Study On Laccase Immobilization And Repair-improvement Of 2,4-Dichlorophenol Contaminated Soil

The chlorophenolic compounds(CPs)are persistent organic pollutants widely existing in the environment.The laccase catalytic reaction is environmentally friendly and broad-spectrum,and the immobilized enzyme technology largely solves the defect that laccase is poorly tolerated and easily inactivated in practical applications.The optimal conditions of laccase immobilization using organic fertilizer and biochar and the properties and stability of laccase under different states were studied in this paper.Then,the 2,4-dichlorophenol(2,4-DCP)was selected as the target pollutant to study the repair of contaminated soil by laccase under different states,at the same time,the improvement effect of soil was studied through ecological evaluation.The main conclusions are as follows:(1)The optimal carrier particle size for organic fertilizer/biochar immobilized laccase was 30 mesh,the amount of added enzyme was 15 mL and 20 mL respectively,the adsorption time was 4h and 6h respectively,the glutaraldehyde volume fraction was 5% and 4% respectively,and the crosslinking time was 6h and 4h respectively.Principal component analysis showed that the particle size,the adsorption time and the glutaraldehyde volume fraction are all important for activity of immobilized laccase.(2)The effects of pH,temperature and moisture content on laccase activity under different states were significantly different(p<0.05);The optimum action conditions for free laccase,organic fertilizer immobilized laccase and biochar immobilized laccase: the pH is 5,4 and 4 respectively,the temperature is 40°С,40°С and 35°С respectively,the moisture content is all 40%;The immobilization process improved the laccase stability,and the stability of biochar immobilized laccase was the best: when treated at 50°C or pH = 8 for 2.5h,the relative enzyme activity of biochar immobilized laccase was 81% and 75%,respectively,and the relative enzyme activity was 61% after using 6 times.(3)The activity loss of free laccase in soil was rapid;Immobilization did not affect the pathway of degradation of 2,4-DCP by laccase,however,immobilized laccase could remove more 2,4-DCP from soil,the degradation rate of biochar immobilized laccase was the highest,reaching 64.4%;Ecological evaluation showed that organic fertilizer carrier and biochar carrier could improve soil,and organic fertilizer carrier had better improvement effect in general.