Exploring facile synthesis of Irpex lacteus laccase-coated copper-ferrite nanoconjugate for enhanced catalytic degradation of heterocyclic azo dyes from wastewater

The widespread release of recalcitrant heterocyclic azo dyes from the textile industry poses a significant environmental and health hazard. This study demonstrates a facile, green synthesis of a novel bio-hybrid nano-catalyst by immobilising laccase from the white-rot fungus Irpex lacteus onto Cu(II) nanoparticles. The laccase served a dual role as a reducing and capping agent, forming a stable laccase-coated copper ferrite nanoconjugate. Optimisation revealed that 0.3 M CuFe2O4, 1% (v/v) laccase extract, and a 30-minute reaction time yielded the most effective conjugates, as confirmed by a distinct Surface Plasmon Resonance peak at 344 nm. Comprehensive characterisation showed that the laccase-doped copper ferrite nanoconjugate had a hydrodynamic size of 80 nm, a negative zeta potential, and a dense enzyme coating, as observed via scanning electron microscopy, which enhanced colloidal stability and prevented aggregation. The catalytic proficiency of the laccase-doped copper ferrite nanoconjugate was evaluated against Methyl Red and Malachite Green dye. The nanoconjugate exhibited superior degradation efficiency under both fluorescent and photocatalytic light, outperforming free laccase and bare copper-oxide nanoparticles. Notably, for malachite green dye, a 30% laccase-doped copper ferrite nanoconjugate concentration under photocatalytic light reduced absorbance by 93% (from 1.52 to 0.1 AU). Similarly, for Methyl red dye, the same treatment achieved over 80% degradation. The laccase-doped copper ferrite nanoconjugate also demonstrated excellent reusability. This work establishes the immobilised nanoparticles as a potent, sustainable, and synergistic nano-biocatalytic system for the efficient remediation of hazardous dye-laden wastewater.