Immobilization of laccase in a sponge-like hydrogel for enhanced durability in enzymatic degradation of dye pollutants

A highly stable and efficient biocatalyst was fabricated by encapsulating Trametes versicolor laccase within a chitosan grafted polyacrylamide hydrogel (denoted as Lac-PAM-CTS). Scanning electron microscopy and nitrogen adsorption-desorption tests demonstrated that channels of diameter of 10-20 mu m were regularly distributed throughout the sponge-like Lac-PAM-CTS. Besides, there were massive mesopores and macropores in the lamellar walls of the hydrogel. Such a network structure reduced the diffusion resistance of the hydrogel to the target substrates. The recovered activity of the obtained Lac-PAM-CTS was 40.8%. As compared to free laccase, the Lac-PAM-CTS showed enhanced thermal and chemical stability. The positive surface charge of the Lac-PAM-CTS endowed it with a pre-enrichment effect in the treatment of anionic dyes. In a continuous six-cycle batch decoloration of Malachite Green, the Lac-PAM-CTS showed much better durability than the free laccase. The results here suggest that sponge-like hydrogel is a good supporting matrix for laccase. (C) 2015 Elsevier Inc. All rights reserved.