Abstract

This work explores for the first time the stability and selectivity of Trametes versicolor laccase immobilized on the glyoxyl support Immobead 150 P. Different buffers (pH 6-10) were tested for enzyme immobilization, with citrate buffer (pH 6) yielding the highest immobilization yield (85%). The immobilized enzyme retained its activity during five reaction cycles in the reaction with 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). In contrast, in the 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO)-mediated 5-hydroxymethylfurfural (HMF) oxidation reaction (5 mM), the biocatalyst's activity decreased by 40% in the fifth reaction cycle, indicating that the biocatalyst's stability is affected by TEMPO. The thermal stability of the immobilized enzyme was almost twice that of the free enzyme. The enzyme immobilized on the support functionalized with glyoxyl/glutaraldehyde groups reached a half-life of 173 h. In comparison, the laccase immobilized on the unmodified support (epoxy groups) reached a half-life time of 115.5 h. In the HMF oxidation, an approximate 90% yield of 5-formyl-2-furancarboxylic acid (FFCA) was achieved, indicating that the immobilization process altered the enzyme's selectivity. This study demonstrated the possibility of obtaining a highly selective biocatalyst for the synthesis of FFCA.