Resin Immobilized Laccase And Its Degradation Congo Red Dye Wastewater

As a biocatalyst, free laccase was more sensitive to the surrounding environment and difficult to reuse, the enzyme immobilization technology is an effective means to solve the above problems. In this paper, application of weakly basic epoxy anion exchange resin, using glutaraldehyde as cross linking agent on the immobilized laccase. The factors that affected the relative activities of immobilized laccase were discussed, such as cross-linked time, cross-linked temperature,immobilized pH and so on. When the cross-linking agent concentration was 1%, cross-linked time was 8h, cross-linked temperature was 30℃, immobilized pH was 4.0, the enzyme dilution was 100, the enzyme was 10 mL, the PBS ion concentration was 0.1 mol/L, the immobilized time was 5 hours and the immobilized temperature was 25℃, the activities of immobilized laccase was the highest.Response surface methodology (RSM) was used for the evaluation of effects of various parameters and their interactions on relative activities of immobilized laccase. The results show that enzyme dilution was the principal factor and the interaction between ion concentration and immobilized temperature was significant during the enzymatic process. The test results under the optimum conditions are: the average a result of immobilized enzyme activity was 11.26 U/g; the difference value was only 0.73 U/g as the model of the theoretical value (15.95 U/g), and further shows that the model is feasible.ABTS as a substrate, enzymatic properties of immobilized and free laccase were compared: the activities of immobilized laccase after 1 hour staying in buffer still kept 80% at the pH range of 3-5, compare with the activities of free laccase was 70%, indicating the pH of immobilized laccase was more stable than free enzyme stability; the immobilized laccase in 25℃-40℃heating for thermal stability test, indicating that its thermal stability has been significantly improved; the immobilized laccase was used in recycled 10 times, it was still maintain 45% of the activity, indicating that immobilized laccase can be used repeatedly. The immobilized laccase was used in the biocatalysts of Congo red. Results indicated that the best pH condition was 6.0; and the suitable substrate concentration was 10 mg/L, which degradation ratio came to 70%; after continuous use of 5 times, the activities still maintain above 40%; Most of the inhibitory effect of metal ions on the enzyme activity was not significant, With the increasing concentration of metal ions, the relative activities was decreased, the Fe²⁺ inhibited the activities significantly, while the Cu²⁺ was active; Decolorization rate of Congo red has little effect when most of metal ions exist except Fe²⁺; increasing the concentration of Cu²⁺ and Cr⁶⁺ appropriately, decolorization was increased to some extent; the activities was decreased by 13% when added mixed metal ions, generally, immobilized laccase has some accommodate capacity with most metal ions except Fe²⁺.