Characterization of the heteropolysaccharides produced by Liquorilactobacillus sicerae CUPV261 and Secundilactobacillus collinoides CUPV237 isolated from cider

Some lactic acid bacteria (LAB) strains isolated from alcoholic beverages are able to produce exopolysaccharides (EPS). The present work focuses on the physico-chemical characterization of the heteropolysaccharides (HePS) produced by Liquorilactobacillus sicerae CUPV261T (formerly known as Lactobacillus sicerae) and Secundilactobacillus collinoides CUPV237 (formerly known as Lactobacillus collinoides) strains isolated from cider. Genome sequencing and assembly enabled the identification of at least four putative HePS gene clusters in each strain, which correlated with the ability of both strains to secrete EPS. The crude EPS preparation from CUPV261^T contained glucose, galactose and rhamnose, and that of CUPV237 was composed of glucose, galactose and N-acetylglucosamine. Both EPS were mixtures of HePS of different composition, with two major soluble components of average molecular weights (M_w) in the range of 10⁶ and 10⁴ g.mol^-1. These HePS were resistant to gastric stress conditions in an in vitro model, and they significantly reduced zebrafish larvae mortality in an in vivo model of inflammatory bowel disease.

Heteropolysaccharides in sustainable corrosion inhibition: 4E (Energy, Economy, Ecology, and Effectivity) dimensions

Carbohydrate polymers (polysaccharides) and their derivatives are widely utilized in sustainable corrosion inhibition (SCI) because of their various fascinating properties including multiple adsorption sites, high solubility and high efficiency. Contrary to traditional synthetic polymer-based corrosion inhibitors, polysaccharides are related to the 4E dimension, which stands for Energy, Economy, Ecology, and Effectivity. Furthermore, they are relatively more environmentally benign, biodegradable, and non-bioaccumulative. The current review describes the SCI features of various heteropolysaccharides, including gum Arabic (GA), glycosaminoglycans (chondroitin-4-sulfate (CS), hyaluronic acid (HA), heparin, etc.), pectin, alginates, and agar for the first time. They demonstrate impressive anticorrosive activity for different metals and alloys in a variety of corrosive electrolytes. Through their adsorption at the metal/electrolyte interface, heteropolysaccharides function by producing a corrosion-protective film. In general, their adsorption follows the Langmuir isotherm model. In their molecular structures, heteropolysaccharides contain several polar functional groups like -OH, -NH₂, -COCH₃, -CH₂OH, cyclic and bridging O, -CH₂SO₃H, -SO₃OH, -COOH, -NHCOCH₃, -OHOR, etc. that serve as adsorption centers when they bind to metallic surfaces.

Prebiotic potential and chemical characterization of the poly and oligosaccharides present in the mucilage of Opuntia ficus-indica and Opuntia joconostle

The mucilage extracted from the convection-dried cladodes of O. ficus-indica and O. joconostle, two species of economic importance, delivered three fractions after methanol precipitation. Two were composed of high molar mass polysaccharides, and one included water-soluble mono-, di-, and oligosaccharides. The large polysaccharides have a molar mass range of 4.0 × 10³ to 8.0 × 10⁵ g·mol^-1 and are consistently composed of galactose, arabinose, xylose, and rhamnose; however, the content of galacturonic acid was different between both fractions and species. Their fermentability by selected probiotics was relatively low, 11-27 % compared to glucose, and decreased with increasing levels of galacturonic acid in the molecules. In the third fraction, previously unreported oligosaccharides were found. These include simple- and complex-structured galactooligosaccharides with arabinosyl-, xylosyl- and galacturonosyl acid residues. Their fermentability by prebiotic species can be ascribed more to their structural characteristics and monosaccharide composition than their molecular dimensions.

Submerged cultivation, characterization and in vitro antitumor activity of polysaccharides from Schizophyllum radiatum

Production of polysaccharides by white-rot-fungi in submerged cultivation has several advantages due to process control. This work deals with the submerged cultivation, extraction and antitumor activity of polysaccharides from a wild strain of Schizophyllum radiatum isolated from a tropical forest of Colombia. The mushroom was cultivated in laboratory conditions, and classified by classical and molecular taxonomy. Submerged cultivation was performed in a bioreactor of 5 L using a ligninolytic residue as substrate. The fermentation conditions were 30 ± 1 °C, pH 4.5, 300 rpm and 1.5 vvm of air for 4 days. The yields were 16.8 g/L (w/v) of biomass, and after extraction, 0.6 g/L of water-soluble exopolysaccharide (SEPS) and 2.01 % (w/w) of water-soluble intrapolysaccharide (SIPS) were obtained. In each extract total carbohydrate, glucans and protein contents were determined. Also, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), high performance liquid chromatography with refraction index detection (HPLC-RI), high performance gel permeation chromatography (HPGPC) and Nuclear Magnetic Resonance (NMR) analysis were performed. Results indicated that SEPS and SIPS are heteropolysaccharides with amorphous structure and high molecular weights. Antitumor and immunostimulant activity was evaluated in different cancer cell lines. The results suggest these polysaccharides have direct and indirect antitumor activity activating immune cells such as macrophages. These findings enhance our knowledge about new sources of fungal metabolites that serve as adjuvant, cheaper and less harmful alternatives to cancer treatment.

