Immobilization Of Laccase And Preparation Of Composite Hydrogels

Laccase(Lac)is a common copper-containing biocatalyst in nature,and different kinds of Lac can be extracted from plants and microorganisms(fungi,bacteria and protists).In this study,Lac from Trametes versicolor was selected.Lac was covalently coupled with the regenerated silk fibroin(SF)by photochemical crosslinking under mild conditions.Using these enzyme-containing hydrogel as templates,different composite materials can be prepared by catalysis of immobilized Lac such as catalyzing pyrrole(Py)in an aerobic environment to prepare a electrically conductive hydrogels coated with polypyrrole(PPy)or catalyzing alkaline lignin(AL)to prepare AL-SF composite hydrogels.(1)In the second chapter of this thesis,SF was extracted from raw silk first.Then,SF and Lac were cross-linked by the photo-crosslinking method and prepared SF based hydrogels with Lac immobilized.The enzyme-containing hydrogels were incubated in Py solution with bubbling O2 stream.PPy was synthesized from Py in the hydrogels by catalysis of immobilized Lac.This method of preparing PPy-SF based hydrogels is abbreviated as the "enzymic" method.PPy uniformly coated in hydrogels and was firmly bind with was firmly bound with SF amino acid residues by H-bonds and covalent bonds,giving the hydrogels electrical property.Finally,those hydrogels were analyzed by a series of tests.The conductivity of hydrogels was analyzed by electrochemical impedance spectroscopy(EIS).(2)In chapter 3,the method of preparing AL-SF composite hydrogels was introduced.The Lac-containing hydrogels were put into AL solution.Lac catalyzed the linking of AL with the residues of SF by covalent bonds,which made more cross-linking sites formed inside the hydrogels.AL-SF based hydrogels were characterized and analyzed by UV-Vis,SEM,etc.The crosslinking network of AL-SF based hydrogels became more complex.Mechanical tensile tests showed that the Young’s modulus of hydrogels was significantly improved after combining with AL.In addition,because of the high ultraviolet(200 nm～420 nm)absorption capability of AL,the AL-SF hydrogel membranes had stronger resistance to ultraviolet penetration.The above results show that SF based hydrogels immobilized with Lac can obtain additional and good properties.This study offers a promising strategy to exploit the potential of natural biopolymers and biocatalyst,and shows great potential in the field of new materials.