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Xu X.,Shanghai JiaoTong University | Xu X.,Institute of Bright Dairy and Food Co. | Li Y.,Shanghai JiaoTong University | Shen Y.,Shanghai JiaoTong University | Guo S.,Shanghai JiaoTong University
International Journal of Biological Macromolecules | Year: 2013

Norcantharidin-conjugated chitosan conjugates (NCTD-CSs) with different degrees of substitution (DS, 60.2% and 97.9%) were synthesized and characterized by 1H NMR, FT-IR, and XRD. In comparison with CS, the NCTD-CSs had lower crystallinity and better water solubility. Less than 6% NCTD was released from the NCTD-CSs through the hydrolysis of ester bonds in phosphate-buffered solution (PBS, pH 5.0 and 7.4) within 16 days, showing sustained drug release characteristic. The result of cytoxicity study showed that the NCTD-CSs were cytotoxic to MGC80-3 cells and their cytotoxicity was lower than that of NCTD. Fluorescence microscope and flow cytometry analysis demonstrated that the amount of the NCTD-CSs uptaken by MGC80-3 cells increased as incubation time. Confocal microscopy study showed that the NCTD-CSs were internalized into cells by endocytosis and mainly localized in lysosomes within 24h. It was found that the NCTD-CSs arrested MGC80-3 cell cycle at G2/M phase and induced cell death via cell apoptosis similarly to NCTD. These results indicated that the NCTD-CSs might be an efficient NCTD delivery system for cancer therapy. © 2013 Elsevier B.V. Source

Chen C.,Shanghai Institute of Technology | Chen C.,Jiangnan University | Zhao G.,Jiangnan University | Chen W.,Jiangnan University | And 2 more authors.
Applied and Environmental Microbiology | Year: 2015

Although fructooligosaccharides (FOS) can selectively stimulate the growth and activity of probiotics and beneficially modulate the balance of intestinal microbiota, knowledge of the molecular mechanism for FOS metabolism by probiotics is still limited. Here a combined transcriptomic and physiological approach was used to survey the global alterations that occurred during the logarithmic growth of Lactobacillus plantarum ST-III using FOS or glucose as the sole carbon source. A total of 363 genes were differentially transcribed; in particular, two gene clusters were induced by FOS. Gene inactivation revealed that both of the clusters participated in the metabolism of FOS, which were transported across the membrane by two phosphotransferase systems (PTSs) and were subsequently hydrolyzed by a β-fructofuranosidase (SacA) in the cytoplasm. Combining the measurements of the transcriptome- and membrane-related features, we discovered that the genes involved in the biosynthesis of fatty acids (FAs) were repressed in cells grown on FOS; as a result, the FA profiles were altered by shortening of the carbon chains, after which membrane fluidity increased in response to FOS transport and utilization. Furthermore, incremental production of acetate was observed in both the transcriptomic and the metabolic experiments. Our results provided new insights into gene transcription, the production of metabolites, and membrane alterations that could explain FOS metabolism in L. plantarum. © 2015, American Society for Microbiology. Source

Chen C.,Institute of Bright Dairy and Food Co. | Chen C.,Jiangnan University | Zhou F.,Institute of Bright Dairy and Food Co. | Ren J.,Institute of Bright Dairy and Food Co. | And 6 more authors.
Process Biochemistry | Year: 2014

Fructooligosaccharides (FOS) are prebiotics that selectively stimulate the growth and activity of lactobacilli and bifidobacteria. These strains metabolize FOS with endogenous β-fructofuranosidase. In this study, a β-fructofuranosidase gene from Lactobacillus plantarum ST-III designated sacA was cloned into Escherichia coli, and the properties of the recombinant protein (SacA) were examined. The sacA gene encodes a peptide of 501 amino acids with a predicted molecular weight of 56.7 kDa. Sequence alignment revealed the presence of three highly conserved motifs, NDPNG, RDP and EC, indicating that the enzyme belongs to glycoside hydrolase family 32. The predicted three-dimensional structure of the SacA enzyme was similar to β-fructofuranosidases of bifidobacteria, such that it contained a five-blade β-propeller module and a β-sandwich domain with one additional N-terminal α-helix. The optimal reaction temperature and pH of the enzyme were 37 °C and 6.0, respectively. Substrate hydrolysis and kinetic parameters demonstrated that β-fructofuranosidase from L. plantarum ST-III liberated fructosyl residues from the non-reducing terminus of fructans, such as sucrose, FOS, levan or inulin, and FOS was the preferred substrate. The expression of the sacA gene in a non-FOS-fermenting strain, Lactobacillus rhamnosus GG, enabled the recombinant strain to metabolize FOS and sucrose. © 2014 Elsevier Ltd. Source

Zhou F.,Institute of Bright Dairy and Food Co. | Wu Z.,Institute of Bright Dairy and Food Co. | Chen C.,Institute of Bright Dairy and Food Co. | Han J.,Institute of Bright Dairy and Food Co. | And 2 more authors.
Food Hydrocolloids | Year: 2014

Exopolysaccharides (EPSs) produced by a number of bacteria genera are very attractive to food industries because of their stabilizing and emulsifying capabilities. Rhizobium radiobacter S10, an EPS-producing strain, was isolated from kefir. The chemical and rheological properties of the produced EPS were investigated. The EPS yield of the strain can reach 2834.2mgL-1. The flow and viscoelastic behavior of S10 EPS were investigated by steady-shear and small-amplitude oscillatory experiments, respectively. The EPS solution (0.1%-1.0%, w/v) exhibited non-Newtonian and shear thinning behavior (pseudoplasticity) at shear rates that ranged from 0.01s-1 to 1000s-1. Weak gels were obtained with EPS concentrations as high as 0.75% at room temperature (25°C). The changes in the elastic (G') and viscous (G″) moduli during the heating and cooling cycles indicated that S10 EPS can form a thermal reversible gel. The predominant fraction of S10 EPS, PK2, was composed of galactose and glucose at a molar ratio of 1.00:4.92 and had an approximate molecular weight of 3.03×106Da. © 2013 Elsevier Ltd. Source

Xu X.,Institute of Bright Dairy and Food Co. | Gao C.,Institute of Bright Dairy and Food Co. | Liu Z.,Institute of Bright Dairy and Food Co. | Wu J.,Institute of Bright Dairy and Food Co. | And 3 more authors.
Carbohydrate Polymers | Year: 2016

Paenibacillus bovis sp. nov BD3526 synthesizes a large amount of exopolysaccharides (EPSs) (36.25 g/L) in a semi-defined chemical medium containing 20% (w/v) sucrose. The EPSs were extracted from the cultured broth by ethanol precipitation and purified via anion-exchange and gel permeation chromatography. The Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra showed that the primary EPS fraction (F1) was a linear β (2 → 6)-linked levan. The peak molecular weight (Mp) of the levan exceeded 2.6 × 106 Da based on high-performance size-exclusion chromatography (HPSEC). The levan adopted a spherical conformation in aqueous solution as confirmed by transmission electron microscopy (TEM). The corresponding levansucrase was identified by SDS-PAGE analysis and in situ polymer synthesis. The in vitro assay demonstrated that the levan significantly stimulated the proliferation of spleen cells and induced the expression of TNF-α, indicating its potential as a natural immunomodulator. © 2016 Elsevier Ltd. All rights reserved. Source

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