Immunomodulating activity of exopolysaccharide-producing Leuconostoc mesenteroides strain NTM048 from green peas

Lipoteichoic acid composed of poly-glycerolphosphate containing l-lysine and involved in immunoglobulin A-inducing activity in Apilactobacillus genus

Lipoteichoic acid (LTA) in the gram-positive bacterial cell wall acts as an immunomodulatory factor in host cells. The chemical structures vary among bacterial species and strains, and may be related to biological activities. In our previous work, much higher immunoglobulin A (IgA)-inducing activity was observed in cells of the Apilactobacillus genus (Apilactobacillus kosoi 10HT, Apilactobacillus apinorum JCM 30765T, and Apilactobacillus kunkeei JCM 16173T) than other lactic acid bacteria, and their LTA was responsible for the activity. In the present study, we elucidated the chemical structures of LTA from these Apilactobacillus strains to explore the structure-function relationship of the IgA-inducing activity. The 1H-nuclear magnetic resonance spectra suggested that their LTA structures were similar. All have a poly-glycerolphosphate main chain, which comprised 12 to 20 average number of the repeating units, with partial substitutions of glucose(α1-, glucosyl(α1-2)glucose(α1- (α-linked-kojibiose), and l-lysine at the C-2 hydroxy group of the glycerol residue. l-Lysine is a substituent never seen before in LTA, and is a probable characteristic of the Apilactobacillus genus. Removal of l-lysine residue from LTA by mild alkaline treatment decreased IgA induction in murine Peyer's patch experiments. The novel l-lysine residue in Apilactobacillus LTA plays a crucial role in the remarkably high IgA-inducing activity.

Leuconostoc mesenteroides subsp. strain NTM048 ameliorated nasal symptoms in patients with Japan cedar pollinosis: Randomized, double-blind, and placebo-controlled trial

BACKGROUND

Lactobacillales including L mesenteroides have beneficial effects on human health, including improvement of psychological status and alleviation of allergic rhinitis. In mice, L mesenteroides subsp. strain NTM048 (NTM048) increased intestinal s-IgA. In humans, however, the effects of NTM048 on s-IgA secretion have been unclear.

STUDY

This 16-week trial was performed using a double-blind, placebo-controlled, parallel group design. We aimed to establish whether Leuconostoc mesenteroides subsp. strain NTM048 increases the secretion of s-IgA in saliva. Forty healthy adults and forty patients with Japanese cedar pollinosis were recruited. Participants took either 2 test capsules including NTM048 (1010 CFU/day), or 2 placebo capsules per day, for 16 weeks. They were asked to collect their saliva and answered POMS2, a questionnaire about psychological status. The patients also answered questions about nasal symptoms. Blood samples were collected from the patients with Japanese Cedar pollinosis. Stool samples were collected at the start and on the last day of the trial.

RESULTS

All subjects completed the trial. It was conducted during the season when Japanese cedar pollen is most scattered. Serum concentration of Japanese cedar pollen-specific IgE was > 2.0 UA/mL in patients with Japanese cedar pollinosis. The amount of s-IgA in saliva was not increased by NTM048 in overall subjects, and Japanese cedar pollen-specific IgE was not changed by NTM048 in patients with Japanese cedar pollinosis. The symptom of nasal blockage was improved by NTM048 12 weeks after the start of trial. post hoc analysis indicated a positive correlation between improving psychological status and the increase in occupation ratio of lactobacillus including NTM048.

CONCLUSION

The amount of s-IgA in saliva was not increased by NTM048, but nasal blockage was improved by it. Psychological status might be improved if dosage of NTM048 is raised to the degree that NTM048 might be increased in the intestinal tract.

Lactic acid bacteria-derived exopolysaccharide: Formation, immunomodulatory ability, health effects, and structure-function relationship

Exopolysaccharides (EPSs) synthesized by lactic acid bacteria (LAB) have implications for host health and act as food ingredients. Due to the variability of LAB-EPS (lactic acid bacteria-derived exopolysaccharide) gene clusters, especially the glycosyltransferase genes that determine monosaccharide composition, the structure of EPS is very rich. EPSs are synthesized by LAB through the extracellular synthesis pathway and the Wzx/Wzy-dependent pathway. LAB-EPS has a strong immunomodulatory ability. The EPSs produced by different genera of LAB, especially Lactobacillus, Leuconostoc, and Streptococcus, have different immunomodulatory abilities because of their specific structures. LAB-EPS possesses other health effects, including antitumor, antioxidant, intestinal barrier repair, antimicrobial, antiviral, and cholesterol-lowering activities. The bioactivities of LAB-EPS are tightly related to their structures such us monosaccharide composition, glycosidic bonds, and molecular weight (MW). For the excellent physicochemical property, LAB-EPS acts as product improvers in dairy, bakery food, and meat in terms of stability, emulsification, thickening, and gelling. We systematically summarize the detailed process of EPS from synthesis to application, with emphasis on physiological mechanisms of EPS, and specific structure-function relationship, which provides theoretical support for the potential commercial value in the pharmaceutical, chemical, food, and cosmetic industries.

