High-Molecular-Weight Dextran-Type Exopolysaccharide Produced by the Novel Apilactobacillus waqarii Improves Metabolic Syndrome: In Vitro and In Vivo Analyses.

Metabolic syndrome is a leading medical concern that affects one billion people worldwide. Metabolic syndrome is defined by a clustering of risk factors that predispose an individual to cardiovascular disease, diabetes and stroke. In recent years, the apparent role of the gut microbiota in metabolic syndrome has drawn attention to microbiome-engineered therapeutics. Specifically, lactic acid bacteria (LAB) harbors beneficial metabolic characteristics, including the production of exopolysaccharides and other microbial byproducts. We recently isolated a novel fructophilic lactic acid bacterium (FLAB), Apilactobacillus waqarii strain HBW1, from honeybee gut and found it produces a dextran-type exopolysaccharide (EPS). The objective of this study was to explore the therapeutic potential of the new dextran in relation to metabolic syndrome. Findings revealed the dextran's ability to improve the viability of damaged HT-29 intestinal epithelial cells and exhibit antioxidant properties. In vivo analyses demonstrated reductions in body weight gain and serum cholesterol levels in mice supplemented with the dextran, compared to control (5% and 17.2%, respectively). Additionally, blood glucose levels decreased by 16.26% following dextran supplementation, while increasing by 15.2% in non-treated mice. Overall, this study displays biotherapeutic potential of a novel EPS to improve metabolic syndrome and its individual components, warranting further investigation.

Production of a high molecular weight levan by Bacillus paralicheniformis, an industrially and agriculturally important isolate from the buffalo grass rhizosphere.

A new exopolysaccharide (EPS) producing Gram-positive bacterium was isolated from the rhizosphere of Bouteloua dactyloides (buffalo grass) and its EPS product was structurally characterized. The isolate, designated as LB1-1A, was identified as Bacillus paralicheniformis based on 16S rRNA gene sequence and phylogenetic tree analysis. The EPS produced by LB1-1A was identified as a levan, having ß(2 → 6) linked backbone with ß(2 → 1) linkages at the branch points (4.66%). The isolate LB1-1A yielded large amount (~ 42 g/l) of levan having high weight average molecular weight (Mw) of 5.517 × 107 Da. The relatively low degree of branching and high molecular weight of this levan makes B. paralicheniformis LB1-1A a promising candidate for industrial applications.

Production of bimodal molecular weight levan by a Lactobacillus reuteri isolate from fish gut.

An exopolysaccharide (EPS) synthesizing potentially probiotic Gram-positive bacterial strain was isolated from fish (Tor putitora) gut, and its EPS was structurally characterized. The isolate, designated as FW2, was identified as Lactobacillus reuteri through 16S rRNA gene sequencing and phylogenetic analysis. This isolate produces fructan-type EPS using sucrose as a substrate. Based on 13C-NMR spectroscopy, methylation analysis and monosaccharide composition, the EPS was identified as a linear levan polymer with fructose as main constituent linked via ß(2 → 6) linkages. Based on molecular weight (MW) distribution, two groups of levan were found to be produced by the isolate FW2: one with high MW (4.6 × 106 Da) and the other having much lower MW (1.2 × 104 Da). The isolate yielded about 14 g/L levan under optimized culturing parameters including aeration conditions, pH, temperature and substrate concentration. The obtained bimodal molecular weight linear levan is the first of its type to be synthesized by a L. reuteri isolate from fish gut. Bimodal molecular weight prebiotic levan together with the probiotic potential of the producing strain would provide a new promising synbiotic combination for use in aqua culture.

Growth Inhibition of Common Enteric Pathogens in the Intestine of Broilers by Microbially Produced Dextran and Levan Exopolysaccharides.

Antibiotics are generally applied for treatment or as subtherapeutic agents to overcome diseases caused by pathogenic bacteria including Escherichia coli, Salmonella and Enterococcus species in poultry. However, due to their possible adverse effects on animal health and to maintain food safety, probiotics, prebiotics, and synbiotics have been proposed as alternatives to antibiotic growth promoters (AGPs) in poultry production. In this study, the effects of prebiotics on the augmentation of broiler's indigenous gut microbiology were studied. Day old 180 broilers chicks were divided into four treatment groups: G, L, C1, and C2. The groups G and L were fed with basal diet containing 3% dextran and 3% levan, respectively. Control groups were fed with basal diets without antibiotic (C1) and with antibiotics (C2). The experimental groups showed decreased mortality as compared to control groups. After 35 days, the chickens were euthanized and intestinal fluid was analyzed for enteric pathogens on chromogenic agar plates and by 16S rRNA gene sequencing. Inhibition of the growth of E. coli and Enterococcus was observed in groups G and L, respectively, whereas Salmonella was only present in group C1. Also, high populations of lactic acid bacteria were detected in the intestine of prebiotic fed birds as compared to controls. These results depict that dextran and levan have the potential to replace the use of antibiotics in poultry feed for inhibiting the growth of common enteric pathogens. To the best of our knowledge, this is the first study where effects of dextran and levan on intestinal microbiota of broilers have been reported.

Raman spectroscopy for the analysis of different exo-polysaccharides produced by bacteria.

In this study, Raman spectroscopy is employed for the characterization and comparison of two different classes of exo-polysaccharides including glucans and fructans which are produced by different bacteria. For this purpose, nine samples are used including five samples of glucans and four of fructans. Raman spectral results of all these polysaccharides show clear differences among various glucans as well as fructans showing the potential of this technique to identify the differences within the same class of the compounds. Moreover, these two classes are also compared on the basis of their Raman spectral data and can be differentiated on the basis of their unique Raman features. Multivariate data analysis techniques, Principle Component Analysis (PCA) is found very helpful for the comparison of the Raman spectral data of these classes of the carbohydrates.