Hossain Kazi-Zakir, Monreal Carlos M, Sayari Abdelhamid
Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada.
Colloids Surf B Biointerfaces. 2008 Mar 15;62(1):42-50. doi: 10.1016/j.colsurfb.2007.09.016. Epub 2007 Sep 21.
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.
孔径扩大的MCM-41（PE-MCM-41）二氧化硅具有高比表面积（约1000 m²/g）、孔径（高达25 nm）和孔体积（高达3.5 cm³/g）的独特组合。因此，这种材料非常适合吸附大型生物分子。当前的研究主要集中在将PE-MCM-41材料用作脲酶（镍基大型金属酶）在尿素受控水解中的合适载体。吸附在PE-MCM-41、常规MCM-41和硅胶（SGA）上的脲酶被用作尿素水解反应的催化剂。在pH 7.2的水溶液中对脲酶在这些材料上的吸附研究表明，PE-MCM-41的吸附容量（102 mg/g）明显高于MCM-41（56 mg/g）和SGA（21 mg/g）。平衡吸附数据使用Langmuir-Freundlich模型拟合良好。此外，动力学研究表明脲酶的摄取遵循准一级动力学。对原始脲酶和不同负载脲酶的催化剂进行的体外尿素水解反应表明，与本体脲酶以及MCM-41和SGA上的脲酶相比，U/PE-MCM-41上的水解反应速率明显较慢。该技术可能是使用脲酶抑制剂来控制尿素肥料中氨释放的替代方法。
