Characteristics of the Mixed Yogurt Fermented from Cow-Soy Milk in the Presence of Transglutaminase.

The mixed yogurt was fermented from Cow-Soy milk and modified by transglutaminase (TG). The effects of mixed milk and TG on the quality characteristics of mixed yogurt were investigated by texture characteristics, rheology (rheometer) and structure (scanning electron microscopy). The findings revealed that the mixed yogurt with 50% cow milk exhibited lower hardness, viscosity and consistency. Furthermore, when TG was added, the yogurt showed better rheological properties, sensory score and a more stable microstructure. Compared with the samples without TG modification, the viscosity and cohesiveness of the modified samples increased by 10% and 100%, respectively. The combination of cow milk and soy milk improved the texture of yogurt, and the TG addition further improved the physicochemical properties of yogurt. This finding provided a meaningful reference for the development of mixed yogurt with a suitable taste from animal and plant milk, and laid a basis for the practical application of mixed yogurt in the dairy industry, which will meet the requirements for dairy products for consumers in future.

Novel casein-derived immunomodulatory peptide PFPEVFG: Activity assessment, molecular docking, activity site and mechanism of action.

Nowadays, there is still a gap in the knowledge of the structure-activity relationship of immunomodulatory peptides. In this study, PFPEVFG was selected as a peptide with immunomodulatory activity from casein hydrolysate by virtual screening and its immunomodulatory activity was verified by the phagocytosis, proliferation, and expression of cytokines (IL-6, IL-1ß, TNF-α) and chemokines (CXCL1, CXCL2) in RAW 264.7 macrophages. Next, molecular docking and double-stranded small interfering RNA (siRNA) mutually verified that the immunomodulatory activity of PFPEVFG was mediated by TLR2/4. Furthermore, the highest occupied molecular orbital (HOMO) analysis showed that the C19 = O20 site with a HOMO contribution of 32.22988% was its active site, and the phenylalanine, where the C19 = O20 site was located, was its active amino acid. Finally, the combination of pathway inhibitors and Western blot revealed that PFPEVFG activated macrophages through the nuclear factor-κB (NF-κB) signaling pathway. In summary, this study provided a new perspective on deeply understanding the structure-activity relationship of casein-derived immunomodulatory peptides, as well as a further theoretical and technological basis for the application of immunomodulatory peptides.

Study on the interaction mechanism of whey protein isolate with phosphatidylcholine: By multispectral methods and molecular docking.

The elucidation of the interaction mechanism between phospholipids and milk proteins within emulsions is pivotal for comprehending the properties of infant formula fat globules. In this study, multispectral methods and molecular docking were employed to explore the relationship between phosphatidylcholine (PC) and whey protein isolate (WPI). Observations indicate that the binding constant, alongside thermodynamic parameters, diminishes as temperature ascends, hinting at a predominantly static quenching mechanism. Predominantly, van der Waals forces and hydrogen bonds constitute the core interactions between WPI and PC. This assertion is further substantiated by Fourier transform infrared spectroscopy, which verifies PC's influence on WPI's secondary structure. A detailed assessment of thermodynamic parameters coupled with molecular docking reveals that PC predominantly adheres to specific sites within α-lactalbumin, ß-lactoglobulin, and bovine serum albumin, propelled by a synergy of hydrophobic interactions, hydrogen bonding, and van der Waals forces, with binding energies noted at -5.59, -6.71, and -7.85 kcal/mol, respectively. An increment in PC concentration is observed to amplify the emulsification properties of WPI whilst concurrently diminishing the zeta potential. This study establishes a theoretical foundation for applying the PC-WPI interaction mechanism in food.

Modulating Whey Proteins Antigenicity with Lactobacillus delbrueckii subsp. bulgaricus DLPU F-36 Metabolites: Insights from Spectroscopic and Molecular Docking Studies.

