Simple Design of Laccase-Coated Polymer Membranes and Evaluation of Their Biocatalytic Performances in Flow Reactors

Enzymatic degradation of harmful micropollutants using laccase is currently one of the most studied alternatives to tackling the continuous accumulation of these compounds in natural water. More specifically, laccase-coated membranes offer the advantage of continuous operability and compatibility with water treatment processes. In this work, laccase is immobilized within nanoporous polycarbonate membranes by using the layer-by-layer (LbL) assembly approach. First, the impacts of different parameters on the buildup of polyelectrolyte–enzyme multilayers are investigated on flat surfaces. This study reveals that the optimal buildup method consists of selecting polyethylenimine as the polycation, using MES buffer as the assembly medium and performing a cross-linking after each bilayer deposition. Under these conditions, very active (enzymatic activity of 1.3 mU·cm–2) and stable (79% of the activity is maintained after the fifth catalytic cycle) coatings are obtained. Polycarbonate membranes coated with this method achieve a capacity as high as 55 nmol·min–1·cm–2 of oxidized ABTS when operated in a flow reactor and remain stable after 45 days of storage. Overall, this work provides insight into the mechanisms underlying LbL assembly and cross-linking of laccase-containing films and demonstrates the potential of laccase-coated membranes as efficient and stable materials for use in flow reactors.