(316g) Functionalized Magnetic Graphene Oxide Sheets for Efficient Cota Laccase Immobilization

In the recent decades, massive industrial revolution of textile dyes brought a serious environmental pollution, especially for water. Synthetic dyes gave warning not only for the environment but also for human health because of their existence in wool, textiles, papers, and leathers. As environmentally friendly biocatalysts, laccases can degrade a broad range of industrial toxic contaminants. However, the industrial applications are limited due to the low stability and poor reusability of free laccases.

Enzyme immobilization can reduce the restrictions by increasing the stability, durability and realizing continuous operations. Up to now, laccase has been successfully immobilized on various kinds of carriers, such as microspheres, nanoparticles, nanofibers and membrane. Among these carriers, the specific magnetic particles can be produced by immobilization of an affinity ligand on the surface of prefabricated magnetic beads, which can be quickly separated from the reaction medium and controlled by applying a magnetic field; then the catalytic efficiency and stability properties of the enzyme can be greatly improved.

In the current study, functionalized magnetic graphene oxide (MGO) support attached with Nα,Nα-Bis (carboxymethyl)-L-lysine hydrate (NTA-NH₂) and chelated with Cu²⁺ were synthesized. The Cu²⁺-chelated MGO (MGO-NTA-Cu²⁺) exhibited the highest adsorption capacity of 177 mg/g-support for CotA laccase among all synthesized nano-composites. The maximum activity recovery of laccase using MGO-NTA-Cu²⁺ was 114%. The catalytic properties of MGO-NTA-Cu-CotA laccase were significantly improved in comparison with those of free laccase. MGO-NTA-Cu-CotA laccase showed efficient decolorization rate for Congo red (CR) reached 100 % after 5 h reaction at 60 °C and pH 8. MGO-NTA-Cu-CotA laccase retained 89.4 % of its initial activity after 10 consecutive cycles. These MGO-NTA-Cu²⁺ supports provide promising potential for large-scale laccase immobilization in practice.