Extraction and Characterization of Alginate from an Edible Brown Seaweed (Cystoseira barbata) Harvested in the Romanian Black Sea.

Cystoseira barbata is an edible brown seaweed, traditionally used in the Black Sea area as functional food. Both alginate and brown seaweed biomass are well known for their potential use as adsorbents for heavy metals. Alginate was extracted from C. barbata recovered from the Romanian coast on the Black Sea with a yield of 19 ± 1.5% (w/w). The structural data for the polysaccharide was obtained by HPSEC-MALS, 1H-NMR. The M/G ratio was determined to be 0.64 with a molecular weight of 126.6 kDa with an intrinsic viscosity of 406.2 mL/g. Alginate beads were used and their adsorption capacity with respect to Pb2+ and Cu2+ ions was determined. The adsorption kinetics of C. barbata dry biomass was evaluated and it was shown to have an adsorption capacity of 279.2 ± 7.5 mg/g with respect to Pb2+, and 69.3 ± 2 with respect to Cu2+. Alginate in the form of beads adsorbs a maximum of 454 ± 4.7 mg/g of Pb2+ ions and 107.3 ± 1.7 mg/g of Cu2+ ions.

Polyethyleneimine as a tool for compounds fractionation by flocculation in a microalgae biorefinery context.

In the context of emerging biorefinery for microalgae, polyethyleneimine (PEI), has been tested in order to achieve separation of fat-soluble and water-soluble compounds from Haematococcus pluvialis. Several parameters were taken into account (ratio between sample and PEI, pH, and ionic strength) and 2 conditions (0.075% PEI pH 7.4, and 0.100% PEI pH8.5) were studied for up-scalability, with a recovery of flocculated compounds (lipids and pigments), and a complete characterization of both phases. Using 0.075% PEI, pH7.4, 100% sugars and 89.8% proteins were retained in the supernatant, but some trace of beta-carotene were also detected. For 0.100% PEI, pH 8.5, a loss in proteins content was highlighted (61.2% proteins retained), but no residual lipids or pigments were detected. PEI could therefore be considered as an efficient method to fractionate fat-soluble and water-soluble compounds from microalgae.

Rheological and functional properties of asafoetida gum.

The asafoetida gum was extracted and purified from oleo-gum-resin of Ferula assa foetida root and characterized by high pressure anions exchange chromatography after acidic hydrolysis. It was composed of Gal:Ara:Rha:GlcA with the ratio 11.5:5.0:2.1:1.0. This monosaccharide composition was found similar to that of a commercial Arabic gum which exhibited a Gal:Ara:Rha:GlcA ratio of 11.7:5.4:3.2:1.0. As the Arabic gum is currently used for its emulsifying properties, the two gums were evaluated for their functional and rheological behaviors. Surface and interfacial tensions values were lower for asafoetida gum compared to Arabic gum. Critical micelle concentration was achieved at concentrations of 0.5% w/w and 1% w/w for asafoetida and Arabic gums, respectively. Values of emulsion capacity, emulsion stability and foaming properties were considerably higher for asafoetida gum in contrast to emulsion activity index that was lower than that of Arabic gum. As those of Arabic gum, solutions of asafoetida gum (2-30% w/w) exhibited Newtonian flow behavior at shear rates between 1 and 500 s-1. Apparent viscosities of Arabic and asafoetida gums were close and logically decreased by increasing temperature (10-80 °C). Higher viscosities were achieved at higher pH and CaCl2 concentrations.

Structural characterization and thermal behavior of a gum extracted from Ferula assa foetida L.

The gum asafoetida, an oleo-gum-resin from root of Ferula assa foetida, was extracted through alcoholic procedure followed by water extraction and then biochemically characterized using colorimetric assays, Fourier infrared spectroscopy, gas chromatography coupled to mass spectrometry, and 1D and 2D nuclear magnetic resonance. The gum was mainly composed of carbohydrates (67.39% w/w) with a monosaccharide distribution of 11.5: 5.9: 2.3: 1 between Gal, Ara, Rha and GlcA (molar ratio) and proteins (arabinogalactan protein). The polysaccharide consisted of a (1→3)-ß-d-galactan backbone ramified predominantly from O-6 but also from O-4 and O-4,6. Side chains included terminal-α-l-Araf, terminal-α-l-Rhap, (1→3)-α-l-Araf, (1→5)-α-l-Araf, terminal-ß-d-Galp, ß-d-GlcA and traces of (1→4)-ß-d-GlcA. X-ray diffraction pattern showed a semi crystalline microstructure. Thermal behavior of the gum was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed temperatures below and upper 200°C as dominant regions of weight loss.

