Linked D-glucopyranose Units Research Articles

The exopolysaccharides produced by Leuconostoc mesenteroides XR1 and its effect on silk drawing phenomenon of yoghurt

Yoghurt fermented by Leuconostoc mesenteroides XR1 from Kefir grains was found to produce a unique silk drawing phenomenon. This property was found to be associated with the exopolysaccharides (EPS), X-EPS, produced by strain XR1. In order to better understand the mechanism that produced this phenomenon, the X-EPS was extracted, purified and characterized. The molecular weight and monosaccharide composition were determined by size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS) and ion chromatography (IC) analysis, respectively. The results showed that its molecular weight was 4.183 × 106 g/mol and its monosaccharide composition was glucose, and glucuronic acid, with the contents of 567.6148 and 0.2096 μg/mg, respectively. FT-IR and NMR analyses showed that X-EPS was an α-pyranose polysaccharide and was composed of 92.22 % α-(1 → 6) linked d-glucopyranose units and 7.77 % α-(1 → 3) branching. Furthermore, it showed a chain-like microstructure with branches in atomic force microscopy (AFM) and scanning electron microscopy (SEM) experiments. These results suggested that the unique structure of X-EPS, gave the yoghurt a strong viscosity and cohesiveness, which resulted in the silk drawing phenomenon. This work suggested that X-EPS holds the potential for food and industrial applications.

Characterization of Dextran Biosynthesized by Glucansucrase from Leuconostoc pseudomesenteroides and Their Potential Biotechnological Applications

Glucansucrase was purified from Leuconostoc pseudomesenteroides. The glucansucrase exhibited maximum activity at pH 5.5 and 30 °C. Ca2+ significantly promoted enzyme activity. An exopolysaccharide (EPS) was synthesized by this glucansucrase in vitro and purified. The molecular weight of the EPS was 3.083 × 106 Da. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy showed that the main structure of glucan was 97.3% α-(1→6)-linked D-glucopyranose units, and α-(1→3) branched chain accounted for 2.7%. Scanning electron microscopy (SEM) observation of dextran showed that its surface was smooth and flaky. Atomic force microscopy (AFM) of dextran revealed a chain-like microstructure with many irregular protuberances in aqueous solution. The results showed that dextran had good thermal stability, water holding capacity, water solubility and emulsifying ability (EA), as well as good antioxidant activity; thus it has broad prospects for development in the fields of food, biomedicine, and medicine.

Characterization of exopolysaccharide produced by Levilactobacillus brevis HDE-9 and evaluation of its potential use in dairy products

The bacterial strain HDE-9 was isolated from sauerkraut and identified as Levilactobacillus brevis. An exopolysaccharide (EPS) was isolated and purified from L. brevis HDE-9, and a preliminary investigation of its structural characteristics and biological activity was conducted. The molecular weight of the EPS was >1.0 × 106 Da. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy revealed that the EPS was composed of α-(1 → 6) linked d-glucopyranose units. X-ray diffraction (XRD) data on the EPS revealed its non-crystalline amorphous structure. Scanning electron microscopy (SEM) of the EPS revealed a smooth surface with sheet structures. The EPS exhibited the high value in thermal stability, water solubility, water holding capacity (WHC), and emulsification activity (EA). The water contact angle of the EPS revealed relatively high hydrophobicity in the presence of sucrose. The EPS also showed a strong milk solidification capacity in a dose-dependent manner. The EPS could significantly improve the texture of yoghurt, indicating its potential application as a functional starter in the production of fermented dairy products.

Beneficial Effects of Three Dietary Cyclodextrins on Preventing Fat Accumulation and Remodeling Gut Microbiota in Mice Fed a High-Fat Diet.

Globally, obesity and its metabolic complications, which are intimately linked to diet, are major public health problems. Cyclodextrins (CDs) are cyclic oligosaccharides consisting of (α-1,4)-linked D-glucopyranose units that can reduce fat bioavailability and affect metabolism by improving intestinal flora as prebiotics. We compared the effects of three CDs on preventing fat accumulation and remodeling gut microbiota in a high-fat diet-fed C57BL/6J mouse model. α-CD maximized energy expenditure by 12.53%, caused the RER value to drop from 0.814 to 0.788, and increased the proportion of fatty acid oxidation for energy supply. β-CD supplementation resulted in a marked 24.53% reduction in weight gain and a decrease in epididymal-fat-relative weight from 3.76% to 2.09%. It also minimized ectopic fat deposition and improved blood lipid parameters. γ-CD maximized the concentration of SCFAs in the cecum from 6.29 to 15.31 μmol/g. All three CDs reduced the abundance ratio of Firmicutes and Bacteroidetes to a low-fat diet level, increased the abundance of Lactobacillus and Akkermansia, and reduced the abundance of Allobaculum and Ruminococcus. These findings imply that a combination of multiple CDs may exert superior effects as a potential strategy for obesity prevention.

