abstract
The biocatalytic performance of immobilized enzyme systems depends mostly on the intrinsic properties of both biomolecule and support, immobilization technique and immobilization conditions. Multi-walled carbon nanotubes (MWCNTs) possess unique features for enzyme immobilization by adsorption. Enhanced catalytic activity and stability can be achieved by optimization of the immobilization conditions and by investigating the effect of operational parameters. Laccase was immobilized over MWCNTs by adsorption. The hybrid material was characterized by Fourier transformed infrared (FTIR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM, respectively). The effect of different operational conditions (contact time, enzyme concentration and pH) on laccase immobilization was investigated. Optimized conditions were used for thermal stability, kinetic, and storage and operational stability studies. The optimal immobilization conditions for a laccase concentration of 3.75 mu L/mL were a pH of 9.0 and a contact time of 30 min (522 U-lac/g(carrier)). A decrease in the thermal stability of laccase was observed after immobilization. Changes in Delta S and Delta H of deactivation were found for the immobilized enzyme. The Michaelis-Menten kinetic constant was higher for laccase/MWCNT system than for free laccase. Immobilized laccase maintained (or even increased) its catalytic performance up to nine cycles of utilization and revealed long-term storage stability. (C) 2015 Elsevier Inc. All rights reserved.
keywords
REACTIVE TEXTILE DYES; TRAMETES-VERSICOLOR LACCASE; GREEN COCONUT FIBER; PHENOLIC-COMPOUNDS; COVALENT IMMOBILIZATION; COMMERCIAL LACCASE; MEDIATOR SYSTEM; OXIDATION; ENZYME; STABILIZATION
subject category
Chemistry
authors
Tavares, APM; Silva, CG; Drazic, G; Silva, AMT; Loureiro, JM; Faria, JL
our authors
Ana Paula Mora Tavares
Assistant Researcheracknowledgements
This work was financed by FCT/MEC and FEDER under Programe PT2020 (Project UID/EQU/50020/2013), and co-financed by QREN, ON2, and FEDER through Project NORTE-07-0124-FEDER-000015 (C.G.S.). A.P.M.T. acknowledges the financial support (Programme Ciencia 2008) from FCT. A.M.T.S. and G.D. acknowledge the financial support of the Slovenian Research Agency. A.M.T.S. acknowledges the FCT Investigator 2013 Programme (IF/01501/2013), with financing from the European Social Fund and the Human Potential Operational Programme. We are indebted to Dr. Carlos SA and the CEMUP team (Portugal) for technical assistance and advice with SEM/EDXS measurements. We also acknowledge Prof. Natercia Teixeira from the Faculty of Pharmacy of the University of Porto for the assistance with the isoelectric focusing analysis and Dr. Marcia C. Neves from CICECO - Aveiro Institute of Materials, University of Aveiro for the technical assistance dealing with Raman spectroscopy.