Extraction and characterization of an alginate from the Iranian brown seaweed Nizimuddinia zanardini.

Sodium alginate from Nizimuddinia zanardini (an Iranian brown algae) was extracted with acid and alkaline solutions, partially and totally hydrolyzed and analyzed for its biochemical composition. 1H NMR spectroscopy, SEC-MALLS, HPAEC and FT-IR were performed to determine its structure and its physico-chemical properties. This alginate has a M/G ratio of 1.1, a molecular weight of 103 kDa, a polydispersity index of 1.22, and an intrinsic viscosity of 342 mL/g. Its antioxidant activity was tested by DPPH radical scavenging showing its potential for food preservation. Rheological properties of solutions of this alginate with concentrations between 1 and 5% (w/v) in water and 0.5 M NaCl were investigated indicating a Newtonian fluid type behaviour in water and a shear thinning fluid type behaviour in NaCl solutions.

Haematococcus pluvialis soluble proteins: Extraction, characterization, concentration/fractionation and emulsifying properties.

A water-soluble matrix was extracted from green vegetative Haematococcus pluvialis through high-pressure cell disruption either at native pH (5.7) or with pH shifting to neutral (7). The resulting supernatant is mainly composed of carbohydrates and proteins, with the highest yield of proteins obtained at neutral pH (73±2% of total biomass proteins). The key emulsification properties of the proteins isolated in neutral supernatant (emulsification capacity (EC): 534±41mLoilg(-1) protein, emulsification stability (ES): 94±3% and emulsification activity index (EAI): 80±1m(2)g(-1)) were comparable to the native supernatant values (EC: 589±21mLoilg(-1) protein, ES: 84±3% and EAI: 75±1m(2)g(-1)). Confronted to sodium caseinate (EC: 664±30mLoilg(-1) protein, ES: 63±4%, and EAI: 56±4m(2)g(-1)) these results highlighted the strong potential of proteins isolated from H. pluvialis as emulsifier agent. Moreover, experiments have shown that the stability of emulsions obtained from supernatants is due to the proteins rather than the carbohydrates.

Extraction, fractionation and functional properties of proteins from the microalgae Chlorella vulgaris.

This paper deals with the extraction and emulsifying properties of proteins from Chlorella vulgaris. Solubilisation of proteins has been achieved using high pressure cell disrupter under pH=7 or pH=12. The higher solubilisation yield (52±3%w/w) was obtained using a combination of alkaline conditions and mechanical treatments (2.7kbar). After solubilisation, proteins were recovered by two procedures: precipitation in acid media and concentration/fractionation by tangential ultrafiltration. Proteins were analysed for their molecular weights, isoelectric points and amino acids compositions and their emulsifying properties were quantified and compared to those of commercial ingredients. In spite of lower yield, better emulsifying capacity was obtained when protein solubilisation takes place at pH=7 and when using proteins from permeate of tangential ultrafiltration. In all cases, emulsifying capacity (1780±20 and 3090±50mLoil/g protein) and stability (72±1% and 79±1%) of microalgae proteins remained comparable or higher than the commercial ingredients such as sodium caseinate.

Separation and fractionation of exopolysaccharides from Porphyridium cruentum.

In this work the extraction of EPSs from culture media of Porphyridium cruentum, by dialysis, solvent-precipitation with 3 polar alcohols (methanol, ethanol and isopropanol) and membrane separation techniques has been studied. Diafiltration (DF) using a membrane with a 300 kDa molecular weight cut off was the most efficient technique compared to solvent-extraction and dialysis methods. After extraction, EPS fraction was characterized in terms of rheological properties and biochemical content. The product exhibited shear thinning behavior and a critical overlap concentration equal to 0.6 g/L. The monosaccharide composition was investigated after acidic hydrolysis. Xylose, galactose, glucose and glucuronic acid were identified as the main constitutive monomers.