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Catalytic Properties of Lipases Immobilized onto Ultrasound-treated Chitosan Supports
Matheus Dorneles de Mello,Deborah Cordeiro,Lilian Terezinha Costa,Cristian Follmer 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.6
Ultrasound sonication has been utilized toproduce fragmentation of chitosan polymer and hence increasethe chitosan surface area, making it more accessible tointeractions with proteins. In this context, we haveinvestigated the catalytic properties of lipases from differentsources immobilized onto ultrasound-treated chitosan (ChiS)pre-activated with glutaraldehyde (ChiS-G). Atomic forcemicroscopy indicated that ChiS-G displays a more cohesiveframe without the presence of sheared/fragmented structureswhen compared with ChiS, which might be attributed tothe cross-linking of the polysaccharide chains. Theimmobilization efficiency onto ChiS-G and ChiS wereremarkably higher than using conventional beads. Incomparison with the free enzymes, lipases immobilizedonto ChiS show a slight increase of apparent Km anddecrease of apparent Vmax. On the other hand, immobilizationonto ChiS-G resulted in an increase of Vmax, even though aslight increase of Km was also observed. These datasuggest that the activation of chitosan with glutaraldehydehas beneficial effects on the activity of the immobilizedlipases. In addition, the immobilization of the lipases ontoChiS-G displayed the best reusability results: enzymesretained more than 50% of its initial activity after fourreuses, which might be attributed to the covalent attachmentof enzyme to activated chitosan. Overall, our findingsdemonstrate that the immobilization of lipases ontoultrasound-treated chitosan supports is an effective andlow-cost procedure for the generation of active immobilizedlipase systems, being an interesting alternative to conventionalchitosan beads.