Laccase aggregates via poly-lysine-supported immobilization onto PEGA resin, with efficient activity and high operational stability and can be used to degrade endocrine-disrupting chemicals

Abstract

Immobilized enzymes possess catalytic activity as well as substrate specificity. Even though enzyme immobilization techniques for industrial applications are well established, the operational stability of immobilized enzymes often needs to be improved. Laccases have been applied for the degradation of endocrine-disrupting chemicals (EDCs) or organic synthesis. In this study, using the technique of poly-lysine (poly-Lys)-supported cross-linking, laccase molecules were for the first time immobilized as enzyme aggregates onto PEGA resin (Lac–PEGA) and the prepared Lac–PEGA was evaluated in its operational stability and ability to degrade the EDC bisphenol A (BPA). Lac–PEGA was prepared through a simple and inexpensive immobilization technique without any costly equipment. Lac–PEGA showed similar thermal and pH stabilities to those of free laccase, suggesting that immobilized laccase maintains the conformation required for its catalytic activity. Compared with free laccase and Lac–PEGA(−), which was prepared without addition of poly-Lys, Lac–PEGA was more stable in organic solvents and could be reused for 50 cycles without appreciable loss of activity. Moreover, Lac–PEGA could effectively remove BPA and its derivatives in a batch reactor. In the batch reactor, a BPA removal efficiency of 144 μM h⁻¹ was obtained at 30 °C. Due to its good operational stability, Lac–PEGA was successfully applied for reactions with high removal efficiency in a flow reactor. In the flow reactor, a BPA removal efficiency of 2880 μM h⁻¹ was obtained at 50 °C, much superior to other reported reactors by the laccase immobilized with traditional carrier-bound immobilization methods. These results demonstrated that Lac–PEGA with specific enzymatic activity and high operational stability can be used as catalysts not only for the efficient removal of BPA from the environment but also for promising applications in the fields of chemistry and biotechnology.