Urease adsorption immobilization on ionic liquid-like macroporous polymeric support

Abstract

In this work, we report the synthesis and application of polymeric macroporous materials functionalized with ionic liquid (IL)-like moieties to serve as a support for enzyme immobilization. The method was based on bottom-up approach, where poly(styrene–divinylbenzene) (PS–DVB) nanoparticles were used as building blocks to form porous structures. Surface functionalization was done by introducing 1-butyl imidazole into the PS–DVB support to form IL-like imidazolium, which was consequently used for enzyme adsorption immobilization on the porous surface. To demonstrate activity of immobilized enzyme, hydrolysis of urea catalyzed by Jack bean urease was used as a model reaction. The enzymatic activity of the urease to convert urea solution into carbon dioxide (hydrocarbonates in water solution) and ammonia under acidic conditions were monitored both by measuring changes in pH and by a color change in cresol red pH indicator. The immobilized urease was able to provide hydrolysis of urea solution for 30 days while maintaining its activity over 100% compared to free enzyme solution. The activity of freshly immobilized enzyme was increased up to 285% compared to free urease solution under acidic conditions, which is caused by an acidic shift of activity–pH bell-shaped curve. Prepared porous material with immobilized urease was able to undergo four consequent cycles over the period of 4 days with only 15% decrease in activity. Overall, the results indicated that the polymeric support is well suitable to combine the advantages of macroporous material with IL-like surface moieties for enzyme immobilization and its consequent application in bio-catalytic reactions.