Laccase-catalyzed Environmental-friendly Polymerization And Immobilization Of Laccase

Laccase is a copper-containing polyphenol oxidase,which is widely used in environmental treatment because it can degrade many organic pollutants efficiently under aerobic conditions.The existence of adjustable copper atoms in laccase enables the successful application of laccase in catalytic atom transfer radical polymerization（ATRP）,which avoids the pollution of traditional metal catalysts to the polymerization products,and achieves the clean and environmental protection of the catalytic system.However,the vulnerability of free laccase in harsh environments and the irreversible decline of its activity after use have hindered the industrial application of laccase.The stability and tolerance of laccase were improved by enzyme immobilization technology,and the reuse of laccase was realized.The focus of this thesis was on the research and preparation of new environmentally functional polymer materials,and attempted to apply this type of environmentally functional polymer materials to the removal of phenolic pollutants in water.Herein,a series of nitrogen-containing ligands were added into the system using laccase as the ATRPase for activators regenerated by electron transfer（ARGET）ATRP.The utilization of additional ligands such as tris（2-（dimethylamino）ethyl）amine could efficiently remove copper atoms from laccase to form copper-ligand coordination compounds as co-catalysts for polymerization,which significantly increased the conversion and yielded well-defined polymers and enzymes with maintained activities,which proved that the ligand and the laccase had a good interaction.The synthesis of the poly(PEGA₄₈₀)was comprehensively studied using different ligands,catalysts,monomers and initiators with different solubility.The SEC figures showed two peaks structure,indicating that there may be two polymer chain populations in almost all polymerization reactions.Subsequently,poly（ethylene glycol）-based hydrogels were prepared in one-pot using water as the solvent under 25℃.The rheological properties,coating rates,release rates and water absorptions of the hydrogels coated with laccase were adjusted by cross-linking agents with different crosslinking degrees.Immobilized enzymes in the hydrogels have shown decreased yet considerable activity compared with the pristine laccase.After that,the recovered hydrogels via simple filtration were reused for up to six times with no significant decrease of enzyme activity.Finally,the immobilized laccase was successfully applied to the removal of hydroquinone,catechol and resorcinol.There are two different removal mechanisms,including the degradation of the immobilized laccase oxidized polymerized benzenediol and the adsorption of the hydrogels.The degradation of hydroquinone by immobilized enzyme at different temperature and p H were measured to determine the optimum degradation conditions.Such enzyme-loaded hydrogels may find potential application in protein delivery and water treatment.