Background/Objectives: Chlorella pyrenoidosa polysaccharides (CPPs) exhibit digestion-resistant properties, with their bioactivity largely driven by gut microbiota metabolism. However, the fermentation characteristics of CPPs within the intestinal tract remain to be fully elucidated. Elucidating the utilization and metabolic processes of CPPs with respect to the gut microbiota aids in understanding the potential mechanisms underlying the biological activity of these polysaccharides. Methods: This work fractionated CPPs into a neutral polysaccharide fraction (CPP-1) and an acidic polysaccharide fraction (CPP-2), followed by the characterization of their structure, physicochemical properties, and in vitro fermentation characteristics. Results: The results demonstrated that both CPP-1 and CPP-2 were non-starch heteropolysaccharides linked primarily by α-glycosidic bonds and lacking a triple helix structure. Both samples exhibited exceptional thermal stability, high water solubility, and low viscosity properties. CPP-2 selectively promoted Enterocloster, whereas CPP-1 significantly enriched Bacteroides and Bifidobacterium in gut microbiota. This differential regulation may be attributable to structural variations between the polysaccharides. Functional predictions indicated that CPP-1 enhances intestinal barrier integrity and immune homeostasis, whereas CPP-2 has anti-inflammatory activity. CPP-1 and CPP-2 interventions significantly upregulated the levels of health-promoting metabolites, including nicotinamide adenine dinucleotide, putrescine, and 3′-adenosine monophosphate. CPP-1 predominantly modulated amino acid metabolic pathways, while CPP-2 could effectively regulate purine, pyrimidine, amino acid, and butanoate metabolic pathways. Conclusions: This work identifies CPPs (CPP-1 and CPP-2) as novel modulators of gut homeostasis and host metabolism through microbiota–metabolite axis remodeling, supporting their prebiotic potential for functional food innovation.

Most studies on resistant starch are limited to its effect on blood glucose; there are few studies on the prebiotic effects of resistant starch on the gut. In this experiment, through in vivo metabolism verification and in vitro simulated fermentation experiments, it was found that hydroxypropyl oxide (OHS) had a prebiotic effect on the intestine. The results of bioinformatics showed that the structure of the microbiota changed significantly, and the in vitro and in vivo fermentation results of Bacteroides uniformis and Parabacteroides distasonis showed an upward trend. The results of a KEGG prediction of the metabolic pathway showed that Phenylalanine metabolism and Cysteine and methionine metabolism showed an enhanced trend. At the same time, the results of in vitro and in vivo metabolite assays further confirmed this point, and the content of L-Homocystine and Phenylalanine in metabolites decreased significantly, with the decrease in L-Homocystine posing a reduction in cardiovascular disease risk and the decrease in Phenylalanine having a positive significance for phenylketonuria patients. This study proved that hydroxypropyl oxide can regulate the intestinal microbiota and has intestinal prebiotic effects, which can be used to guide the development of functional foods.

Background/Objectives: Alcoholic liver disease (ALD) is intricately linked to gut microbiota dysbiosis and metabolic disturbances along the gut–liver axis. Octenyl succinic anhydride (OSA) starch escapes digestion in the small intestine and ferments in the colon, modulating gut microbiota and metabolism. This study explored the protective effects of OSA starch against ALD and elucidated the underlying gut microbiota–metabolite interactions. Methods: A chronic ethanol-fed mouse model was conducted to evaluate the protective effects of OSA starch against ALD, and multi-omics analyses integrating 16S rRNA sequencing, PICRUSt2 functional predictions, and metabolomics were used to reveal potential mechanism. Results: OSA starch supplementation in ALD mice significantly reduced liver fat accumulation, lowered the liver index to 4.11%, and restored serum transaminase levels closer to normal. Multi-omics analyses revealed that OSA starch enriched beneficial gut bacteria such as Faecalibaculum rodentium and Bifidobacterium adolescentis. OSA starch also enhanced microbial metabolic functions, including pyruvate, butanoate, and propanoate metabolism. These shifts were accompanied by regulation of fecal and serum metabolites, including pyruvate, 2-hydroxybutanoic acid, and lactic acid. Structural equation modeling further confirmed that OSA starch ameliorates ALD via coordinated modulation of gut microbiota, microbial functions, metabolites, and serum markers. Conclusions: OSA starch protects against alcoholic liver injury by remodeling the gut–liver metabolic network, presenting a promising dietary strategy for ALD.

Dietary polysaccharides regulate gut microbiota and exhibit diverse prebiotic activity, which is highly dependent on their structural properties. To explore the underlying structure-prebiotic relationship, this study selectively compared the structural characteristics of Ginseng polysaccharide (GP), Ganoderma lucidum polysaccharide (GLP), and Dendrobium officinale polysaccharide (DOP) and investigated their digestive stability and gut microbiota modulation via in vitro simulated digestion and fecal fermentation. Structural analysis revealed distinct differences in molecular weight, monosaccharide composition, and glycosidic linkages among the three polysaccharides. Moreover, GP is partially digested in the upper gastrointestinal tract, while GLP and DOP were resistant to upper-tract digestion. All three polysaccharides differentially modulate gut microbial fermentation, intestinal microbial community structure, and the expression of functional carbohydrate-active enzymes. Specifically, the high glucose content of GP selectively promoted the abundance of genera putatively linked to glucose utilization, including Bacteroides, Bifidobacterium, and Alistipes. GLP preferentially enriched possible genera with galactose-metabolizing ability, such as Blautia, Collinsella, and Megamonas, while DOP selectively enriched microbiota putatively associated with mannose utilization, including Fusicatenibacter and Lachnospiraceae. Taken together, monosaccharide composition is a key structural feature that is closely associated with fermentation efficiency and gut microbial responses to polysaccharides, providing valuable insights for the precision utilization of bioactive polysaccharides.