Environmentally friendly novel covalently immobilized enzyme bionanocomposite: From synthesis to the destruction of pollutant

Abstract

Herein, nanozeolite - carbon nanotube composites with the covalently immobilized enzyme (Laccase) as novel bionanocomposites were synthesized and used for pollutant (Direct Red 23) bio-degradation. Different amounts of carbon nanotube (30, 50, and 70 mg) were used to synthesize carbon nanotube -zeolite nanocomposites. The synthesized nanomaterials were silanized and cross-linked by glutaraldehyde. Finally, the enzyme was immobilized on them to prepare Laccase immobilized nanomaterials. The biocatalysts were characterized using Scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), and Transmission Electron Microscopy (TEM). The effect of operational parameters on bio-degradation was investigated and optimized. The synthesized biocatalyst nanocomposite retained more than 95% of its initial activity over the first 5 cycles and its efficiency is still intact. After 10 cycles relative activity decreased gradually to 69%. Results revealed much higher stability for Laccase after the immobilization and 84% of the maximum activity of nanocomposite was preserved at 80 °C. The activity of free Laccase lost over 60% of its activity after 8 days of incubation while the nanocomposite retained about 80% of its maximal activity. They had high storage stability over 8 incubation days and good performance at thermal stability experiments (45–80 °C for 1 h).