Exopolysaccharide from marine microalgae belonging to the Glossomastix genus: fragile gel behavior and suspension stability.

With the aim to find new polysaccharides of rheological interest with innovated properties, rhamnofucans produced as exopolysaccharides (EPS) in a photobioreactor (PBR) and an airlift bioreactor (ABR) by the marine microalgae Glossomastix sp. RCC3707 and RCC3688 were fully studied. Chemical characterizations have been conducted (UHPLC - MS HR). Analyses by size-exclusion chromatography (SEC) coupled online with a multiangle light scattering detector (MALS) and a differential refractive index detector showed the presence of large structures with molar masses higher than 106 g.mol-1. The rheological studies of these EPS solutions, conducted at different concentrations and salinities, have evidenced interesting and rare behavior characteristic of weak and fragile hydrogels i.e. gel behavior with very low elastic moduli (between 10-2 and 10 Pa) and yield stresses (between 10-2 and 2 Pa) according to the EPS source, concentration, and salinity. These results were confirmed by diffusing wave spectroscopy. Finally, as one of potential application, solutions of EPS from Glossomastix sp. have evidenced very good properties as anti-settling stabilizers, using microcrystalline cellulose particles as model, studied by multiple light scattering (MLS) with utilization in cosmetic or food industry. Compared to alginate solution with same viscosity for which sedimentation is observed over few hours, microalgae EPS leads to a stable suspension over few days.

A Screening Approach to Assess the Impact of Various Commercial Sources of Crude Marine λ-Carrageenan on the Production of Oligosaccharides with Anti-heparanase and Anti-migratory Activities.

Oligosaccharides derived from λ-carrageenan (λ-COs) are gaining interest in the cancer field. They have been recently reported to regulate heparanase (HPSE) activity, a protumor enzyme involved in cancer cell migration and invasion, making them very promising molecules for new therapeutic applications. However, one of the specific features of commercial λ-carrageenan (λ-CAR) is that they are heterogeneous mixtures of different CAR families, and are named according to the thickening-purpose final-product viscosity which does not reflect the real composition. Consequently, this can limit their use in a clinical applications. To address this issue, six commercial λ-CARs were compared and differences in their physiochemical properties were analyzed and shown. Then, a H2O2-assisted depolymerization was applied to each commercial source, and number- and weight-averaged molar masses (Mn and Mw) and sulfation degree (DS) of the λ-COs produced over time were determined. By adjusting the depolymerization time for each product, almost comparable λ-CO formulations could be obtained in terms of molar masses and DS, which ranged within previously reported values suitable for antitumor properties. However, when the anti-HPSE activity of these new λ-COs was screened, small changes that could not be attributed only to their small length or DS changes between them were found, suggesting a role of other features, such as differences in the initial mixture composition. Further structural MS and NMR analysis revealed qualitative and semi-quantitative differences between the molecular species, especially in the proportion of the anti-HPSE λ-type, other CARs types and adjuvants, and it also showed that H2O2-based hydrolysis induced sugar degradation. Finally, when the effects of λ-COs were assessed in an in vitro migration cell-based model, they seemed more related to the proportion of other CAR types in the formulation than to their λ-type-dependent anti-HPSE activity.

Multifunctional hydrogels based on oxidized pectin and gelatin for wound healing improvement.

Gelatin (G) cross-linked with oxidized pectin (OP) was studied as a potential scaffold material for tissue engineering. The effect of oxidation on the chemical properties of pectin was investigated by determining the carbonyl and carboxyl amounts. The OP treatment led to a significant decrease of all values (Mn, Mw, [η] and Rh) determined by size exclusion chromatography (SEC) coupled on line with multiangle light scattering and viscometer detectors. Cross-linking parameters were elucidated by FTIR and TNBS assay. In general, the degree of crosslinking increased with the oxidation of pectin. It was found that the presence of the crosslinking agents caused a reduction in swelling and in the gelatin release which was determined by the BCA kit assay. From the hemolysis test, the membrane of red blood cells was not disrupted by the contact of films and the rate of release of hemoglobin was lower than 5%. The coagulation properties were evaluated by the dynamic blood clotting test. The G/OP hydrogels manifested a good activity of wound healing in the albino rats' model. Moreover, the films did not produce any unwilling symptoms. So, it was concluded that studied films have the potentiality to be used as wound healing biomaterials.

Structural characterization and rheological behavior of a heteroxylan extracted from Plantago notata Lagasca (Plantaginaceae) seeds.

Plantago notata (Plantaginaceae) is a spontaneous plant from Septentrional Algerian Sahara currently used by traditional healers to treat stomach disorders, inflammations or wound healing. A water-soluble polysaccharide, called PSPN (PolySaccharide fraction from Plantago Notata), was extracted and purified from the seeds of this semi-arid plant. The structural features of this mucilage were evaluated by colorimetric assays, Fourier transformed infrared spectroscopy (FT-IR), gas chromatography coupled to mass spectrometry (GC/MS) and 1H/13C Nuclear Magnetic Resonance (NMR) spectroscopy. PSPN is a heteroxylan with a backbone composed of ß-(1,3)-d-Xylp and ß-(1,4)-d-Xylp highly branched, through (O)-2 and (O)-3 positions of ß-(1,4)-d-Xylp by various side chains and terminal monosaccharides such as α-l-Araf-(1,3)-ß-d-Xylp, ß-d-Xylp-(1,2)-ß-d-Xylp, terminal Xylp or terminal Araf. The physico-chemical and rheological analysis of this polysaccharide in dilute and semi diluted regimes showed that PSPN exhibites a molecular weight of 2.3×106g/mol and a pseudoplastic behavior.

Quantification of Pseudomonas aeruginosa hydrogen cyanide production by a polarographic approach.

Pseudomonas aeruginosa is an opportunistic pathogen responsible for numerous infections acquired in hospital especially in persons whose immune systems are weakened, such as with patient suffering from AIDS or cystic fibrosis. This bacterium produces a great diversity of virulence factors among them hydrogen cyanide (HCN) which is one of the most potent and toxic. A precise quantification of HCN or CN(-) ion is essential to understand the involvement of this toxin in the pathogenesis of P. aeruginosa. In the present study, we present a new technique based on a polarographic approach to measure the production kinetics of HCN/CN(-) by P. aeruginosa strains, in several media commonly used in microbiology labs. The method was validated using mutants (hcnB- and hcnC-) which are unable to produce detectable HCN/CN(-). The kinetics of HCN/CN(-) production by P. aeruginosa in Luria Bertani (LB) medium showed a parabolic shape with a peak observed at 4, 5 and 8h for strains PA14, PAO1 and MPAO1, respectively. When bacteria were grown in ordinary nutrient broth (ONB) 2.5% medium, a less adapted medium for bacterial growth, the general profile of the kinetics was conserved but peak production was delayed (10 and 12h for PAO1 and MPAO1, respectively). When the bacteria were cultured in minimum medium MMC, bacterial growth was particularly slow and HCN/CN(-) production was markedly reduced. Taken together, this new polarographic method appears as a useful technique to detect and quantify HCN/CN(-) in routine media where the bacteria can express and regulate high amounts of toxins. With this method, we demonstrate that HCN/CN(-) production by P. aeruginosa is maximal at the end of the exponential growth phase and depends on the richness of the growth medium used.