Potential prebiotic effect of a long-chain dextran produced by Weissella cibaria: an in vitro evaluation

A structure-functionality insight into the bioactivity of microbial polysaccharides toward biomedical applications: A review

Microbial polysaccharides (MPs) are biopolymers secreted by microorganisms such as bacteria and fungi during their metabolic processes. Compared to polysaccharides derived from plants and animals, MPs have advantages such as wide sources, high production efficiency, and less susceptibility to natural environmental influences. The most attractive feature of MPs lies in their diverse biological activities, such as antioxidative, anti-tumor, antibacterial, and immunomodulatory activities, which have demonstrated immense potential for applications in functional foods, cosmetics, and biomedicine. These bioactivities are precisely regulated by their sophisticated molecular structure. However, the mechanisms underlying this precise regulation are not yet fully understood and continue to evolve. This article presents a comprehensive review of the most representative species of MPs, including their fermentation and purification processes and their biomedical applications in recent years. In particular, this work presents an in-depth analysis into the structure-activity relationships of MPs across multiple molecular levels. Additionally, this review discusses the challenges and prospects of investigating the structure-activity relationships, providing valuable insights into the broad and high-value utilization of MPs.

Probiotics Pediococcus acidilactici GR-1 promotes the functional strains and remodels gut microbiota to reduce the Cr(VI) toxicity in a dual-chamber simulated intestinal system

Numerous animal studies have demonstrated the toxicity of hexavalent chromium [Cr(VI)] and the bioremediative effects of probiotics on the composition and functions of gut microbiota. Since the precise mechanisms of Cr(VI) detoxification and its interactions with human gut microbiota were unknown, a novel dual-chamber simulated intestinal (DCSI) system was developed to maintain both the stability of the simulated system and the composition of the gut microbiota. Probiotic GR-1 was found to regulate intestinal gut microbiota, thereby reducing the toxicity of Cr(VI) within the DCSI system. The results indicate that Cr(VI) levels were reduced from 2.260 ± 0.2438 μg/g to 1.7086 ± 0.1950 μg/g in the gut microbiota cell pellet, and Cr(VI) permeability decreased from 0.5521 ± 0.1132 μg/L to 0.3681 ± 0.0178 μg/L after 48 h in simulated gut fluid. Additionally, the removal rate of 1,1-Diphenyl-2-picrylhydrazyl (DPPH), reducibility (Vitamin C), and total antioxidant capacity (T-AOC) increased by 50.83%, 31.70%, and 27.56%, respectively, following probiotic treatment. The increase in antioxidant capacity correlated with total Cr removal (P < 0.05, r from -0.80 to 0.73). 16S rRNA sequencing analysis showed that gut microbiota composition was reshaped by the addition of probiotics, which regulated the recovery of the functional gut microbiota to normal levels, rather than restoring the entire gut microbiota composition for community function. Thus, this study not only demonstrates the feasibility and stability of culturing gut microbiota but also offers a new biotechnological approach to synthesizing functional communities with functional strains for environmental risk management.

A Long-Chain Dextran Produced by Weissella cibaria Boosts the Diversity of Health-Related Gut Microbes Ex Vivo

Long-chain dextrans are α-glucans that can be produced by lactic acid bacteria. NextDextTM, a specific long-chain dextran with a high degree of polymerisation, produced using Weissella cibaria, was recently shown to exert prebiotic potential in vitro. In this study, the ex vivo SIFR® technology, recently validated to provide predictive insights into gut microbiome modulation down to the species level, was used to investigate the effects of this long-chain dextran on the gut microbiota of six human adults that altogether covered different enterotypes. A novel community modulation score (CMS) was introduced based on the strength of quantitative 16S rRNA gene sequencing and the highly controlled ex vivo conditions. This CMS overcomes the limitations of traditional α-diversity indices and its application in the current study revealed that dextran is a potent booster of microbial diversity compared to the reference prebiotic inulin (IN). Long-chain dextran not only exerted bifidogenic effects but also consistently promoted Bacteroides spp., Parabacteroides distasonis and butyrate-producing species like Faecalibacterium prausnitzii and Anaerobutyricum hallii. Further, long-chain dextran treatment resulted in lower gas production compared to IN, suggesting that long-chain dextran could be better tolerated. The additional increase in Bacteroides for dextran compared to IN is likely related to the higher propionate:acetate ratio, attributing potential to long-chain dextran for improving metabolic health and weight management. Moreover, the stimulation of butyrate by dextran suggests its potential for improving gut barrier function and inflammation. Overall, this study provides a novel tool for assessing gut microbial diversity ex vivo and positions long-chain dextran as a substrate that has unique microbial diversity enhancing properties.

