For the production of fructo-oligosaccharides (FOSs), beta-fructofuranosidase, a fructosyl-transferring enzyme purified from Aspergillus japonicus TIT-KJ1 was immobilized covalently onto oxirane-containing, polymeric beads. A simple kinetic model describing the behaviors of FOS production from sucrose catalyzed by either soluble or immobilized enzyme was developed. The equilibrium concentrations of total FOS, glucose, and sucrose in the final mixture for FOS formation by the action of beta-fructofuranosidase were predictable and not to be changed by immobilization. By using the estimated initial rates, the predictions with the proposed model matched the experimental profiles of the substrate and product concentrations during the enzymatic reaction. The model could predict the time course of the batch reaction as well as the production of FOSs in a packed-bed column reactor by the activity of immobilized beta-fructofuranosidase.