Isolation, purification and characterization of exopolysaccharide produced by Leuconostoc pseudomesenteroides YF32 from soybean paste

A water-soluble exopolysaccharide (EPS)-producing strain YF32 was isolated from soybean paste, which was then identified as Leuconostoc pseudomesenteroides. After culturing the strain in Man-Rogosa-Sharpe (MRS) medium containing 5% sucrose at 30°C for 48h, the EPS was purified, and a yield of 12.5g/L was achieved. The weight-average molecular weight (Mw) was 5.54×106Da by high-performance size-exclusion chromatography (HPSEC). The structural characterization of the purified EPS was determined by gas chromatography (GC), Fourier transform infrared (FT-IR), 1H, 13C nuclear magnetic resonance (NMR) spectroscopy. The results demonstrated that the exopolysaccharide was glucan with a peak, a linear backbone composed of consecutive α-(1→6)-linked d-glucopyranose units. No branching was observed in the dextran structure. The degradation temperature (Td) of EPS was 307.62°C, which suggested that dextran exhibited high thermal stability. YF32 dextran also showed high water solubility and emulsibility. All results suggested that dextran has the potential to be applied in food fields as a food additive.

Characterization of highly branched dextran produced by Leuconostoc citreum B-2 from pineapple fermented product

A strain Leuconostoc citreum B-2 was isolated from homemade fermentation product of pineapple and its polysaccharide yield was 28.3g/L after cultivating the strain in Man-Rogosa-Sharpe (MRS) medium with 75g/L sucrose. The exopolysaccharide (EPS) was characterized by gas chromatography (GC), Fourier-transform infrared (FT-IR) spectra, high-performance size-exclusion chromatography (HPSEC), nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscope (SEM) analysis in present study. The monosaccharide composition of EPS was glucose and molecular weight was 3.77×106Da. FT-IR and NMR spectra revealed that the B-2 EPS was composed of 75% α-(1→6) linked d-glucopyranose units existing in the main chain with 19% α-(1→3) branching and only a few α-(1→2) branching. The SEM of the dried EPS appeared irregular sheets with glittering surface and compact structure. Water solubility index and water holding capacity of B-2 EPS were 80% and 450%, respectively. All the mentioned characteristics suggested that the EPS has a potential application in the food, cosmetic and pharmaceuticals industry.

Optimization, purification and structural characterization of a dextran produced by L. mesenteroides isolated from Chinese sauerkraut

A higher yield of dextran strain Leuconstoc mesenteroides TDS2-19 was isolated from Chinese sauerkraut juice. Effects of the three main factors on exopolysaccharide (EPS) yield were investigated by central composite design (CCD) and the optimum composition was sucrose 117.48g/L, sodium acetate 4.10g/L, and initial pH 6.88. Optimum results showed that EPS yield was increased to 71.23±2.25g/L in 48h fermentation, 31.24% higher than before. The molecular weight (Mw) of ESP was 8.79×107Da, as determined by high-performance size-exclusion chromatography (HPSEC). Fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance spectra (NMR) showed that the polysaccharide synthesized by L. mesenteroides TDS2-19 in the MRS medium was dextran with a peak, a linear backbone composed of consecutive α-(1→6)-linked d-glucopyranose units. No branching was observed in the dextran structure. The present study suggested that L. mesenteroides TDS2-19 might be used for the industrial-scale production of linear dextran.

