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Kinetics and stability of Chitosan-immobilized laccase

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dc.contributor.advisor Li, Qing X Delanoy, Gary A. 2009-03-06T19:36:56Z 2009-03-06T19:36:56Z 2003-12
dc.description ix, 60 leaves
dc.description.abstract Laccase, from Coriolus versicolor, was immobilized to the biopolymers of chitosan with varying average molecular weights (Mw= 130,214,432, and 505 kDa) using the carbodiimide active esther method. The effect of the biopolymer molecular weight on the chitosan-immobilized laccase were analyzed for the activity of soluble chitosan-immobilized laccase conjugates for the oxidation of the substrate 2,2'-azino-bis3-ethylbenzthiazoleine-6-sulfonic acid (ABTS). Although the chitosan Iaccase conjugates of different molecular weights maintained from 20 - 40% residual activity compared to free laccase, the immobilized laccase was capable of being recovered and reused multiple times. During repeated cycles ofprecipitation and dissolution of conjugates prepared with laccase immobilized to chitosan of Mw 214 kDa up to 60% of residual activity was retained after 15 cycles. Activities of the chitosan-laccase conjugates retained similar responsiveness to changes in pH (1.0 to 8.0) and temperature (20-80°C) compared to free laccase. Results of kinetic parameters (Km, Vmax, and Kcat) for analysis comparing the effect of Mw and laccase density on conjugation show two different relationships. Although the affinity of the conjugates, Km, for ABTS showed no apparent trend based on Mw of chitosan, laccase conjugated to chitosan (Mw 132 kDa) resulted in Vmax and Kcat (0.37 umole mL-1 min-1 and 2.1x10+6) to be approximately half the values for free laccase (0.60 umole mL-1 min-1 and 4.4x10+6 respectively) and decreased as Mw increased from 132 to 505 kDa. Increasing the amount of chitosan conjugated to laccase (2.2 to 8.8 mg chitosan/mL) decreased Km values from 349 to 82 uM compared to 65 uM for free chitosan. However, Vmax decreased (268 to 0.63 umole mL-1 min-1)as the amount of chitosan conjugated to laccase increased compared to Vmax for free chitosan (0.46 umole mL-1 min-1). Kcat for conjugated laccase remained 100 times less than that for free laccase (2.0x10+5 and 1.3x10+7, respectively). These results are indicative that the properties of chitosan affect the laccases catalytic sites and global structure of laccase conjugated to chitosan. Keywords: Biopolymer, Chitosan, Bioconjugate, Laccase
dc.publisher University of Hawaii at Manoa
dc.relation Theses for the degree of Master of Science (University of Hawaii at Manoa). Molecular Biosciences and Bioengineering; no. 3824
dc.rights All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
dc.title Kinetics and stability of Chitosan-immobilized laccase
dc.type Thesis
dc.type.dcmi Text
dc.contributor.department Molecular Biosciences & Bioengineering 2003-12
local.identifier.callnumber Q111 .H3 no. 3824
local.thesis.degreelevel MS
Appears in Collections: M.S. - Molecular Biosciences and Bioengineering

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