Modification of Xanthan Gum for a High-Temperature and High-Salinity Reservoir.
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ABSTRACT:
SUBMITTER: Said M
PROVIDER: S-EPMC8659541 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Xanthan gum (XG) is a carbohydrate polymer with anionic properties that is widely used as a rheology modifier in various applications, including foods and petroleum extraction. The aim was to investigate the effect of Na+, K+, and Ca2+ on the physicochemical properties of XG in an aqueous solution as a function of temperature. Huggins, Kraemer, and Rao models were applied to determine intrinsic viscosity, [η], by fitting the relative viscosity (ηrel) or specific viscosity (ηsp) of XG/water and XG/salt/water solutions. With increasing temperature in water, Rao 1 gave [η] the closest to the Huggins and Kraemer values. In water, [η] was more sensitive to temperature increase (~30% increase in [η], 20-50 °C) compared to salt solutions (~15-25% increase). At a constant temperature, salt counterions screened the XG side-chain-charged groups and decreased [η] by up to 60% over 0.05-100 mM salt. Overall, Ca2+ was much more effective than the monovalent cations in screening charge. As the salt valency and concentration increased, the XG coil radius decreased, making evident the effect of shielding the intramolecular and intermolecular XG anionic charge. The reduction in repulsive forces caused XG structural contraction. Further, higher temperatures led to chain expansion that facilitated increased intermolecular interactions, which worked against the salt effect.
| S-EPMC10778890 | biostudies-literature
Project description:The dynamical properties of nanogels of xanthan gum (XG) with hydrodynamic radius controlled in a size range from 5 nm to 35 nm, were studied at the different XG concentrations in water/sodium bis-2-ethylhexyl-sulfosuccinate (AOT)/decane reverse micelles (RMs) vs. mass fraction of nano-droplet (MFD) at W = 40, using dynamic light scattering (DLS). The diffusion study of nanometer-sized droplets by DLS technique indicated that enhancing concentration of the XG polysaccharide resulted in exchanging the attractive interaction between nano-gels to repulsive interaction, as the mass fraction of nano-droplets increased. The reorientation time (?r ) of water nanodroplets decreased with MFD for water-in-oil AOT micro-emulsion comprising high concentration (0.0000625) of XG. On the other hand, decreasing concentration of biopolymer led to increasing the rotational correlation time of water nanodroplets with MFD. In conclusion, a single relaxation curve was observed for AOT inverse microemulsions containing different XG concentrations. Furthermore, the interaction between nanogels was changed from attractive to repulsive versus concentration of XG in the AOT RMs.
| S-EPMC4950164 | biostudies-literature
Project description:The present study examined the effect of polysaccharides gels made of xanthan gum and locust bean gum (gel culture system) on oocyte maturation and explored the molecules causing the beneficial effect of the gel culture system. Oocytes and cumulus cells complexes were collected from slaughterhouse-derived ovaries and cultured on a plastic plate or gel. The gel culture system improved the rate of development to the blastocyst stage. The oocytes that matured on the gel contained high lipid contents and F-actin formation, and the resultant 8-cell stage embryos had low DNA methylation levels compared to their plate counterparts. RNA sequencing of the oocytes and embryos revealed the differentially expressed genes between the gel and plate culture systems, and upstream regulator analysis revealed estradiol and TGFB1 as top activated upstream molecules. The medium of the gel culture system contained higher concentrations of estradiol and TGFB1 than that of the plate cultures system. Supplementation of the maturation medium with either estradiol or TGFB1 resulted in high lipid content in oocytes. In addition, TGFB1 improved the developmental ability of the oocytes and increased F-actin content while reducing DNA methylation levels in the 8-cell stage embryos. In conclusion, the gel culture system is useful for embryo production, potentially through the upregulation of TGFB1.
| S-EPMC9963600 | biostudies-literature
Project description:Foams are increasingly popular in the field of dermatology due to their many advantages such as easy spreading, good skin sensation, and applicability in special skin conditions. One of the critical points of foam formulation is the choice of the appropriate stabilizing ingredients. One of the stability-increasing strategies is retarding the liquid drainage of liquid films from the foam structure. Therefore, our aim was the application of different hydrogel-forming polymers in order to retain the stabilizing liquid film. Dexpanthenol and niacinamide-containing foams were formulated, where xanthan gum and hyaluronic acid were used as foam-stabilizing polymers. Amplitude (LVE range) and frequency sweep (G', G", tanδ, and frequency dependency) were applied as structure- and stability-indicating rheological parameters. The rheological data were compared with the results of the cylinder method, microscopical images, and the spreadability measurements. The application of the gel-forming polymers increased the stability of the dermal foams (increased LVE range, G' values, and decreased frequency dependency). These results were in correlation with the results of the cylinder and spreadability tests. It was concluded that in terms of both foam formation and stability, the combination of xanthan gum and dexpanthenol can be ideal.
