Single-step polydopamine-assisted immobilization of laccase on membranes for reusable biocatalytic degradation of emergent pollutants

Laccases (LC) are highly versatile multicopper oxidoreductases widely used in research and industry for their ability to degrade complex compounds. Despite this range of potential applications, the biocatalyst requires stability improvements, specifically through immobilization processes that typically involve multiple steps and the addition of several chemical compounds. This study introduces a single-step immobilization method using self-polymerized polydopamine (PDA) to attach LC to a PVDF membrane. The immobilization process occurs through the interaction between dopamine and LC, leading to the formation of PDA, which serves as both a coating and an immobilizing agent for LC. Optimal experimental immobilization conditions were 30 min with 2 mg∙mL^-1 LC and 0.25 mg∙mL^-1 dopamine. The biocatalyst showed exceptional activity, remarkable stability across pH and temperature, and outstanding reuse stability (60% after 60 reuse cycles). The functionality of the biocatalyst was demonstrated for the degradation of pharmaceutical pollutants, such as doxorubicin, as a proof-of-concept for sustainable wastewater bioprocesses, and the catalyst achieved 90% degradation within 24 h. In conclusion, the method was tested on various membrane materials, yielding even greater activity (≈3-fold) and confirming its potential for practical application.