| dc.description.abstract | Abstract
In this study chitosan was modified to posses carboxyl group via the enzymatical grafting reaction of tyrosinase, or was used to immobilize tyrosinase. The purpose of this thesis was to find applications of these fabricated chitosans using in chemical process. In chapter three, 3,4-dihydroxybenzoic acid, 3,4- dihydroxyphenylacetic acid, and hydrocaffeic acid were used individually as substrates of tyrosinase to graft onto chitosan. The grafting amounts of these phenol derivatives onto chitosan were examined and the modified chitosan were used in experiments on uptake of the cationic dyes crystal violet and bismarck brown Y by a batch adsorption technique. In chapter four, tyrosinase was used to convert phenol to polyquinone, then polyquinone was removed by chitosan beads and tyrosinase was adsorbed by those carboxylly modified chitosan beads. The thermodynamic and kinetic models of tyrosinase adsorbed by modified chitosan were investigated. In chapter five, Chitosan was activated with glutaraldehyde, epichlorohydrin and ethylene glycol diglycidyl ether respectively in order to immobilize tyrosinase for the production of L-dopa from L-tyrosine. The effects of coupling agents and amine capping agents on the operation stability of immobilized tyrosinase were studied. A practical route to immobilize tyrosinase on chitosan for producing L-dopa from L-tyrosine was found. Finally in chapter six, chitosan was used to prepared tyrosinase-based biosensor on glassy carbon electrode for detecting the concentration of phenols. The effect of immobilizing methods, including chitosan gel mixed with enzyme, sandwich entrapped enzyme between two pieces of chitosan films, and covalently bonded enzyme on chitosan films, upon the apparent response of biosensor were studied. A highly stable biosensor was fabricated. | en_US |