Hydrous titanium oxides–new supports for the simple immobilisation of enzymes

Abstract

Hydrous titanium oxides have been shown to be suitable as matrices on which enzymes may be immobilised with retention of enzymic activity. Various routes to the precipitation of the hydrous oxide have been evaluated in terms of the ability of the product to couple D-glucose oxidase with retention of activity. On account of the ease with which hydrous titanium(III) oxide is oxidised by atmospheric oxygen and other associated practical difficulties, hydrous titanium(IV) oxide was deemed preferable, and the optimum conditions of pH, time, and enzyme concentration in the coupling reaction were determined. Freeze drying of the immobilised enzyme was achieved with 74% retention of activity when sorbitol was included. The enzyme derivative was stable under conventional conditions for enzyme activity, and complete removal of bound protein could be achieved by using sodium carbonate–hydroxide solution. The ligand replacement system by which the enzyme is considered to be immobilised and associated factors are discussed in the light of the chemical and physical structures of hydrous titanium(IV) oxide. This support has the advantage over other matrices in that it can be easily, simply, and quickly produced in situ.