Structural and thermal study of mesomorphic dodecylammonium carrageenates

Structural characteristics and thermal stability of a series of dodecylammonium carrageenates formed by stoichiometric complexation of dodecylammonium chloride and differently charged carrageenans (κ-, ι- and λ-carrageenan, respectively) were investigated. IR spectral analysis confirmed the electrostatic and hydrogen bond interactions between the dodecylammonium and carrageenan species. X-ray diffraction experiments show increased ordering in the complexes compared to that in the parent carrageenans. Dodecylammonium carrageenates have a layer structure, in which a polar sublayer contains layers of carrageenan chains and a nonpolar sublayer consists of conformationally disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. The major factor that determines the dodecylammonium carrageenate structure is cationic surfactant, while the carrageenans moiety plays a major role in determining thermal properties.     

Carrageenan for encapsulation and immobilization of flavor,fragrance, probiotics,and enzymes: A review

Carrageenans are sulfated polysaccharides obtained from sea weed. There are six types of carrageenans. They have been explored as gelling agents, control release vehicles, and encapsulating agents. It has been established that carrageenans, in the form of gels, beads and films, can efficiently encapsulate flavors, fragrances, probiotics, and enzymes. Flavors and fragrances are encapsulated to reduce their volatility. Probiotic encapsulation results in enhanced stability. Immobilization of enzymes in carrageenans improves their biocatalytic performance and stability. This review has summarized how carrageenans have been extensively investigated as potential encapsulating agents for the above-mentioned attributes.     

Novel Gelling Systems of κ‐, ι‐ and λ‐Carrageenans and their Composite Gels with Cellulose Using Ionic Liquid

Gels of three types of carrageenans (κ‐, ι‐ and λ‐), as well as their composite gels with cellulose, were prepared using an ionic liquid, 1‐butyl‐3‐methylimidazolium chloride (BMIMCl), by a heating‐cooling process. κ‐Carrageenan gave the formation of hard gel while the other two carrageenans gave the formation of softer gels with BMIMCl. The gels were characterized by X‐ray diffraction (XRD), thermal analysis (TGA and DSC), scanning electron microscope (SEM) and compressive testing. The results indicated that, among the three types of carrageenans, κ‐ and ι‐carrageenans gave better miscible gels with BMIMCl, followed by λ‐carrageenan. On the other hand, λ‐carrageenan gave a better miscible composite gel with cellulose and BMIMCl, followed by ι‐ and κ‐carrageenans. The stress‐strain curves indicated that the mechanical properties of the above gel systems on the compressive mode were much better than those of the hydrogels of κ‐ and ι‐carrageenans as well as the cellulose gel with BMIMCl.

     

Interaction between biopolyelectrolytes and sparingly soluble mineral particles

We investigate the complex physicochemical behavior of dispersions containing calcium carbonate (CaCO(3)) particles, a sparingly soluble mineral salt; and carrageenans, negatively charged biopolyelectrolytes containing sulfate groups. We reveal that the carrageenans suspend and stabilize CaCO(3) particles in neutral systems by absorbing on the particle surface which provides electrosteric stabilization. In addition, carrageenans provide a weak apparent yield stress which keeps the particles suspended for several months. The absorption measurements of carrageenan on the CaCO(3) particle indicate that more carrageenan is removed from the solution than expected from the case of a simple monolayer adsorption. Confocal laser scanning microscopy observations confirm that polyelectrolyte-containing precipitate is formed in both CaCO(3)-carrageenan and CaCl(2)-carrageenan mixtures. On the basis of these results, we confirm that in the presence of carrageenan some CaCO(3) dissolves and the Ca(2+) ions interact with the sulfate groups leading to aggregation and formation of particle-like structures. These new insights are important for fundamental understanding of other mineral-polyelectrolyte systems and have important implications for various industrial applications where calcium carbonate is used.     

