Low molecular weight chitosan selenium nanoparticles (LCS-SeNPs), a biologically active compound derived from selenium polysaccharides, have demonstrated potential in addressing obesity. However, the mechanism through which LCS-SeNPs alleviate high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) remains unclear. Our results elucidated that LCS-SeNPs significantly inhibited fat accumulation and markedly improved the intestinal barrier by increasing mucus secretion from goblet cells. Moreover, LCS-SeNPs reshaped intestinal flora composition by increasing the abundance of mucus-associated microbiota (Bifidobacterium, Akkermansia, and Muribaculaceae_unclassified) and decreasing the abundance of obesity-contributed bacterium (Anaerotruncus, Lachnoclostridium, and Proteus). The modulation of intestinal microbiota by LCS-SeNPs influenced several metabolic pathways, including bile acid secretion, purine metabolites, and tryptophan derivation. Meanwhile, glycocholic acid and tauro-beta-muricholic acid were significantly reduced in the LCS-SeNP group. Our study suggests the crucial role of intestinal microbiota composition and metabolism, providing a new theoretical foundation for utilizing selenium polysaccharides in the intervention of HFD-induced NAFLD.

Tuna protein serves as a significant source of bioactive peptides, and its functional properties can be elucidated through predictive modeling, followed by experimental validation. In this study, the active polypeptides were obtained from tuna protein via enzymatic hydrolysis (TPP), and their peptide sequences were determined. Furthermore, the potential activity of these peptides was predicted, focusing on antioxidant peptides, and compared to the sequence library of known antioxidant peptides to identify common structural motifs. The accuracy of the prediction results was confirmed through in vitro antioxidant assays and molecular docking studies. We identified seven specific peptide segments derived from tuna protein that exhibit antioxidant potential, accounting for approximately 15% of all active peptides. Molecular docking and cell experiments were employed to provide compelling evidence for the presence of antioxidant peptides within tuna protein. This study not only lays a solid foundation for studying the structure of active peptides but also opens up a novel avenue for an expedited assessment of their properties.

Background: The water-soluble Grifola frondosa polysaccharides (GFPs) are the primary bioactive component of the edible and medicinal fungus Grifola frondosa. However, the digestive behavior of GFPs in the human gastrointestinal (GI) tract and their subsequent interaction with gut microbiota (GM) to exert health effects remain unclear. Methods: In this study, GFPs were extracted based on a traditional hot water decoction. An in vitro simulated GI digestion model and a human fecal microbiota fermentation model were established to systematically investigate the digestive stability of GFPs, GM modulation, and metabolite changes. Results: Results showed that GFPs remained structurally stable during in vitro oral, gastric, and small intestinal digestion, allowing them to reach the colon intact for microbial fermentation. During colonic fermentation, GFPs were efficiently degraded by GM, and significantly increased the relative abundance of beneficial bacteria such as Akkermansia, Bacteroides, Parabacteroides, and Lactobacillus while reducing the abundance of pathogenic Escherichia-Shigella. Meanwhile, GFPs enriched metabolites beneficial for intestinal health, among which γ-aminobutyric acid (GABA) was the most significantly upregulated. Single-strain fermentation confirmed that Lactobacillus (L. plantarum) was the core GABA-producing genus. Conclusions: This study highlights the potential of GFPs as prebiotics for GM modulation, expands the understanding of the health-promoting effects of fungal polysaccharides, and provides a theoretical basis for the development of GFP-based functional foods.

Grifola frondosa polysaccharides (GFP), which possess antitumor properties, can counteract intestinal injury induced by cyclophosphamide (CTX). The objective of this research was to evaluate the efficacy of GFP in protecting the intestinal barrier of mice and investigate the mechanisms behind this effect. Using a CTX-induced intestinal barrier injury model, we found that GFP treatment significantly alleviated body weight loss and organ atrophy, while enhancing serum IgG and IgM levels. Histological analysis showed that GFP effectively repaired the intestinal mucosal structure, increased goblet cell numbers, and led to an upregulation in the gene expression of ZO-1, Occludin, and MUC2. GFP modulated cytokine expression, including IFN-γ, IL-4, IL-10, and IL-22. According to 16S rDNA sequencing results, GFP enhanced the abundance of unclassified_Muribaculaceae while reducing the prevalence of Escherichia_Shigella. Furthermore, GFP elevated the concentrations of several metabolites, including SCFAs and pyridoxal, which are closely related to intestinal barrier protection and mucosal immunity. Overall, this study demonstrated that GFP has strong potential as an immune-enhancing adjuvant and may represent a promising intervention strategy to mitigate chemotherapy-induced intestinal injury.

Isomaltulose is produced via sucrose isomerase catalysis by Serratia plymuthica A30. The enzyme was expressed in Bacillus subtilis using surface display, in combination with Bacillus subtilis spore coat CotC. The promoter was further selected and optimized to determine P_amyE as the most suitable promoter, while the spore coat protein assay reveals CotC as optimal. By scanning and analyzing the catalyst motifs with single-point mutation construction, a maximum isomaltulose yield of 27.21 mg/mL was recorded in the F181I-mutant enzyme. Another strain encoding the H363P-mutant reached a maximum yield of 20.84 mg/mL, while the k_cat value also increased from 17.64 to 24.80. Structural analysis showed that the F181I-mutant had higher thermostability, whereas the H363P-mutant had increased k_cat. Both mutants displayed a 5-fold increase in isomaltulose yield with relatively simple construction procedures, making them suitable for high-level isomaltulose production.