A high-purine diet readily induces hyperuricemia, whereas certain lactic acid bacteria (LAB) can absorb and metabolize purines, thereby modulating uric acid levels. However, studies elucidating the molecular mechanisms by which lactic acid bacteria lower uric acid levels remain limited. In this study, we investigated Levilactobacillus brevis PDD-5, a strain previously shown to alleviate hyperuricemia through efficient purine absorption. Comprehensive metabolic and transcriptomic analyses were performed to compare L. brevis PDD-5 with a non-uric-acid-lowering strain. Using HPLC–MS/MS–based targeted metabolomics, we identified significant differences in purine nucleoside degradation between the two strains. Transcriptomic profiling revealed that L. brevis PDD-5 activates purine catabolism via upregulation of the deoD gene, which encodes purine nucleoside phosphorylase, thereby facilitating nucleoside-to-base conversion. Xanthine served as a key substrate promoting the de novo purine synthesis pathway and remained active under purine-rich conditions, likely because of transcriptional derepression of the purR regulator. These findings elucidate the molecular framework of the uric acid–lowering mechanism of L. brevis PDD-5 and provide a theoretical foundation for the development of safe, effective LAB-based interventions against hyperuricemia.

In this study, we used cherry valley duck carcasses to simulate the production process of braised duck. Freshly prepared marinade was added with different levels (0.01%, 0.02% and 0.03%) of grape seed extract (GSE) and reused for up to 21 times. Samples were collected at different cycles to determine the contents of biogenic amines and nitrite in order to evaluate the inhibitory effect of GSE on the formation of nitrite and biogenic amines during the reboiling process. The results showed that the contents of nitrite, biogenic amines and free amino acids in the stewed soup changed significantly with increasing number of reboiling cycles. Addition of 0.02% and 0.03% GSE had a better inhibitory effect on nitrite in the brine. In addition, GSE also significantly inhibited the formation of putrescine (Put) and tyramine (Tyr), as well as the formation of phenethylamine (Phe) despite its great fluctuations. The content of total free amino acids increased first and then decreased, and the contents of phenethylamine, putrescine, and tyramine were significantly correlated with the contents of various free amino acids in the brine (P < 0.05, P < 0.01). In summary, GSE can effectively reduce the nitrite content and inhibit the accumulation of multiple biological amines (phenethylamine, putrescine and tyramine) during the reboiling of the brine soup.

In order to obtain peptide fractions, duck liver proteins were recovered by isoelectric precipitation, and then hydrolyzed simultaneously by alcalase and flavorzyme. The molecular mass distribution of the hydrolysate was determined by using a gel permeation chromatography (GPC) system followed by fractionation using a combination of gel filtration chromatography (GFC) and reversed phase-high performance liquid chromatography (RP-HPLC). Ten novel peptides with molecular mass less than 1300 Da were identified from the subfraction with high inhibitory effect on cytokine release from macrophages using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The anti-inflammatory activity of the synthetic peptides was tested in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Peptides LVYPFPGPI and VIESPPEI inhibited the release of NO from inflammatory cells in a dose-dependent manner, with inhibition percentages of 48.24% and 56.32% at the concentration of 100 μg/mL, respectively. VIESPPEI at the concentration of 100 μg/mL inhibited TNF-α release by 42.48%. Notably, IDVSPDSPDHY showed the strongest ability to inhibit the release of IL-6, with an inhibition percentage of 27.04% at the concentration of 25 μg/mL. This study may provide new ideas for the high-valued comprehensive utilization of duck by-products and their application in safe treatment of inflammation.

Lipoteichoic acid (LTA), a bacterial cell surface macromolecule, plays a key role in probiotic–host interactions by engaging host pattern recognition receptors in the gastrointestinal mucosa. This study investigates the potential of Lactiplantibacillus plantarum LTA in combating intestinal pathogens and supporting gut health. We demonstrate that L. plantarum LTA, acting as a biosurfactant, significantly inhibits biofilm formation by various intestinal pathogens, including Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. This is achieved by disrupting biofilm structures, reducing extracellular polymer secretion, and downregulating biofilm-related gene expression. Additionally, LTA effectively prevents pathogen adhesion to Caco-2 cells and reduces Escherichia coli-induced apoptosis. LTA also modulates macrophage inflammation by regulating cytokine secretion and decreasing NO and ROS production through the TLR4-MAPK-NF-κB signaling pathway. These findings provide valuable insights into the mechanisms by which L. plantarum LTA supports gut health and highlight its potential applications in preventing intestinal pathogen colonization and enhancing immune modulation.

