Tuning the rheological properties of laccase-crosslinked arabinoxylan hydrogels by prior arabinofuranosidase treatments

Journal article, 2026

Arabinoxylans are the most abundant polysaccharides in the bran from wheat and rye kernels. Ferulic acid moieties covalently bound to arabinosyl substitutions in arabinoxylans can be oxidised and crosslinked by laccase enzymes, forming xylan hydrogels stabilised by chemical and physical interactions. Here, we explore the use of α-L-arabinofuranosidases to tune the rheological properties of laccase-crosslinked feruloylated arabinoxylans from wheat (WAX) and rye (RAX) brans, proposed to be mediated via intermolecular backbone interactions. The effect of subsequent freeze-drying and regeneration of the hydrogels on their multiscale structure and viscoelastic properties was further evaluated by X-ray scattering, microscopy and rheology measurements. The combined use of α-L-arabinofuranosidases from glycosyl hydrolase (GH) families GH62 and GH43 with complementary specificity towards different substitution motifs in arabinoxylan resulted in synergistic arabinose removal with a 48 % and 33 % increase in arabinose removal in WAX and RAX respectively, while retaining the ferulic acid moieties in both WAX and RAX. The extent of ferulic acid oxidation in WAX and RAX seemed to be affected by substrate inaccessibility for the laccase and polysaccharide chain aggregation, which was further accentuated by enzymatic arabinose removal. Rheological investigations revealed that laccase-crosslinked WAX hydrogels pretreated with arabinofuranosidases showed a decrease of 65–95 % in the storage and loss moduli compared to the non-pretreated WAX hydrogels, whereas arabinose removal improved the viscoelastic properties of RAX hydrogels both before and after regeneration, with an increase of storage moduli of 72–100 %. Arabinofuranosidase treatments and freeze-drying/regeneration altered the hydration properties of the hydrogels and their network structure, promoting the occurrence of ordered domains. Our results show that the biophysical properties of the arabinoxylans in terms of aggregation and hydration largely influence substrate accessibility to laccase-mediated oxidation and the multiscale assembly of the hydrogels upon freeze drying and regeneration, thus impacting their overall rheological properties. These dietary fibre hydrogels from cereal side streams have large potential to be used as food hydrocolloids, contributing to the overall circularity of the food system.