A mathematical model using local thermodynamic equilibrium isotherms for adsorption on immobilized adsorbents is proposed in order to optimize the design parameters in in situ bioproduct separation process. The model accurately follows the experimental data on the adsorption of berberine. secondary metabolite produced in plant cell culture. The result shows that the lower loading capacity in immobilized adsorbents is due to the decrease in the maximum solid phase concentration and the isotherm equilibrium constant. not the effective diffusivity. Design parameters in in situ bioproduct separation process, such as the size of the beads, the ratio of beads to bulk volume and the adsorbent content of the bead, are evaluated by using the model. The decrease of bead size is the most effective parameter for adsorption of berberine in immobilized adsorbent due to a reduction in the overall diffusional resistance.