Abstract
Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment.
Highlights
Ionic Polymer-Coated Laccase with High Activity and Enhanced Stability: Application in the Decolourisation of Water Containing acid orange 7 (AO7)
UV-Vis spectra (Supplementary Fig. S1) revealed that a significant increase in the absorption intensity occurred for LacPG from 310 to 550 nm compared to a mixture of Lac and PEI-G at the same concentration level, indicating that LacPG was a new product rather than a simple mixture
The size distributions of Lac and LacPG were measured by dynamic light scattering (DLS) (Fig. 1(c)), which indicated a Lac diameter within 4–6 nm, in agreement with the previously reported value for under otherwise identical conditions and the results were shown in Supplementary Fig. S3
Summary
Ionic Polymer-Coated Laccase with High Activity and Enhanced Stability: Application in the Decolourisation of Water Containing AO7. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. Numerous processes have been developed to minimise the adverse effects of azo dyes on water quality, including adsorption and advanced oxidation processes[8]. Laccase is attracting increasing interest for use in wastewater treatment[14,15,16], including effluents containing dyes[17,18,19,20,21]
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