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Objective: Although the extracellular polysaccharides have been analyzed in the previous period, the biochemical, enzymological characters and stimulation and inhibition effect on glucansucrase are not fully understood. Results: After three steps purification, salting out, DEAE-Sepharose and Sephadex G-75, the final specific activity was 264.84 U/mg protein with 4.31-fold. The SDS-PAGE analysis of fraction gave a single band 170.35 kDa in the stained gel. The active band was analyzed with LC–MS/MS to identify glucansucrase. The highest coverage rate of dextransucrase from Leu. citreum (ACY92456.2) was 55.60%, the results were speculated that the glucansucrase secreted from Leu. citreum B-2 may be a novel glucansucrase. The purified enzyme was optimally active at 20–30 °C and pH 6.0–8.0. Metal ions K+, Na+, Ca2+, Mn2+, Mg2+, and Cr+ had an apparent stimulating effect on enzyme activity, especially in divalent ions Ca2+ and Mn2+, the residual activities were higher than 200%. In a reverse, Hg+, acetonitrile, SDS, salt, and guanidine expressed inhibition effect on enzyme residual activity. The KM and Vmax were detected to be 4.82 mM and 0.97 U/mg, respectively. Conclusion: All these data collectively indicate that B-2 glucansucrase is a novel one, which have good properties and may applied to new food areas. [ABSTRACT FROM AUTHOR]

In this study, we described the optimization of fermentation conditions and biochemical properties of exopolysaccharide (EPS) produced by Leuconostoc citreum B-2. The results of response surface methodology showed that the yield of B-2 EPS was 59.33 ± 1.34 g/L, which was 5.93 times before. The degradation temperature of the B-2 EPS was 313 °C, indicating that it had high thermal stability. B-2 EPS had certain antioxidant activity, especially it had strong scavenging ability to H 2 O 2. Higher concentrations of B-2 EPS had better emulsifying property on vegetable oils than hydrocarbons. Furthermore, our results also showed that B-2 EPS had the ability to coagulate milk and promote the growth of probiotic bacteria. • The yield of EPS from Leuconostoc citreum B-2 was increased 4.93-fold by RSM. • The degradation temperature of B-2 EPS was 313 °C, showing good thermal stability. • B-2 EPS had certain antioxidant activity, especially for H 2 O 2. • The emulsifying activity of B-2 EPS on vegetable oils was higher than hydrocarbons. • B-2 EPS could make skim milk coagulate and had a certain probiotic function. The fermentation conditions for exopolysaccharides (EPS) with a highly branched structure extracted from Leuconostoc citreum B-2 were optimized by response surface methodology (RSM). The results showed that under the optimal fermentation conditions of sucrose, yeast extract and pH of 99.80 g/L, 5.94 g/L and 6.12, respectively, the B-2 EPS yield was 59.33 ± 1.34 g/L, which was 5.93 times greater than that from the initial nonoptimized conditions. Chemical composition analysis showed that the carbon, hydrogen, nitrogen and sulfur contents of the B-2 pure EPS (P-EPS) were 39.05 ± 0.25%, 7.19 ± 0.08%, 0.72 ± 0.03% and 0%, respectively. The content of uronic acid was high, reaching 20.94 ± 6.30%. B-2 EPS had certain 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl (·OH), superoxide anion (O2−), hydrogen peroxide (H 2 O 2), nitroso radical (NO2−) scavenging abilities and reducing power. The degradation temperature of the B-2 EPS was 313 °C, indicating that B-2 EPS have high thermal stability. The emulsification effect on vegetable oils was better than that of hydrocarbons. The EPS produced by Leu. citreum B-2 was activated in different concentrations of sucrose-supplemented skimmed milk, which caused the skimmed milk to have different degrees of solidification. Moreover, B-2 EPS promoted the growth of probiotic bacteria, especially Lactobacillus delbrueckii. [ABSTRACT FROM AUTHOR]

An exopolysaccharide (EPS) was produced by Leuconostoc pseudomesenteroides DRP-5 isolated from homemade wine. The EPS was obtained with ethanol extraction, which was further purified by chromatography of Sephadex G-100 to get a purified fraction. The monosaccharide composition of the EPS was glucose, and its molecular weight (Mw) was 6.23 × 10 6 Da, as determined by gas chromatography (GC) and high-performance size-exclusion chromatography (HPSEC). Fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance spectra (NMR) showed that the EPS was a linear glucan with α-(1→6)-linked glucosidic bonds. The water holding capacity (WHC), water solubility index (WSI) and emulsifying activity (EA) of DRP-5 EPS were 296.76 ± 18.93%, 98.62 ± 3.57% and 87.22 ± 2.18%, respectively. DRP-5 EPS have a higher degradation temperature of 278.36 °C, suggesting high thermal stability of the EPS. Also, DRP-5 EPS was found to have moderate 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical, superoxide anion radical, 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical, Fe 2+ scavenging activities and reducing power. All these characteristics suggest that DRP-5 EPS might have potential applications in the pharmaceutical, cosmetic and food industries. [ABSTRACT FROM AUTHOR]

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 48 h, the EPS was purified, and a yield of 12.5 g/L was achieved. The weight-average molecular weight (Mw) was 5.54 × 10 6 Da 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), 1 H, 13 C 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. [ABSTRACT FROM AUTHOR]