Comparison of the effects of three forms of soluble dietary fiber on the production of IgA in BALB/cAJcl and BALB/cAJcl-nu/nu mice

BACKGROUND

Their ability to induce the production of IgA, especially in the intestine, is one of the health benefits of soluble dietary fibers (SDFs), but the mechanism involved is unclear.

OBJECTIVE

This study was designed to identify the relationship between the induction of IgA by SDFs and the cecal short-chain fatty acids (SCFAs) content, and to evaluate the importance of T cell-independent IgA production for SDF-induced IgA production.

METHODS

We compared the SDFs fructooligosaccharides (FO), indigestible glucan (IG), and polydextrose (PD). Male BALB/cAJcl mice or T cell-deficient BALB/cAJcl-nu/nu (nude) mice were fed diets supplemented with one SDF (3% w/w) for 10 weeks and we measured IgA content in their feces, plasma, lung, and submandibular gland.

RESULTS

In BALB/cAJcl mice, the consumption of all three SDF diets induced fecal IgA production, but the response was stronger in the IG and PD groups than in the FO group. The IgA concentration of the plasma and lung were also higher in the FO and PD groups, and these groups showed significantly higher cecal acetic and n-butyric acid content. In contrast, in nude mice, the induction of IgA production was identified only in fecal samples of mice fed the three SDF diets, even though there were significant increases in cecal SCFAs content.

CONCLUSIONS

The induction of IgA production by SDFs is occurred T cell-independently in the intestine, but that in the plasma, lung, and submandibular gland is T cell-dependent. SCFAs generated in the large intestine might influence the systemic immune system, but there is no clear relationship between the generation of SCFAs and intestinal IgA production in response to SDF consumption.

Host metabolic benefits of prebiotic exopolysaccharides produced by Leuconostoc mesenteroides

Fermented foods demonstrate remarkable health benefits owing to probiotic bacteria or microproducts produced via bacterial fermentation. Fermented foods are produced by the fermentative action of several lactic acid bacteria, including Leuconostoc mesenteroides; however, the exact mechanism of action of these foods remains unclear. Here, we observed that prebiotics associated with L. mesenteroides-produced exopolysaccharides (EPS) demonstrate substantial host metabolic benefits. L. mesenteroides-produced EPS is an indigestible α-glucan, and intake of the purified form of EPS improved glucose metabolism and energy homeostasis through EPS-derived gut microbial short-chain fatty acids, and changed gut microbial composition. Our findings reveal an important mechanism that accounts for the effects of diet, prebiotics, and probiotics on energy homeostasis and suggests an approach for preventing lifestyle-related diseases by targeting bacterial EPS.

Bacterial Exopolysaccharides as Emerging Bioactive Macromolecules: From Fundamentals to Applications

Microbial exopolysaccharides (EPS) are extracellular carbohydrate polymers forming capsules or slimy coating around the cells. EPS can be secreted by various bacterial genera that can help bacterial cells in attachment, environmental adaptation, stress tolerance and are an integral part of microbial biofilms. Several gut commensals (e.g., Lactobacillus, Bifidobacterium) produce EPS that possess diverse bioactivities. Bacterial EPS also has extensive commercial applications in the pharmaceutical and food industries. Owing to the structural and functional diversity, genetic and metabolic engineering strategies are currently employed to increase EPS production. Therefore, the current review provides a comprehensive overview of the fundamentals of bacterial exopolysaccharides, including their classification, source, biosynthetic pathways, and functions in the microbial community. The review also provides an overview of the diverse bioactivities of microbial EPS, including immunomodulatory, anti-diabetic, anti-obesity, and anti-cancer properties. Since several gut microbes are EPS producers and gut microbiota helps maintain a functional gut barrier, emphasis has been given to the intestinal-level bioactivities of the gut microbial EPS. Collectively, the review provides a comprehensive overview of microbial bioactive exopolysaccharides.