Carrageenan Gels in Skim Milk: Formation and Rheological Properties

Phase behavior and mechanical properties of gels of three (kappa-, iota-, and lambda-) carrageenans in skim milk are thoroughly studied. The measurements were performed with the aid of a dynamic rheology in different regimes including determination of frequency dependences of rheological parameters, creep, and critical strain and stress at which the gelled systems are destroyed. Temperature dependences of the rheological parameters were also measured. A set of obtained data allowed to quantitatively characterize the mechanical properties of milk gels and compare the gel-forming properties of various carrageenans. In addition to gels of individual polysaccharides, their mixed gels were studied for the first time. It is shown that kappa-carrageenan formed the most stiff and brittle gels. Its mixing with iota- or lambda-carrageenans made gels softer. This effect is observed when the degree of substitution of kappa-carrageenan was higher than 50% that indicates its prevalent role in the mixed systems. The gelation is explained by the formation of crosslinked structure where the nodes are the casein micelles connected by polysaccharide chains. Their binding occurs due to electrostatic interactions between the sulfo groups of carrageenans and amino groups of kappa-casein. In the case of kappa- or iota-carrageenans, network structure is additionally stabilized due to crosslinking of segments of their molecular chains by the double helices at the gaps between casein micelles.     

Quantitation of κ-, ι- and λ-carrageenans by mid-infrared spectroscopy and PLS regression

Carrageenans are natural products obtained from seaweeds which are used as additives in many industrial fields, mainly in the food industry (labelled as E407). The three most employed ones being the so-called κ-, ι- and λ-carrageenans. So far, their industrial characterisation is based on physical measurements, which exhibit a rather large uncertainty. The aim of this work is to develop a new analytical methodology for the quantitative determination of carrageenans in industrial mixtures employing FTIR and multivariate regression (partial least squares, PLS), avoiding complex sample pre-treatment steps and reducing the turnaround time. The methodology allows to handle liquid (dissolved) carrageenans at room temperature (to prevent degradation), and therefore, their straightforward IR measurement using thin films. The standard prediction errors for the different models selected range from 3.3 to 4.2%, which can be considered as excellent.     

QCM-D研究蛋白质与多糖的相互作用

应用具有耗散因子功能的石英晶体微天平（QCM-D）检测了多糖多层膜的构筑过程以及蛋白质在多层膜上的吸附行为。 研究结果表明,通过层层组装的方法,可以实现多糖卡拉胶多层膜的构筑,并且随着卡拉胶电荷密度的增加,其组装量减少。 研究了牛体血清蛋白(BSA)在卡拉胶上的吸附行为。 结果发现,BSA的吸附行为强烈地依赖于卡拉胶的电荷密度和基体的粗糙度。 通过QCM-D实时监测了BSA在卡拉胶上的动力学吸附曲线,同时根据ΔD值推测了BSA在不同的基底表面上所形成的结构及吸附行为。     

Separation of iota-, kappa and lambda-carrageenans by capillary electrophoresis

The present study reports a novel method for the separation of the high-molecular-weight anionic polysaccharides, iota, kappa, and lambda carrageenans, in capillary electrophoresis (CE). Carrageenan samples are first derivatised with 9-aminopyrene-1,4,6-trisulfonic acid (APTS), separated in an ammonium acetate background electrolyte (BGE) and detected with laser-induced fluorescence (LIF). The effects of changes of instrumental parameters (temperature, injection mode, field strength) and the composition of the BGE (concentration and pH) are reported, and are explained in terms of the physical chemistry of the BGE and the biopolymers. Optimal separation conditions for kappa, iota, and lambda carrageenans, including an APTS internal standard, were found in a polyvinyl alcohol coated capillary with an ammonium acetate BGE of low concentration (25 mM) and moderate pH (8.0). This BGE gave the best reproducibility in tests on iota/kappa mixtures, with relative standard deviations (RSDs) in migration times and normalised peak areas (relative to the APTS internal standard) of less than 0.1% and 1%, respectively. Using this BGE at 50 degrees C and a voltage of 30 kV, all three carrageenan subtypes were separated in a run time of 3 min.     

Direct structural identification of polysaccharides from red algae by FTIR microspectrometry I: Localization of agar inGracilaria verrucosa sections

