Kinetics of ion exchange separation of serine alkaline protease (SAP) by cation- and anion-exchangers, respectively, for the SAP(+)/H+ and SAP(-)/OH- ion exchange reactions were studied with four different resins, i.e. low acidic Macro-prep CM, high acidic Macro-prep HighS, low basic Macro-prep DEAE, and high basic Macro-prep HighQ. The effects of pH on ion exchange equilibria were investigated within pH = 6.5-8.0 and pH = 9.5-11.0, respectively, for the SAP+/H+ cation exchange and SAP-/OH- anion exchange reactions at T = 10-25 degreesC, and the results were interpreted on the basis of the theory of exchange of enzyme-ions. Although Macro-prep CM showed the highest SAP binding capacity at pH = 7.0, maximum recovery of SAP activity was obtained at 15 degreesC and pH = 6.5. Effects of feed concentration and flow rate were investigated in differential-(DIC) and integral (IC) ion exchange columns and 0.025 mol dm(-3) and 1.0 x 10(-2) dm(3) min(-1) gave the highest enzyme recovery as 70%. The overall internal-external mass transfer coefficient which was found by differential analysis showed the importance of liquid phase mass transfer resistances on the process under the operation conditions applied. (C) 2002 Elsevier Science B.V. All rights reserved.