The Regulation of Micro-Organisms' Extra-Cellular Polysaccharides on Immunity: A Meta-Analysis

Extra-cellular polysaccharides (EPSs) have excellent immunomodulatory functions. In order to further promote their application, we studied the ability of extra-cellular polysaccharides from different sources to regulate immunity. We studied the association of extra-cellular polysaccharides with immune factors (Interleukin (IL-2, IL-4, IL-10), Interferon γ (IFN-γ), tumor necrosis factor-α (TNF-α), Immunoglobulin A (IgA), and Immunoglobulin G (IgG)) and different concentrations of EPSs and interfering media on experimental results by using a forest plot under fixed-effect or random-effects models. Through Google, PubMed, Embase, ScienceDirect, and Medline, from 2000 to 2021, 12 articles were included. We found that exopolysaccharides (from bacteria or fungi) could significantly increase the immune index of spleen and thymus, spleen index (SMD: 2.11, ‘95%CI: [1.15, 3.08]’; p < 0.01), and thymus index (SMD: 1.62, ‘95%CI: [0.93, 2.32]’; p = 0.01 < 0.05). In addition, exopolysaccharides had a significant effect on TNF-α (SMD: 0.94, ‘95%CI: [0.29, 1.59]’; p = 0.01 < 0.05). For IL-4 (SMD: 0.49, ‘95%CI: [0.01, 0.98]’; p = 0.046 < 0.05), extra-cellular polysaccharides had a statistically significant effect on immunity. Although the data of other immune factors were not ideal, the comprehensive analysis showed that exopolysaccharides also had an effect on the release of these five immune factors. In the sub-group analysis, different concentrations of EPSs affected the results of experiments on the spleen and thymus, and the CY intervention had a relatively significant effect on immune regulation. Taken together, our study highlighted that EPSs have a significant impact on immune regulation.

Role of Lipoteichoic Acid from the Genus Apilactobacillus in Inducing a Strong IgA Response

Lactic acid bacterium-containing fermentates provide beneficial health effects by regulating the immune response. A naturally fermented vegetable beverage, a traditional Japanese food, reportedly provides health benefits; however, the beneficial function of its bacteria has not been clarified. Apilactobacillus kosoi is the predominant lactic acid bacterium in the beverage. Using murine Peyer's patch cells, we compared the immunoglobulin A (IgA)-inducing activity of A. kosoi 10H^T to those of 29 other species of lactic acid bacteria and found that species belonging to the genus Apilactobacillus (A. kosoi 10H^T, A. apinorum JCM30765^T, and A. kunkeei JCM16173^T) possessed significantly higher activity than the others. Thereafter, lipoteichoic acids (LTAs), important immunostimulatory molecules of Gram-positive bacteria, were purified from the three Apilactobacillus species, and their IgA-inducing activity was compared to those of LTAs from Lactiplantibacillus plantarum JCM1149^T and a probiotic strain, Lacticaseibacillus rhamnosus GG. The results revealed that LTAs from Apilactobacillus species had significantly higher activity than others. We also compared the LTA structure of A. kosoi 10H^T with that of L. plantarum JCM1149^T and L. rhamnosus GG. Although d-alanine or both d-alanine and carbohydrate residues were substituents of free hydroxyl groups in the polyglycerol phosphate structure in LTAs from strains JCM1149^T and GG, d-alanine residues were not found in LTA from strain 10H^T by ¹H nuclear magnetic resonance (NMR) analysis. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis of the glycolipid structure of LTA revealed that LTA from strain 10H^T contained dihexosyl glycerol, whereas trihexosyl glycerol was detected in LTAs from other strains. These structural differences may be related to differences in IgA-inducing activity. IMPORTANCE The components of lactic acid bacteria that exert immunostimulatory effects are of increasing interest for therapeutic and prophylactic options, such as alternatives to antibiotics, cognitive enhancements, and vaccine adjuvants. LTAs act as immunostimulatory molecules in the host innate immune system by interacting with pattern recognition receptors. However, as LTA structures differ among species, detailed knowledge of the structure-function relationship for immunostimulatory effects is required. Comparisons of the IgA-inducing activity of LTAs have demonstrated that LTAs from the genus Apilactobacillus possess distinctive activities to stimulate mucosal immunity. The first analysis of the LTA structure from the genus Apilactobacillus suggests that it differs from structures of LTAs of related species of lactic acid bacteria. This knowledge is expected to aid in the development of functional foods containing lactic acid bacteria and pharmaceutical applications of immunostimulatory molecules from lactic acid bacteria.

