Site directed confinement of laccases in a porous scaffold towards robustness and selectivity
Résumé
We immobilized a fungal laccase with only two spatially close lysines available for functionalization into macrocellular
Si(HIPE) monoliths for the purpose of continuous flow catalysis. Immobilization (30–45 % protein
immobilization yields) was obtained using a covalent bond forming reaction between the enzyme and low
glutaraldehyde (0.625 % (w/w)) functionalized foams. Testing primarily HBT-mediated RB5 dye decolorization
in continuous flow reactors, we show that the activity of the heterogeneous catalyst is comparable to its homogeneous
counterpart. More, its operational activity remains as high as 60 % after twelve consecutive decolorization
cycles as well as after one-year storage, performances remarkable for such a material. We further
immobilized two variants of the laccase 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) to study the effect of the proximity
of the Si(HIPE) surface on enzyme activity. Comparing activities on different substrates for monoliths with
differentially oriented catalysts, we show a twofold discrimination for ABTS relative to ascorbate. This study
provides ground for the development of neo-functionalized materials that beyond allowing stability and reusability
will become synergic partners in the catalytic process.
Domaines
Biotechnologies
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