title: Stability and reactivity of acid phosphatase immobilized on composite beads of chitosan and ZrO2 powders.
abstract: Equal weights of chitosan and ZrO2 powders were mixed in acetic acid solution to prepare the composite beads. They were then cross-linked with glutaraldehyde and stored with and without freeze-drying before use. The physicochemical properties of acid phosphatase immobilized on four types of the supports (wet/dried pure chitosan beads, wet/dried chitosan-ZrO2 composite beads) were compared. Various parameters including glutaraldehyde concentration, cross-linking time, enzyme concentration, temperature, and pH on enzyme activity were studied. It was shown that the activity yield of enzyme immobilized on the dried chitosan-ZrO2 beads was the highest, and the relative activity remained above 83.2% within pH 2.9-5.8. Regardless of wet or dried beads, the Michaelis constant KM and maximum rate of reaction Vmax of acid phosphatase immobilized on chitosan-ZrO2 composite beads were 1.8 times larger than those on pure chitosan beads. Of the four immobilized enzymes, the use of wet chitosan-ZrO2 bead as the support showed the lowest thermal deactivation energy (78 kJ mol(-1)).
authors.affiliation: Department of Chemical Engineering, National United University, Miao-Li 360, Taiwan, ROC.
authors.forename: Min-Yun
authors.initials: MY
authors.lastname: Chang
authors.forename: Ruey-Shin
authors.initials: RS
authors.lastname: Juang
mesh_terms: D000135:Acid Phosphatase / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D048271:Chitosan / Q000737:chemistry*; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012116:Resins, Plant / Q000737:chemistry*; D014908:Triticum / Q000201:enzymology*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D012116:Resins, Plant; D048271:Chitosan; D015040:Zirconium; D000135:Acid Phosphatase; C028541:zirconium oxide