Kinetic analysis of glucoamylase-catalyzed hydrolysis of starch granules from various botanical sources

The kinetics of glucoamylase-catalyzed hydrolysis of starch granules from six different botanical sources (rice, wheat, maize, cassava, sweet potato, and potato) was studied by the use of an electrochemical glucose sensor. A higher rate of hydrolysis was obtained as a smaller size of starch granules was used. The adsorbed amount of glucoamylase on the granule surface per unit area did not vary very much with the type of starch granules examined, while the catalytic constants of the adsorbed enzyme (k(0)) were determined to be 23.3 +/- 4.4, 14.8 +/- 6.0, 6.2 +/- 1.8, 7.1 +/- 4.1, 4.6 +/- 3.0, and 1.6 +/- 0.6 s(-1) for rice, wheat, maize, cassava, sweet potato, and potato respectively, showing that k(0) was largely influenced by the type of starch granules. A comparison of the k(0)-values in relation to the crystalline structure of the starch granules suggested that k(0) increases as the crystalline structure becomes dense.