Influence of the spacer length on the activity of enzymes immobilised on nylon/polyGMA membranes. Part 1. Isothermal conditions.

beta-Galactosidase was immobilised on Nylon-poly(glycidyl methacrylate) membranes through spacers of different length: hexamethylenediamine, ethylenediamine or hydrazine. The effect of the spacer length on the catalytic behavior of the three membranes was studied in isothermal bioreactors. The behavior of the soluble and insoluble enzymes was compared to know the effects of the immobilisation process and of the spacer length. The enzyme derivatives in comparison with the soluble enzyme exhibited shifts of the optimum pH values towards more acidic solutions. These shifts were found decreasing with the spacer length; while an opposite trend was observed when the optimum temperature values were considered. Also the values of the apparent Km were found to decrease with the spacer length. All these results indicated that a soluble enzyme could be considered as an enzyme immobilised on a solid support through a spacer of infinite length.