Co-immobilization of multi-enzyme cascade system into the metal–organic frameworks for the removal of Bisphenol A

Enzymes have emerged as effective biocatalysts for oxidizing and detoxifying numerous toxic organic substrates. On the negative side, enzymatic applications, especially those associated with liquids with un-favored conditions, like pH, temperature, etc., are limited due to poor process/operational stability of the enzymes. In this research, we offer a self-controlled cascade system constituted by glucose oxidase (GOx) and horseradish peroxidase (HRP) incorporated into metal–organic frameworks (MOFs), in which substrates and pH are self-regulated to trigger the cascade catalysis. Besides providing a protective shield for enzymes, MOF facilitates the selective diffusion/permeation of the substrates/products through their porous networks. At the same time, in situ production of the electron donor/organic acid by GOx engineers the MOF microenvironment to effectively activate the HRP. The prepared biocatalyst was characterized well by the SEM, TEM, EDX, XRD, FT-IR, XPS, CLSM, BET, and TGA analyses. The MOF frame could save the enzymes from interfering factors such as the chemicals and thermal stresses that can exist in the real systems and adversely affect the enzymes. Finally, the applicability of the prepared biocatalyst was investigated for the removal of bisphenol A (BPA). The encapsulated cascade system exhibited significant removal of BPA as much as the free cascade system. 80 % of BPA with an initial concentration of 20 ppm was biodegraded by the synthesized biocatalysts throughout 360 min in a green process.