Abstract
Enzyme immobilization onto nanomaterials is a strategy to overcome the difficulties of the free enzymes applications where the immobilization process affords excellent reusability and operational stability against temperature and pH, and high surface area for the catalytic reaction. In this work, poly(Acrylonitrile-co-Styrene/Pyrrole), (poly(AN-co-ST/ Py)), copolymer nanofibers were successfully fabricated using the electrospinning technique. Laccase enzyme from Trametes versicolor was immobilized onto functionalized poly(AN-co-ST/Py) nanofibers by covalent attachment using polyethylenediamine (PEI) via physical adsorption and multipoint covalent attachment to the functional groups onto the polymeric surface. Since the relative activity of the immobilized Laccase depends on the amount of the coupled PEI onto the polymeric nanofibers, a colorimetric assay via copper ions complex formation was applied for the estimation of the process yield. Accordingly, the various factors affecting the PEI coupling process such as concentration, time, pH and temperature were investigated; Besides their influence on the morphology of the resultant nanofibers. Furthermore, thermal and pH stability, storage stability, and reusability were evaluated and compared. The optimum reaction temperature and pH for the immobilized enzyme were 70 degrees C and 6.0, respectively. The scanning electron microscopy (SEM) images showed that the modified nanofibers with PEI have kept its nanofibers structure and uniform morphology with an average diameter of approximately 559.2 nm. Within 35 days, the immobilization process reduces the activity loss from 59 % to 29 %, while thermal incubation at 50 degrees C for 2 hrs causes activity loss for the free and immobilized enzymes by 65 % and 30 % respectively. Therefore, the prepared copolymer nanofibers proposed in this work showed promising potential for applications to enzyme immobilization.