Numerous studies have highlighted the potential of Lactic acid bacteria (LAB) fermentation of whey proteins for alleviating allergies. Nonetheless, the impact of LAB-derived metabolites on whey proteins antigenicity during fermentation remains uncertain. Our objective was to elucidate the impact of small molecular metabolites on the antigenicity of α-lactalbumin (α-LA) and ß-lactoglobulin (ß-LG). Through metabolomic analysis, we picked 13 bioactive small molecule metabolites from Lactobacillus delbrueckii subsp. bulgaricus DLPU F-36 for coincubation with α-LA and ß-LG, respectively. The outcomes revealed that valine, arginine, benzoic acid, 2-keto butyric acid, and glutaric acid significantly diminished the sensitization potential of α-LA and ß-LG, respectively. Moreover, chromatographic analyses unveiled the varying influence of small molecular metabolites on the structure of α-LA and ß-LG, respectively. Notably, molecular docking underscored that the primary active sites of α-LA and ß-LG involved in protein binding to IgE antibodies aligned with the interaction sites of small molecular metabolites. In essence, LAB-produced metabolites wield a substantial influence on the antigenic properties of whey proteins.

Lactic acid bacteria and yeast co-fermented milk alleviate cow milk allergy.

Cow milk allergy is one of the common food allergies. Our previous study showed that the allergenicity of fermented milk is lower than that of unfermented skimmed milk in vitro, and the antigenicity of ß-lactoglobulin and α-lactalbumin in fermented milk was decreased by 67.54% and 80.49%, respectively. To confirm its effects in vivo, allergic BALB/C mice model was used to further study the allergenicity of fermented milk. It was found that compared with the skim milk (SM) group, the intragastrically sensitization with fermented milk had no obvious allergic symptoms and the fingers were more stable: lower levels of IgE, IgG, and IgA in serum, lower levels of plasma histamine and mast cell protein-1, and immune balance of Th1/Th2 and Treg/Th17. At the same time, intragastrically sensitization with fermented milk increased the α diversity of intestinal microbiota and changed the microbiota abundance: the relative abundance of norank-f-Muribaculaceae and Staphylococcus significantly decreased, and the abundance of Lachnospiraceae NK4A136 group, Bacteroides, and Turicibacter increased. In addition, fermented milk can also increase the level of short-chain fatty acids in the intestines of mice. It turns out that fermented milk is much less allergenicity than SM. PRACTICAL APPLICATION: Fermentation provides a theoretical foundation for reducing the allergenicity of milk and dairy products, thereby facilitating the production of low-allergenic dairy products suitable for individuals with milk allergies.

Effects of the Lactiplantibacillus plantarum YB-106 and Leuconostoc mesenteroides YB-23 strains on the quality and microbial diversity of spicy cabbage.

Spicy cabbage is a popular fermented vegetable food. The study aimed to determine the physicochemical properties, volatile flavor components, sensory evaluation, and microbial diversity of spicy cabbage prepared using different methods. Three methods were used: single-bacteria fermentation with Lactiplantibacillus plantarum YB-106 and Leuconostoc mesenteroides YB-23, mixed fermentation (LMP) using both strains, and natural fermentation as the blank control (CON). The LMP group has the best quality of spicy cabbage and the highest sensory score. Esters and alkenes were the main volatile flavor components of the spicy cabbage by GC-MS. The fermentation time of LMP group was shorter, and the nitrite degradation rate was >60 %, which was significantly higher than that of other groups (p < 0.05). From the perspective of microbial diversity, the dominant bacteria genera in each group were Lactobacillus, Pantoea, Enterococcus and Pseudomonas. However, mixed fermentation decreased the abundance of pathogenic bacteria, of which the abundance of Serratia was <0.1 %. In conclusion, mixed fermentation can significantly improve the quality of spicy cabbage and shorten the fermentation time. These findings laid the theoretical foundation for the industrial production of high-quality spicy cabbage.

Exploring lipid digestion discrepancies between preterm formula and human milk: Insights from in vitro gastrointestinal digestion and the impact of added milk fat.

Lipids play a pivotal role in the nutrition of preterm infants, acting as a primary energy source. Due to their underdeveloped gastrointestinal systems, lipid malabsorption is common, leading to insufficient energy intake and slowed growth. Therefore, it is critical to explore the reasons behind the low lipid absorption rate in formulas for preterm infants. This study utilized a simulated in intro gastrointestinal digestion model to assess the differences in lipid digestion between preterm human milk and various infant formulas. Results showed that the fatty acid release rates for formulas IF3, IF5, and IF7 were 58.90 %, 56.58 %, and 66.71 %, respectively, lower than human milk's 72.31 %. The primary free fatty acids (FFA) and 2-monoacylglycerol (2-MAG) released during digestion were C14:0, C16:0, C18:0, C18:1n-9, and C18:2n-6, in both human milk and formulas. Notably, the higher release of C16:0 in formulas may disrupt fatty acid balance, impacting lipid absorption. Further investigations are necessary to elucidate lipid absorption differences, which will inform the optimization of lipid content in preterm infant formulas.

