Covalent Immobilization of Penicillin G Acylase onto Chemically Activated Surface of Poly(vinyl chloride) Membranes for 6-Penicillic Acid Production from Penicillin Hydrolysis Process I. Optimization of Surface Modification and Its Characterization M. S. Mohy Eldin, 1 H. A. El Enshasy, 2,3 M. El Sayed, 1 S. El Sayed, 4 B. Haroun, 5 E. A. Hassan 5 1 Polymer Materials Research Department, Advanced Technology and New Materials Research Institute, Mubarak City for Scientific Research and Technology Applications, New Burg Al Arab, 21934 Alexandria, Egypt 2 Bioprocess Development Department, Mubarak City for Scientific Research and Technology Applications, New Burg Al Arab, 21934 Alexandria, Egypt 3 Chemical Engineering Pilot Plant, Faculty of Chemical Engineering and Natural Resources, University Technology Malaysia, 81310 Skudai, Johor, Malaysia 4 Biotechnology Pilot Plant, Mubarak City for Scientific Research and Technology Applications, New Burg Al Arab, 21934 Alexandria, Egypt 5 Faculty of Science, Al Azhar University, Cairo, Egypt Received 12 August 2009; accepted 1 August 2011 DOI 10.1002/app.35390 Published online 29 November 2011 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: The covalent immobilization of penicillin G acylase (PGA) onto the surface of NH 2 –poly(vinyl chloride) (PVC) membranes was studied. PGA was chosen because it plays a relevant role in the pharmaceutical industry, catalyz- ing the production of an important intermediate for the industrial production of semisynthetic penicillin and cepha- losporine. Because PVC has no functional groups in its structure, in this work, we focused on the functionalization of PVC with primary amine functional groups for the cova- lent immobilization of PGA. This goal was achieved through an aminoalkylation process of the surface of the PVC mem- branes with ethylene diamine followed by activation with glutaraldehyde to finally immobilize the enzyme. Different factors affecting the modification and activation processes were studied, and their impacts on the catalytic activity of the immobilized PGA were followed. The functionalized membranes were characterized with Fourier transform infra- red spectroscopy, thermogravimetric analysis, and scanning electron microscopy to verify the modification process. In addition, the changes resulting from the modification in physical characteristics, such as surface roughness, water uptake, and mechanical properties, were monitored. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: E27–E36, 2012 Key words: biological applications of polymers; biomaterials; enzymes; films; functionalization of polymers INTRODUCTION Enzyme immobilization is considered as to be one of the most used biotechnological applications of different synthetic polymers, including poly(vinyl chloride) (PVC). 1–9 Among the various methods available for enzyme immobilization, covalent bind- ing is particularly important because it leads to the preparation of stable enzyme derivatives. 10–19 Suita- ble functional groups are essential for conducting such immobilization techniques. PVC has no func- tional groups in its structure, so chemical modifica- tion was carried out to introduce the proper functional groups. The grafting technique, with dif- ferent types of polymers possessing different func- tional groups, has been presented extensively as the main solution, with either a chemical or radiation initiation system. 20–23 On the other hand, another simple technique using the aminoalkylation reaction with diamine was presented. 24 This technique depends on the reaction between the available chlo- rine atoms on the PVC surface and the amine groups of diamine. The introduced amine groups were further activated with a symmetric coupling agent, glutaraldehyde (GA), which covalently binds with the enzyme. The mechanism of PVC modifica- tion, activation, and immobilization with an enzyme is presented in Scheme 1. Even though such a tech- nique has been investigated since almost 29 years ago, 9 still, no studies have been concerned with the optimization of the modification, and the activation processes have been published. Recently, the same Correspondence to: M. S. M. Eldin (mohyeldinmohamed@ yahoo.com). Journal of Applied Polymer Science, Vol. 124, E27–E36 (2012) V C 2011 Wiley Periodicals, Inc.