Development Of Zwitterionic Polymer-coated Porous Microspheres For Lipase Immobilization

Development of creative and efficient carries for immobilized enzymes is an important subject in the field of enzyme engineering for improving the catalytic efficiency,stability and reusability of enzyme.In this work,in order to develop a new type of efficient carrier for lipase immobilization,we proposed zwitterionic polymer-coated porous hydrophobic microspheres for lipase immobilization to improve its activity and stability.First of all,a porous poly(vinyl acetate–divinyl benzene)hydrophobic microsphere(MS)coated by a zwitterionic polymer contained cetane side chains,poly(maleic anhydride-alt-1-octadecene)and N,N-dimethylethylenediamine derivative,was prepared(p-MS).The results of SEM,EDS,thermogravimetric and elemental analysis demonstrated the success of MS and p-MS preparation and the strong hydrophobic adsorption between zwitterionic polymer and MS.The pore size of MS averaged 21.9 nm measured by BJH method.The pore size of p-MS decreased with the increasing of polymer coating density,which was 17.1 nm with 13.0%of coating density.Afterwards,the lipase(CRL)was immobilized onto MS and p-MS via hydrophobic interaction.The immobilized lipase prepared with p2-MS(p2-MS-CRL)reached 27.6 mg/g dry carrier,and the interaction between lipases and carries was strong.Due to the interfacial activation effect regulated by the hydrophobic side chain of zwitterionic polymer,p2-MS-CRL displayed a specific activity 1.5 times higher than free CRL and a stronger enzyme-substrate affinity(the K_mof p2-MS-CRL was only half of free lipase).Besides,p-MS-CRL exhibited significantly enhanced thermal stability,p H tolerance and storage stability.P2-MS-CRL remained about 50%of its initial activities after eight cycles.The hydrolysis of methyl mandelate catalyzed by p2-MS-CRL showed that the catalytic activity of p2-MS-CRL was about twice that of free enzyme,demonstrated the application prospects in the preparation of mandelic acid.This study has thus proved the advantages of the zwitterionic polymer-coated porous carrier for lipase immobilization and its potential for further development.