Structural analysis and properties of dextran produced by Weissella confusa and the effect of different cereals on its rheological characteristics

Structure and Properties of Exopolysaccharide Produced by Gluconobacter frateurii and Its Potential Applications

An exopolysaccharide (EPS)-producing bacterium was isolated from apricot fermentation broth and identified as Gluconobacter frateurii HDC-08 (accession number: OK036475.1). HDC-08 EPS is a linear homopolysaccharide mainly composed of glucose linked by α-(1,6) glucoside bonds. It contains C, H, N and S elements, with a molecular weight of 4.774 × 106 Da. Microscopically, it has a smooth, glossy and compact sheet structure. It is an amorphous noncrystalline substance with irregular coils. Moreover, the EPS showed surface hydrophobicity and high thermal stability with a degradation temperature of 250.76 °C. In addition, it had strong antioxidant properties against DPPH radicals, ABPS radicals, hydroxyl radicals and H2O2. The EPS exhibited high metal-chelating activity and strong emulsifying ability for soybean oil, petroleum ether and diesel oil. The milk solidification test indicated that the EPS had good potential in fermented dairy products. In general, all the results demonstrate that HDC-08 EPS has promise for commercial applications as a food additive and antioxidant.

Influence of dextrans on the textural, rheological, and microstructural properties of acid-induced faba bean protein gels

Dextrans (DXs) are a group of natural polysaccharides with different branching patterns. Previous studies examining the effects of DXs on plant protein gels have only focused on α-(1 → 3)-branched DXs. Here, we compared the effects of α-(1 → 3)-branched DX L12 with those of two α-(1 → 2)-branched DXs on the properties of glucono-δ-lactone-induced faba bean protein isolate (FPI) gels. DX L12 showed stronger effects in decreasing gel hardness and enhancing gel viscoelasticity than the other two DXs. Moreover, DX L12 decreased the water-holding capacity of FPI gels, whereas the other DXs enhanced it. Microstructural analysis revealed that DX addition promoted phase separation during gel formation. However, FPI/L12 gels exhibited greater phase separation than the other two gels and contained larger void spaces. These differences could be attributed to the varying water adsorption and self-association properties of the DXs. These findings could guide the application of DX in the tailored preparation of plant protein gels.

Structural Characterization and Functional Studies of Exopolysaccharide by Native Lacticaseibacillus rhamnosus P14 Isolated from the Moroccan Region

Exopolysaccharides (EPS) are natural polymers synthesized by several microorganisms, including lactic acid bacteria (LAB). They are characterized by a great structural diversity, which gives them interesting biological and pharmacological properties. This work investigates the physicochemical and biological characterization of a new exopolysaccharide (EPS) produced by a wild Lacticaseibacillus rhamnosus P14. The functional groups, chemical bonds, and thermal and morphological properties of the purified EPS-P14 were determined using Fourier Transform Infrared, Nuclear Magnetic Resonance, and X-ray diffraction spectroscopies, as well as Thermo-gravimetric analysis, Differential Scanning Calorimetry and Scanning Electron Microscopy. The functional properties, namely antioxidant and emulsifying activities, were also assessed. The physicochemical analysis revealed that EPS-P14 is a porous and thermally stable polysaccharide with a degradation temperature of 307 °C. NMR and FT-IR studies identified it as a homogeneous α-D-glucan with mainly α-(1 → 6) glycosidic linkage and some α-(1 → 3) branching. EPS-P14 was highly water-soluble and exhibited strong emulsifying and stabilizing properties in a concentration-dependent manner. Furthermore, EPS-P14 demonstrated significant DPPH scavenging and ferric-reducing capacities. These findings suggest that EPS-P14 is a bioactive polysaccharide with potential effects, which could be a promising natural candidate for prospective application.

