestion by glucoamylase II was very weak, but was accelerated by adding α-amylase contrary to the case of glucoamylase II of black-koji.