Semi-interpenetrating networks (IPN)-structured chitosan/beta-cyclodextrin (CS/CD) composite membranes were prepared to investigate the influence of beta-cyclodextrin on permselectivity and permeate flux of CS composite membranes in the enantiomer separation of tryptophan (Trp) racemate. Diffusion selectivity, sorption selectivity, and olverall permselectivity of the composite membranes toward Trp racemate were investigated in detail. Diffusion selectivity, compared with sorption selectivity, was found to be preponderant in the enantiomer separation process. With the increase of beta-cyclodextrin polymer (beta-CDP) content within the CS/CD composite membrane, the permselectivity decreased considerably due to relatively lower complexation selectivity of beta-CDP that reduced both the diffusion selectivity and the overall permselectivity. Therefore, the more the P-CDP content within the membrane, the lower the permselectivity of the membrane; on the other hand, permeate flux was found to increase significantly as a result of the facilitated Trp mass transport through beta-CDP within the membrane. (c) 2007 Elsevier B.V. All rights reserved.