Lentilactobacillus kosonis sp. nov., isolated from kôso, a Japanese sugar-vegetable fermented beverage

A novel lactic acid-producing, Gram-stain-positive, catalase-negative and rod-shaped strain, designated as strain C06_No.73^T, was isolated from a traditional Japanese fermented beverage called kôso. According to the results of phylogenetic analysis based on 16S rRNA gene sequences, strain C06_No.73^T belongs to the genus Lentilactobacillus. The closest type strain was Lentilactobacillus curieae CCTCC M 2011381^T, with a sequence identity of 98.1 %. The identity values with other strains were all below 97 %. The isolate propagated under the conditions of 18-39 °C (optimum, 27 °C for 48 h incubation) and pH 4.0-7.0 (optimum, pH 6.5). The G+C content of its genomic DNA was determined to be 37.9 mol%. The main fatty acids were C_16 : 0, C_18 : 1 ω7c, C_18 : 1 ω9c and C_19 : 0 cyclopropane 11,12. The major polar lipid was identified as phosphatidylglycerol. No isoprenoid quinone was detected. The predominant cell-wall amino acids were lysine, alanine, glutamic acid and aspartic acid. Neither meso-diaminopimelic acid nor ornithine were detected. On the basis of this polyphasic taxonomic study, the isolate is concluded to represent a novel species, for which the name Lentilactobacillus kosonis sp. nov. is proposed. The type strain is C06_No.73^T (=NBRC 111893^T=BCRC 81282^T).

Metagenomic Investigation Uncovers Presence of Probiotic-Type Microbiome in Kalparasa® (Fresh Unfermented Coconut Inflorescence Sap)

The phloem sap tapped from unopened inflorescence (spadix) of coconut palm using a novel collecting device, “coco-sap chiller,” has been branded Kalparasa^® (henceforth as Kalparasa in the text) to distinguish its properties not found in sap harvested by traditional methods. To know its hitherto unidentified microbiome profile, we employed high-throughput sequencing to uncover the bacteriome and mycobiome in fresh and 12-h fermented samples. Fresh Kalparasa had a pH of 7.2, which dropped to 4.5 after 12 h, signifying fermentation of the sap. Diversity analysis indicated fresh Kalparasa having higher bacterial species than the fermented one. Contrary to this, fresh sap had lower fungal/yeast diversity than the fermented sample. Fresh Kalparasa had relatively higher abundance of probiotic-type Leuconostoc genus followed by equal proportions of Gluconobacter, Acetobacter, and Fructobacillus. The 12-h fermented Kalparasa showed a significant increase in Gluconobacter with a sharp decrease in Leuconostoc. Mycobiome data revealed fresh Kalparasa to be preponderant in Saccharomyces and Hanseniaspora genera of yeasts while the fermented sap had higher representation of Hanseniaspora and Cortinarius and lesser Saccharomyces. This suggested that the fermentation of Kalparasa was probably driven by symbiotic culture of bacteria and yeasts (SCOBY), particularly acetic acid bacteria and non-Saccharomyces yeasts. The bacteriome-function predictions highlighted the enrichment of glycerophospholipid, ABC transporters, purine, and pyrimidine metabolisms. Based on our findings, Kalparasa containing large population of Leuconostoc mesenteroides, Fructobacillus fructosus, Saccharomyces cerevisiae, and Hanseniaspora guilliermondii can be promoted as a healthy “unfermented” plant edible food containing live probiotic-type microbiome during its consumption.

Exopolysaccharides as Antimicrobial Agents: Mechanism and Spectrum of Activity

Exopolysaccharides (EPSs) are metabolites synthesized and excreted by a variety of microorganisms, including lactic acid bacteria (LAB). EPS serve several biological functions such as interactions between bacteria and their environments, protection against hostile conditions including dehydration, the alleviation of the action of toxic compounds (bile salts, hydrolyzing enzymes, lysozyme, gastric, and pancreatic enzymes, metal ions, antibiotics), and stresses (changing pH, osmolarity), and evasion of the immune response and phage attack. Bacterial EPSs are considered valuable by the food, pharmaceutical, and nutraceutical industries, owing to their health-promoting benefits and rheological impacts. Numerous studies have reported the unusual antimicrobial activities of various EPS against a wide variety of pathogenic microbes (bacteria, virus, and fungi). This review aims to provide a comprehensive examination of the in vitro and in vivo antimicrobial activities of different EPSs, mainly against foodborne bacterial, fungal, and viral pathogens. The mechanism of EPS action against these pathogens as well as the methods used to measure antimicrobial activities are critically reviewed.

