The utility of an immobilized enzyme, gluco-amylase on cellulose support, for the hydrolysis of potato starch, has been studied in a fixed bed biochemical reactor to evaluate the influence of flow parameters on conversion. The effect of parameters like pellet size, packed bed height and substrate concentration, has been studied. Maximum conversions are obtained for pellet size of 0.57 cm, packed bed height of 70 cm, and substrate concentration of 10 mg/ml. The kinetic behavior of heterogeneous enzyme, has been studied, with the aid of an appropriate mathematical model, which takes into account, simultaneous mass transfer and reaction kinetics. Based on the experimental observations and the mathematical model, intrinsic kinetic parameters are determined by decoupling diffusion effects. This knowledge is used in the design of an immobilized enzyme reactor.