Pectin-based biohydrogels reinforced with eucalyptus sawdust: Synthesis, characterization, β-D-Galactosidase immobilization and activity

Abstract

In this work, pectin-based biohydrogels with and without eucalyptus sawdust were synthesized via radical crosslinking and characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), swelling assays (SA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and rheological tests (RT). The immobilization of β-D-galactosidase in the biohydrogel networks was performed by adsorption, and the immobilized enzyme activity was studied during lactose hydrolysis reactions. Strong inter and intramolecular interactions among enzyme and biohydrogel chemical groups increased the biopolymer network crosslinking densities, decreasing the swelling capacities. The water diffusion mechanism in the biopolymer networks was governed by non-Fickian transport, being affected by the pH and temperature values of the aqueous solutions. The incorporation of eucalyptus sawdust in the biopolymer network increased the final biomaterial thermal and mechanical resistance, preserving the immobilized enzyme stability. Pectin-based biohydrogels reinforced with eucalyptus sawdust proved to be potential solid supports for the immobilization of β-D-galactosidase. These polymeric matrices preserved the enzyme stability in more acidic aqueous solutions and enabled the application of the immobilized enzyme for at least six successive lactose hydrolysis cycles. Overall, β-D-galactosidase immobilized in pectin-based biohydrogels appears as an alternative for the production of either lactose-free or low-dosage lactose foods.