Enzymatically synthesized exopolysaccharide of a probiotic strain Leuconostoc mesenteroides NTM048 shows adjuvant activity to promote IgA antibody responses

Leuconostoc mesenteroides strain NTM048 produces an exopolysaccharide (EPS; glucose polymers 94% and fructose polymers 6%) with adjuvanticity for mucosal vaccination. Strain NTM048 includes three putative EPS-synthesizing genes, gtf1 and gtf2 for synthesizing glucose polymers, and lvnS for synthesizing fructose polymer. To elucidate the key polymer structure for adjuvanticity, two genes, gtf1 and gtf2, which were annotated as glycoside hydrolase family 70 enzyme genes, were expressed in Escherichia coli. Glycosyl-linkage composition analysis and NMR analysis showed that the recombinant enzyme Gtf1 produced a soluble form of α-1,6-glucan, whereas the recombinant enzyme Gtf2 produced glucans with approximately equal percentages of α-1,6- and α-1,3-glucose residues both in the supernatant (S-glucan) and as a precipitate (P-glucan). Comparison of polysaccharides synthesized by Gtf1, Gtf2, and LvnS revealed that Gtf2-S-glucan, which was produced in the supernatant by Gtf2 and formed particles of 7.8 µm, possessed 1.8-fold higher ability to stimulate IgA production from murine Peyer's patch cells than native NTM048 EPS. Evaluation of adjuvanticity by intranasal administration of mice with an antigen (ovalbumin) and Gtf2-S-glucan or NTM048 EPS showed that Gtf2-S-glucan induced the production of higher antigen-specific antibodies in the airway mucosa and plasma, suggesting a pivotal role of Gtf2-S-glucan in the adjuvanticity of NTM048 EPS.

Administration of Enterococcus faecium HS-08 increases intestinal acetate and induces immunoglobulin A secretion in mice

A probiotic is considered a live microbial feed supplement that has beneficial effects on the host. In this study, the probiotic property by which Enterococcus faecium HS-08 strengthens the immune system was investigated. Using a murine model, we evaluated the abilities of this strain to increase intestinal short-chain fatty acid contents and to induce the production of mucosal immunoglobulin A (IgA), which are crucial for mucosal immune systems. Various amounts (0%, 0.0038%, 0.038%, or 0.38%) of strain HS-08 cells were administered to BALB/cAJcl mice, which resulted in a dose-dependent increase of fecal IgA levels. A qRT-PCR analysis of Peyer's patch cells revealed that the gene expression of retinal-dehydrogenase, interleukin 6, B-cell-activating factor, and a proliferation-inducing ligand were increased, which leads to IgA secretion via a T-cell-independent mechanism. The administration of 0.038% and 0.38% of strain HS-08 cells also increased fecal acetate levels, which plays an important role for maintaining immune functions. This cecal floral analysis and the stability of strain HS-08 against gastrointestinal digestion suggest that this strain can inhabit the host intestine. In conclusion, the administration of E. faecium HS-08 increased intestinal acetate levels and enhanced IgA secretion, which may result in strengthening of the mucosal immune system.

High Levels of CO2 Induce Spoilage by Leuconostoc mesenteroides by Upregulating Dextran Synthesis Genes

During nonventilated storage of carrots, CO2 gradually accumulates to high levels and causes modifications in the carrot's microbiome toward dominance of Lactobacillales and Enterobacteriales The lactic acid bacterium Leuconostoc mesenteroides secretes a slimy exudate over the surface of the carrots. The objective of this study was to characterize the slime components and the potential cause for its secretion under high CO2 levels. A proteomic analysis of the exudate revealed bacterial glucosyltransferases as the main proteins, specifically, dextransucrase. A chemical analysis of the exudate revealed high levels of dextran and several simple sugars. The exudate volume and dextran amount were significantly higher when L. mesenteroides was incubated under high CO2 levels than when incubated in an aerated environment. The treatment of carrot medium plates with commercial dextransucrase or exudate protein extract resulted in similar sugar profiles and dextran production. Transcriptome analysis demonstrated that dextran production is related to the upregulation of the L. mesenteroides dextransucrase-encoding genes dsrD and dsrT during the first 4 to 8 h of exposure to high CO2 levels compared to aerated conditions. A phylogenetic analysis of L. mesenteroides YL48 dsrD revealed a high similarity to other dsr genes harbored by different Leuconostoc species. The ecological benefit of dextran production under elevated CO2 requires further investigation. However, this study implies an overlooked role of CO2 in the physiology and fitness of L. mesenteroides in stored carrots, and perhaps in other food items, during storage under nonventilated conditions.IMPORTANCE The bacterium Leuconostoc mesenteroides is known to cause spoilage of different types of foods by secreting a slimy fluid that damages the quality and appearance of the produce. Here, we identified a potential mechanism by which high levels of CO2 affect the spoilage caused by this bacterium by upregulating dextran synthesis genes. These results have broader implications for the study of the physiology, degradation ability, and potential biotechnological applications of Leuconostoc.

