Search

In this study, a Bacillus halotolerans (B. halotolerans) strain DT1 capable of producing exopolysaccharides (EPS) was isolated from dried cabbages of Tianjin, a local fermented vegetable product. Three distinct polysaccharide fractions were isolated from the fermentation broth of DT1, namely, DT1-0, DT1-2, and DT1-5. The structural composition and properties of these fractions were investigated. The predominant EPS, DT1-0, was identified as a novel heteropolysaccharide composed of fructose and glucose with branched structures. The repeating unit was determined to be [4)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-β-D-Fruf-(2→6)-β-D-Fruf-(2→6-)-β-D-Fruf-(2→], with fructose and glucose connected by β-(2→1) and α-(1→4) glycosidic linkages between the third fructose and the first glucose, respectively. The molecular weight (Mw) was estimated to be 4.253 × 103 Da. DT1-0 presented a smooth and porous surface structure as observed through SEM and exhibited a water-holding capacity of 504 ± 5.3%, maximum thermal stability at 245 °C, and an oil-holding capacity of 387 ± 1.9% for coconut oil. DT1-2 was identified as a fructooligosaccharide. DT1-5 was characterized as a polysaccharide composed of glucose and fructose. In conclusion, these findings provide substantial support for the further application of B. subtilis strain DT1 and its EPS fractions, DT1-0, DT1-2, and DT1-5, as potential alternatives for functional food additives or ingredients. [ABSTRACT FROM AUTHOR]

• PC EPS is a dextran consisting of consecutive α-(1→6)-linked D-glucopyranose units. • The dextran polymer showed an irregular sheet structure and porous surface. • The dextran displayed heat tolerance and high viscosity at low pH properties. • The dextran could coagulate sucrose-supplemented milk. • The dextran has potential applications in food and dairy processing. An exopolysaccharide (EPS)-producing bacterial strain, PC, was isolated from pickled Chinese cabbage and identified as Leuconostoc pseudomesenteroides. EPS yield was up to 30.5 g/L when bacteria were cultivated in Man-Rogosa-Sharpe (MRS) medium containing 5% sucrose at 30°C for 48 h. Further analysis by gas chromatography, high performance size exclusion chromatography, and nuclear magnetic resonance revealed that the EPS consisted of glucose with α-(1→6) linkages and had a molecular weight of 3.13 × 106 Da. Scanning-electron microscopy demonstrated an irregular sheet structure and porous surface, and lumps with an average height of 77.803 nm were observed by atomic force microscopy. Physical-chemical analysis showed that the EPS exhibited excellent thermal stability and possessed high viscosity at high concentration, low temperature and acidic pH, making it promising to be used in thermal processed foods and fermentation of acidic food products. Milk solidification test also suggested the promising potential for application as a dairy and food additive since the EPS could activate the solidification of sucrose-supplemented milk. Taken together, this study provides a commercial guidance for the practical application of PC EPS in food industry and other areas. [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]

A strain Leuconostoc citreum B-2 was isolated from homemade fermentation product of pineapple and its polysaccharide yield was 28.3 g/L after cultivating the strain in Man-Rogosa-Sharpe (MRS) medium with 75 g/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 × 10 6 Da. 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. [ABSTRACT FROM AUTHOR]

Response surface methodology (RSM) was used to optimize the fermentation condition of exopolysaccharide (EPS) producing strain Leuconostoc mesenteroides DRP105. Result showed that the optimum condition was sucrose 86.83 g/L, tryptone 15.47 g/L, initial pH 7.18 and maximum yield was 53.79 ± 0.78 g/L in 36 h fermentation. Chain conformation was characterized by Congo red test, β -elimination and circular dichroism (CD), which indicated that the EPS was O-linkage and exhibited random coil structure in aqueous solution. CD results concluded hydrogen-bond interaction and chirality might be connected with concentration. Purified EPS has a higher degradation temperature of 279.42 °C, suggesting high thermal stability of the EPS. The absolute value of zeta potential and particle size were enhanced with increasing concentration. Crude EPS and its purified fraction were found to have moderate DPPH, hydroxyl, superoxide anion radicals scavenging activities and reducing power. This study provided a high yield EPS with unique characteristics for industrial applications. [ABSTRACT FROM AUTHOR]

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 117.48 g/L, sodium acetate 4.10 g/L, and initial pH 6.88. Optimum results showed that EPS yield was increased to 71.23 ± 2.25 g/L in 48 h fermentation, 31.24% higher than before. The molecular weight (Mw) of ESP was 8.79 × 10 7 Da, 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. [ABSTRACT FROM AUTHOR]