Non-isothermal bioreactors utilizing catalytic Te¯on membranes M.S. Mohy Eldin 1,a , A. De Maio a,b , S. Di Martino a , M. Portaccio a,b , S. Stellato a , U. Bencivenga a , S. Rossi a , M. Santucci a , P. Canciglia 2,a , F.S. Gaeta a , D.G. Mita a,b,* a International Institute of Genetics and Biophysics of CNR, via Guglielmo Marconi, 12, 80125 Naples, Italy b Department of Human Physiology and Integrated Biological Functions, Second University of Naples, via SM di Costantinopoli, 16, 80138 Naples, Italy Received 1 December 1997; received in revised form 1 April 1998; accepted 3 April 1998 Abstract A hydrophobic and catalytic membrane has been obtained by grafting with -radiations a Te¯on membrane in presence of methylmethacrylate solution and by immobilizing on it, after treatment with glutaraldehyde, the b-Galactosidase enzyme. When employed in a non-isothermal bioreactor, the membrane showed an increase in catalytic activity proportional to the applied temperature gradients. The results have been explained in terms of distinct contributions from the process of thermodialysis and the conformational changes induced in the dynamic structure of the enzyme by the presence of heat ¯ow. The increase of the yield of the process has been evaluated in terms of a coef®cient  representing the percent increase of enzyme activity when a temperature difference of 18C is applied across the membrane. The catalytic Te¯on membrane used here gave values of 20%, which are comparable to those obtained with other membrane systems, making this kind of membrane useful for practical applications in industrial processes. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Biocatalytic membranes; Non-isothermal bioreactors; b-Galactosidase; Grafted membranes 1. Introduction Catalytic membranes are commonly employed in industrial processes and in analytical apparatuses [1±5]. All these applications are performed with bio- reactors or instruments operating under isothermal conditions. It has been recently demonstrated that the ef®ciency of enzymatic processes is increased [6±12] when the catalytic membranes are employed in bioreactors operating under non-isothermal conditions. The increase is linearly proportional to the temperature gradient applied across the catalytic membrane and depends on the nature of the enzyme and on the immobilization methods. Mesophilic and thermophi- lic enzymes were employed in these studies. Analo- gous results have been obtained with immobilized microorganisms. In this case the temperature gradients affected the activity of either wall or internal enzymes. In all the non-isothermal experiments performed until now the membrane system employed used two Journal of Membrane Science 146 (1998) 237±248 *Corresponding author. Tel.: +39 81 2395887; fax: +39 81 2395887; e-mail: Mita@iigbna.iigb.na.cnr.it 1 Permanent address: Department of Polymers and Pigments, National Research Center, Dokki, Cairo, Egypt. 2 Permanent address: Institute of General Physiology of the University of Messina, Salita Sperone, 36, Messina, Italy. 0376-7388/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved. PII S0376-7388(98)00112-4