Prebiotic effects of lotus seed starch-C18 fatty acid complexes: Role of structural changes during in vitro digestion...

Despite growing interest in starch-lipid complexes as prebiotic ingredients, the impact of fatty acid (FA) unsaturation on their fermentative behavior and gut microbiota modulation remains controversial, largely due to inconsistent structural characterization across studies. Herein, lotus seed starch (LS), notable for its high amylose content, was used to systematically fabricate complexes with C18 FAs of varying unsaturation, such as stearic (SA), oleic (OA), linoleic (LA), and α-linolenic (ALA) acids, via dynamic high-pressure microfluidization. Complex stability and digestive resistance decreased with increasing FA unsaturation. LS-SA exhibited the slowest digestion and enriched butyrate-producing genera (Bifidobacterium, Clostridium). LS-OA promoted Sutterellaceae, potentially linked to β-oxidation. LS-LA and LS-ALA enhanced unclassified_c__Bacilli, Litchfieldia, and Turicibacter, with LS-LA also stimulating Ligilactobacillus, known for conjugated linoleic acid production. Notably, LS-ALA significantly boosted acetate, propionate, and butyrate levels. These findings suggest that differences in FA unsaturation are associated with the structural stability and prebiotic efficacy of LS-FA complexes through synergistic effects between the starch matrix and FA ligand. This work clarifies previous contradictions regarding FA unsaturation and provides a mechanistic framework for the rational design of starch-based formulations aimed at targeted modulation of gut microbiota.