Both live and heat killed Lactiplantibacillus plantarum DPUL-F232 alleviate whey protein-induced food allergy by regulating cellular immunity and repairing the intestinal barrier.

Postbiotics have been proposed as clinically viable alternatives to probiotics, addressing limitations and safety concerns associated with probiotic use. However, direct comparisons between the functional differences and health benefits of probiotics and postbiotics remain scarce. This study compared directly the desensitization effect of probiotics and postbiotics derived from Lactiplantibacillus plantarum strain DPUL-F232 in the whey protein-induced allergic rat model. The results demonstrate that administering both live and heat killed F232 significantly alleviated allergy symptoms, reduced intestinal inflammation, and decreased serum antibody and histamine levels in rats. Both forms of F232 were effective in regulating the Th1/Th2 balance, promoting the secretion of the regulatory cytokine IL-10, inhibiting mast cell degranulation and restoring the integrity of the intestinal barrier through the upregulation of tight junction proteins. Considering the enhanced stability and reduced safety concerns of postbiotics compared to probiotics, alongside their ability to regulate allergic reactions, we suggest that postbiotics may serve as viable substitutes for probiotics in managing food allergies and potentially other diseases.

Mechanism Explanation on Improved Cognitive Ability of D-Gal Inducing Aged Mice Model by Lactiplantibacillus plantarum MWFLp-182 via the Microbiota-Gut-Brain Axis.

Gut microbiota can influence cognitive ability via the gut-brain axis. Lactiplantibacillus plantarum MWFLp-182 (L. plantarum MWFLp-182) was obtained from feces of long-living individuals and could exert marked antioxidant ability. Interestingly, this strain reduced the D-galactose-induced impaired cognitive ability in BALB/c mice. To comprehensively elucidate the underlying mechanism, we evaluated the colonization, antioxidant, and anti-inflammatory activities of L. plantarum MWFLp-182, along with the expression of potential genes associated with cognitive ability influenced and gut microbiota. L. plantarum MWFLp-182 enhanced the expression of anti-inflammatory cytokines, reduced the expression of proinflammatory cytokines, and increased tight junction protein expression in the colon. Moreover, L. plantarum MWFLp-182 could modify the gut microbiota. Notably, treatment with L. plantarum MWFLp-182 upregulated the expression of postsynaptic density protein-95, nuclear factor erythroid 2-related factor, nerve growth factor, superoxide dismutase, and brain-derived neurotrophic factor/neuronal nuclei, while downregulating the expression of bcl-2-associated X and malondialdehyde in the hippocampus and upregulating short-chain fatty acids against D-galactose-induced mouse brain deficits. Accordingly, L. plantarum MWFLp-182 could improve cognitive ability in a D-galactose-inducing mouse model.

Exopolysaccharides and Surface-Layer Proteins Expressed by Biofilm-State Lactiplantibacillus plantarum Y42 Play Crucial Role in Preventing Intestinal Barrier and Immunity Dysfunction of Balb/C Mice Infected by Listeria monocytogenes ATCC 19115.

Our previous study showed that Lactiplantibacillus plantarum Y42 in the biofilm state can produce more exopolysaccharides and surface-layer proteins and showed a stronger promoting effect on intestinal barrier function than that in the planktonic state. In this study, oral administration of the live/pasteurized planktonic or biofilm L. plantarum Y42 and its metabolites (exopolysaccharides and surface-layer proteins) increased the expression of Occludin, Claudin-1, ZO-1, and MUC2 in the gut of the Balb/C mice after exposure to Listeria monocytogenes ATCC 19115 and inhibited the activation of the NLRP3 inflammasome pathway, which in turn reduced the levels of inflammatory cytokines IL-1ß and IL-18 in the serum of the mice. Furthermore, oral administration of the live/pasteurized planktonic or biofilm L. plantarum Y42 and its metabolites increased the abundance of beneficial bacteria (e.g., Lachnospiraceae_NK4A136_group and Prevotellaceae_UCG-001) while reducing the abundance of harmful bacteria (e.g., norank_f__Muribaculaceae) in the gut of the mice, in line with the increase of short-chain fatty acids and indole derivatives in the feces of the mice. Notably, biofilm L. plantarum Y42 exerted a better preventing effect on the intestinal barrier dysfunction of the Balb/C mice due to the fact that biofilm L. plantarumY42 expressed more exopolysaccharides and surface-layer proteins than the planktonic state. These results provide data support for the use of exopolysaccharides and surface-layer proteins extracted from biofilm-state L. plantarum Y42 as functional food ingredients in preventing intestinal barrier dysfunction.