Isolation and characterization of dextran produced by Leuconostoc citreum NM105 from manchurian sauerkraut

A water-soluble exopolysaccharide (EPS) was produced by Leuconostoc ctireum NM105 from homemade manchurian sauerkraut. After culturing the strain in Man–Rogosa–Sharpe medium containing 5% sucrose at 25°C for 48h, the EPS was purified and a yield of 23.5g/L was achieved. The EPS consisted exclusively of glucose and the weight-average molecular weight was 1.01×108Da. The structural characterization of the purified EPS determined by FT-IR, 1H, 13C and two-dimensional NMR spectroscopy demonstrated that the glucan contained α-(1→6)-linked d-glucopyranose units, 2,6-linked d-glucopyranose units and terminal α-d-glucopyranose units at a ratio of 1:1:1. The microstructure of the dried dextran appeared a sheet-like smooth glittering and highly branched surface. The NM105 dextran showed high water solubility and excellent water retention. All the results suggested that the highly α-(1→2) branched dextran might have the potential to serve as valuable polymers applied in foods, cosmetics and other fields.

Characterisation of a novel water-soluble polysaccharide from Leuconostoc citreum SK24.002

Water-soluble polysaccharides that are produced from sucrose by lactobacillus strains isolated from Chinese traditional pickled vegetables were investigated. Strain SK24.002, which secreted an exopolysaccharide with a high dextranase resistance, was identified as Leuconostoc citreum via 16S rDNA sequence analysis. A polysaccharide yield of 35 g/L was achieved at 20 h in Man-Rogosa-Sharpe medium containing 100 g/L sucrose. The water-soluble polysaccharide consisted exclusively of glucose, and the weight-average molecular weight was 4.62 × 107 Da. Spectroscopy results demonstrated that the water-soluble exopolysaccharide was mainly composed of α-1,3 and α-1,6 linked d-glucopyranose units. Methylation analysis revealed that the ratio of α-1,6 linkages to α-1,3 linkages was 5:4. These results suggested a possible molecular structure for the water-soluble exopolysaccharide that consists of a backbone chain of alternating α-1,3 and α-1,6 linkages with a branched point at the C6 of the 1,3,6-linked d-glucopyranose unit. This novel polysaccharide may have applications as a functional ingredient in processed foods.

Topical emulgel formulation containing inclusion complex of calcipotriol with cyclodextrin

Psoriasis is a relatively common, chronic, inflammatory disease that affects the skin, scalp, and joints. Calcipotriol is one of the most commonly used topical agents for the treatment of psoriasis. However, it is a water-insoluble active substance and frequently leads to skin irritation in patients. Cyclodextrins (CDs) are cyclic oligosaccharides consisting of (α-1,4-)-linked d-glucopyranose units. CD molecules have a hydrophilic outer surface and a lipophilic central cavity, and they are able to form inclusion complexes in aqueous solutions with many drugs. They can increase bioavailability, aqueous solubility, and stability and also reduce the side effects of the drugs. The aim of this study was to develop a new topical drug delivery system of calcipotriol in order to improve the solubility and dissolution characteristics of the drug and reduce the undesirable side effects. For this purpose, an inclusion complex of calcipotriol with Captisol® was prepared, and complex formation was confirmed. The inclusion complex and pure drug were formulated separately in an emulgel base. Dissolution profiles of calcipotriol from emulgel formulations were compared with a commercial product of the drug. The drug release was significantly increased with the emulgel formulations compared to the commercial cream product.

COMPARATIVE EVALUATION OF THE ANTIOXIDANT ACTIVITIES OF THYMOL AND CARVACROL AND THE CORRESPONDING β-CYCLODEXTRIN COMPLEXES

Cyclodextrins are cyclic oligosaccharides of α-(1,4)-linked D-glucopyranose units in a ring formation. They are able to form inclusion complexes with a wide variety of molecules, improving their aqueous solubility and chemical stability, the dissolution and release rates of several molecules as well as suppressing their volatility and unpleasant odours or tastes. Thymol and carvacrol are two aromatic compounds present in the essential oils of Thymus and Origanum species, which show antioxidant properties. The main goal of this work was to evaluate the antioxidant ability of thymol and carvacrol and of the corresponding β-cyclodextrin complexes. Oxygen Radical Absorbance Capacity (ORAC), Trolox Equivalent Antioxidant Capacity (TEAC) and 2,2-diphenyl-2-picryl-hydrazil (DPPH) methods were used for evaluating the thymol and carvacrol and the β-cyclodextrin complexes scavenging free radicals capacity. With ORAC method, thymol showed better antioxidant activity than carvacrol, 47 and 33 μmol Trolox equivalent/mg (TE), respectively. Thymol- and carvacrol-β-cyclodextrin complexes maintained their capacity for scavenging the free radical with 47 and 28 μmol TE/mg, respectively. With TEAC method, thymol and carvacrol showed similar antioxidant activities: 421 and 450 μmol TE/mg, respectively. In contrast, carvacrol-β-cyclodextrin complex attained 494 μmol TE/mg while thymol complex showed only 184 μmol TE/mg. This complex seems to loose the capacity for scavenging free radicals. Different results were obtained with DPPH method. IC 50 values for thymol and the corresponding complex were similar 0.03 mg, whereas carvacrol and carvacrol-β-cyclodextrin complex showed an IC 50 =0.03 and 0.02 mg, respectively.

