Cell Wall-Degrading Enzymes Differentially Mediate Aleurone Cell Release and Structural Integrity in Wheat Bran

The aleurone layer (AL) is the most nutrient-rich fraction of wheat bran. However, its tight adhesion to the outer pericarp (OP) and intermediate layer (IL) within wheat bran limits its application in foods. In this study, cell wall-degrading enzymes (xylanase, pectinase, and β-glucanase) were employed to release the AL and its cells from wheat bran and to elucidate the underlying mechanism of this process. The results showed that all cell wall-degrading enzymes exhibited limited capacity to degrade the OP and IL. Xylanase and pectinase were the most effective in inducing AL detachment from wheat bran and intercellular dissociation of AL cells, whereas β-glucanase exerted a negligible effect. In comparison, xylanase enhanced the release of cell wall polysaccharides and phenolic acids, with ferulic acid release from the AL reaching 8.91 mg/g after treatment, but it also caused partial structural damage to AL cells. In contrast, pectinase caused less disruption to the AL cell walls and therefore better preserved cell integrity. The β-glucanase hydrolyzed β-glucan in the AL cell wall into glucose (22.17 mg/g) but did not lead to cell dissociation, plausibly because arabinoxylans overlay β-glucans and restrict enzyme access. Using coarse wheat bran (20–40 mesh) as the starting material yielded a higher proportion of intact AL cell-rich fraction than using a fine bran fraction (80–100 mesh). These findings highlight pectinase-assisted hydrolysis as an effective strategy for releasing intact aleurone cells for food applications.