Sulfoethylation of polysaccharides-A comparative study

The heterogeneous sulfoethylation of cellulose, xylan, α-1,3-glucan, glucomannan, pullulan, curdlan, galactoglucomannan, and agarose was studied using sodium vinylsulfonate (NaVS) as reagent in presence of sodium hydroxide and iso-propanol (i-PrOH) as slurry medium. The influence of the concentration of polymer, water, and NaOH (solid or aqueous solution) on the degree of substitution (DS) was investigated. The sulfoethylation rendered the polysaccharides studied water-soluble. Sulfoethylation of heteropolysaccharides yielded products with higher DS compared to the conversion of homopolysaccharides. Structure characterization was carried out by means of ¹³C-NMR spectroscopy.

Structural investigation and comparative cytotoxic activity of water-soluble polysaccharides from fruit bodies of the medicinal fungus quinine conk

The structures and cytotoxic activities of water-soluble polysaccharides were investigated to search for biologically active polysaccharides from the fruit bodies of quinine conks (Fomitopsis officinalis). The decoctions of this medical fungus are actively used in folk medicine in many countries and traditional Chinese medicine. From the fungal extract we prepared, only branched β-glucan had cytotoxic activity among all the water-soluble polysaccharides. This glucan is characterized by a regular structure. Its backbone is formed by 1,3-linked β-D-Glcp residues, of which every third residue is substituted at O-6 by a single β-D-Glcp residue. It has a triple helix conformation according to the data obtained from a colorimetric assay with Congo red dye and is characterized by a high-weight average molar mass (Mw > 800 kDa). β-Glucan possessed cytotoxic activity against HeLa cells (IC₅₀ = 318 ± 47 μg/mL) and induced the formation of apoptotic bodies around most cancer cells at a concentration of 200 μg/mL. It should be noted that extraction with boiling water, which is usually used to obtain extracts and decoctions, is unable to isolate active β-glucan. Active β-glucan can be obtained in an individual state by cold alkali extraction after dehydration of the fruit bodies and removal of the components extractable by boiling water.

Environmentally triggered genomic plasticity and capsular polysaccharide formation are involved in increased ethanol and acetic acid tolerance in Kozakia baliensis NBRC 16680

BACKGROUND

Kozakia baliensis NBRC 16680 secretes a gum-cluster derived heteropolysaccharide and forms a surface pellicle composed of polysaccharides during static cultivation. Furthermore, this strain exhibits two colony types on agar plates; smooth wild-type (S) and rough mutant colonies (R). This switch is caused by a spontaneous transposon insertion into the gumD gene of the gum-cluster, resulting in a heteropolysaccharide secretion deficient, rough phenotype. To elucidate, whether this is a directed switch triggered by environmental factors, we checked the number of R and S colonies under different growth conditions including ethanol and acetic acid supplementation. Furthermore, we investigated the tolerance of R and S strains against ethanol and acetic acid in shaking and static growth experiments. To get new insights into the composition and function of the pellicle polysaccharide, the polE gene of the R strain was additionally deleted, as it was reported to be involved in pellicle formation in other acetic acid bacteria.

RESULTS

The number of R colonies was significantly increased upon growth on acetic acid and especially ethanol. The morphological change from K. baliensis NBRC 16680 S to R strain was accompanied by changes in the sugar contents of the produced pellicle EPS. The R:ΔpolE mutant strain was not able to form a regular pellicle anymore, but secreted an EPS into the medium, which exhibited a similar sugar monomer composition as the pellicle polysaccharide isolated from the R strain. The R strain had a markedly increased tolerance towards acetic acid and ethanol compared to the other NBRC 16680 strains (S, R:ΔpolE). A relatively high intrinsic acetic acid tolerance was also observable for K. baliensis DSM 14400^T, which might indicate diverse adaptation mechanisms of different K. baliensis strains in altering natural habitats.

CONCLUSION

The results suggest that the genetically triggered R phenotype formation is directly related to increased acetic acid and ethanol tolerance. The polE gene turned out to be involved in the formation of a cell-associated, capsular polysaccharide, which seems to be essential for increased ethanol/acetic tolerance in contrast to the secreted gum-cluster derived heteropolysaccharide. The genetic and morphological switch could represent an adaptive evolutionary step during the development of K. baliensis NBRC 16680 in course of changing environmental conditions.