Isolation of immune-regulatory Tetragenococcus halophilus from miso

Tetragenococcus halophilus is a halophilic lactic acid bacterium that exists in the traditional Japanese seasoning miso-a fermented soy paste. Considering the popularity of miso as a component of healthy diet, we attempted to evaluate the immunoregulatory functions of T. halophilus spices isolated from miso. We screened 56 strains that facilitated the upregulation of activation markers such as CD86 and CD69 on B cells and T cells in vitro. Of these, 7 strains (Nos. 1, 3, 13, 15, 19, 30, and 31) were found to preferentially induce the CD86 expression on B cells. Furthermore, DNA microarray analysis revealed that T. halophilus strain No. 1 significantly augmented the gene expressions of CD86, CD70, IL-10, INF-γ, and IL-22 in B cells. We confirmed these results at the protein level by flow cytometry. Mice feeding diet containing 1% T. halophilus No. 1 exhibited significantly greater IgA production in the serum. Furthermore, a diet containing 1% T. halophilus No. 1 augmented ovoalbumin (OVA)-specific IgG titer in mice upon OVA/alum immunization. Thus, we demonstrated that T. halophilus No. 1 is a strong immunomodulatory strain with potential as a probiotic.

Effects of chocolate containing Leuconostoc mesenteroides strain NTM048 on immune function: a randomized, double-blind, placebo-controlled trial

Background

Previous reports showed that oral administration of Leuconostoc mesenteroides strain NTM048 increases IgA levels and CD4+ T cell population in feces and mice, respectively, as revealed by flow cytometric analysis of splenocytes. This study aimed to evaluate the effect of chocolate supplemented with L. mesenteroides strain NTM048 (> 1.00 × 10⁹ CFU/day, NTM048) on the immune parameters of healthy subjects, using a randomized, placebo-controlled, double-blinded study design.

Methods

Participants (mean age: 46.3 years) ingested 28 g of test food daily, at a time of their own choice, for 4 weeks. The immunological parameters of all participants were evaluated two times (pre- and post- ingestion). At the end of the study, various immunological parameters of the participants were measured and scoring of immunological vigor (SIV) was performed using a comprehensive algorithm.

Results

Ingestion of NTM048-supplemented chocolate significantly improved SIV in the NTM048 group (18.6 ± 1.6) compared to that in the placebo group (17.8 ± 2.0) after 4 weeks (p = 0.049). Several immunological parameters (CD8⁺T cells, CD8⁺CD28⁺ T cells, and memory T cells) were significantly elevated in the NTM048 group as compared to the placebo group (all p < 0.05). In addition, T cell proliferation index at post-ingestion significantly increased compared with that at pre-ingestion in the NTM048 (p = 0.017) and placebo groups (p = 0.037), although no differences were observed between the two groups.

Conclusion

Our results suggest that ingestion of chocolate supplemented with NTM048 is effective against the age-related decline in T cell-related immune functions.

Trial registration

UMIN Clinical Trials Registry UMIN000021989. Registered 19 April 2016, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000025321

Dietary fibers, prebiotics, and exopolysaccharides produced by lactic acid bacteria: potential health benefits with special regard to cholesterol-lowering effects

The gastrointestinal (GIT) microbiota, which plays a crucial role in human health, is influenced by a number of factors including diet. Consumption of specific dietary ingredients, such as dietary fibers and prebiotics, is an avenue by which the microbiota can be positively modulated. These substances may also reduce serum cholesterol levels through various mechanisms. Interest has increased in methods of reducing blood cholesterol level, because dyslipidemia is recognized as a contributory risk factor for the development of cardiovascular diseases. Several drugs have been developed for the treatment of hypercholesterolemia; however, undesirable side effects were observed, which have caused concerns about their long-term therapeutic use. Alternatively, many nonpharmacological approaches were tested to reduce elevated serum cholesterol levels. Dietary fibers and prebiotics have particularly beneficial effects on the GIT microbiome, and can also reduce serum cholesterol level through various mechanisms. Lactic acid bacteria (LAB) are potentially capable of synthesizing different polysaccharides, e.g. exopolysaccharides (EPS), which may play a role as prebiotics. LAB-based EPS have the potential to affect the gastrointestinal microbiome and reduce cholesterol. However, as dietary fibers comprise a complex group of substances with remarkably diverse structures, properties, and impacts, EPS also differ greatly and show a multitude of beneficial health effects. This review discusses the current knowledge related to the effects of dietary fibers and prebiotics on the human GIT microbiome, the prebiotic properties of EPS produced by LAB, and the health-promoting benefits of these polymers with special emphasis being given to cholesterol lowering.

