Exploring the functionality of an active ZrF-laccase biocatalyst towards tartrazine decolorization

Abstract

This work describes the design and fabrication of zirconia-fucoidan (ZrF) using the modified sol–gel method as the substrate for laccase immobilization (ZrF-laccase). Based on Bradford analysis, the amount of immobilized laccase and the immobilization efficiency were determined at 130 mglaccase/gsupport and 87%, respectively. The immobilization efficiency was also confirmed by determining physicochemical parameters (such as spectroscopic, thermal stability, electrokinetic, surface area and pore volume) of the prepared zirconia-fucoidan materials with and without laccase immobilization. The decrease in the value of the isoelectric point (from 6.4 to 4.0), the specific surface area (from 366 to 108 m2/g) and the pore volume (from 0.33 to 0.18 mL/g) after the immobilization process indicates effective immobilization of the laccase on the zirconia-fucoidan material. The relative activity of immobilized laccase was determined using the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) oxidation reaction. The ZrF-laccase biocatalytic system exhibits higher enzymatic activity than free laccase under a range of pH and temperature conditions (above 40% of initial activity) and can be reused in ten reaction cycles, retaining approximately 80% of its initial activity. The ZrF-laccase biocatalytic system was evaluated for the degradation of tartrazine as a model azo dye. The ZrF-laccase biocatalytic system could achieve 95% tartrazine decolorization in five repetitive cycles. Based on mass spectroscopy analysis, the pathway of tartrazine degradation was also proposed. Proposed methodology as well combination of zirconia, fucoidan and laccase appear to be a promising approach and open new pathways for production of highly effective biocatalyst for various applications focused on removal of emerging pollutants from the environment.