Enhanced biocatalytic sustainability of laccase by immobilization on functionalized carbon nanotubes/polysulfone membranes


Chemically functionalized multi-walled carbon nanotubes (CNTs) are used as carriers for laccase immobilization. In this work, CNTs were modified using different approaches with a combination of methods involving hydrothermal oxidation with nitric acid, treatment with 3-aminopropyltriethoxysilane, glutaraldehyde, N-ethyl-N-(3-(dimethyl-amino)- propyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The enzyme immobilization efficiency and recovered activity were evaluated towards 2,2'-azino-bis(3-ethylbenzathiazoline-6-sulfonic acid) biocatalytic oxidation. The best compromise between immobilization efficiency and recovered activity was obtained using the CNTs functionalized with 0.3M HNO3, treated with N-ethyl-N-(3-(dimethylamino) propyl) carbodiimide hydrochloride and N-hydroxysuccinimide. This catalyst also showed the best thermal stability (at 50 and 60 degrees C). The bioconjugate based on this material was characterized by vibrational spectroscopies (FTIR and Raman) and by N-2 adsorption. The results from reutilization tests showed that laccase activity was kept above 65% of its initial value after five consecutive cycles of reuse. The biocatalytic performance of the immobilized enzyme was evaluated for the degradation of a mixture of phenolic compounds in water containing phenol, resorcinol, 4-methoxyphenol and 4-chlorophenol. As means of cost efficient to enzyme reutilization, laccase was immobilized over polysulfone membranes blended with the functionalized CNTs and studied in the degradation of 4-methoxyphenol.



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Costa, JB; Lima, MJ; Sampaio, MJ; Neves, MC; Faria, JL; Morales-Torres, S; Tavares, APM; Silva, CG

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This work was financially supported by Projects POCI-01-0145-FEDER-006984 - Associate Laboratory LSRE-LCM and POCI-01-0145-FEDER-031268 funded by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) - and by national funds and by national funds (OE), through FCT/MCTES Fundacao para a Ciencia e a Tecnologia. The work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and co-financed by FEDER under the PT2020 Partnership Agreement. M.C.N. acknowledges FCT the post-doctoral grants SFRH/BPD/110423/2015. M.J.L. acknowledges FCT for the research grant PD/BD/52623/2014, while C.G.S. and M.J.S. acknowledge the FCT Investigator Programme (IF/00514/2014) with financing from the European Social Fund and the Human Potential Operational Programme. A.P.M. Tavares acknowledges FCT for the research contract under the IF (IF/01634/2015) Investigator Programme. S.M.T. acknowledges the financial support from the University of Granada, Programme: Proyectos de Investigacion para la Incorporacion de Jovenes Doctores. We are indebted to Dr. Carlos Sa and the CEMUP team (Portugal) for technical assistance and advice with SEM/EDXS measurements.

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