Immobilization of laccase on phase-change microcapsules as self-thermoregulatory enzyme carrier for biocatalytic enhancement

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The immobilized enzymes on conventional solid carriers usually have to suffer from progressive deterioration in biocatalytic activity at high temperatures. To address such an annoying problem, we designed a self-thermoregulatory enzyme carrier system based on phase-change microcapsules for immobilization of laccases. A primary phase-change microcapsule system was first fabricated with n-docosane as a phase change material core and silica as an inorganic shell via interfacial polycondensation, and then a polydopamine/gold nanoparticles hybrid layer was coated on the surface of silica shell through surfactant-assisted self-assembly and in-situ reduction of Au ions to form the enzyme carrier. The introduction of n-docosane core endows the enzyme carrier with a thermal self-regulation function through phase transition. A laccase was immobilized onto the surface of this enzyme carrier by using an immobilized copper chelate method. The resultant immobilized laccase exhibits a perfect layer-by-layer core-shell microstructure and a satisfactory latent heat-storage capacity over 120 J/g. By a unique combination of laccase and the self-thermoregulatory enzyme carrier, the resulting immobilized laccase not only achieves a significant improvement in biocatalytic activity at high temperatures due to in-situ thermal management and temperature regulation by its n-docosane core during the biocatalytic process, but also gains an enhancement in thermal and storage stabilities. In addition, the immobilized laccase on the novel enzyme carrier developed by this work demonstrates outstanding performance in operation reliability, phase-change reversibility, thermal and shape stabilities, reusability, and tolerance to various metal ions and organic solvent for practical biocatalytic applications along with effective thermal self-regulation. This study offers an innovative strategy for design and development of immobilized enzymes with an enhanced enzyme activity for biocatalytic applications in a wider temperature region.