The adsorption isotherms of glucoamylase (E.C.3.2.1.3) on modified molecular sieves DY with mesopore and macropore were determined. The enzyme adsorption amount and the shapes of the isotherm were related to the properties such as point of zero charge (PZC), pore volume, pore diameter and acidity of the molecular sieves DY and the pH of the adsorbing solution. The relationship among acidity, pore structure of molecular sieves, adsorption amount of enzyme and activity of the enzyme adsorbed was also discussed. Th results show that the adsorption amount is closely related to the procedure that applied to modify the molecular sieve, which makes the molecular sieves DY with different Si/Al ratio, pore distribution and specific surface area. Thus, the different Si/Al ratio causes the molecular sieves DY to have different acidity properties and different PZC. It is found that the main drive force for glucoamylase adsorbing on molecular sieves is electrostatic interaction. The experimental results also show that for the molecular sieves DY the enzyme adsorption amount increases with the increase of the surface acidity, the pore diameter and pore volume, and the enzyme activity increases with the increase of enzyme adsorption amount while the specific acitivity decreases with the increase of enzyme adsorption amount and the decrease of mesopore diameter and volume of the molecular sieves DY.

Key words: MOLECULAR SIEVE, GLUCOSE, AMYLASE, ADSORPTION, FIXED ENZYME