Lactiplantibacillus plantarum-Derived Indole-3-lactic Acid Ameliorates Intestinal Barrier Integrity through the AhR/Nrf2/NF-κB Axis.

Our previous studies have shown that Lactiplantibacillus plantarum DPUL-S164-derived indole-3-lactic acid (ILA) ameliorates intestinal epithelial cell barrier injury by activating aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways and promoting tight junction protein expression. This study further explored the crucial substances of L. plantarum DPUL-S164 in alleviating intestinal barrier damage in mice through a dextran sodium sulfate-induced ulcerative colitis mouse model. Compared to dead L. plantarum DPUL-S164 (D-S164), live L. plantarum DPUL-S164 (S164) and its tryptophan metabolite, ILA, showed an effective ameliorating effect on the intestinal barrier injury of mice treated by antibiotic cocktail and sodium dextran sulfate, suggesting that the crucial substances of L. plantarum DPUL-S164 ameliorating intestinal barrier injury are its extracellular metabolites. Furthermore, S164 and its tryptophan metabolite, ILA, ameliorate intestinal barrier injury and suppress intestinal inflammation by activating the AhR-Nrf2 pathway and inhibiting the nuclear factor kappa-B (NF-κB) pathway. These results suggest that L. plantarum DPUL-S164 ameliorates intestinal epithelial barrier damage in mice, primarily by producing ILA as a ligand to activate the AhR pathway.

Oral Administration of Fermented Milk from Co-Starter Containing Lactobacillus plantarum Y44 Shows an Ameliorating Effect on Hypertension in Spontaneously Hypertensive Rats.

Fermented dairy foods such as yogurt exhibit some beneficial effects on consumers, including relieving the symptoms of hypertension. This study aims to obtain fermented dairy products from a co-starter that have a great flavor and the auxiliary function of reducing blood pressure after longtime consumption. Commercial starter cultures composed of Lactobacillus delbrueckii subsp. bulgaricus CICC 6047 and Streptococcus thermophilus CICC 6038 were combined with Lactobacillus plantarum strains Y44, Y12, and Y16, respectively, as a combined starter culture to ferment the mixed milk of skim milk and soybean milk. The fermented milk produced using the combined starter culture mixed with L. plantarum Y44 showed an angiotensin-converting-enzyme (ACE) inhibitory activity (53.56 ± 0.69%). Some peptides that regulate blood pressure were released in the fermented milk, such as AMKPWIQPK, GPVRGPFPII, LNVPGEIVE, NIPPLTQTPV, and YQEPVL. In spontaneously hypertensive rat (SHR) oral-administration experiments compared with the gavage unfermented milk group, the gavage feeding of SHRs with the fermented milk produced using the combined starter culture mixed with L. plantarum Y44 significantly reduced the blood pressure of the SHRs after long-term intragastric administration, shown with the systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreasing by 23.67 ± 2.49 mmHg and 15.22 ± 2.62 mmHg, respectively. Moreover, the abundance of short-chain fatty acids (SCFA), bacterial diversity in the gut microbiota, and SCFA levels including acetic acid, propionic acid, and butyric acid in the feces of the SHRs were increased via oral administration of the fermented milk produced using the combined starter culture containing L. plantarum Y44. Furthermore, the ACE-angiotensin II (Ang II)-angiotensin type 1 (AT 1) axis was downregulated, the angiotensin-converting-enzyme 2 (ACE 2)-angiotensin(1-7) (Ang1-7)-Mas receptor axis of the SHRs was upregulated, and then the RAS signal was rebalanced. The fermented milk obtained from the combined starter culture shows the potential to be a functional food with antihypertension properties.

