Preparation and characterization of urease immobilized onto porous chitosan beads for urea hydrolysis

Abstract

Urease was covalently immobilized onto porous chitosan beads via primary amine groups connected to the backbone via a six-carbon linear alkyl spacer. The optimum conditions for enzyme immobilization are activating the beads with 1%(w/w) glutaraldehyde, reacting the activated beads in pH 7 buffer with the enzyme, using an enzyme to bead weight ratio of 25, and without lyophilization. Chitosan-bound urease was found to fully retain its speci®c activity. Properties of the immobilized urease were characterized under batch and¯ow conditions. Increased optimum reaction temperature, enhanced thermal stability and storage stability, and excellent reusability were found after enzyme immobilization. Continuous hydrolysis of urea solution was studied in a column packed with the enzyme-containing beads for its possible application in regenerating dialysate solution during hemodialysis.

Present and Future Role of Chitin and Chitosan in Food

“…using chitin and its derivatives as a support in the form of powders, gels, beads, membranes, amylase, galactosidase, lactase, glucose oxidase, fructosidase, chymotrypsin, and so on. [39][40][41][42][43][44][45] Use of immobilized enzymes in cheese production has been considered to be a promising approach for the rational use of rennin and the inherent advantages of continuous reactor systems. [46,47] Proteolytic enzymes initiate milk-clotting by cleaving kcasein molecules on the surfaces of casein micelles to form para-k-casein and a macropeptide.…”

Preparation and characterization of chitosan membranes by using a combined freeze gelation and mild crosslinking method

“…Crosslinking procedure may be performed by reaction of chitosan with different bifunctional reagents such as glutaraldehyde [1,5], carbondiimide [6], crown ether [7], dicarboxylic acids [8], poly(ethylene glycol) dialdehydes [9] and glyoxal [10]. Crosslinking promotes the formation of uniform porous network-like structure of chitosan, change its crystal structure from a-type to b-type and may also smoothen the surface of chitosan [10][11][12][13]. The adsorption of metal on chitosan may require crosslinking treatment to prevent polymer dissolving in the case the metal is adsorbed in acidic aqueous media.…”

“…It is well known that rapid freezing rather than slow freezing gives smaller size ice crystals in frozen foods [25,26]. In chitosan-based materials obtained by freezing and lyophilization of chitosan solutions and gels, the ice crystal size and, hence, their mean pore size and pore orientation have been controlled by varying the freezing temperature or freezing rate by thermal gradients [11,27,28].…”

Reactive poly(ethylene-co-vinyl alcohol) monoliths with tunable pore morphology for enzyme immobilization

“…It could also be used for construction of biosensors to detect urea contained in urine or serum [30,31]. Various kinds of matrix have been reported for urease immobilization, such as gels, membranes, nanoparticles, and beads [32][33][34].…”