Lactobacillus kosoi sp. nov., a fructophilic species isolated from kôso, a Japanese sugar-vegetable fermented beverage

A novel Gram-positive, fructophilic, catalase negative, and rod-shaped strain, designated strain 10H^T was isolated from kôso, a Japanese sugar-vegetable fermented beverage obtained from a food processing factory in Saku City, Nagano Prefecture, Japan. Phylogenetic analysis based on 16S rRNA gene sequences revealed strain 10H^T to belong to the genus Lactobacillus, with closely related type strains being Lactobacillus kunkeei YH-15^T (95.5% sequence similarity), Lactobacillus ozensis Mizu2-1^T (95.4% sequence similarity), and Lactobacillus apinorum Fhon13N^T (95.3% sequence similarity). The isolate was found to grow at 18-39 °C (optimum 27 °C), pH 4.0-7.0 (optimum pH 6.5) and in the presence of 0-2% NaCl (optimum 0% NaCl). The G + C content of its genomic DNA was determined to be 30.5 mol%. The major fatty acid (≥ 10%) components identified included C_16:0, C_19:0 cyclo ω7c, C_19:0 cyclo ω9c, and C_18:1 ω9c. The polar lipids were identified as lysophosphatidylethanolamine, phosphatidylethanolamine and glycolipids. The predominant isoprenoid quinones (> 10%) were identified as MK-7, MK-8, MK-9 and MK-10. The amino acid composition of the cell wall was detected as comprising Asp, Glu, Ala, and Lys but the strain lacks meso-diaminopimelic acid. As with other fructophilic lactic acid bacteria, such as L. kunkeei and L. apinorum, strain 10H^T was found to prefer D-fructose to D-glucose as a growth substrate. On the basis of these genetic and phenotypic results, the isolate is concluded to represent a novel species, for which the name Lactobacillus kosoi is proposed. The type strain is 10H^T (= NBRC 113063^T = BCRC 81100^T).

Genome-scale modeling and transcriptome analysis of Leuconostoc mesenteroides unravel the redox governed metabolic states in obligate heterofermentative lactic acid bacteria

Obligate heterofermentative lactic acid bacteria (LAB) are well-known for their beneficial health effects in humans. To delineate the incompletely characterized metabolism that currently limits their exploitation, at systems-level, we developed a genome-scale metabolic model of the representative obligate heterofermenting LAB, Leuconostoc mesenteroides (iLME620). Constraint-based flux analysis was then used to simulate several qualitative and quantitative phenotypes of L. mesenteroides, thereby evaluating the model validity. With established predictive capabilities, we subsequently employed iLME620 to elucidate unique metabolic characteristics of L. mesenteroides, such as the limited ability to utilize amino acids as energy source, and to substantiate the role of malolactic fermentation (MLF) in the reduction of pH-homeostatic burden on F0F1-ATPase. We also reported new hypothesis on the MLF mechanism that could be explained via a substrate channelling-like phenomenon mainly influenced by intracellular redox state rather than the intermediary reactions. Model simulations further revealed possible proton-symporter dependent activity of the energy efficient glucose-phosphotransferase system in obligate heterofermentative LAB. Moreover, integrated transcriptomic analysis allowed us to hypothesize transcriptional regulatory bias affecting the intracellular redox state. The insights gained here about the low ATP-yielding metabolism of L. mesenteroides, dominantly controlled by the cellular redox state, could potentially aid strain design for probiotic and cell factory applications.