Fecal fermentation and high-fat diet-induced obesity mouse model confirmed exopolysaccharide from Weissella cibaria PFY06 can ameliorate obesity by regulating the gut microbiota

Obesity associated with diet and intestinal dysbiosis is a worldwide public health crisis, and exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) have prebiotic potential to ameliorate obesity. Therefore, the present study obtained LAB with the ability to produce high EPS, examined the structure of EPS, and explained its mechanism of alleviating obesity by in vivo and in vitro models. The results showed that Weissella cibaria PFY06 with a high EPS yield was isolated from strawberry juice, and pure polysaccharide (PFY06-EPS) was purified by Sephadex G-100. The structural characteristics of PFY06-EPS showed that the molecular weight was 8.08 × 10⁶ Da and composed of α-(1,6)-D glucosyl residues. An in vitro simulated human colon fermentation test demonstrated that PFY06-EPS increased the abundance of Prevotella and Bacteroides. Cell tests confirmed that PFY06-EPS after fecal fermentation inhibited fat accumulation by promoting the secretion of endogenous gastrointestinal hormones and insulin and inhibiting the secretion of inflammatory factors. Notably, PFY06-EPS reduced weight gain, fat accumulation, inflammatory reactions and insulin resistance in a high-fat diet-induced obesity mouse model and improved glucolipid metabolism. PFY06-EPS intervention reversed obesity-induced microflora disorders, such as reducing the Firmicutes/Bacteroides ratio and increasing butyrate-producing bacteria (Roseburia and Oscillibacter), and reduced endotoxemia to maintain intestinal barrier integrity. Therefore, in vivo and in vitro models showed that PFY06-EPS had potential as a prebiotic that may play an anti-obesity role by improving the function of the gut microbiota.

In Vitro Assessment of Probiotic and Technological Properties of Lactic Acid Bacteria Isolated from Indigenously Fermented Cereal-Based Food Products

The present study concerns the isolation and characterization of potential probiotic bacteria isolated from indigenously fermented cereal-based products commonly produced by tribal people of the Aravali hills region of India and the documentation of their unexplored probiotic attributes. The isolated strains were evaluated for probiotic attributes, such as bile salt and acid tolerance, lysozyme and phenol tolerance, antagonistic and antifungal activity, cell autoaggregation, cell-surface hydrophobicity, simulated gastric and pancreatic digestion, antioxidative potential, bile salt hydrolase activity, and H2O2 production. The safety of isolates was assessed by antibiotic sensitivity, hemolytic activity, DNase activity, and biogenic amine production assays, while technological properties, such as fermenting ability, amylolytic activity, and EPS production, were also evaluated. A total of 70 LAB isolates were screened initially, and 6 strains showed good potential as probiotic candidates in in vitro assessments. The efficient strains were identified using phenotyping and biochemical characterization, which results were further confirmed and recognized at the strain level using phylogenetic analysis and 16S rDNA sequencing. The current study has shown that Lactiplantibacillus plantarum KMUDR7 isolated from “Makka ki Raab” has excellent probiotic attributes and could be a potential probiotic for product preparation. However, other strains, Lactobacillus delbrueckii subsp. bulgaricus KMUDR1 and Lacticaseibacillus rhamnosus KMUDR9, showed good properties, while KMUDR14, -17, and -20 also have comparable probiotic attributes.

Analysis of the structure and properties of dextran produced by Weissella confusa

An EPS produced by Weissella confusa H2 was purified through Sephadex G-100, and the preliminary structure characteristics and biological activities of H2 EPS were analyzed. Molecular mass of purified H2 EPS was 2.705 × 10⁶ Da as measured with gel permeation chromatography (GPC). Composition of monosaccharides, nuclear magnetic resonance (NMR) spectroscopy spectroscopy and fourier transform infrared (FT-IR) showed that the EPS was a linear homopolysaccharide, mainly constituted of glucose and it is suggested that the EPS was dextran with α-(1 → 6) glycosidic bonds and a few α-(1 → 3) branches. Atomic force micrograph (AFM) and scanning electron microscopy (SEM) analysis of dextran further revealed sheets branched microstructure anchored with many irregular protuberances in aqueous solution. The XRD pattern reflected non-crystalline amorphous nature. In addition, the solubility, water-holding capacity, thermal property, rheological property and heavy metal chelating activity of the purified H2 dextran were determined. The dissolution percentage and water holding capacity of the dextran were 98.78 ± 1.37% and 426.03 ± 7.26%, respectively. The dextran exhibited good hydrophilicity, thermal stability and heavy metal chelating activity. Rheological studies exhibited rotational speed, pH, temperature, metal ions solutions dependent semiviscous nature. These results support its use as an additive in the food and environmental protection fields.

