A green approach combining polyelectrolyte-based core-shell microparticles and laccase for indigo carmine degradation

Highly effective composite biocatalysts were developed by the immobilization of laccase (LAC), a copper oxidoreductase, on core-shell microparticles obtained by the layer-by-layer deposition of polyelectrolytes, SP/(PEI/PAA) 4.5 and SP/(PEI/PMANa) 4.5 . The relation design – properties – applications was successfully elucidated by a comprehensive characterization performed using a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), potentiometric titrations, energy dispersive X-ray (EDX) spectroscopy and catalytic activity assays. The core-shell composite microparticles were able to immobilize more than 50 % of the enzyme, conserving a satisfactory enzymatic activity. LAC@SP/(PEI/PAA) 4.5 and LAC@SP/(PEI/PMANa) 4.5 were further employed in the degradation of indigo carmine as a model pollutant under various experimental conditions. The influence of the amount of enzyme immobilized, the pH, the mediator and the dye concentration were assessed, observing that LAC n @SP/(PEI/PAA) 4.5 and LAC n @SP/(PEI/PMANa) 4.5 performed better when syringaldehyde was used as a mediator. The obtained immobilized LAC achieved 100 % discoloration efficiency, demonstrating their potential as green catalysts for water cleaning applications. Additionally, the immobilized LAC exhibited significantly enhanced stability upon reuse, being able to completely discolour the dye sample up to 4 reuse cycles. • Composites design by LbL polymers deposition on silica core, stepwise crosslinked. • The laccase immobilization controlled by its concentration and hydrophobic support. • Biocatalysts important catalytic activity/stability in varied process conditions. • Indigo carmine successfully degraded by immobilized enzyme, reusable in 4 cycles.