Polymer-assisted biocatalysis: polyamide 4 microparticles as promising carriers of enzymatic function

This study reports a new strategy for enzyme immobilization based on passive immobilization in neat and magnetically responsive polyamide 4 (PA4) highly porous particles. The microsized particulate supports were synthesized by low-temperature activated anionic ring-opening polymerization. The enzyme of choice was laccase from Trametes versicolor and was immobilized by either adsorption on prefabricated PA4 microparticles (PA4@iL) or by physical in situ entrapment during the PA4 synthesis (PA4@eL). The surface topography of all PA4 particulate supports and laccase conjugates, as well as their chemical and physical structure, were studied by microscopic, spectral, thermal, and synchrotron WAXS/SAXS methods. The laccase content and activity in each conjugate were determined by complementary spectral and enzyme activity measurements. PA4@eL samples displayed >93% enzyme retention after five incubation cycles in an aqueous medium, and the PA4@iL series retained ca. 60% of the laccase. The newly synthesized PA4-laccase complexes were successfully used in dyestuff decolorization aiming at potential applications in effluent remediation. All of them displayed excellent decolorization of positively charged dyestuffs reaching ~100% in 15 min. With negative dyes after 24 h the decolorization reached 55% for PA4@iL and 85% for PA4@eL. A second consecutive decolorization test revealed only a 5–10% decrease in effectiveness indicating the reusability potential of the laccase-PA4 conjugates.The authors gratefully acknowledge the financial support of the project TSSiPRONORTE-01-0145-FEDER-000015, supported by the regional operation program NORTE2020, under the Portugal2020 Partnership Agreement, through the European Regional Development Fund, as well as the support byNational Funds throughFundação para a Ciência e Tecnologia(FCT), project UID/CTM/50025/2019. D.S. and I.G.wish to thank the Research Foundation of the State of New York for partial funding through Materials Network ofExcellence. N.D. is also grateful for the personal program-contract CTTI-51/18-IPC