Unlike carrageenans, agars have not been studied very extensively by infrared spectroscopy, in so far as the structures of this kind of polygalactanes are not as well defined as carrageenans. However, in a previous work we have carried out a vibrational analysis of both carrageenans and agars and some important assignments of the main absorptions have been made. Consequently, the present work has been undertaken in order to identify agars without any extraction directly in various seaweeds using the infrared microspectrometry method. The main advantage of this method is that the sample consists only of a dehydrated algal section. The red algaeGradlaria verrucosa has been the subject of the present study. In the first place, spectra of extracted agars were recorded, as they can help us to confirm the nature of the compound identified by this technique. In a second stage, spectra of different parts of the sections have been carried out. The comparison between the resulting spectra with those of the extracted polysaccharides, has demonstrated, firstly that the best results are obtained from the cortical area, because, as expected, the agar is mainly located in the cell wall of this area of the algae. Indeed, the feature bands of agars are all observed, especially the intense ones between 1000 and 1100 cm^–1 and the more characteristic absorptions in the wavenumbers range below 1000 cm^–1 so as the ones at 988, 965, 930, 890, 870, 771 and 741 cm^–1. Secondly, it may be also identified in smaller amounts in the medullar area, the cells are greater than in the cortical area and the cytoplasm is preponderent. However, in the latter case a coexisting polysaccharide, present in a considerable quantity and called floridean starch (Its structure is not very well known, as it varies from one algae to another), masks the spectra of agar, as its spectrum is very similar to those of polygalactanes.     

Comparative analysis of enzymatically digested kappa-carrageenans, using liquid chromatography on ion-exchange and porous graphitic carbon columns coupled to an evaporative light scattering detector

Enzymatically digested kappa (A-G4S)-carrageenans, apart from their biological activities in plants, could be used as 'model' molecules to elucidate potential problems in nuclear magnetic resonance spectroscopy of carrageenans. Thus, oligosaccharides obtained from kappa-carrageenan by enzymatic digestion using kappa-carrageenase have been separated on silica and polymeric based ion-exchange and porous graphitic carbon (PGC) columns, coupled to an evaporative light scattering detector. Oligomers were separated on ion-exchange columns using a gradient of ammonium acetate as a developing ion, while analysis on PGC column presented an additional adjacent peak next to each main one, using a gradient of ammonium acetate in water/acetonitrile as a mobile phase. The phenomenon can be attributed to different retention mechanisms that govern the PGC surface. Furthermore, it has been demonstrated that acetonitrile can regulate the selectivity between the peaks raising hopes for preparative chromatography.     

Microscopic and Molecular Insights into Heterogeneous Phase Degradation of Agars and Carrageenans by Marine Bacterial Galactanases

Agars and carrageenans are sulfated galactans and are the main matrix component of the cell wall of red algae. They form gels made of a 3D network of fibres built by the aggregation of polysaccharide double-helices. Agarases and carrageenase are enzymes produced by marine bacteria involved in the conversion of algal biomass. We have analyzed the structures and the modes of action of these enzymes adapted to the degradation of anionic polysaccharides in heterogeneous phase. We found that κ- and ι-carrageenases proceed via an endo-processive mode of action as it was already described for other enzymes active on neutral polysaccharides (cellulose, starch).     

Agarose‐ and alginate‐based biopolymers for sample preparation: Excellent green extraction tools for this century

Recently, there has been considerable interest in the use of miniaturized sample preparation techniques before the chromatographic monitoring of the analytes in unknown complex compositions. The use of biopolymer‐based sorbents in solid‐phase microextraction techniques has achieved a good reputation. A great variety of polysaccharides can be extracted from marine plants or microorganisms. Seaweeds are the major sources of polysaccharides such as alginate, agar, agarose, as well as carrageenans. Agarose and alginate (green biopolymers) have been manipulated for different microextraction approaches. The present review is focused on the classification of biopolymer and their applications in multidisciplinary research. Besides, efforts have been made to discuss the state‐of‐the‐art of the new microextraction techniques that utilize commercial biopolymer interfaces such as agarose in liquid‐phase microextraction and solid‐phase microextraction.     

Evaluation of anticoagulant activity of two algal polysaccharides

Marine algae are important sources of phycocolloids like agar, carrageenans and alginates used in industrial applications. Algal polysaccharides have emerged as an important class of bioactive products showing interesting properties. The aim of our study was to evaluate the potential uses as anticoagulant drugs of algal sulphate polysaccharides extracted from Ulva fasciata (Chlorophyta) and Agardhiella subulata (Rhodophyta) collected in Ganzirri Lake (Cape Peloro Lagoon, north-eastern Sicily, Italy). Toxicity of algal extracts through trypan blue test and anticoagulant action measured by activated partial thromboplastin time (APTT), prothrombin time (PT) test has been evaluated. Algal extracts showed to prolong the PT and APTT during the coagulation cascade and to avoid the blood coagulation of samples. Furthermore, the algal extracts lack toxic effects towards cellular metabolism and their productions are relatively at low cost. This permits to consider the algae as the biological source of the future.     