Dextran-Chitosan Composites: Antioxidant and Anti-Inflammatory Properties

This study presents the development of new formulations consisting of dextran (Dex) and chitosan (Ch) matrices, with fillings such as chitosan stearate (MCh), citric acid, salicylic acid, or ginger extract. These materials were characterized using Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and mechanical tests, and evaluated for antioxidant properties, including scavenging activities, metal chelation, and ferric ion reducing power, as well as anti-inflammatory properties, measuring the binding affinity between serum albumin and the bioactive substances, which can influence their bioavailability, transport, and overall anti-inflammatory effect. Compounds in ginger such as 6-gingerol reduce inflammation by inhibiting the production of inflammatory substances, such as prostaglandin, cytokines, interleukin-1β, and pro-inflammatory transcription factor (NF-κB) and, alongside citric and salicylic acids, combat oxidative stress, stabilizes cell membranes, and promote membrane fluidity, thereby preserving membrane integrity and function. Incorporating chitosan stearate in chitosan:dextran samples created a dense, stiff film with an elastic modulus approximately seventeen times higher than for the chitosan:dextran matrix. The Dex:Ch:MCh sample exhibited low compressibility at 48.74 ± 1.64 kPa, whereas the Dex:Ch:MCh:citric acid:salicylic acid composite had a compact network, allowing for 70.61 ± 3.9% compression at 109.30 kPa. The lipid peroxidation inhibitory assay revealed that Dex:Ch:MCh:citric acid had the highest inhibition value with 83 ± 0.577% at 24 h. The study highlights that adding active substances like ginger extract and citric acid to Dex:Ch composites enhances antioxidant properties, while modified chitosan improves mechanical properties. These composites may have potential medical applications in repairing cell membranes and regulating antioxidant enzyme activities.

Structural Characterization of Exopolysaccharide Produced by Leuconostoccitreum B-2 Cultured in Molasses Medium and Its Application in Set Yogurt

Sugarcane molasses is an agricultural by-product containing sucrose. In this study, the exopolysaccharide (M-EPS) produced by Leuconostoc citreum B-2 in molasses-based medium was characterized, optimized, and its application in set yogurt was investigated. The structure analysis, including gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, revealed that the M-EPS was a linear dextran composed of D-glucose units, which were linked by α-(1→6) glycosidic bonds with 19.3% α-(1→3) branches. The M-EPS showed a lower molecular weight than that produced from sucrose. The M-EPS was added into the set yogurt, and then the water holding capacity, pH, and microstructure of set yogurt were evaluated. Compared with the controls, the addition of M-EPS improved the water holding capacity and reduced the pH of set yogurt. Meanwhile, the structure of the three-dimensional network was also observed in the set yogurt containing M-EPS, indicating that M-EPS had a positive effect on the stability of set yogurt. The results provide a theoretical basis for the cost-effective utilization of sugarcane molasses.

Prebiotic activities of dextran from Leuconostoc mesenteroides SPCL742 analyzed in the aspect of the human gut microbial ecosystem

The aim of this study was to investigate the prebiotic activities of dextran (LM742) produced by Leuconostoc mesenteroides SPCL742 in the aspect of the human gut microbial ecosystem focusing on microbiome and metabolome changes in in vitro colonic fermentation. LM742 dextran had a medium-chain structure with the molecular weight of 1394.87 kDa (DP = 7759.22) and α-1,6 and α-1,3 linkages with a 26.11 : 1 ratio. The LM742 dextran was resistent to digestive enzymes in the human gastrointestinal conditions. The individual cultivation of 30 intestinal bacteria with LM742 dextran showed the growth of Bacteroides spp., whereas in vitro human fecal fermentation with LM742 exhibited the symbiotic growth of Bacteroides spp. and beneficial bacteria such as Bifidobacterium spp. Further co-cultivation of Bacteroides xylanisolvens and several probiotics indicated that B. xylanisolvens provides a cross-feeding of dextran to probiotics. In fecal fermentation, LM742 dextran resulted in increased concentrations of short-chain fatty acids, valerate and pantothenate, but it rarely affected the conversion of betaine to trimethylamine. Lastly, LM742 dextran inhibited the adhesion of pathogenic E. coli to human epithelial cells. Taken together, these results demonstrate the prebiotic potential of LM742 dextran as a health-beneficial polysaccharide in the human intestine.

