Shorter galacturonic acid backbone, enhanced prebiotic potential: a guide to pectin processing based on gut microbiota and SCFAs production

Background: Pectin is a polysaccharide with an α-(1→4)-linked galacturonic acid backbone with diverse monosaccharides combined. Current processing extraction methods, including hydrochloric acid, citric acid, cellulase-assisted, and microwave-assisted chelating agent extraction, significantly impact the structural characteristics of pectin. Factors such as pH and extraction temperature influence the composition of the final product, leading to notable variations in galacturonic acid content. However, determining the optimal processing method remains a subject of debate. Given that pectin exerts its physiological effects primarily through its metabolism by gut microbiota after ingestion, our study proposes an evaluation framework based on the interactions between pectin and gut microbiota.

Methodology: In this study, four purified pectin molecules with distinct structural characteristics derived from plant sources were selected and a detailed analysis of their molecular features was conducted. Using in vitro fermentation, we investigated how different pectin parameters influence gut microbiota composition and short-chain fatty acids (SCFAs) production. Fermentation samples were collected for analysis, and microbial diversity and composition were determined through full-length 16S rRNA gene sequencing. SCFAs concentrations and untargeted metabolites were quantified using liquid chromatography-mass spectrometry.

Conclusion: Through metabolomics and bioinformatic analysis, the galacturonic acid content, arabinose content, and protein conjugation in pectin were identified to significantly influence gut microbiota composition. Notably, galacturonic acid in the main-chain backbone negatively correlated with SCFAs production, where higher galacturonic acid content resulted in lower total SCFAs. Conversely, side-chain monosaccharide residues, including arabinose, galactose, and rhamnose, promoted SCFAs production. During fermentation, bacterial genera such as Bacteroides, Alistipes, and Dorea played a crucial role in SCFAs production. Given that SCFAs are essential metabolic products of pectin fermentation and contribute to gut health, we suggest that pectin processing methods should be optimized to obtain a shorter galacturonic acid backbone, which may better enhance the prebiotic properties of pectin and promote gut health.