Construction and utilization of Fe3O4@Al3+ immobilized laccase for enhancing organic diethylstilbestrol removal: a multi-spectroscopy and molecular docking investigation

As one of the endocrine-disrupting compounds (EDCs), diethylstilbestrol (DES) poses significant risks to ecosystems and human health. This study reports the development of a magnetic nanocomposite (Fe₃O₄@Al³⁺@laccase) via glutaraldehyde (GA) crosslinking to enhance DES degradation. The single factor experiments revealed that the optimum immobilization conditions were: temperature 40℃, pH 5, enzyme concentration 1.0   mg/mL, and immobilization time 1.0   h. Under these conditions, Fe₃O₄@Al³⁺@laccase achieved 91.71%±2.95% DES degradation within 12   h, as validated by HPLC, retaining 31.29%±1.99% of its initial catalytic activity after 10 reuse cycles. Notably, the immobilized laccase exhibited superior stability in organic solvents compared to free laccase. Fourier-transform infrared (FTIR) analysis confirmed that laccase was successfully conjugated onto Fe₃O₄@Al³⁺. Scanning electron microscopy and transmission electron microscopy revealed that the immobilization process preserved the original morphology and crystalline structure of Fe₃O₄@Al³⁺. Multi-spectroscopic analyses, including enzyme kinetics, fluorescence, and three-dimensional (3D) spectroscopy, elucidated the binding affinity and conformational changes between laccase and DES. Molecular docking simulations predicted a binding free energy of −6.4   kJ·mol⁻¹, indicating that the conformation stability between laccase and surrounding free amino acids was mainly maintained via van der Waals, pi-pi T-shaped, Pi-Donor Hydrogen Bond, and Pi-Alkyl. This work provides proof-of-concept for using Fe₃O₄@Al³⁺ as a reusable magnetic support for laccase, offering a promising strategy for DES degradation and guiding the design of advanced nanomaterials for environmental bioremediation.