Mingsheng Dong

Characterization of a novel exopolysaccharide with antitumor activity from Lactobacillus plantarum 70810.

Three methods were used to prepare the cell-bound exopolysaccharides (c-EPS) of Lactobacillus plantarum 70810, and the maximum yield (64.17 mg/mL) was obtained by ultrasonic extraction. After anion exchange and gel filtration chromatography, the c-EPS was fractionated as a single peak with a molecular weight of 169.6 kD. Its structural characteristics were investigated by gas chromatography (GC), methylation, Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analysis. Based on obtained data, the novel c-EPS was found to be a galactan containing a backbone of α-D-(1→6)-linked galactcosyl, β-D-(1→4)-linked galactcosyl, β-D-(1→2,3)-linked galactcosyl residues and a tail end of β-D-(1→)-linked galactcosyl residues. Preliminary in vitro tests revealed that c-EPS significantly inhibited the proliferation of HepG-2, BGC-823, especially HT-29 tumor cells. Our results suggested that the c-EPS produced by L. plantarum 70810 might be suitable for use as functional foods and natural antitumor drugs.

Structural elucidation and antioxidant activities of exopolysaccharides from Lactobacillus helveticus MB2-1.

In the present study, the crude polysaccharides (EPS) from Lactobacillus helveticus MB2-1 were fermented with reconstituted whey medium and further fractionated on DEAE-52 cellulose and Sephadex G-100 chromatography to afford three purified fractions of EPS-1, EPS-2 and EPS-3. Then, their preliminary structures and antioxidant activities in vitro were investigated. Three purified EPS fractions (EPS-1, EPS-2 and EPS-3) had similar molecular weight distributions (about 2 × 10(5)Da), and it was composed of galactose, glucose and mannose with a molar ratio of 1.33:2.75:1.00, 1.00:1.43:9.34 and 1.17:1.00:2.96, respectively. In addition, the antioxidant activity of EPS-1, EPS-2 and EPS-3 was evaluated with the in vitro scavenging abilities. The results indicated that both crude and purified EPS showed strong scavenging activities on three kinds of radical and chelating activities on ferrous ion, and their antioxidant activities decreased in the order of crude EPS>EPS-3>EPS-2>EPS-1.

Structural characterization and bioactivity of released exopolysaccharides from Lactobacillus plantarum 70810

Two released exopolysaccharides (r-EPS1 and r-EPS2) were isolated from the culture supernatant of Lactobacillus plantarum 70810 by ethanol precipitation, anion exchange and gel filtration chromatography and characterization of the structures were conducted. The r-EPS1 and r-EPS2 were homogenous polysaccharides with average molecular weights of, respectively, 204.6 and 202.8kDa, and composed of glucose, mannose and galactose with molar ratios of 18.21:78.76:3.03 and 12.92:30.89:56.19, respectively. Methylation and NMR analysis revealed r-EPS1 was consisted of alpha configuration sugar residues, whereas r-EPS2 contained both alpha and beta configuration sugar residues. Antioxidant and antitumor activities of the two exopolysaccharides were evaluated in vitro. The results showed that r-EPS1 and r-EPS2 exhibited potent antioxidant activities regarding hydroxyl and DPPH radicals scavenging and reducing power assays, and possessed antitumor activities against Caco-2, BGC-823 and HT-29 cells, which suggested that they could be potential sources of antioxidant and antitumor drug.

Study of Water Dynamics in the Soaking, Steaming, and Solid-State Fermentation of Glutinous Rice by LF-NMR: A Novel Monitoring Approach

Solid-state fermentation (SSF) of starchy grain is a traditional technique for food and alcoholic beverage production in East Asia. In the present study, low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of water dynamics and microstructure alternations during the soaking, steaming, and SSF of glutinous rice as a rapid real-time monitoring method. Three different proton fractions with different mobilities were identified based on the degree of interaction between biopolymers and water. Soaking and steaming significantly changed the proton distribution of the sample. The different phases of SSF were reflected by the T2 parameters. In addition, the variations in the T2 parameters were explained by the microstructure changes of rice induced by SSF. The fermentation time and T2 parameters were sigmoidally correlated. Thus, LF-NMR may be an effective real-time monitoring method for SSF in starch systems.

Water distribution in tofu and application of T2 relaxation measurements in determination of tofu's water-holding capacity.

Low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of tofu in the present study. After multiexponential analysis of relaxation decays, three water fractions centered at about 1.5-2.6, 24-114, and 132-305 ms were detected and identified as T2b, T21, and T22, respectively. Principal component analysis (PCA) of the data revealed that sample aggregation was dependent on solubility of coagulants and contained anions. Stepwise centrifugation and microwave drying were employed as dehydration methods. Significant correlations were observed between T21 and T22 relaxation times and water-holding capacity (WHC) in both dehydration processes, which implied LF-NMR measurements could be an efficient method for determination and prediction of tofus water-holding capacity. Ten linear equations that could be applied in prediction of WHC for tofu were reported. LF-NMR was suggested to be a powerful tool for the study of tofu.