Rheological and DSC study of sol-gel transition in aqueous dispersions of industrially important polymers and colloids

 Gelation kinetics, mechanical spectra, thermal scanning rheology (TSR), and differential scanning calorimetry (DSC) in aqueous solutions of gelling polymers and colloids such as seaweed polysaccharides (agarose, carrageenans), microbial polysaccharides (gellan, curdlan), plant polysaccharides (methylcellulose), globular proteins (casein, glycinin, β-conglycinin), fibrous proteins (gelatin, fibrin), and polyvinyl alcohol, which are related to foods, cosmetics, biomedical and pharmaceutical applications, are described. Some gelation processes at a constant temperature have been treated successfully by an equation of first order kinetics or by other modified equations, and the molecular mechanism of gel formation is discussed briefly. For water-soluble polymers, the criterion of the gel or sol based on the frequency dependence of storage and loss moduli gives valuable informations. TSR and DSC are complementary, and the combination of these methods has been proved to be useful. Received: 17 June 1997 Accepted: 28 August 1997     

Carrageenan–oligochitosan microcapsules: optimization of the formation process

The formation of new microcapsules based on polyelectrolyte complexes between carrageenans and oligochitosan has been investigated. The optimization of the process, which includes the selection of the most suitable solvent and investigation of the influence of reaction conditions on capsule properties, is presented. Iota-carrageenan (1.2–2% wt.) prepared in HEPES buffer was found to be the most suitable for the formation of mechanically stable capsules. These new capsules combine extremely high deformability (>90%) and elasticity with permeability control and can be applied in various bioencapsulation technologies. It has been shown that the reaction time influences the mechanical properties, whereas carrageenan concentration and the temperature during the capsule formation effect both mechanical and porosity characteristic of the membrane. Moreover, the temperature influences the kinetics of the diffusion through the complex iota-carrageenan/oligochitosan membrane. In general egress is faster above the sol–gel transition point, indicating applicability in thermo-induced releasing systems.     

Carrageenan-oligochitosan microcapsules: optimization of the formation process(1)

The formation of new microcapsules based on polyelectrolyte complexes between carrageenans and oligochitosan has been investigated. The optimization of the process, which includes the selection of the most suitable solvent and investigation of the influence of reaction conditions on capsule properties, is presented. Iota-carrageenan (1.2-2% wt.) prepared in HEPES buffer was found to be the most suitable for the formation of mechanically stable capsules. These new capsules combine extremely high deformability (>90%) and elasticity with permeability control and can be applied in various bioencapsulation technologies. It has been shown that the reaction time influences the mechanical properties, whereas carrageenan concentration and the temperature during the capsule formation effect both mechanical and porosity characteristic of the membrane. Moreover, the temperature influences the kinetics of the diffusion through the complex iota-carrageenan/oligochitosan membrane. In general egress is faster above the sol-gel transition point, indicating applicability in thermo-induced releasing systems.     

Polysaccharides of algae 69. Monosaccharide composition of polysaccharides of several Pacific red algae studied by reductive hydrolysis of biomass

Polysaccharide composition of 23 species of red algae collected from the coastal waters of Kamchatka and Commander Islands has been determined. Total acid hydrolysis of biomass was carried out in the presence of borane-4-methylmorpholine complex under the conditions where 3,6-anhydrogalactose liberating from sulfated galactans was protected from the acid degradation due to reduction into 3,6-anhydrogalactitol. Partial hydrolysis of biomass in the presence of the same reducing agent gave rise to diastereomeric agarobiitol or carrabiitol (3,6-anhydro-4-O-β-d-galactopyranosyl-l-or -d-galactitol, respectively). Identification of these fragments made it possible to attribute the algal galactans to agars or carrageenans. The data obtained was used to confirm the correlations between the taxonomic status and polysac-charide composition of the red algae.

