Purification and properties of the raw-starch-digesting glucoamylases from Corticium rolfsii.

Corticium rolfsii AHU 9627, isolated from a tomato stem, is one of the strongest producers of raw-starch-digesting amylase. The amylase system secreted by C. rolfsii AHU 9627 consisted of five forms of glucoamylase (G1-G5) and a small amount of alpha-amylase. Among these amylases, G1, G2 and G3 were able to hydrolyze raw starch. Five forms of glucoamylase were separated from each other and purified to an electrophoretically homogeneous state. The molecular masses were: G1 78 kDa, G2 78 kDa, G3 79 kDa, G4 70 kDa, and G5 69 kDa. The isoelectric points were: G1 3.85, G2 3.90, G3 3.85, G4 4.0, and G5 4.1. These glucoamylases showed nearly identical characteristics except that G4 and G5 were unable to hydrolyze raw starch.