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

The importance of acetate, pyruvate, and citrate feeding times in improving xanthan production by Xanthomonas citri

Xanthan gum is a microbial polysaccharide produced by Xanthomonas and widely used in various industries. To produce xanthan gum, the native Xanthomonas citri-386 was used in a cheese-whey-based culture medium. The culture conditions were investigated in batch experiments based on the response surface methodology to increase xanthan production and viscosity. Three independent variables in this study included feeding times of acetate, pyruvate, and citrate. The maximum xanthan gum production and viscosity within 120 h by X. citri-386 using Box-Behnken design were 25.7 g/l and 65 500 cP, respectively, with a 151% and 394% increase as compared to the control sample. Overall, the findings of this study recommend the use of X. citri-386 in the cheese-whey-based medium as an economical medium with optimal amounts of acetate, pyruvate, and citrate for commercial production of xanthan gum on an industrial scale. The adjustment of the pyruvate and acetate concentrations optimized xanthan gum production in the environment.

Rational modification of xanthan gum based on assistance of molecular dynamics simulation

Graft copolymerization is an effective approach to improve performance of polysaccharide. However, selecting the most suitable modification strategy can be challenging due to the intricate molecular structure. Rational design through computer aided molecular dynamics (MD) simulations requires substantial computational resources. This study designed a simplified MD simulation strategy and suggested that grafting acrylamide (AM) could effectively adjust the molecular conformation of xanthan gum (XG) and its derivatives, thus regulating its viscosity and gelation properties. To rationally modify XG, a uniform experimental design was applied to tune the grafting ratios ranging from 72 % to 360 %, resulting in XG-AM solutions with viscosity ranging from 9 to 104 mPa•s at a concentration of 0.3 %. XG-AM was crosslinked by acid phenolic resin to generate gel with the viscosity of 7890 mPa·s in 3 days, which was 13 times the viscosity of unmodified XG. The controllable gelation will enhance the efficacy of XG-AM in oil recovery. By integrating rational selection of grafting strategies based on simplified MD simulation of polysaccharide derivatives and controllable grafting modification with specified grafting rates, customized production of polysaccharide derivatives can meet the requirements of a diverse range of applications.

A review of the enzymatic, physical, and chemical modification techniques of xanthan gum

Xanthan gum (XG), a bacterial polysaccharide has numerous valuable characteristics in the food, biomedical, pharmaceuticals, and agriculture sector. However, XG has also its particular limitations such as its vulnerability to microbial contamination, inadequate mechanical and thermal stability, unusable viscosity, and poor water solubility. Therefore, XG's structure and conformation need to be modified enzymatically, chemically, or physically to improve its optimistic features and decrease the formation of crystals, increase antioxidant ability, and radical scavenging activity. We have found out different means to modify XG and elaborate the importance and significance of the modified structure of XG. In this review, different enzymes are reviewed for XG degradation, which modifies their structure from different points (main chain or side chain). This article also reviews various physical methods (ultrasound, shear, pressure, sonication, annealing, and heat treatments) based on prevailing publications to alter XG conformation and produce low molecular weight (LMW) and less viscous end-product. Moreover, some chemical means are also discussed that result in modified XG through crosslinking, grafting, acetylation, pyruvation, as well as by applying different chemical agents. Overall, the current progress on XG degradation is very auspicious to develop a new molecule with considerable uses, in various industries with future assessments.

The Use of Xanthan Gum as Vaccine Adjuvant: An Evaluation of Immunostimulatory Potential in BALB/c Mice and Cytotoxicity In Vitro

The successful production of new, safe, and effective vaccines that generate immunological memory is directly related to adjuvant feature, which is responsible for increasing and/or modulating the immune response. Several compounds display adjuvant activity, including carbohydrates. These compounds play important roles in the immune response, as well as having biocompatible properties in vaccine formulations. One such carbohydrate is xanthan gum, a polysaccharide that is produced by the plant-pathogenic bacterium Xanthomonas spp., which has adjuvant attributes. This study evaluated the immune response induced by xanthan gum associated with ovalbumin in BALB/c mice, which were subcutaneously immunized, in terms of antibody production (IgG1, IgG2a, IgG2b, and IgG3), and assessed the levels of IFN-γ in the splenocyte culture using indirect ELISA. Furthermore, we investigated in vitro cytotoxicity of xanthan in the embryo fibroblasts cell line of the NIH/3T3 mouse by MTT assay and propidium iodide uptake assay. The mice immunized with ovalbumin plus xanthan gum exhibited higher antibody IgG1 responses than control groups. Furthermore, the xanthan polysaccharide was capable of increasing the immunogenicity of antigens by producing IFN-γ and did not exhibit cytotoxicity effects in NIH/3T3 mouse fibroblast cells, considered a promising candidate for vaccine adjuvant.

Characterization of high yield exopolysaccharide produced by Phyllobacterium sp. 921F exhibiting moisture preserving properties

A new strain bacteria was isolated and named as Phyllobacterium sp. 921F, due to its high production capacity of exopolysaccharide (EPS). Characterization of physico-chemical properties of the EPS and optimization for high production were conducted to aim at industrial applications. The optimum pH and temperature were 7.0 and 30°C, respectively. The following scale-up fermentation was carried out in 30L bioreactor and amounts of EPS (21.9g/L) were produced. The EPS with a molecular mass of 1082kDa was composed of glucose, galactose, and pyruvate. The EPS solution behaved as Newtonian at low concentrations (≤0.3%) and as shear thinning at higher concentration (e.g, 1%). The moisture retention ability of the EPS was found to be superior to hyaluronic acid. Results suggest that Phyllobacterium sp. 921F is a good candidate for large-scale production of the EPS which might be utilized in food and cosmetics industries.

Preparation of biodegradable xanthan-glycerol hydrogel, foam, film, aerogel and xerogel at room temperature

Polymers, hence hydrogels, pollute waters and soils accelerating environmental degradation. Environmentally benign hydrogels were made in water from biodegradable xanthan (X) and glycerol (G) at 22.5±2.5°C. Molar ratio [G]/[X]<3.0 was used to maximize crosslinking by mono-glycerol instead by poly-glycerol. XG-hydrogels were transformed into: XG-foams, XG-films, and XG-aerogel. Anionic character of XG-materials changes with changing [G]/[X] ratio. XG-films made from XG-hydrogels absorb up to 40 times more water than XG-films made from XG-foams. The films made from XG-foams and HCl do not dissolve in water during 48h. Making XG-materials is a no-waste process which decreases pollution, eliminates waste disposal costs, and minimizes energy expenses. XG-materials are suitable for both industrial and environmental applications including slow release and concentration of cations. XG-materials, made of xanthan, microbial polysaccharide, could also be used in applications targeting populations that do not consume meat or meat based products.

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.

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 (s(o)(20,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.