Prebiotic, Antioxidant, and Immunomodulatory Properties of Acidic Exopolysaccharide From Marine Rhodotorula RY1801

In this study, an extracellular acidic polysaccharide (EAPS) from marine Rhodotorula sp. RY1801 was extracted, and its biological properties were investigated. EAPS is mainly composed of monosaccharides, including mannose, rhamnose, glucose, galactose, and fucose, had an average molecular weight of 5.902 × 107 Da. The results indicated that EAPS can promote the growth of Lactobacillus acidophilus and L. acidophilus plantarum. EAPS is capable of scavenging both superoxide anion and hydroxyl radicals in vitro. The highest scavenging rate of superoxide anion and hydroxyl radicals is 29 and 84%, respectively. Using in vivo model, we found that the EAPS can expand the lifespan and increase the disease resistance of Caenorhabditis elegans against Klebsiella pneumoniae infection via the DAF-2/DAF-16 pathway. These results suggested that EAPS from marine Rhodotorula sp. RY1801 could promote the growth of beneficial bacteria and can be used as an antioxidant and immunomodulator, which had considerable potential in the food and health industry.

Diversity and Composition of Gut Bacterial Community in Giant Panda with Anorexia

The giant panda (GP) is the most precious animal in China. Gastrointestinal tract disease, especially associated with dysbiosis of gut microbiota, is the leading cause of death in GPs. Here, we performed 16S rRNA high-throughput sequencing to investigate the gut microbiota of GPs having symptoms of anorexia. Results showed that gut microbiota of GP with anorexia had lower richness (Chao1 index) than the healthy GP. However, no significant differences in alpha diversity were observed. There is a significance in the microbial structure between anorexia and healthy GPs. The abundance of phylum Firmicutes (99.23% ± 7.1%), unidentified genus Clostridiales (24.75% ± 2.5%), was significantly higher in the subadult anorexia group (P < 0.01), and that of the unidentified genus Clostridiales (4.53% ± 1.2%) was also significantly higher in the adult anorexia group (P < 0.01). Weissella and Streptococcus were found to be decreased in both anorexia groups. The decreased abundance of Weissella (0.02% ± 0.0%, 0.08% ± 0.0%) and Streptococcus (73.89% ± 4.3%, 91.15% ± 7.6%) and increase in Clostridium may cause symptoms of anorexia in giant pandas. The correlation analysis indicated that there is a symbiotic relationship among Streptococcus, Leuconostoc, Weissella, and Bacillus which are classified as probiotics (r > 0.6, P < 0.05). Importantly, a negative correlation has been found between Streptococcus and unidentified_Clostridium in two groups (r > 0.6, P < 0.05). Our results suggested that Streptococcus might be used as probiotics to control the growth of Clostridium causing the anorexia.

Design of a "Clean-Label" Gluten-Free Bread to Meet Consumers Demand

The market of gluten-free (GF) products has been steadily increasing in last few years. Due to the technological importance of gluten, the GF food production is still a challenge for the industry. Indeed, large quantities of fat, sugars, structuring agents, and flavor enhancers are added to GF formulations to make textural and sensorial characteristics comparable to conventional products, leading to nutritional and caloric intake imbalances. The formulation of the novel "clean-label" GF bread included a commonly used mixture of maize and rice flour (ratio 1:1) fortified with selected protein-rich flours. Naturally hydrocolloids-containing flours (psyllium, flaxseed, chia) were included in the bread formulation as structuring agents. A type-II sourdough was obtained by using a selected Weissella cibaria P9 and a GF sucrose-containing flour as substrate for fermentation to promote the exo-polysaccharides synthesis by the starter lactic acid bacterium. A two-step protocol for bread-making was set-up: first, the GF sourdough was fermented (24 h at 30 °C); then, it was mixed with the other ingredients (30% of the final dough) and leavened with baker's yeast before baking. Overall, the novel GF bread was characterized by good textural properties, high protein content (8.9% of dry matter) and in vitro protein digestibility (76.9%), low sugar (1.0% of dry matter) and fat (3.1% of dry matter) content, and an in vitro predicted glycemic index of 85.

Biliaderis C. Fermented Cereal-based Products: Nutritional Aspects, Possible Impact on Gut Microbiota and Health Implications

Fermentation, as a process to increase the security of food supply, represents an integral part of food culture development worldwide. Nowadays, in the evolving functional food era where new sophisticated technological tools are leading to significant transformations in the field of nutritional sciences and science-driven approaches for new product design, fermentation technology is brought to the forefront again since it provides a solid foundation for the development of safe food products with unique nutritional and functional attributes. Therefore, the objective of the present review is to summarize the most recent advances in the field of fermentation processes related to cereal-based products. More specifically, this paper addresses issues that are relevant to nutritional and health aspects, including their interrelation with intestinal (gut) microbiome diversity and function, although clinical trials and/or in vitro studies testing for cereal-based fermented products are still scarce.