Exoenzymic activity of alpha-amylase immobilized on a phenol-formaldehyde resin.

Amylose and amylopectin from two starch sources were partially degraded by alpha-amylase immobilized on a phenol-formaldehyde resin. The degradation products were fractioned by gel-permeation chromatography and high-pressure, liquid chromatography. Two distinct fractions were obtained from tapioca amylose. One is a fragment having a molecular weight exceeding 200,000, and the other consists of oligosaccharides of low molecular weight with a degree of polymerization of 1-8. In contrast, treatment of tapioca amylose with soluble alpha-amylase produces a single fraction, nearly all of which has a molecular weight of less than 35,000, with only traces of small oligosaccharides detectable by high-pressure, liquid chromatography. Even wider differences were observed in degradation products from tapioca amylopectin. Similar activity-patterns were obtained with immobilized and soluble enzyme, using corn amylose and corn amylopectin as substrates. Immobilization of alpha-amylase on the resin apparently restricts the activity of the enzyme to the ends of the starch molecules, making it appear to be limited to exoenzymic activity.