Characterization and mechanism probe of enzymatic extraction and thiolation modification of wheat bran arabinoxylan

This study successfully extracted arabinoxylan (AX) from wheat bran employing enzymatic and graded alcohol precipitation methods, and subsequently thiolated via an amidation grafting reaction with cysteine. AX extracted from extruded wheat bran by 80% (v/v) ethanol precipitation (E-AX₈₀) has high purity (69.64%), uronic acid (2.47%) and FA content (7.23 μg/mg). Thiolated modified AX (E-AX@SH) was determined to contain 134.32-349.76 μmol/g of free sulfydryl (-SH) via Ellman method. Elemental analysis, molecular dynamics simulation, FTIR, and NMR were employed to validate the successful modification and inter/intra-molecular chemical interactions of E-AX@SH (e.g., hydrogen bonds, hydrophobic interactions, and disulfide bonds). Structural analyses (XRD, SAXS, SEM, AFM, and fluorescence spectroscopy) revealed that modification induced a configurational rearrangement of E-AX@SH molecule, leading to a more compact structure, a rougher surface, and a more hydrophobic internal microenvironment. The antioxidant capacity of E-AX@SH was remarkably higher than E-AX₈₀. Furthermore, rheological behavior and Raman spectroscopy demonstrated that E-AX@SH forms disulfide bonds with intestinal mucus to construct a robust viscoelastic network, exhibiting outstanding mucosal adhesion properties. This work presents a noval perspective for the high-value utilization of wheat bran and the construction of targeted carriers.