Degradation of tetrachloroguaiacol by an enzyme embedded in a magnetic composite cage structure of MNPs@ALG@SiO2

Abstract

Entrapment of enzyme in a cage structure of alginate/silica composite gel can maintain the chemical or configurational structures unchanged in the enzyme, providing a promising means of enzyme immobilization. The alginate/silica composite gel can also provide more adsorption sites for the substrate, which is biocompatible and will carry out degradation and adsorption of pollutants within a cage-like structure reactor simultaneously. In this study, we used a magnetic host-guest cage structured MNPs@ALG@SiO2 composite with a specific enzyme embedded as its guest in the host matrix, to enhance its performance. Additionally, its swelling, leakage rate and immobilization conditions were optimized. The magnetic nanoparticles (MNPs) were used to compensate for the ease of collapse of the internal structure of alginic acid, while SiO2 was used to enhance the swelling resistance of the carrier and prevent the degradation of polysaccharides in the natural environment, thereby maintaining the enzyme biological activity and immobilization rate. Finally, the effects on the degradation of tetrachloroguaiacol (TeCG) by the immobilized enzyme embedded in the MNPs@ALG@SiO2 composite were investigated. When the concentration of ALG was 2% and the TEOS concentration was 40 %, the immobilized MNPs@ALG@SiO2 was found to perform the best. The optimum conditions of immobilizing laccase are pH = 5, enzyme concentration 0.4 g/L, adsorption time 12 h and temperature 20 ℃. The degradation conditions of TeCG are pH = 6, degradation temperature 40 ℃, degradation time 10 h and the degradation products of TeCG were acetic acid and ethanol according to GC–MS.