Effect of lactic acid bacteria fermentation on cow milk allergenicity and antigenicity: A review.

Cow milk is a major allergenic food. The potential prevention and treatment effects of lactic acid bacteria (LAB)-fermented dairy products on allergic symptoms have garnered considerable attention. Cow milk allergy (CMA) is mainly attributed to extracellular and/or cell envelope proteolytic enzymes with hydrolysis specificity. Numerous studies have demonstrated that LAB prevents the risk of allergies by modulating the development and regulation of the host immune system. Specifically, LAB and its effectors can enhance intestinal barrier function and affect immune cells by interfering with humoral and cellular immunity. Fermentation hydrolysis of allergenic epitopes is considered the main mechanism of reducing CMA. This article reviews the linear epitopes of allergens in cow milk and the effect of LAB on these allergens and provides insight into the means of predicting allergenic epitopes by conventional laboratory analysis methods combined with molecular simulation. Although LAB can reduce CMA in several ways, the mechanism of action remains partially clarified. Therefore, this review additionally attempts to summarize the main mechanism of LAB fermentation to provide guidance for establishing an effective preventive and treatment method for CMA and serve as a reference for the screening, research, and application of LAB-based intervention.

Exopolysaccharide secreted by Lactiplantibacillus plantarum Y12 showed inhibitory effect on the pathogenicity of Shigella flexneri in vitro and in vivo.

Shigella flexneri is a prevalent foodborne and waterborne pathogen that threatens human health. Our previous research indicated that the Lactiplantibacillus plantarum Y12 exopolysaccharide (L-EPS) potentially inhibited the pathogenicity of S. flexneri. The in vitro results of this study demonstrated that L-EPS effectively mitigated the symptoms induced by S. flexneri in HT-29 cells, including inhibited gene expression levels of IL-1ß, IL-6, IL-8, TNF-α, TLR 2/4, and NOD1/2; decreased apoptosis ratio; and alleviated damage degree of intestinal barrier function (Zona occludens 1, Occludin, and Claudin-1). The in vivo results demonstrated that S. flexneri treated with L-EPS elicited mild adverse physiological manifestations, an inflammatory response, and tissue damage. The infection of S. flexneri caused significant alterations in the abundance of phylum (Firmicutes, Bacteroidota, Actinobacteriota, and Proteobacteria), family (Lachnospiraceae, Muribaculaceae, Rikenellaceae, Prevotellaceaea, Ruminococcaceae, and Lactobaillaceae), and genus (Escherichia Shigella and Lachnospirillaceae NK4A136 group) within the cecal microbiota. These changes were accompanied by perturbations in taurine and hypotaurine metabolism, tricarboxylic acid (TCA) cycle activity, arginine biosynthesis, and histidine metabolic pathways. However, intervention with L-EPS attenuated the dysbiosis of cecal microbiota and metabolic disturbances. In summary, our research suggested a potential application of L-EPS as a functional food additive for mitigating S. flexneri infection.

Peptidome comparison on the immune regulation effects of different casein fractions in a cyclophosphamide mouse model.

The protein composition of human milk plays a crucial role in infant formula milk powder formulation. Notably, significant differences exist between bovine casein and human milk casein. Previous studies have shown that casein hydrolysates could enhance immune function; however, gastrointestinal dyspepsia in infants affects the type and function of peptides. Therefore, the present study used peptidomics to sequence and analyze hydrolyzed peptides from different casein fractions. Additionally, animal experiments were conducted to assess the functionality of these casein fractions and elucidate their differences. The results revealed variations in peptide composition among the different casein fractions of formula milk powder. Interestingly, milk powder formulated with both ß- and κ-casein (BK) exhibited significant enrichment of peptides related to the immune system. Moreover, the BK group significantly alleviated immune organ damage in cyclophosphamide-treated mice and regulated serum levels of pro-inflammatory and anti-inflammatory factors. Furthermore, feeding different casein fractions influenced the intestinal microflora of cyclophosphamide-treated mice, with the BK group mitigating the changes caused by cyclophosphamide. In conclusion, the findings suggest that BK formula in milk powder has the potential to positively enhance immunity. This study provides a robust theoretical basis for human-emulsified formula milk powder development.