Structural Characterization and Anticancer Activity of Cell-Bound Exopolysaccharide from Lactobacillus helveticus MB2-1

A novel cell-bound exopolysaccharide (c-EPS) was isolated from Lactobacillus helveticus MB2-1 by ultrasonic extraction, anion exchange, and gel filtration chromatography before being structurally characterized. The c-EPS is a heteropolysaccharide with an average molecular weight of 1.83 × 10(5) Da and is composed of glucose, mannose, galactose, rhamnose, and arabinose at a molar ratio of 3.12:1.01:1.00:0.18:0.16. Methylation analysis and nuclear magnetic resonance analysis revealed that the c-EPS is a linear glucomannogalactan containing repeating units of → 6)-β-D-Manp-(1 → 3)-β-D-Glcp-(1 → 3)-β-D-Glcp-(1 → 3)-β-D-Glcp-(1 → 4)-α-D-Galp-(1 → and trace amounts of Rhap-(1 → and (1 → 4)-Arap residues. Complex formation with Congo red demonstrated a triple-strand helical conformation for the c-EPS. Scanning electron microscopy of the c-EPS revealed many regular feather-like structural units. Topographical examination of c-EPS by atomic force microscopy revealed that the c-EPS formed rounded-to-spherical lumps with different sizes and chain formations. Furthermore, preliminary in vitro tests revealed that c-EPS significantly inhibited the proliferation of HepG-2, BGC-823, and especially HT-29 cancer cells.

Characterization of an antiproliferative exopolysaccharide (LHEPS-2) from Lactobacillus helveticus MB2-1.

In this study, we reported that three purified exopolysaccharides fractions (LHEPS-1, LHEPS-2 and LHEPS-3) and crude LHEPS from the Lactobacillus helveticus MB2-1 inhibited the proliferation potential of human gastric cancer BGC-823 cells. We found that all the LHEPS fractions and crude LHEPS exerted concentration and time dependent inhibitory activities in vitro on BGC-823 cells. LHEPS-2 exhibited higher antiproliferative activity against BGC-823 cells in vitro than LHEPS-1, LHEPS-3 and crude LHEPS. With the consideration of the outstanding antiproliferative effect of LHEPS-2 on BGC-823 cells, more fine structural characterization of LHEPS-2 was further identified. The structure of LHEPS-2 was elucidated by methylated analysis, GC-MS, (1)H NMR and (13)C NMR spectroscopy, together with two-dimensional (2D) COSY, TOCSY, HSQC, HMBC and NOESY spectroscopy. Results showed that the LHEPS-2 was consisted of the following repeating units:

A systematic optimization of medium chain fatty acid biosynthesis via the reverse beta-oxidation cycle in Escherichia coli

Medium-chain fatty acids (MCFAs, 6-10 carbons) are valuable precursors to many industrial biofuels and chemicals, recently engineered reversal of the β-oxidation (r-BOX) cycle has been proposed as a potential platform for efficient synthesis of MCFAs. Previous studies have made many exciting achievements on functionally characterizing four core enzymes of this r-BOX cycle. However, the information about bottleneck nodes in this cycle is elusive. Here, a quantitative assessment of the inherent limitations of this cycle was conducted to capitalize on its potential. The selection of the core β-oxidation reversal enzymes in conjunction with acetyl-CoA synthetase endowed the ability to synthesize about 1g/L MCFAs. Furthermore, a gene dosage experiment was developed to identify two rate-limiting enzymes (acetyl-CoA synthetase and thiolase). The de novo pathway was then separated into two modules at thiolase and MCFA production titer increased to 2.8g/L after evaluating different construct environments. Additionally, the metabolism of host organism was reprogrammed to the desired biochemical product by the clustered regularly interspaced short palindromic repeats interference system, resulted in a final MCFA production of 3.8g/L. These findings described here identified the inherent limitations of r-BOX cycle and further unleashed the lipogenic potential of this cycle, thus paving the way for the development of a bacterial platform for microbial production of high-value oleo-chemicals from low-value carbons in a sustainable and environmentally friendly manner.

Chemical modification, characterization and bioactivity of a released exopolysaccharide (r-EPS1) from Lactobacillus plantarum 70810

In the present study, a released exopolysaccharide (r-EPS1) from L. plantarum 70810 was modified by acetylation, phosphorylation and carboxymethylation. Scanning electron micrograph (SEM) and thermogravimetric analysis (TGA) showed the r-EPS1 derivatives had different surface morphology and thermal behavior. Compared with r-EPS1, the derivatives exhibited stronger antioxidant and antitumor activities. The study provided experimental evidences that chemical modification could be an effective way to improve the bioactivity of exopolysaccharide from L. plantarum 70810. It is noted that these derivatives could be explored as novel potential antioxidant and antitumor agents.

Characterization of a novel polysaccharide with anti-colon cancer activity from Lactobacillus helveticus MB2-1.

The present study aimed at investigating the potential anti-colon cancer activity of three purified exopolysaccharides fractions (LHEPS-1, LHEPS-2 and LHEPS-3) from the Lactobacillus helveticus MB2-1. The experimental evidence showed that LHEPS-1 significantly inhibited cell proliferation of human colon cancer Caco-2 cells in both time- and concentration-dependent manners. In contrast, no significant improvements of the inhibitory effects of LHEPS-2 and LHEPS-3 on Caco-2 cells were observed with increasing sample concentrations or prolonged incubation time. Furthermore, the structure of LHEPS-1 was elucidated using methylated analysis, gas chromatography-mass spectroscopy (GC-MS) and nuclear magnetic resonance spectroscopy (NMR), including one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR). Results indicated that the LHEPS-1 consisted of a decasaccharide repeating unit with the following structure (n ≈ 122)： Our results suggested that the LHEPS-1 produced by L. helveticus MB2-1 might be suitable for using as natural anti-colon cancer drugs and functional foods ingredients.