| Laccase is a kind of polyphenol oxidase,which can use oxygen as the only receptor to catalyze the oxidation of various refractory organic compounds,such as phenols,aromatic amines,carboxylic acids,steroids and so on.However,free laccase is easy to inactivate and cannot be reused in polluted environment.Immobilization of laccase can remove the limitation of laccase application.At present,the pollution of phenolic compounds is serious,which poses a threat to the environment and human health.Immobilized laccase is an effective way to solve this problem.In this paper,three kinds of immobilized laccase were prepared by using sodium alginate（SA）-sodium carboxymethylcellulose（CMC）composite as carrier,ethylene glycol diglycidyl ether（EGDE） and glutaraldehyde（GLU） as crosslinking agents.The immobilized laccase was characterized by SEM,FTIR and XRD.The stability of free laccase and immobilized laccase was studied,the effects of different factors on the removal of 2,4-dichlorophenol（2,4-DCP） by immobilized laccase were discussed,and the possible degradation pathways of pollutants were given.The main conclusions are as follows:（1）The optimum conditions of Lac@SC were as follows:SA concentration 2.5%,CMC concentration 0.75%,CaCl2 concentration 5%,enzyme dosage 2mg/ml,pH=6,immobilization time 30 min;The optimal concentration of Lac@SCE and Lac@SCG crosslinking agent was 5%,and the optimal crosslinking time was 30 min and 40 min,respectively.（2）SEM results showed that laccase particles could be seen on the surface of three kinds of immobilized laccase,indicating that laccase was successfully encapsulated in the carrier or cross-linked on the surface.FTIR and XRD results showed that laccase was immobilized on the carrier,and the three kinds of immobilized laccase belonged to amorphous disordered structure.（3）Compared with free laccase,the stability of p H,heat and storage of immobilized laccase were improved.The immobilization of laccase has better activity at pH 3-6,and the immobilization behavior broadens the pH application range of laccase;the heat resistance of immobilized laccase is improved,and the pH value of immobilized laccase is improved,the activity was maintained high in the temperature range of 25℃ to 65℃.The storage stability of immobilized laccase was better than that of free laccase,After 30 days storage of Lac@SCG in 4℃ refrigerator,the relative enzyme activity still has more than 40%;Lac@SC has best reusability among three kinds of immobilized laccase,the results showed that the activity of the enzyme was still more than 50% after 5 times of use.（4）The removal efficiency of 2,4-DCP by three immobilized laccase was compared,The removal rate of 2,4-DCP by Lac@SCE was higher at different pH and temperature.When pH = 5,temperature 35℃ and reaction time 25 h,the removal rate of 2,4-DCP（initial concentration 30 mg/L）by Lac@SCE can reach 95.2%. |