The role of S-layer proteins (SLP), which form the outermost layer of cell walls in lactic acid bacteria (LAB), plays a crucial role in regulating immune-stimulating activity, thereby closely influencing LAB’s ability to boost host immunity. In this study, the heterologous expression, purification, and characterization of Lactobacillus acidophilus CICC6074-derived slpX protein and the molecular mechanism of its anti-inflammatory effect on LPS-induced RAW264.7 cells were investigated. Initially, the PCR results were shown to successfully clone the slpX DNA sequence by homologous recombination to obtain the pet-32a-slpX recombinant plasmid. SDS-PAGE results revealed that slpX protein with a molecular weight of 54 kDa was successfully obtained under 0.7 mmol/L IPTG-induced conditions, which was further demonstrated by Western blot (WB) and LC-MS/MS. ELISA, WB and molecular docking results indicated that slpX protein can inhibit LPS-induced cellular inflammatory responses by linking to TLR4 and MD2 via hydrogen bonding and increasing the levels of anti-inflammatory factor IL-10 and decreasing the levels of inflammatory factors (TNF-α, IL-6, NO) and ROS via MAPK and NF-κB signaling pathways. The study is essential for the preparation of pure slpX protein and revealing its anti-inflammatory molecular mechanism.

In this study, 10 novel anti-inflammatory peptides were identified from duck liver, and their molecular mechanism was demonstrated based on machine learning and molecular docking. Using Sephadex G-15 gel chromatography separation, reversed-phase high-performance liquid chromatography purification, liquid chromatography-tandem mass spectrometry identification, and BIOPEP database comparison, 10 novel anti-inflammatory peptides were initially found. Their splendid angiotensin-converting enzyme (ACE) inhibition and anti-inflammatory properties were confirmed by machine learning. With binding energies less than –20.93 kJ/mol, molecular docking revealed that they could efficiently bind to the active pockets of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), cyclooxygenase 2 (COX-2), and nuclear factor κB (NF-κB) proteins with efficiency, indicating that the compounds can spontaneously form complexes through hydrogen bonding and hydrophobic interactions with the protein binding pockets. In the lipopolysaccharide-induced RAW264.7 cell model, the release of NO, TNF-α, and IL-6 and the mRNA expression of inflammatory factors (TNF-α, IL-6, COX-2, and NF-κB) were significantly inhibited by these peptides. We concluded it might be due to their anti-inflammatory effects by inhibiting the protein phosphorylation of inhibitor of NF-κB (IκBα) in the cytoplasm and preventing the translocation of NF-κB p65 in the cytoplasm to the nucleus, thereby regulating the NF-κB signaling pathway. This study is essential for the screening of anti-inflammatory peptides and the investigation of the mechanism of action.

Hyperuricemia is a metabolic disorder caused by abnormal purine metabolism, resulting in abnormally high serum uric acid. In this study, a novel Levilactobacillus brevis PDD-5 isolated from salty vegetables was verified with the function of alleviating hyperuricemia. The relevant effects of L. brevis PDD-5 in lowering uric acid were analyzed by in vitro and in vivo experiments. The results showed that the L. brevis PDD-5 has (68.86 ± 15.46)% of inosine uptake capacity and (95.75 ± 3.30)% of guanosine uptake capacity in vitro. Oral administration of L. brevis PDD-5 to hyperuricemia rats reduced uric acid, creatinine, and urea nitrogen in serum, as well as decreased inosine and guanosine levels in the intestinal contents of rats. Analysis of relevant markers in the kidney by ELISA kits revealed that L. brevis PDD-5 alleviated oxidative stress and inflammation. Moreover, the gene expression of uric acid transporter 1 (URAT1) and glucose transporter 9 (GLUT9) was down-regulated, and the gene expression of organic anion transporter 1 (OAT1) was up-regulated after treatment with L. brevis PDD-5. Western blot analysis showed that L. brevis PDD-5 alleviated hyperuricemia-induced kidney injury through the NLRP3 pathway. These findings suggest that L. brevis PDD-5 can lower uric acid, repair kidney damage, and also has the potential to prevent uric acid nephropathy.

Lactic acid bacteria (LAB) fermentation is the simplest and safest way of food preservation, and the use of probiotics in yoghurt could provide dairy products with unique flavors, textures and health benefits. In this study, Lactobacillus bulgaricus, Streptococcus thermophilus, L. reuteri DSMZ 8533 and the potential probiotic strain L. plantarum A3 were used for the milk fermentation. Results found the texture properties such as hardness, consistency, and viscosity of the yoghurt were enhanced in the mixed culture condition. Furthermore, components like amino acid (leucine), vanilla (vanillin), C_18:3n6 (unsaturated fatty acids) were also accumulated in L. plantarum A3 fermented yoghurt, which leads to the significant sensory profiling difference compared with the former plain yoghurt. All these results proved L. plantarum A3 is a potential probiotic strain which could enhance the sensory and nutrition profiling of the fermented milk. Future work still needs to be done on the synergistic interaction between the traditional strains and the probiotics during the fermentation process.