Glucansucrases produced by fructophilic lactic acid bacteria Lactobacillus kunkeei H3 and H25 isolated from honeybees

Twenty fructophilic isolates from the stomachs of honeybee Apis mellifera ligustica from the region of Plovdiv, Bulgaria were obtained. Fructophilic isolates H3 and H25 showed formation of mucous colonies during cultivation on medium with sucrose, suggesting exopolysaccharide synthesis. The sequencing analysis of 16S rRNA identified isolates H3 and H25 as fructophilic lactic acid bacteria Lactobacillus kunkeei. The in situ analysis and periodic acid-Schiff's staining, showed that Lb. kunkeei H3 and H25 produce extracellular glucansucrases with molecular weight of about 300 kDa. In the cell-associated fractions, additional glucansucrase is detected with molecular weight of about 180 kDa. The content of α-(1 → 6) linkages in the glucans synthesized with extracellular glucansucrases from H3 and H25 after dextranase hydrolysis was significantly lower than this one of the classical dextran - about 35 and 62%, respectively. These results suggest a more branched structure of the studied polymers.

Immunoregulatory Effects Triggered by Lactic Acid Bacteria Exopolysaccharides: New Insights into Molecular Interactions with Host Cells

Researchers have demonstrated that lactic acid bacteria (LAB) with immunomodulatory capabilities (immunobiotics) exert their beneficial effects through several molecules, including cell wall, peptidoglycan, and exopolysaccharides (EPS), that are able to interact with specific host cell receptors. EPS from LAB show a wide heterogeneity in its composition, meaning that biological properties depend on the strain and. therefore, only a part of the mechanism of action has been elucidated for these molecules. In this review, we summarize the current knowledge of the health-promoting actions of EPS from LAB with special focus on their immunoregulatory actions. In addition, we describe our studies using porcine intestinal epithelial cells (PIE cells) as a model to evaluate the molecular interactions of EPS from two immunobiotic LAB strains and the host cells. Our studies showed that EPS from immunobiotic LAB have anti-inflammatory capacities in PIE cells since they are able to reduce the production of inflammatory cytokines in cells challenged with the Toll-like receptor (TLR)-4-agonist lipopolysaccharide. The effects of EPS were dependent on TLR2, TLR4, and negative regulators of TLR signaling. We also reported that the radioprotective 105 (RP105)/MD1 complex, a member of the TLR family, is partially involved in the immunoregulatory effects of the EPS from LAB. Our work described, for the first time, that LAB and their EPS reduce inflammation in intestinal epithelial cells in a RP105/MD1-dependent manner. A continuing challenge for the future is to reveal more effector-receptor relationships in immunobiotic-host interactions that contribute to the beneficial effects of these bacteria on mucosal immune homeostasis. A detailed molecular understanding should lead to a more rational use of immunobiotics in general, and their EPS in particular, as efficient prevention and therapies for specific immune-related disorders in humans and animals.

Exopolysaccharides produced by lactic acid bacteria: from health-promoting benefits to stress tolerance mechanisms

A wide range of lactic acid bacteria (LAB) is able to produce capsular or extracellular polysaccharides, with various chemical compositions and properties. Polysaccharides produced by LAB alter the rheological properties of the matrix in which they are dispersed, leading to typically viscous and "ropy" products. Polysaccharides are involved in several mechanisms such as prebiosis and probiosis, tolerance to stress associated to food process, and technological properties of food. In this paper, we summarize the beneficial properties of exopolysaccharides (EPS) produced by LAB with particular attention to prebiotic properties and to the effect of exopolysaccharides on the LAB-host interaction mechanisms, such as bacterial tolerance to gastrointestinal tract conditions, ability of ESP-producing probiotics to adhere to intestinal epithelium, their immune-modulatory activity, and their role in biofilm formation. The pro-technological aspect of exopolysaccharides is discussed, focusing on advantageous applications of EPS in the food industry, i.e., yogurt and gluten-free bakery products, since it was found that these microbial biopolymers positively affect the texture of foods. Finally, the involvement of EPS in tolerance to stress conditions that are commonly encountered in fermented beverages such as wine is discussed.

Comparison of activity to stimulate mucosal IgA production between Leuconostoc mesenteroides strain NTM048 and type strain JCM6124 in mice

The effects of Leuconostoc mesenteroides strain NTM048 and type strain JCM6124^T on the murine immune system were characterized. Although the bacterial cells and exopolysaccharides of each strain induced immunoglobulin A production in Peyer’s patch cells, the effects of NTM048 were more potent than those of JCM6124^T. Oral administration of the cells of each strain increased the fecal immunoglobulin A content in NTM048-treated mice, but not in JCM6124^T-treated mice. A flow cytometric analysis showed that the CD4⁺ T-cell populations in the mouse spleens tended to increase in the NTM048 group. These results suggest that immunomodulating ability is characteristic of strain NTM048.