A hydrodynamic study of microbial polysaccharides considered for use in food and health products

Microbial polysaccharides are widely used in many industrial and therapeutic applications as bioactive compounds, drug release and encapsulation materials for pharmaceuticals, and as natural ingredients or additives in food applications. To increase the utilisation or to improve for the food and healthcare applications of these polysaccharides, it is critical to have the detailed knowledge of macromolecular properties and interactions with other polymers. In this study, to properly understand the relationship between physical properties and functionality, the microbial polysaccharides-namely xanthan, gellan, microbial hyaluronic acid (HA) and schizophyllan, which have widely been used for many food and medical applications, were investigated. Taking advantage of recent advances in hydrodynamic techniques, including analytical ultracentrifugation (AUC) based on sedimentation velocity and equilibrium, size exclusion chromatography coupled to multi angle light scattering (SEC-MALS) and viscometry, the solution properties of these polysaccharides were studied. Since conformation analyses are important for macromolecular structure function relationships, the conformation of these microbial polysaccharides were examined using the accomplished method-Multi-HYDFIT. For schizophyllan and gellan, the samples were depolymerised using heat treatment to estimate the conformation. The results indicated that, the three microbial polysaccharides (xanthan, gellan, schizophyllan) adapted the rigid rod conformation whereas another polysaccharide-microbial HA adapted semi-flexible coil structure. Then, the possible interactions of these polysaccharides were investigated with chitosan of different degrees of acetylation using the principle of co-sedimentation in AUC. Xanthan-chitosan mixture presented strong evidence by proving a clear interaction on the basis of changes in the distribution of sedimentation coefficients in the solution form of mixture whereas the mixture of chitosan schizophyllan and chitosan-HA did not show or prove any clear interactions at studied concentrations and solution conditions

Recent advances in the analysis of macromolecular interactions using the matrix-free method of sedimentation in the analytical ultracentrifuge

Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or “hetero”-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10−12 M to 10−1 M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions

A hydrodynamic study of microbial polysaccharides considered for use in food and health products

Microbial polysaccharides are widely used in many industrial and therapeutic applications as bioactive compounds, drug release and encapsulation materials for pharmaceuticals, and as natural ingredients or additives in food applications. To increase the utilisation or to improve for the food and healthcare applications of these polysaccharides, it is critical to have the detailed knowledge of macromolecular properties and interactions with other polymers. In this study, to properly understand the relationship between physical properties and functionality, the microbial polysaccharides-namely xanthan, gellan, microbial hyaluronic acid (HA) and schizophyllan, which have widely been used for many food and medical applications, were investigated. Taking advantage of recent advances in hydrodynamic techniques, including analytical ultracentrifugation (AUC) based on sedimentation velocity and equilibrium, size exclusion chromatography coupled to multi angle light scattering (SEC-MALS) and viscometry, the solution properties of these polysaccharides were studied. Since conformation analyses are important for macromolecular structure function relationships, the conformation of these microbial polysaccharides were examined using the accomplished method-Multi-HYDFIT. For schizophyllan and gellan, the samples were depolymerised using heat treatment to estimate the conformation. The results indicated that, the three microbial polysaccharides (xanthan, gellan, schizophyllan) adapted the rigid rod conformation whereas another polysaccharide-microbial HA adapted semi-flexible coil structure. Then, the possible interactions of these polysaccharides were investigated with chitosan of different degrees of acetylation using the principle of co-sedimentation in AUC. Xanthan-chitosan mixture presented strong evidence by proving a clear interaction on the basis of changes in the distribution of sedimentation coefficients in the solution form of mixture whereas the mixture of chitosan schizophyllan and chitosan-HA did not show or prove any clear interactions at studied concentrations and solution conditions

Comparative heterogeneity, molecular weights and viscosities of xanthans of different pyruvate and acetate content

Introduction: The bacterial exopolysaccharide xanthan is a well-known hydrocolloid, with a high viscosity deriving from its large molecular weight and volume. Materials and methods: Four different xanthans deriving from Xanthomanas campestris -two with similar pyruvate and acetate contents and two with different contents e were characterized in dilute aqueous buffered solution (pH 7.0, ionic strength 0.3 M) using sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge, supplemented by dynamic light scattering. Results: This facilitated a comparison with regards heterogeneity (sedimentation coefficient distribution) and molecular weight, despite their large size and low critical overlap concentration. The xanthans were also compared with regard to reduced specific and intrinsic viscosity behaviour. The xanthans generally show strong similarity in properties with the exception of the lowest pyruvate xanthan, a finding which should be useful for future applications of these materials

