For studying penicillin G acylase (PGA) purification efficiency, various chain lengths of diamine (n = 2-10) were applied as spacer arm to prepare the regenerated cellulose-based immobilized metal affinity membrane (IMAM). The effects of spacer arm length on water content of the IMAM, immobilized metal ion capacity, and batch PGA adsorption were investigated. The use of 1, 10-diaminodecane led to the smallest water content of membrane and the maximum capacity of Cu2+ (62.06 mu mol/disc), whereas the optimal PGA adsorption capacity (2.6 IU/disc) was achieved with 1,8-diaminooctane. When applying the IMAMs with the spacer arm of 1,8-diaminooctane to the flow chromatographic experiments, a performance of 2.73-fold purification and 70.27% recovery was obtained. The employment of diamine spacer arm on the preparation of IMAMs resulted in higher PGA adsorption amount but less purification efficiency. (c) 2004 Elsevier B.V. All rights reserved.