Effect of chitosan molecular weight on the formation of chitosan-pullulanase soluble complexes and their application in the immobilization of pullulanase onto Fe3O4-κ-carrageenan nanoparticles

The interactions between pullulanase and chitosans of different molecular weights (Mw) were comprehensively studied, and their applications in pullulanase immobilization onto Fe3O4-j-carrageenan nanoparticles upon chitosan-pullulanase complexation were also evaluated. Chitosan (CS) complexation with pullulanase was found to be dependent on pH and chitosan Mw. The critical pH of structure-forming events during complexation shifted significantly (p < 0.05) to a lower pH with a low Mw chitosan (50 kDa) compared to other chitosan types. Binding constants for the chitosan-pullulanase interaction increased in the following order: CS-500 < CS-400 < CS-50 < CS-200. The binding induced alterations in the protein secondary structure, which may affect the enzymatic properties of immobilized pullulanase. Pullulanase immobilized upon CS-50 complexation exhibited the most desirable enzymatic properties. These results indicated that the complexation behavior was mainly dependent on chitosan Mw. This study presents a technique for the production of immobilized pullulanase upon complexation that exhibits potential for applications in continuous syrup production. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.