Chitosan with modified porosity and crosslinked with genipin: A dynamic system structurally characterized

Abstract

In this work, a deep structural characterization of the chitosan-genipin complex was performed by techniques like small-angle X-ray scattering, dye absorption, atomic force microscopy, compression strength, nitrogen adsorption/desorption, scanning electronic microscopy, and thermogravimetric analysis to understand the changes in the structure through all steps of the process. For this, chitosan beads were modified with Na2CO3 to change porosity and then crosslinked with genipin. The prepared particles were used as support for enzyme immobilization. Our results demonstrated modification in the porosity of the chitosan beads, changing the number of pores and pore volume. After crosslinking process (pH 9), especially the microstructure of chitosan-genipin beads was modified, enhancing the fractality and, after enzyme immobilization (pH 4.5) the fractality increased at the higher scale (∼100 nm) and reduced at the lower scale (∼1–10 nm). β-galactosidase immobilized on the modified particles presented high stability on the continuous production of galactooligosaccharides for 30 days. Our results indicate that the chitosan-genipin complex can be characterized as a plastic and dynamic system due to its structural modifications, particularly in response to changes in the pH environment, even after the crosslinking process.