Lactiplantibacillus plantarum DLPT4 Protects Against Cyclophosphamide-Induced Immunosuppression in Mice by Regulating Immune Response and Intestinal Flora.

In this study, the strain Lactiplantibacillus plantarum DLPT4 was investigated for the immunostimulatory activity in cyclophosphamide (CTX)-induced immunosuppressed BALB/c mice. L. plantarum DLPT4 was administered to BALB/c mice by oral gavage for 30 days, and CTX was injected intraperitoneally from the 25th to the 27th days. Intraperitoneal injection of CTX caused damage to the thymic cortex and intestines, and the immune dysfunction of the BALB/c mice. L. plantarum DLPT4 oral administration exerted immunoregulating effects evidenced by increasing serum immunoglobulin (IgA, IgG, and IgM) levels and reducing the genes expression of pro-inflammatory factors (IL-6, IL-1ß, and TNF-α) of the CTX-induced immunosuppressed mice. The results of the metagenome-sequencing analysis showed that oral administration of L. plantarum DLPT4 could regulate the intestinal microbial community of the immunosuppressed mice by changing the ratio of Lactiplantibacillus and Bifidobacterium. Meanwhile, the abundance of carbohydrate enzyme (CAZyme), immune diseases metabolic pathways, and AP-1/MAPK signaling pathways were enriched in the mice administrated with L. plantarum DLPT4. In conclusion, oral administration of L. plantarum DLPT4 ameliorated symptoms of CTX-induced immunosuppressed mice by regulating gut microbiota, influencing the abundance of carbohydrate esterase in the intestinal flora, and enhancing immune metabolic activity. L. plantarum DLPT4 could be a potential probiotic to regulate the immune response.

Allergenicity evaluation of fermented milk prepared by co-fermentation of Lactobacillus plantarum 7-2 and commercial starters after in vitro digestive.

Milk allergy is one of the most common food allergies, in which αS-casein is the major milk allergen. Under optimized conditions, mixed starter (containing Lactobacillus plantarum 7-2 and commercial starter) effectively degraded αS-casein of skimmed milk and reduced the pressure of stomach digestion. The fermented milk prepared by mixed starter was determined by ELISA, the antigenicity of αS-casein was reduced by 77.53%. Compared with the fermented milk prepared by commercial starter, label-free quantitative proteomics demonstrated that the mixed starter more efficiently degraded the epitopes of major milk allergens and influenced the digestion pattern of the fermented milk. Therefore, L. plantarum 7-2 shows positive potential in reducing the antigenicity of αS-casein and others. In addition, this study predicted that the new epitopes produced in the fermentation process could induce immunity using molecular simulation.

Indole-3-Lactic Acid, a Tryptophan Metabolite of Lactiplantibacillus plantarum DPUL-S164, Improved Intestinal Barrier Damage by Activating AhR and Nrf2 Signaling Pathways.

A growing body of evidence suggests that microbial tryptophan metabolites play a crucial role in maintaining intestinal barrier stability and modulating host immunity. Our previous study showed that the Lactiplantibacillus plantarum (L. plantarum ) DPUL-S164 intervention in mice with a high tryptophan (Trp) diet promotes indole-3-lactic acid (ILA) production in the mice's intestinal tract and ameliorates dextran sodium sulfate(DSS)-induced intestinal barrier damage in mice. In this study, we used the HT-29 cell monolayer model to evaluate the effect of the L. plantarum DPUL-S164 Trp metabolites (DPUL-S164-TM) on the intestinal barrier. We found that L. plantarum DPUL-S164-TM alleviated lipopolysaccharide (LPS)-induced intestinal barrier damage and inflammation of the HT-29 cell monolayer by promoting the expression of tight junction proteins (ZO-1, occludin, claudin1), activating the AhR and Nrf2 signaling pathways, and inhibiting the NF-κB signaling pathway. We found that the promotion of tight junction protein expression and the activation of the Nrf2 signaling pathway by L. plantarum DPUL-S164-TM were dependent on the AhR expression of HT-29 cells. Additionally, L. plantarum DPUL-S164-TM showed a dramatic increase in the ILA content. Therefore, we inferred that ILA in L. plantarum DPUL-S164-TM plays a key role in improving the intestinal barrier function and alleviating inflammation.

