Homologous amino acids promoted co-immobilization of laccase and mediator onto geopolymer microspheres for enhancing degradation of dyes in water

A new strategy for co-immobilization of laccase (Lac) and mediator 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) on geopolymer microspheres (GM) was reported in this work, which was promoted by pre-embedded homologous amino acids, i.e., histidine (His) and cysteine (Cys). The GM-H2C1 produced with a His/Cys ratio of 2:1 was highly efficient in co-immobilizing Lac and ABTS. The as-prepared composite biocatalyst (Lac-ABTS@GM-H2C1) exhibited the highest degradation rate (94.78%) to the model pollutant (Congo Red, CR), which was superior to free Lac-ABTS (79.23%) and Lac@GM-H2C1 (53.82%). The enhanced degradation efficiency of CR by the Lac-ABTS@GM-H2C1 was due to the promoted electron transfer and shortened mass transfer distance. Moreover, Lac-ABTS@GM-H2C1 demonstrated good pH resistance, competitive storage stability, and good reusability during ten cycles of CR degradation.