Adsorption of urease on PE-MCM-41 and its catalytic effect on hydrolysis of urea

Pore-expanded MCM-41 (PE-MCM-41) silica exhibits a unique combination of high specific surface area (ca. 1000 m(2)/g), pore size (up to 25 nm) and pore volume (up to 3.5 cm(3)/g). As such, this material is highly suitable for the adsorption of large biomolecules. The current study focused primarily on the application of PE-MCM-41 material as suitable host for urease (nickel-based large metalloenzyme) in controlled hydrolysis of urea. Urease adsorbed on PE-MCM-41, regular MCM-41 and silica gel (SGA) were used as catalysts for urea hydrolysis reaction. Adsorption studies of urease on these materials from aqueous solution at pH 7.2 revealed that the adsorption capacity of PE-MCM-41 (102 mg/g) is significantly higher than that of MCM-41 (56 mg/g) and SGA (21 mg/g). The equilibrium adsorption data were well fitted using the Langmuir-Freundlich model. Furthermore, the kinetic study revealed that the uptake of urease follow the pseudo-first order kinetics. The in vitro urea hydrolysis reaction on pristine urease and different urease-loaded catalysts showed that the rate of hydrolysis reaction is significantly slower on U/PE-MCM-41 compared to that of bulk urease and urease on MCM-41 and SGA. This technique could be an alternative means to the use of urease inhibitors to control the ammonia release from urea fertilizer. (c) 2007 Elsevier B.V. All rights reserved.