Exopolysaccharide produced by Lactiplantibacillus plantarum Y12 exhibits inhibitory effect on the Shigella flexneri genes expression related to biofilm formation.

Shigella is a specific enteric pathogen in humans, causing symptoms of bacterial dysentery. The biofilm formation of S. flexneri contributes to the emergence of multidrug resistance and facilitates the establishment of persistent chronic infections. This study investigated the regulatory effects of Lactiplantibacillus plantarum Y12 exopolysaccharide (L-EPS) on gene expression and its spatial hindrance effects in inhibiting the biofilm formation of S. flexneri. The transcriptome analysis revealed a significant impact of L-EPS on the gene expression profile of S. flexneri, with a total of 968 genes showing significant changes (507 up-regulated and 461 down-regulated). The significantly down-regulated KEGG metabolic pathway enriched in phosphotransferase system, Embden-Meyerhf-Parnas, Citrate cycle, Lipopolysaccharide biosynthesis, Cationic antimicrobial peptide resistance, Two-component system. Moreover, L-EPS significantly down-regulated the gene expression levels of fimbriae synthesis (fimF), lipopolysaccharide synthesis (lptE, lptB), anchor protein repeat domain (arpA), virulence factor (lpp, yqgB), antibiotic resistance (marR, cusB, mdtL, mdlB), heavy metal resistance (zraP), and polysaccharide synthesis (mtgA, mdoB, mdoC). The expression of biofilm regulator factor (bssS) and two-component system suppressor factor (mgrB) were significantly up-regulated. The RT-qPCR results indicated that a major component of L-EPS (L-EPS 2-1) exhibited the gene regulatory effect on the S. flexneri biofilm formation. Furthermore, electrophoresis and isothermal microtitration calorimetry demonstrated that the interaction between L-EPS 2-1 and eDNA is electrostatic dependent on the change in environmental pH, disrupting the stable spatial structure of S. flexneri biofilm. In conclusion, L-EPS inhibited the biofilm formation of S. flexneri through gene regulation and spatial obstruction effects.

Changes in Intracellular and Extracellular Metabolites of Mixed Lactobacillus Strains Enhance Inhibition of Pathogenic Bacterial Growth and Lipopolysaccharide-Induced Alleviation of RAW264.7 Cellular Inflammation.

It is important to explore whether there are antagonistic and synergistic effects between different strains of Lactobacillus when developing mixed Lactobacillus strain products. In this study, we investigated the antagonistic and symbiotic effects of co-cultured Lactobacillus strains, as well as their amelioratory effects on lipopolysaccharide (LPS)-induced inflammation and oxidative stress in RAW264.7 cells. The Lactobacillus strains tested in this paper showed no antagonism. Co-culture of Lactiplantibacillus plantarum Y44 and L. plantarum AKS-WS9 was found to show inhibiting effects on the growth of Escherichia coli and Staphylococcus aureus. Additionally, the co-cultured Lactiplantibacillus plantarum Y44 and L. plantarum AKS-WS9 relieved inflammation in RAW264.7 cells induced by LPS by inhibiting the activation of NF-κB and P38 signaling pathways and down-regulating the expression of pro-inflammatory cytokines NO, ROS, iNOs and TNF-α. And the co-cultured Lactobacillus strains activated the Nrf2 signaling pathway in the LPS-induced RAW264.7 cells to promote the expression of antioxidant enzymes in response to oxidative stress. There was a difference in intracellular and extracellular metabolites between single or co-cultured Lactobacillus strains, and the co-cultured Lactobacillus strains significantly increased extracellular metabolites 4-chlorobenzaldehyde, psoromic acid, and 2-dodecylbenzenesulfonic acid and intracellular metabolites 9(S)-HODE, pyocyanin, and LysoPA. We inferred that the better antibacterial and anti-inflammatory ability of the co-cultured Lactobacillus strains were related to the changes in the metabolites of the co-cultured Lactobacillus strains. The co-cultured L. plantarum Y44 and L. plantarum AKS-WS9 strains exhibited better anti-inflammatory abilities and had the potential to alleviate the symptoms of inflammatory diseases as mixed probiotics.