Structural characterization and digestion stability of iron-chelating peptides from Ophiocordyceps gracilis fermented by Limosilactobacillus reuteri

Traditional iron supplements often exhibit low bioavailability due to intestinal precipitation and trigger adverse effects such as gastrointestinal irritation and oxidative stress. In contrast, iron-chelating peptide is a novel bioavailable iron formulation with a high absorption rate and good safety profile. In this study, Limosilactobacillus reuteri fermentation was used to prepare iron-chelating Ophiocordyceps gracilis peptides (OGP-Fe). Fermentation parameters were optimized using a combination of single-factor experiments and response surface methodology. Analysis of amino acid composition and spectral analysis indicated that Fe 2+ coordinate with polypeptide chains through interactions involving carboxyl oxygen and amino nitrogen atoms. Molecular docking simulations further corroborated these findings, predicting that Fe 2+ primarily binds to the carboxyl oxygen atoms of Asp and Glu, along with the imidazole nitrogen of His. Scanning electron microscope revealed that OGP-Fe exhibited a loose and blocky morphology. Energy dispersive spectroscopy confirmed the successful chelation between Fe 2+ and OGP. Furthermore, simulated gastrointestinal digestion experiments demonstrated that OGP-Fe exhibited great stability in simulated gastrointestinal fluids. In vitro anaerobic fermentation demonstrated that OGP-Fe preserved microbial diversity and favorably modulated gut microbiota composition by selectively promoting beneficial genera and iron-assimilating bacteria. Therefore, this study provides theoretical support for microbial fermentation as a method for producing iron-chelating peptides.