| S-EPMC9321585 | biostudies-literature
Project description:The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of xanthan gum (E 415) as food additive. Following the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010, the Panel considered that adequate exposure and toxicity data were available. Based on the reported use levels, a refined exposure of up to 64 mg/kg bw per day in children for the general population, 38 mg/kg bw per day for children consumers only of food supplements at the high level exposure and 115 mg/kg bw per day for infants consuming foods for special medical purposes and special formulae (FSMPs), were estimated. Xanthan gum (E 415) is unlikely to be absorbed intact and is expected to be fermented by intestinal microbiota. No adverse effects were reported at the highest doses tested in chronic and carcinogenicity studies and there is no concern with respect to the genotoxicity. Repeated oral intake by adults of xanthan gum up to 214 mg/kg bw per day for ten days was well tolerated, but some individuals experienced abdominal discomfort, an undesirable but not adverse effect. The Panel concluded that there is no need for a numerical ADI for xanthan gum (E 415), and that there is no safety concern for the general population at the refined exposure assessment of xanthan gum (E 415) as food additive. Considering the outcome of clinical studies and post-marketing surveillance, the Panel concluded that there is no safety concern from the use of xanthan gum (E 415) in FSMPs for infants and young children at concentrations reported by the food industry. The current re-evaluation of xanthan gum (E 415) as a food additive is not considered to be applicable for infants under the age of 12 weeks.
| S-EPMC7009887 | biostudies-literature
Project description:In this work, the rheological behavior of stable poly(lactic acid) (PLA) dispersions in water, intended for coating applications, was investigated. The newly prepared dispersion consists of PLA particles with an average diameter of 222 ± 2 nm based on dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses, at concentrations varying in the 5-22 wt % range. Xanthan gum (XG), a bacterial polysaccharide, was used as a thickening agent to modulate the viscosity of the formulations. The rheological properties of the PLA dispersions with different XG and PLA contents were studied in steady shear, amplitude sweep, and frequency sweep experiments. Under steady shear conditions, the viscosity of all the formulations showed a shear-thinning behavior similar to XG solutions in the whole investigated 1-1000 s-1 range, with values dependent on both PLA particles and XG concentrations. Amplitude and frequency sweep data revealed a weak-gel behavior except in the case of the most diluted sample, with moduli dependent on both PLA and XG contents. A unified scaling parameter was identified in the volume fraction (ϕ) of the PLA particles, calculated by considering the dependence of the continuous phase density on the XG concentration. Accordingly, a master curve at different volume fractions was built using the time-concentration-superposition approach. The master curve describes the rheological response of the system over a wider frequency window than the experimentally accessible one and reveals the presence of a superimposed β relaxation process in the high-frequency region.
| S-EPMC9026014 | biostudies-literature
Project description:BackgroundDysphagia is a well-known stroke complication characterised by difficulty in swallowing. It may affect the majority of stroke patients and increases mortality and morbidity, due to aspiration pneumonia and malnutrition. Food thickening may help patients to feed themselves, and its effectiveness was demonstrated. However, the cost-effectiveness studies are lacking. We evaluate the cost-utility of xanthan gum-based consistency modification therapy (Nutilis Clear®) in adult post-stroke patients from the public payer perspective in Poland.MethodsRoutine clinical practice was used as a comparator, as no alternative specific treatment for dysphagia is available. To verify the robustness of the results against the modelling approach, we built two models: a static (a fixed simple-equations model, 8-week time horizon of dysphagia) and a dynamic one (Markov model, with a possible dysphagia resolution over a 1-year horizon). In both models, the treatment costs, health state utilities, and clinical events (i.e. aspiration, aspiration pneumonia, death) were included. Parameters were estimated jointly for both models, except for the duration of dysphagia and the risk of aspiration pneumonia (specific to the time horizon). We only assumed Nutilis Clear® to prevent aspirations, without affecting dysphagia duration.ResultsThe average cost of one quality-adjusted life year (i.e. the incremental cost-utility ratios, ICURs) amounted to 21,387 PLN (€1 ≈ 4.5 PLN), and 20,977 PLN in static and dynamic model, respectively; far below the cost-effectiveness threshold in Poland (147,024 PLN). The one-way, scenario, and probabilistic sensitivity analysis confirmed these findings.ConclusionsNutilis Clear® is highly cost-effective in Poland from the public payer perspective. Our approach can be used in other countries to study the cost-effectiveness of food thickening in stroke patients.