Dissection of exopolysaccharide biosynthesis in Kozakia baliensis

Background

Acetic acid bacteria (AAB) are well known producers of commercially used exopolysaccharides, such as cellulose and levan. Kozakia (K.) baliensis is a relatively new member of AAB, which produces ultra-high molecular weight levan from sucrose. Throughout cultivation of two K. baliensis strains (DSM 14400, NBRC 16680) on sucrose-deficient media, we found that both strains still produce high amounts of mucous, water-soluble substances from mannitol and glycerol as (main) carbon sources. This indicated that both Kozakia strains additionally produce new classes of so far not characterized EPS.

Results

By whole genome sequencing of both strains, circularized genomes could be established and typical EPS forming clusters were identified. As expected, complete ORFs coding for levansucrases could be detected in both Kozakia strains. In K. baliensis DSM 14400 plasmid encoded cellulose synthase genes and fragments of truncated levansucrase operons could be assigned in contrast to K. baliensis NBRC 16680. Additionally, both K. baliensis strains harbor identical gum-like clusters, which are related to the well characterized gum cluster coding for xanthan synthesis in Xanthomanas campestris and show highest similarity with gum-like heteropolysaccharide (HePS) clusters from other acetic acid bacteria such as Gluconacetobacter diazotrophicus and Komagataeibacter xylinus. A mutant strain of K. baliensis NBRC 16680 lacking EPS production on sucrose-deficient media exhibited a transposon insertion in front of the gumD gene of its gum-like cluster in contrast to the wildtype strain, which indicated the essential role of gumD and of the associated gum genes for production of these new EPS. The EPS secreted by K. baliensis are composed of glucose, galactose and mannose, respectively, which is in agreement with the predicted sugar monomer composition derived from in silico genome analysis of the respective gum-like clusters.

Conclusions

By comparative sugar monomer and genome analysis, the polymeric substances secreted by K. baliensis can be considered as unique HePS. Via genome sequencing of K. baliensis DSM 14400 + NBRC 16680 we got first insights into the biosynthesis of these novel HePS, which is related to xanthan and acetan biosynthesis. Consequently, the present study provides the basis for establishment of K. baliensis strains as novel microbial cell factories for biotechnologically relevant, unique polysaccharides.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0572-x) contains supplementary material, which is available to authorized users.

Bacteroides fragilis metabolises exopolysaccharides produced by bifidobacteria

BACKGROUND

Bacteroides fragilis is the most frequent species at the human intestinal mucosal surface, it contributes to the maturation of the immune system although is also considered as an opportunistic pathogen. Some Bifidobacterium strains produce exopolysaccharides (EPS), complex carbohydrate polymers that promote changes in the metabolism of B. fragilis when this microorganism grows in their presence. To demonstrate that B. fragilis can use EPS from bifidobacteria as fermentable substrates, purified EPS fractions from two strains, Bifidobacterium longum E44 and Bifidobacterium animalis subsp. lactis R1, were added as the sole carbon source in cultures of B. fragilis DSMZ 2151 in a minimal medium. Bacterial counts were determined during incubation and the evolution of organic acids, short chain fatty acids (SCFA) and evolution of EPS fractions was analysed by chromatography.

RESULTS

Growth of B. fragilis at early stages of incubation was slower in EPS than with glucose, microbial levels remaining higher in EPS at prolonged incubation times. A shift in metabolite production by B. fragilis occurred from early to late stages of growth, leading to the increase in the production of propionate and acetate whereas decrease lactate formation. The amount of the two peaks with different molar mass of the EPS E44 clearly decreased along incubation whereas a consumption of the polymer R1 was not so evident.

CONCLUSIONS

This report demonstrates that B. fragilis can consume some EPS from bifidobacteria, with a concomitant release of SCFA and organic acids, suggesting a role for these biopolymers in bacteria-bacteria cross-talk within the intestine.

Chemical characterization of heteropolysaccharides from green and black teas (Camellia sinensis) and their anti-ulcer effect

In order to obtain polysaccharides from green and black teas (Camellia sinensis), commercial leaves were submitted to infusion and then to alkaline extraction. The extracts were fractionated by freeze-thawing process, giving insoluble and soluble fractions. Complex arabinogalactan protein from the soluble fractions of both teas (GTPS and BTPS) were determined by methylation analysis and (1)H/(13)C-HSQC spectroscopy, showing a main chain of (1→3)-β-Galp, substituted at O-6 by (1→6)-linked β-Galp with side chains of α-Araf and terminal units of α-Araf, α-Fucp and α-Rhap. A highly branched heteroxylan from the insoluble fractions (GTPI and BTPI) showed in methylation analysis and (1)H/(13)C-HSQC spectroscopy the main chain of (1→4)-β-Xylp, substituted in O-3 by α-Araf, β-Galp and α-Glcp units. Evaluating their gastroprotective activity, the fractions containing the soluble heteropolysaccharides from green (GTPS) and black teas (BTPS) reduced the gastric lesions induced by ethanol. Furthermore, the fraction of insoluble heteropolysaccharides of green (GTPI) and black (BTPI) teas also protected the gastric mucosa. In addition, the maintenance of gastric mucus and reduced glutathione (GSH) levels was involved in the polysaccharides gastroprotection.