Abstract
Herewith we report the first attempt towards non-covalent immobilization of Trametes versicolor laccase on neat and magnetically responsive highly porous polyamide 6 (PA6) microparticles and their application for catechol oxidation. Four polyamide supports, namely neat PA6 and such carrying Fe, phosphate-coated Fe and Fe3O4 cores were synthesized in suspension by activated anionic ring-opening polymerization (AAROP) of ε-caprolactam (ECL). Enzyme adsorption efficiency up to 92% was achieved in the immobilization process. All empty supports and PA6 laccase complexes were characterized by spectral and synchrotron WAXS/SAXS analyses. The activity of the immobilized laccase was evaluated using 2,2’-Azino-bis-(3- ethylbenzothiazoline-6-sulfonic acid (ABTS) and compared to the native enzyme. The PA6 laccase conjugates displayed up to 105% relative activity at room temperature, pH 4, 40 °C and 20 mM ionic strength (citrate buffer). The kinetic parameters of the ABTS oxidation were also determined. The reusability of the immobilized laccase-conjugates was proven for five consecutive oxidation cycles of catechol.
Highlights
Extracellular enzymes attract nowadays much attention by both industry and academia in the constant search of greener, safer, and more cost-effective alternatives to traditional catalytic systems [1,2]
Laccase from Trametes versicolor was immobilized by physical adsorption on these four supports thereby preparing four conjugates: PA6-L, PA6Fe-L PA6FeP-L, and PA6Fe3O4-L; the generic name for all laccase conjugates being PA6@L
The polymer yields were in the 40–50% wt% range indicating that the presence of iron (0) micro- and iron (II, III) oxide nanosized particles did not affect the activity of DL/C20 catalytic system and the kinetics of the activated anionic ring-opening polymerization (AAROP) reaction
Summary
Extracellular enzymes attract nowadays much attention by both industry and academia in the constant search of greener, safer, and more cost-effective alternatives to traditional catalytic systems [1,2]. The complete and fast recovery of enzymes from the reaction medium in order to avoid sensory or toxicological effects, as well as to allow their reuse, is still quite problematic [3]. These limitations can be resolved by immobilization (conjugation) of the enzymes to prefabricated matrices of various nature, geometry, and topography. The immobilization process necessitates a careful control to avoid deactivation of the enzyme. The immobilization method is selected on a case-bycase basis, attempts to optimize this process by computer analysis and molecular modelling have been reported [6,7]
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