Hydrolysis of starch or pullulan by glucoamylase or pullulanase immobilized on poly(N-isopropylacrylamide) gel

Abstract

Starch or pullulan was hydrolyzed using glucoamylase or pullulanase immobilized on N-isopropylacrylamide gel. The gel used is temperature sensitive; its mesh size becomes smaller at higher temperatures (30 °C) and larger at lower temperatures (20 °C). The molecular weight distribution of starch is wide and it consists of high-molecular-weight amylopectin, amylose and glucose. From the change in the chromatograms for the substrate and products, it was found that the hydrolysis rate at 30 °C was faster than that at 20 °C for amylose, though it was the reverse for amylopectin. This finding suggests that the smaller molecular sized amylose can enter the gel phase at both temperature, while the larger molecular sized amylopectin can hardly do so; only the end group, which can partly enter the gel phase at 20 °C (larger mesh size), was hydrolyzed. Further, several molecular weight pullulans (monodisperse) were hydrolyzed and the experimental chromatograms for substrate and products confirm the hydrolysis mechanism estimated.