The preparation of an immobilised glucose isomerase II. Immobilisation and properties of the immobilised enzyme

Glucose isomerase ex Lactobacillus brevis was successfully immobilised on microcrystalline cellulose, using the transition metal-link method. Immobilisation could be performed over a pH range of 5 to 9, and usually resulted in an apparent specific activity increase. The immobilised glucose isomerase generally displayed properties similar to those of the soluble enzyme, with the exception of the following differences: (i) a pH optimum at pH = 6, an acid shift of 0.5 units on immobilisation; (ii) an optimum reaction temperature at 50 °C, lower than that for the soluble enzyme; (iii) on incubation at 4 °C, a retention of 53% of the initial specific activity, when stored in 0.02 M, pH = 7, Tris buffer, after 8 weeks, compared with an apparent activation of the soluble enzyme after 10 and 19 weeks' storage. Storage properties of the immobilised enzyme at 4 °C in Tris were apparently improved by the presence of Mn++ and Co++, although associated with some protein release. Storage at 4 °C in water alone, as opposed to Tris, resulted in a more rapid activity loss.