A DEA group-containing polymer chain grafted onto a porous PE membrane. BSA was immobilized by the permeation of a BSA solution through the pore of the DEA membrane. The immobilized BSA was cross-linking with glutaraldehyde to prevent leakage. DL-tryptophan solution was forced to permeate through the BSA immobilized membrane at a flow 50 mL/h. As a result, Adsorption of D-,L-tryptophan increase with increasing of BSA immobilized as a function of the degree of GMA grafting.