Exuberant Immobilization of Urease on an Inorganic SiO 2 Support Enhances the Enzymatic Activities by 3-fold for Perennial Utilization.

Urease has been covalently immobilized on a 3-D networking silica gel (SG) using dimethyldichlorosilane (DMDCS) as second generation silane coupling reagent and m-nitroaniline as linker component in a robust methodology and subsequently characterized as [{S-i(OSi)(4)(H2O)(0.05)}(205.2)](n=4){OSi(CH3)(2)-NH-C-6-H-4-N=N-urease}center dot 282.5H(2)O (molecular mass 263 445 g or 263.4 kDa). Selective coupling of tyrosine residue with an identifiable m-nitroaniline modified SG unit prevents enzyme-enzyme cross-linking leading to enhancement of enzymatic activity. The material worked at room temperature and its activity (luminescent and ammonia releasing efficiency) was enhanced by 3 fold (for both synthetic and real sample) compared to native enzyme values at neutral pH. Up to 30 days and 30 cycles, this 3-fold activity remains as such but reduces gradually to native enzyme level after 60 days and 60 cycles of reuse.