Trehalose–protein interaction in aqueous solution

A variety of sugars are known to enhance the stability of biomaterials. Trehalose, a nonreducing disaccharide composed of two alpha, alpha(1 --> 1)-linked D-glucopyranose units, appears to be one of the most effective protectants. Both in vivo and in vitro, trehalose protects biostructures such as proteins and membranes from damage due to dehydration, heat, or cold. However, despite the significant amount of experimental data on this disaccharide, no clear picture of the molecular mechanism responsible for its stabilizing properties has emerged yet. Three major hypotheses (water-trehalose hydrogen-bond replacement, coating by a trapped water layer, and mechanical inhibition of the conformational fluctuations) have been proposed to explain the stabilizing effect of trehalose on proteins. To investigate the nature of protein-trehalose-water interactions in solution at the molecular level, two molecular dynamics simulations of the protein lysozyme in solution at room temperature have been carried out, one in the presence (about 0.5 M) and one in the absence of trehalose. The results show that the trehalose molecules cluster and move toward the protein, but neither completely expel water from the protein surface nor form hydrogen bonds with the protein. Furthermore, the coating by trehalose does not significantly reduce the conformational fluctuations of the protein compared to the trehalose-free system. Based on these observations, a model is proposed for the interaction of trehalose molecules with a protein in moderately concentrated solutions, at room temperature and on the nanosecond timescale.

Isolation, Purification, and Characterization of Cyclomaltodecaose (.EPSILON.-Cyclodextrin), Cyclomaltoundecaose (.ZETA.-Cyclodextrin) and Cyclomaltotridecaose (.THETA.-Cyclodextrin).

Cyclomaltodecaose (ε-cyclodextrin, ε-CD), cyclomaltoundecaose (ζ-CD) and cyclomaltotridecaose (θ-CD) are a series of cyclomalto-oligosaccharides composed of ten, eleven and thirteen α-(1→4)-linked D-glucopyranose units, respectively. ε-CD, ζ-CD and θ-CD were purified from the commercially available CD powder mainly using the combined treatment of HPLC and column chromatographies. The molecular weights of ε-CD, ζ-CD and θ-CD were determined by FAB-MS, and their cyclic structures were identified by 1H-NMR and 13C-NMR. Furthermore, the 13C-NMR chemical shift of large-ring cyclodextrins composed of several α-(1→4)-linked D-glucopyranose units, in which numbers 9, 10, 11, 12, and 13 are named δ-, ε-, ζ-, η-, θ-CD, were elucidated and compared with those of conventional α-, β-, and γ-CD.

Characterization, Biosynthesis, and Regulation of Granulose in Clostridium acetobutylicum

Synthesis of granulose was investigated in 15 solvent-producing Clostridium strains. Only one of the strains did not produce granulose. The structure of granulose in Clostridium acetobutylicum P262 consisted of a high-molecular-weight polyglucan containing only (1-->4) linked d-glucopyranose units. Biosynthesis of granulose in C. acetobutylicum P262 was dependent on ADPglucose pyrophosphorylase, and granulose synthase and mutants defective in granulose accumulation lacked either one or both enzyme activities. Granulose-positive revertants exhibited both enzyme activities. ADPglucose pyrophosphorylase and granulose synthase were not subject to allosteric control by metabolites. Granulose accumulation and the biosynthetic enzyme activities were initiated immediately before the pH breakpoint and were detected in cells only at the end of the exponential growth phase. Granulose accumulation did not occur under conditions of nitrogen limitation, excess carbon, or excess energy.