Characterization of cellulose acetate micropore membrane immobilized acylase I

Immobilization of urease in alginate, paraffin and lac

The enzyme urease (EC.3.5.1.5) from jack bean meal was immobilized by various techniques, such as entrapment in calcium alginate gel spheres in aqueous suspension, lac impregnated muslin cloth as dry films and by embedding in paraffin wax impregnated muslin cloth. The activity of the free and immobilized enzymes as a function of pH, temperature, storage stability, kinetic parameters and periodic use were compared. The immobilized enzyme showed good storage stability. After repeated use, the alginate beads turned brown and deteriorated, hence the storage stability was not good. The paraffin films were preserved dry because during wet preservation, the film slightly softened and the protein leached out slightly. The alginate beads had moderate mechanical stability. The lac films were tougher than the paraffin wax films in terms of mechanical stability. The Km and Vmax values were altered after immobilization. The Km values for calcium alginate and lac were low, while it was larger in paraffin film as compared to the free enzyme. This may be due to the fact that immobilization on calcium alginate and lac in presence of CaCl2 and methanol exposed certain active sites of the urease. While immobilization on paraffin masks the active sites and may lead to reduced binding of the substrate.

Glucose oxidase immobilization on a novel cellulose acetate–polymethylmethacrylate membrane

Glucose oxidase (GOD) was immobilized on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane. The immobilized GOD showed better performance as compared to the free enzyme in terms of thermal stability retaining 46% of the original activity at 70 degrees C where the original activity corresponded to that obtained at 20 degrees C. FT-IR and SEM were employed to study the membrane morphology and structure after treatment at 70 degrees C. The pH profile of the immobilized and the free enzyme was found to be similar. A 2.4-fold increase in Km value was observed after immobilization whereas Vmax value was lower for the immobilized GOD. Immobilized glucose oxidase showed improved operational stability by maintaining 33% of the initial activity after 35 cycles of repeated use and was found to retain 94% of activity after 1 month storage period. Improved resistance against urea denaturation was achieved and the immobilized glucose oxidase retained 50% of the activity without urea in the presence of 5M urea whereas free enzyme retained only 8% activity.