Ulvan acts as a prebiotic polysaccharide enhancing the production of indoles and short-chain fatty acids in vitro: a metabolomics study

This study investigated the fermentability and prebiotic potential of ulvan, a sulfated polysaccharide from Ulva lactuca L., using an in vitro human colonic fermentation model. Targeted metabolomics quantified SCFA and tryptophan-derived metabolites to assess saccharolytic activity and fiber-driven modulation of amino acid metabolism. Ulvan supplementation significantly stimulated SCFA production, particularly acetic acid, achieving levels comparable to the well-established prebiotic inulin. In parallel, ulvan selectively modulated tryptophan metabolism, enhancing the production of health-associated metabolites such as indole-3-propionic acid and indole-3-acetic acid, suggesting cross-feeding interactions among saccharolytic and indole-producing taxa. Untargeted metabolomics revealed distinct metabolites associated with ulvan treatment, including cyclic proline dipeptides, which points to a selective stimulation of beneficial microbial species. Collectively, these findings demonstrate that ulvan is a soluble and fermentable dietary fiber, supporting its potential as a functional food ingredient or dietary supplement for promoting gut health.