Xiaolu Jiang

ANTI-OXIDATION OF AGAR OLIGOSACCHARIDES PRODUCED BY AGARASE FROM A MARINE BACTERIUM

In order to prepare the active agar oligosaccharide, agarase extracted from a strain of unidentified marine bacterium from the South China Sea coast was selected for the agar depolymerization. The optimum decomposing conditions were determined to be pH 7.0, 35 °C and halophilic properties 2%. Three main degraded products, AOS-1, AOS-2 and AOS-3, were separated by ethanol fractionation and anion exchange chromatography. The molecular mass was analyzed by MALDI-TOF-MS. The agar oligosaccharides exhibited antioxidative activities in scavenging hydroxyl free radical, scavenging superoxide anion radical and inhibiting lipid peroxidation. The fragment with the sulfate group showed stronger antioxidative activities than that without the sulfate group. Higher antioxidative activities were found when the molecular mass was increased. The results indicated that the antioxidative activities were closely related to the molecular mass of the agar oligosaccharides and the substitute groups binding the carbohydrate ring.

Promotive effects of alginate-derived oligosaccharide on maize seed germination

The influence of alginate-derived oligosaccharide (molecular weight 1445 Da) was tested on the maize seed germination at different concentrations. Assays of α-and β-amylase and protease activities showed the highest response at 0.75‰.Compared with the control, root growth on days 3 and 7 showed increases of 34% and18%, respectively; and shoot growth on day 7 an increase of 46%. In the case of protease activity, treatments with both 0.75‰ and 1.50‰ alginate-derived oligosaccharide gave higher activities than the control. These results indicate that the rate of seed germination was enhanced by increasing the activities of several enzymes beneficial for germination.

In vitro antioxidative activities of three marine oligosaccharides

The antioxidant activities of three marine oligosaccharides, alginate oligosaccharides (AOs), chitosan oligosaccharides (COs), and fucoidan oligosaccharides (FOs), were investigated in vitro by several antioxidant assays, including hydroxyl radical scavenging, superoxide radical scavenging, erythrocyte hemolysis inhibiting, metal chelating activities, and anti-lipid peroxidation. The results show that these oligosaccharides exhibited different activities in various assays. AOs had the highest scavenging hydroxyl radical activity than FOs and COs at all the tested amounts. COs had the highest scavenging superoxide radical and inhibiting erythrocyte hemolysis activity than AOs and FOs at all the tested amounts. In the assay of chelating Fe2+, COs and FOs indicated good chelation while AOs hardly had any activity. In the assay of anti-lipid peroxidation, only COs had significantly high antioxidant activity.

Preparation and In Vivo. Antitumor Activity of κ-Carrageenan Oligosaccharides

Abstract Carrageenan oligosaccharides were produced from the final products of commercial extractions of gelling carrageenan and thickening carrageenan, which were specifically depolymerized by κ-carrageenase extracted from the marine bacterium Cytophaga. MCA-2. The weight-average molecular weights of the two oligosaccharides produced were 681 and 798 Da. The sulfate contents were assayed as 17.2% and 21.8%. Antitumor activities of the oligosaccharides were tested on Sarcoma 180 tumor transplanted in mice. The carrageenan oligosaccharide from the thickening carrageenan product showed much higher tumor inhibition (70.8%) and catalase activity at a dosage of 100 mg kg−1 compared with the control group. The gelling and thickening carrageenan oligosaccarides could also significantly increase the weight of immune organs such as the thymus, which suggests that the antitumor mechanism of the carrageenan oligosaccharides may be initiated via organ-mediated defense reactions.

Purification and characterization of an alginate lyase from marine Bacterium Vibrio sp. mutant strain 510-64.

Marine Vibrio sp. 510 was chosen as a parent strain for screening high producers of alginate lyase using the complex mutagenesis of Ethyl Methanesulphonate and UV radiation treatments. The mutant strain Vibrio sp. 510-64 was selected and its alginate lyase activity was increased by 3.87-fold (reaching 46.12 EU/mg) over that of the parent strain. An extracellular alginate lyase was purified from Vibrio sp. 510-64 cultural supernatant by successive fractionation on DEAE Sepharose FF and two steps of Superdex 75. The purified enzyme yielded a single band on SDS-PAGE with the molecular weight of 34.6 kDa. Data of the N-terminal amino acid sequence indicated that this protein might be a novel alginate lyase. The substrate specificity results demonstrated that the alginate lyase had the specificity for poly G block.