     

Matrix-assisted laser desorption/ionization mass spectrometric analysis of polysulfated-derived oligosaccharides using pyrenemethylguanidine

A better understanding of the biological roles of carbohydrates requires the use of tools able to provide efficient and rapid structural information. Unfortunately, highly acidic oligomers-such as polysulfated oligosaccharides-are very challenging to characterize because of their high polarity, structural diversity, and sulfate lability. These features pose special problems for matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) analysis because polysulfated carbohydrates exhibit poor ionization efficiency and usually do not produce any signal. The present report demonstrates how MALDI-MS can be used to derive structural and compositional information from pure and mixed fractions of polysulfated oligosaccharides. Indeed, pyrenemethylguanidine (pmg, a derivatizing agent and ionization efficiency enhancer) was used for the analysis of di- to decasaccharides, carrying from two to nine sulfate groups. The method is applied to various highly sulfated chondroitin and carrageenan oligosaccharides as well as to the analysis of mixtures of compounds. In the mass spectra, the observation of a unique pmg-complexed ladder of peaks in both ionization modes allows an easy and rapid determination of both the number of sulfate groups carried by the analyte and its molecular weight. Moreover, we have developed a software tool for the rapid and automatic structural elucidation of carrageenans based on the mass spectra obtained.     

Sol-gel-derived biomaterials of silica and carrageenans

A new precursor, tetrakis(2-hydroxyethyl) orthosilicate (THEOS), introduced by Hoffmann et al. (J. Phys. Chem. B 106 (2002) 1528-1533), was used to synthesize monolithic hybrid biomaterials on the basis of silica and three main types of carrageenans, kappa-, iota-, and lambda-carrageenans. The advantage of THEOS over the currently applied TEOS and TMOS is in its complete solubility in water. This negated the need to add organic solvents, thus excluding a denaturating effect on biopolymers. In their turn, carrageenans introduced into the precursor solution made use of common catalysts unneeded to trigger the sol-gel transition. It was found that they promoted the mineralization, acting as a template for the inorganic component. The kinetics of sol-gel processes, mechanical properties, phase behavior, and structure of novel hybrid biomaterials were studied by dynamic rheology, differential scanning calorimetry, and scanning electron microscopy. The material properties were regulated by both the precursor and carrageenan. The increase of silicate concentration led to a rise in the stiffness and brittleness of the material, whereas the polysaccharide addition made it softer and more elastic. It was shown that the formation and properties of mixed gels were determined by the nature of carrageenan. kappa-Carrageenans brought about shrinkage of hybrid materials that led to water separation, while iota- and lambda-carrageenans did not induce the syneresis. This is in line with the difference in polysaccharide properties when they are in aqueous solutions without silicate. Furthermore, kappa- and iota-carrageenans experienced a thermoreversible phase transition in the hybrid materials owing to the helix-coil transition. This resulted in a step like change in the mechanical properties of mixed systems in the corresponding temperature range. lambda-Carrageenan is a nongelling polysaccharide, which is why the rheological parameters of its hybrid gel were unchanged with the temperature. It was found that the polysaccharides modified the structure of silica-based materials. They transformed a three-dimensional network of connected silica particles into that consisting of crossed fibers.     

Polysaccharides of algae 67. Carrageenan from Pacific red alga Turnerella mertensiana (Gigartinales,Rhodophyta)

A sulfated galactan composed of nearly equimolar amounts of d-galactose, 3,6-anhydro-d-galactose, and sulfate was isolated from the red alga Turnerella mertensiana collected in the Sea of Japan. The structures of native polysaccharide and its alkaline modification products were studied by NMR spectroscopy. The polysaccharide molecules were shown to contain a linear carbohydrate chain consisting of alternating 3-linked β-d-galactopyranose 4-sulfate and 4-linked 3,6-anhydro-α-d-galactopyranose residues (known as к-carrageenan), which is typical of carrageenans, but the regularity of polymer structure is masked by the presence of some 3,6-anhydro-α-d-galactose 2-sulfate (ι-carrageenan units) and α-D-galactose 6-sulfate (µ-carrageenan units) instead of 3,6-anhydro-α-d-galactose. Upon addition of potassium chloride (up to 4%) to a solution of the native polysaccharide, about half of the substance transforms into gel. The gel-forming fraction is к-ι-µ-hybrid carrageenan with the ～65 : 15 : 20 ratio of к-, ι-, and µ-units. The non-gelling fraction contains the к-, ι-, and µ-units at the ratio of ～46 : 12 : 42. The gel-forming carrageenan product free of µ-units can be otained in ～30% yield (based on the dry biomass) by alkaline treatment of the alga prior to extraction of the polysaccharide.