Thesis defense : Mrs. Fangfang YANG [10/19/2021, 9h]
Heterogeneous catalysts are now widely developed to obtain improved stability, reusability, and localization. In this view, we first prepared the enzyme-based heterogeneous catalysts by the immobilization of a fungal laccase containing only two spatially close surface lysines (K40, K71) and its variants containing a unique lysine -one located in the vicinity of the substrate oxidation site (K157) and one at the opposite side of this oxidation site (K71)- into Si(HIPE) type silica foams bearing controlled porosities. Immobilization was achieved by a covalent bond forming reaction between the enzyme and the low glutaraldehyde activated foam. Testing dye decolorization in a continuous flow reactor, we show that the activity of the heterogeneous catalyst is comparable to its homogeneous counterpart. Its operational activity remains as high as 60 % after twelve consecutive decolorization cycles and one-year storage. More importantly, comparing activities on different substrates for differentially oriented catalysts, we show a two-fold discrimination for ABTS relative to ascorbate. In addition, artificial metalloenzymes can use the advantages of both metallic and enzymatic catalysts to perform aerobic oxidation in a sustainable fashion. We thus co-immobilized a biquinoline-based-Pd(II) complex and laccase into silica monoliths for veratryl alcohol oxidation. To address the control of reactivity, three methods of immobilization were used for the construction of the heterogeneous hybrid catalysts. The immobilized hybrid catalysts show an improved activity compared to the immobilized Pd complex alone for each tested method, attesting for the synergy between Pd and laccase. By tuning enzyme orientation towards Pd(II) complex and silica foam, we show that the activity of the Pd(II)/UNIK157 hybrid exhibits an averaged two-fold increase compared to Pd(II)/UNIK71. A good stability and reusability is observed for both enzyme orientations. This study provides insights into the use of solid supports that beyond allowing stability and reusability becomes synergistic partners in the catalytic process.
Keywords : Artificial metalloenzyme, heterogeneous catalyst, palladium, laccase, aerobic oxidation, veratryl alcohol, dye decolorization.
Thesis defense : Mrs. Fangfang YANG
Date : 19 octobre 2021, à 9h00
Place : Amphi INSPE, faculté Saint Jérôme (52 Avenue Escadrille Normandie Niemen, 13013 Marseille)
Title : Développement ciblé de systèmes hybrides supportés à base de laccase pour la catalyse en flux continu
Doctoral school : ED 250 Sciences Chimiques (Chemical sciences)
Specialty : Chemical sciences
Mrs. Belen ALBELA, Lecturer, Ecole Normale Supérieure de Lyon, France.
Mr. Nicolas MANO, CNRS Research director, Univ. Bordeaux, CRPP, France.
Mrs. Belen ALBELA, Lecturer, Ecole Normale Supérieure de Lyon, France
Mr. Nicolas MANO, CNRS Research director, Univ. Bordeaux, CRPP, France
Mrs. Yasmina MEKMOUCHE, Research officer, Aix-Marseille Université, France
Mrs. Ling PENG, Research director, Aix-Marseille Université, France
Mr. Thierry TRON, Research director, Aix-Marseille Université, France
Mrs. Laurence HECQUET, Professor, Université Clermont Auvergne, France.