| S-EPMC7302358 | biostudies-literature
Project description:Oil reservoirs can represent extreme environments for microbial life due to low water availability, high salinity, high pressure and naturally occurring radionuclides. This study investigated the microbiome of saline formation water samples from a Gulf of Mexico oil reservoir. Metagenomic analysis and associated anaerobic enrichment cultures enabled investigations into metabolic potential for microbial activity and persistence in this environment given its high salinity (4.5%) and low nutrient availability. Preliminary 16S rRNA gene amplicon sequencing revealed very low microbial diversity. Accordingly, deep shotgun sequencing resulted in nine metagenome-assembled genomes (MAGs), including members of novel lineages QPJE01 (genus level) within the Halanaerobiaceae, and BM520 (family level) within the Bacteroidales. Genomes of the nine organisms included respiratory pathways such as nitrate reduction (in Arhodomonas, Flexistipes, Geotoga and Marinobacter MAGs) and thiosulfate reduction (in Arhodomonas, Flexistipes and Geotoga MAGs). Genomic evidence for adaptation to high salinity, withstanding radioactivity, and metal acquisition was also observed in different MAGs, possibly explaining their occurrence in this extreme habitat. Other metabolic features included the potential for quorum sensing and biofilm formation, and genes for forming endospores in some cases. Understanding the microbiomes of deep biosphere environments sheds light on the capabilities of uncultivated subsurface microorganisms and their potential roles in subsurface settings, including during oil recovery operations.
| S-EPMC8621343 | biostudies-literature
Project description:Xanthan gum is an important commercial polysaccharide produced by Xanthomonas species. In this study, xanthan production was investigated using a local isolate of Xanthomonas campestris MO-03 in medium containing various concentrations of chicken feather peptone (CFP) as an enhancer substrate. CFP was produced with a chemical process and its chemical composition was determined. The addition of CFP (1-8?g/l) increased the conversion of sugar to xanthan gum in comparison with the control medium, which did not contain additional supplements. The highest xanthan production (24.45?g/l) was found at the 6?g/l CFP containing control medium in 54?h. This value was 1.73 fold higher than that of control medium (14.12?g/l). Moreover, addition of CFP improved the composition of xanthan gum; the pyruvate content of xanthan was 3.86% (w/w), higher than that of the control (2.2%, w/w). The xanthan gum yield was also influenced by the type of organic nitrogen sources. As a conclusion, CFP was found to be a suitable substrate for xanthan gum production.
| S-EPMC6353776 | biostudies-literature
Project description:Xanthan is an industrially important exopolysaccharide produced by the phytopathogenic, gram-negative bacterium Xanthomonas campestris pv. campestris. It is composed of polymerized pentasaccharide repeating units which are assembled by the sequential addition of glucose-1-phosphate, glucose, mannose, glucuronic acid, and mannose on a polyprenol phosphate carrier (L. Ielpi, R. O. Couso, and M. A. Dankert, J. Bacteriol. 175:2490-2500, 1993). A cluster of 12 genes in a region designated xpsI or gum has been suggested to encode proteins involved in the synthesis and polymerization of the lipid intermediate. However, no experimental evidence supporting this suggestion has been published. In this work, from the biochemical analysis of a defined set of X. campestris gum mutants, we report experimental data for assigning functions to the products of the gum genes. We also show that the first step in the assembly of the lipid-linked intermediate is severely affected by the combination of certain gum and non-gum mutations. In addition, we provide evidence that the C-terminal domain of the gumD gene product is sufficient for its glucosyl-1-phosphate transferase activity. Finally, we found that alterations in the later stages of xanthan biosynthesis reduce the aggressiveness of X. campestris against the plant.
| S-EPMC107069 | biostudies-literature