Valorization of Arabinoxylans from Wheat Bran via NaOH/Urea Extraction for Enhanced Prebiotic and Fermentation Properties

Arabinoxylans (AXs), the predominant hemicellulose in wheat bran (WB), have recognized prebiotic potential but are underutilized due to extraction inefficiencies. In this study, a NaOH/urea solvent system was applied for the sustainable valorization of WB into functional AXs. Under optimized conditions (6.25% NaOH, 8.18% urea), the process achieved a significantly improved AX yield of 16.44%. The extracted AX (WBAX) and its fractions─soluble AX (SAX) and insoluble AX (IAX)─were structurally and functionally characterized. SAX exhibited a higher arabinose-to-xylose ratio (1.51), lower molecular weight (189.55 kDa), and more porous morphology compared to IAX, contributing to its enhanced solubility and fermentability. In vitro fecal fermentation demonstrated that both SAX and IAX increased microbial biomass, lowered pH, and promoted short-chain fatty acid (SCFAs) production, particularly propionic and butyric acids. Notably, SAX more effectively modulated gut microbiota by enriching beneficial genera such as Lactobacillus and Limosilactobacillus. Furthermore, fermentation increased antioxidant activity, as indicated by improved DPPH• and ABTS+• radical scavenging. These findings highlight the efficacy of the NaOH/urea system as a scalable and green approach for converting wheat bran into high-value prebiotic ingredients, supporting sustainable development of functional bioproducts from agricultural residues.