Structural characterization and in vitro fermentation by rat intestinal microbiota of a polysaccharide from Porphyra haitanensis

A sulfated polysaccharide (PHP1) produced by the marine red alga Porphyra haitanensis was structurally characterized, and its effect on rat fecal microbiota fermentations and short chain fatty acids production were investigated. PHP1 was mainly composed of galactose and the main linkage types were identified as → 3)G4Sβ(1 → 3)G(1 → 6)G4Sα(1 → 4)LA(1 → 6)G4Sα(1→. The surface morphology of dried PHP1 films appears to be related to its chemical structure. PHP1 promoted the growth of both propionic acid-producing bacteria and propionic acid production, as well as influencing the composition and abundance of beneficial microbiota species in rats, which may be related to its high level of sulfation. The molecular weight of PHP1 decreased significantly after fermentation, which may result from hydrolysis of the galactan (with α- and β-linkages between galactose residues) by α- or β-galactosidase secreted by the microbiota. These results provided new insights into the structure–activity relationships between P. haitanensis polysaccharide and its regulation of microbiota in vivo.