Immobilization and stabilization of glutaryl acylase on aminated sepabeads supports by the glutaraldehyde crosslinking method

We have investigated the use of the glutaraldehyde chemistry to stabilize glutaryl acylase (GAC). GAC has been immobilized on different aminated supports (ethylendiamine (EA) or polyethylenimine (PEI) coated supports) and the effect of the treatment with glutaraldehyde on both stability and activity has been analyzed. It was determined that immobilization on aminated supports increased the enzyme stability, and that this stabilization increased with the size of the polyethylenimine. The treatment with glutaraldehyde presented a low impact on the enzyme activity (activity recoveries were over 80%) and greatly improved the enzyme stability. A similar treatment using the enzyme immobilized on supports that cannot react with glutaraldehyde did not give rise to stabilization, suggesting that this stabilization was due to a reaction between the enzyme and the support through the glutaraldehyde chemistry. Curiously, the larger the PEI, the lower the stabilization observed. Therefore, final differences between different immobilized GAC preparations treated with glutaraldehyde were not very significant. Other variables, such as glutaraldehyde concentration, were found to have a great impact on the final results (optimal concentration was in the range 0.5-0.65%). After optimization, the stability of the best immobilized GAC was over 250-fold higher than that of the soluble enzyme, retaining 90% of the immobilized activity and much more stable than commercially available GAC preparations or the enzyme immobilized on pre-activated supports. The simple preparation of this immobilized GAC, its good activity and stability, make this strategy very suitable for its industrial implementation.