Isolation, Purification, Characterization, and Immunomodulatory Activity Analysis of α-Glucans from Spirulina platensis

Crude polysaccharides from Spirulina platensis (SP) were isolated by maceration with a hot alkali solution and further fractionated by DEAE-52 cellulose and Sephadex G-100 chromatography into two purified fractions PSP-1 and PSP-2. The monosaccharide composition analysis indicated that SP was mainly composed of rhamnose and glucose, while PSP-1 and PSP-2 were composed only of glucose. The composition analysis of PSP-1 and PSP-2 by HPLC, FT-IR, and NMR showed that PSP-1 and PSP-2 were branching dextran, and their structures were (1 → 4)-linked-α-D-Glcp as the main chain, and C-6 replaced the single α-D-Glcp as the linear structure of the branch chain. The glucans (SP/PSP-1/PSP-2) can significantly improve the phagocytic ability of macrophages, enhance iNOS activity, promote NO production, and increase IL-6 mRNA expression, so they may possess certain immunomodulatory activity.

Characterization of exopolysaccharides produced by Weissella confusa XG-3 and their potential biotechnological applications

In this study, exopolysaccharides (EPSs) produced by Weissella confusa XG-3 were characterized. The monosaccharide composition of XG-3 EPS was determined to include glucose according to GC data, and its molecular weight was 3.19 × 10⁶ Da, as determined by HPLC. Scanning electron microscopy (SEM) revealed a smooth, porous, and branched structure, and atomic force microscopy (AFM) confirmed the presence of round lumps and chains on irregular surfaces of XG-3 EPS. The results of the Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses suggested that XG-3 EPS is a linear α-(1,6)-linked dextran. X-ray diffraction (XRD) data confirmed the noncrystalline amorphous structure, and the results of the Congo red assay corresponded to the random coiled chain conformation of XG-3 dextran. XG-3 dextran exhibited good radical scavenging activity and reducing power and possessed high thermal stability, with a degradation temperature (Td) of 306.8 °C. The absolute value of the zeta potential and particle size of XG-3 dextran continually increased with increasing dextran concentration. The water contact angle showed that XG-3 dextran had relatively high hydrophobicity in the presence of sucrose. XG-3 dextran stimulated the growth of Lactobacillus spp. and Bifidobacterium spp. These findings indicate that XG-3 dextran has unique characteristics and can be potentially applied as a food additive and an antioxidant.

Weissella: An Emerging Bacterium with Promising Health Benefits

Weissella strains have been the subject of much research over the last 5 years because of the genus' technological and probiotic potential. Certain strains have attracted the attention of the pharmaceutical, medical, and food industries because of their ability to produce antimicrobial exopolysaccharides (EPSs). Moreover, Weissella strains are able to keep foodborne pathogens in check because of the bacteriocins, hydrogen peroxide, and organic acids they can produce; all listed have recognized pathogen inhibitory activities. The Weissella genus has also shown potential for treating atopic dermatitis and certain cancers. W. cibaria, W. confusa, and W. paramesenteroides are particularly of note because of their probiotic potential (fermentation of prebiotic fibers) and their ability to survive in the gastrointestinal tract. It is important to note that most of the Weissella strains with these health-promoting properties have been shown to be save safe, due to the absence or the low occurrence of virulence or antibiotic-resistant genes. A large number of scientific studies continue to report on and to support the use of Weissella strains in the food and pharmaceutical industries. This review provides an overview of these studies and draws conclusions for future uses of this rich and previously unexplored genus.