Structure-guided design of fructan-based carbohydrate polymers: From molecular architecture to microbial recognition and gut-interface performance.

Fructans are structurally diverse carbohydrate polymers composed mainly of fructofuranosyl residues, and their functionality is governed by linkage pattern, degree of polymerization (DP), molecular-weight distribution, branching, terminal or internal glucose configuration, purity, and processing history. However, fructooligosaccharides (FOS), inulin, levan, graminan-type fructans, and neoseries fructans are still frequently discussed as broad ingredient categories, which obscures the structural determinants that control microbial recognition, fermentation kinetics, metabolite production, gut-interface responses, and food-material performance. This review deepens the structure-guided interpretation of fructan-based carbohydrate polymers by connecting defined architectures with preparation-induced structural editing, DP-resolved characterization, microbial enzyme systems, cross-feeding networks, SCFA profiles, mucus and epithelial barrier responses, immune tone, gut-organ axes, and processing functionality. Representative examples include DP-defined inulin fractions, high-molecular-weight levan, Ophiopogon-derived neoseries or polyfructan fractions, and mixed-linkage plant fructans. By treating linkage pattern, DP distribution, branching, glucose positioning and processing stability as design variables rather than descriptive labels, this review provides a polymer-level framework for interpreting fructan functionality and designing application-specific fructan materials. The review further proposes an evidence hierarchy and application-specific design rules to support the transition from broad prebiotic ingredient claims to precision carbohydrate polymer design.