Effect of digestive properties and gut microbiota structure of steam-exploded Laminaria japonica polysaccharide: in vitro dynamic human gastrointestinal systems

The aim of this study is to investigate the effect of steam explosion on the dynamic in vitro digestion properties and gut microbiota structure of Laminaria japonica polysaccharide (LJP). Here, steam-exploded Laminaria japonica polysaccharide (LJPS) was partially degraded during gastric digestion and recovered in intestinal digestion based on the results of molecular weight, functional groups and surface morphology. Notably, many pores appeared on the surface of LJPS during the fermentation. The data suggested that LJPS resisted the digestion in the simulated saliva fluid, simulated gastric fluid, simulated small intestinal fluid, and partially utilized by gut microbiota. Furthermore, LJPS modulated the structure of gut microbiota and improved the proliferation of Phascolarctobacter , Parasutterella and Megasphaera . The level of acetic, propionic and n-butyric acids was increased by LJPS after 48 h of fermentation, which were 2.39, 2.57 and 7.00 folds compared with the control group. Therefore, our study will provide scientific evidence for LJPS as a potential prebiotic to promote gut health. • The digestion properties of LJPS were characterized by dynamic bionic digestion system in vitro. • LJPS entered the large intestine and regulated the gut microbiota. • LJPS increased the level of acetic, propionic, and n-butyric acids.