Antioxidant activity of polysaccharides produced by Hirsutella sp. and relation with their chemical characteristics

Extracellular polysaccharide (EPS) and intracellular polysaccharide (IPS) were produced in a mycelial liquid culture of the Hirsutella sp. liquid fermentation. The polysaccharides were precipitated with 50% ethanol (EPS-1, IPS-1), 65% ethanol (EPS-2, IPS-2) and 80% ethanol (EPS-3, IPS-3). The polysaccharide fragments precipitated in lower ethanol percentages had a lower neutral sugar content and a larger molecular weight. EPS-1, EPS-2, IPS-1 and IPS-2 were composed of glucose (Glu), galactose (Gal) and mannose (Man). Galactose was not detected in EPS-3 and IPS-3. Evaluated by the 1/IC50 values of hydroxyl radical scavenging activity, the polysaccharides with higher protein content, lower neutral sugar content and molecular weight about 10-20 kDa were found to have better radical scavenging activity. Significant correlations demonstrated that the antioxidant effect of the polysaccharides was influenced by monosaccharide composition (mannose, r=0.942; glucose, r=-0.905).

Antitumour activities of alginate-derived oligosaccharides and their sulphated substitution derivatives

Alginate lyase, isolated from a marine culture of Vibrio sp. 510, was used to depolymerize alginate. Two alginate-derived oligosaccharides (ADOs) of different molecular weight were sulphated with the formamide-chlorosulphonic acid method. The antitumour activities of the two ADOs and their sulphated substitution derivatives that exhibited no direct cytotoxic effects on tsFT210 cells, were subsequently determined on Kunming mice. The best antitumour performer was Oligosaccharide A (molecular weight 3798 Da, sulphation degree 1.3), which exhibited 70.4 and 66.0% tumour inhibition against solid Sarcoma 180 at doses of 100 and 50 mg kg − 1, respectively. For ADOs and their sulphated derivatives, an indirect antitumour effect via modulation of the host-mediated immune defences is postulated.

Preparation, purification and characterization of alginate oligosaccharides degraded by alginate lyase from Pseudomonas sp. HZJ 216.

Alginate lyase which was purified from the fermentation solution of marine bacteria Pseudomonas sp. HJZ216 was applied to hydrolyze algae alginate. Six oligosaccharides, including di- and trisaccharides, were isolated and purified through anion exchange chromatography. The oligosaccharide structures were elucidated based on electrospray ionization-mass spectrometry (ESI-MS) and 2D NMR spectra analysis.

Antibacterial activity of lyase-depolymerized products of alginate

A series of mannuronic acid (M-block) and guluronic acid (G-block) fractions (M1–M5 and G1–G5) with different molecular weights were obtained by lyase depolymerization of alginate and evaluated for in vitro antibacterial activity against 19 bacterial strains. The antibacterial data revealed that both types of fractions generally showed activity against certain tested bacteria, whereas M-block fractions showed broader spectra and more potent inhibition than G-block fractions. Among these fractions, M3 (molecular weight 4.235 kDa) exhibited the broadest spectrum of inhibition and high inhibitory activity against Escherichia coli (minimal inhibitory concentration, MIC = 0.312 μg mL−1), Salmonella paratyphi B (MIC = 0.225 μg mL−1), Staphylococcus aureus (MIC = 0.016 μg mL−1) and Bacillus subtilis (MIC = 0.325 μg mL−1).

Synergistic combination of marine oligosaccharides and azithromycin against Pseudomonas aeruginosa

In this paper we describe how utilization of low molecular weight alginate-derived oligosaccharide (ADO) and chito-oligosaccharide (COS) in conjunction with antibiotics, could more effectively inhibit the growth of wild-type and resistant Pseudomonas aeruginosa. Inhibition is effected by modulating the bacterias quorum sensing (QS) system, thus regulating biofilm formation and reducing resistance to antibiotic treatment. This can be demonstrated by using conventional MIC screening. COS showed synergistic effects with azithromycin, whereas ADO indicated additive effects against wild-type P. aeruginosa. Using electrospray-ionization mass spectroscopy (ESI-MS), matrix-assisted laser desorption/ionization-time of flightmass spectroscopy (MALDI-TOF-MS) and nuclear magnetic resonance (NMR), the chemical structure of ADO and of COS was characterized. The wild-type and resistant strains were identified by 16S rRNA sequence analysis. This report demonstrates the feasibility of attenuating the tolerance of P. aeruginosa to azithromycin by using specific marine oligosaccharides.