Comparison of the probiotic characteristics of Lactic Acid Bacteria (LAB) isolated from sourdough and infant feces

Probiotics are beneficial microorganisms with certain characteristics such as survival under gastrointestinal conditions, adhesion to intestinal surface and different functions which result in several health benefits to host. With this regards, this study aimed to isolate Lactic Acid Bacteria (LAB) from sourdough and human feces as two different environments and to test their potential probiotic functions. In total nine distinct isolates were assessed with several probiotic functions such as in vitro adhesion to human colon cells, antimicrobial activities and survival under harsh gastrointestinal conditions. In general, distinct strains showed strong antimicrobial activity against the pathogenic and fungal strains tested in this study. Importantly, the adhesion levels to HT29 cells were determined between 0.29 % and 9.54% and Lactobacillus paracasei F7B showed the highest adhesion. All isolates tolerated the bile salt after 24 h and the infant feces isolates showed good survival characteristics at pH 4

Isolation and Biophysical Characterisation of Bioactive Polysaccharides from Cucurbita Moschata (Butternut Squash)

Cucurbits are plants that have been used frequently as functional foods. This study includes the extraction, isolation, and characterisation of the mesocarp polysaccharide of Cucurbita moschata. The polysaccharide component was purified by gel filtration into three fractions (NJBTF1, NJBTF2, and NJBTF3) of different molecular weights. Characterisation includes the hydrodynamic properties, identification of monosaccharide composition, and bioactivity. Sedimentation velocity also indicated the presence of small amounts of additional discrete higher molecular weight components even after fractionation. Sedimentation equilibrium revealed respective weight average molecular weights of 90, 31, and 19 kDa, with the higher fractions (NJBTF1 and NJBTF2) indicating a tendency to self-associate. Based on the limited amount of data (combinations of 3 sets of viscosity and sedimentation data corresponding to the 3 fractions), HYDFIT indicates an extended, semi-flexible coil conformation. Of all the fractions obtained, NJBTF1 showed the highest bioactivity. All fractions contained galacturonic acid and variable amounts of neutral sugars. To probe further, the extent of glycosidic linkages in NJBTF1 was estimated using gas chromatography–mass spectrometry (GCMS), yielding a high galacturonic acid content (for pectin polysaccharide) and the presence of fructans—the first evidence of fructans (levan) in the mesocarp. Our understanding of the size and structural flexibility together with the high bioactivity suggests that the polysaccharide obtained from C. moschata has the potential to be developed into a therapeutic agent

Hydrodynamic characterisation of chitosan and its interaction with two polyanions: DNA and xanthan

Chitosan, a soluble polycationic derivative of insoluble chitin, has been widely considered for use in the food, cosmetic and pharmaceutical industries. Commercial (“C”) and in-house laboratory (“L”) prepared chitosan samples extracted from crustaceous shells with different molecular weight and degrees of acetylation (25% and 15%) were compared with regards to (i) weight–average molecular weight (Mw); (ii) sedimentation coefficient (so20,w) distribution, and (iii) intrinsic viscosity ([η]). These parameters were estimated using a combination of analytical ultracentrifugation (AUC), size exclusion chromatography coupled to multi-angle laser light scattering (SEC–MALS) and differential pressure viscometry. Polydisperse distributions were seen from sedimentation coefficient distributions and elution profiles from SEC–MALS. Mw values obtained for each sample by sedimentation equilibrium measurements were in excellent agreement with those obtained from SEC–MALS. Mark–Houwink–Kuhn–Sakurada (MHKS) and Wales van Holde analyses of the data all suggest a semi-flexible conformation. The principle of co-sedimentation was then used to monitor the interactions of the two different molecular weights of L chitosans with two polyanions, DNA and xanthan (another double helical high molecular weight molecule). Interactions were clearly observed and then quantified from the changes in the sedimentation coefficient distribution of the mixture compared to unmixed controls using sedimentation velocity. The interactions appeared to show a strong dependence on molecular weight. The relevance of this for DNA condensation applications is indicated

Disappearance of Biodiversity and Future of Our Foods

“I. Uluslararası Organik Tarım ve Biyoçeşitlilik Sempozyumu 27-29 Eylül Bayburt