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• Experiments are presented detailing particle migration in inertial Taylor–Couette flow of complex fluids. • Particles are observed to migrate oppositely within Taylor vortices with inelastic and elastic fluids. • A weaker elastic fluid shows a transition between an initial migration to the center of the Taylor vortices, switching to migration to the perimeter of the vortices as rotation rate is increased. • A preliminary numerical Euler-Euler calculation using a White–Metzner constitutive model captures the migration. A drilling process comprises a drill-pipe rotating within a borehole where fluid is pumped down the pipe and returns, with drilled cuttings, along the annulus. Predominantly the axis of the system is horizontal. Thus, in the absence of axial flow the process geometry is that of a Taylor–Couette flow. Formulated drilling fluids themselves are usually regarded as Bingham or Hershel-Bulkley in nature, but nevertheless encompass elastic behaviour. We have thus studied the distribution of dense (i.e. sedimenting) non-Brownian solid particles in Taylor–Couette flow of model drilling fluids as a function of center body rotation speed. In all cases Taylor vortices are formed above some critical, fluid dependent, Taylor number. However, depending on the fluid properties, particles decorate the vortices differently: particles in a polymeric fluid move to the centroids of the vortices, whereas in a colloidal fluid they move to the outer periphery of the vortices, as previously observed for Newtonian fluids. With a mixed fluid, a clear transition between the two regimes is found. We postulate that this behaviour is a result of a balance between elastically derived lift forces and inertially driven Saffman lift forces acting antagonistically on the particles. [ABSTRACT FROM AUTHOR]

The inefficient decomposition of polysaccharides, particularly branched polysaccharides limits their large-scale industrial applications. Further understanding and modification of glycoside hydrolases (GHs) processivity is expected to overcome this limitation. Here, a novel xanthan-binding CBM (Mi XBM), which was supposed to alter the processivity of GHs, was systematically characterized. Phylogeny and structure analyses indicated that Mi XBM is closely related to putative polysaccharide side chain-binding modules. Quantitative binding assays further revealed that Mi XBM probably has a high affinity for xanthan side chain via a variable loop site. Moreover, catalytic performance demonstrated that xanthanase chimeras containing Mi XBM promote highly efficient hydrolysis of xanthan because of improved substrate accessibility. Notably, Mi XBM was observed to enhance the processivity of xanthanase, owing to its high substrate affinity to the repeating unit xanthan. Furthermore, sequential hydrolysis of xanthan by xanthanases with varying processivity resulted in significantly increased hydrolytic efficiency and focused oligoxanthans array. These results expand understanding of CBM-substrate recognition and shed light on efficient degradation of other regularly branched polysaccharides using modified GHs. [Display omitted] [ABSTRACT FROM AUTHOR]

Biopolymers like guar and xanthan gums are considered to be sustainable soil stabilisers that can improve engineering properties of earthen construction materials. Recent studies indicate that water-based soil washing has achieved partial success in recycling these materials. In this study, β-mannanase was used in the washing process for recycling. An engineered soil mixture was stabilised using these biopolymers and then recycled in two stages, initially with water and then with β-mannanase. The impact of recycling was ascertained in terms of particle size distribution and Atterberg limits. The recycled soil was subsequently used to produce earthen construction materials, and their mechanical performance was evaluated. Two recycling cycles were conducted to explore the potential of recycling after repeated cycles of biopolymer amendment. Using β-mannanase proved effective in recovering more original material than washing with water and notably more effective for guar gum. Mechanical tests indicated that the recycled material was suitable for earthen construction. [Display omitted] • The study uses β-mannanase to recycle guar and xanthan gum stabilised earthen construction materials. • Two cycles of recycling have been undertaken to compare between water-based and β-mannanase based washing. • β-mannanase has been more effective for guar than xanthan in retrieving original soil particles and plasticity. • Xanthan gum's regenerative capabilities revive mechanical properties after recycling ensuring its reuse. [ABSTRACT FROM AUTHOR]

Synergistic interaction gels (SIGs) hold immense promise for applications in 3D printing, colonic drug delivery, and sustained release. The amalgamation of xanthan and tamarind gum (TMG) gives rise to SIGs through molecular interaction; however, the intricacies of their assembly behaviors remain elusive. This work elucidates that in xanthan-rich systems, the predominant formation of xanthan aggregations shapes network assembly structure, with TMG clusters adhering to them. Conversely, in TMG-rich systems, TMG clusters actively participate in creating a "sea-island" assembly structure enveloped by xanthan aggregations. Higher concentration of TMG contributes to augmenting the association extent of TMG and xanthan. The heightened binding between TMG and xanthan correlates with an increase in chain distance in scatters and the compactness of scatter arrangement. These favor the development of micro-structures with a relatively larger mesh size and the enhancement of gel hardness. This study serves to facilitate the design and production of SIGs-based artificial gel foods with the requisite performance characteristics, such as artificial sea cucumber and porcine back fat. [Display omitted] • Xanthan aggregation shapes network structure in xanthan-rich system. • "Sea-island" structure is formed in tamarind gum (TMG)-rich system. • Higher TMG content increases association extent of xanthan and TMG. • Higher association extent causes higher gel hardness of TMG/xanthan SIGs. [ABSTRACT FROM AUTHOR]

Synergistic interaction gels (SIGs) have become attractive in food industry due to their ability to modify rheology features, realize safe swallowing and apply as fat simulants. Locust bean gum (LBG) and xanthan give rise to SIG, however, their assembly process remain elusive. This work demonstrated that, in xanthan-rich system, xanthan chains transformed into helical structure and aggregated into thick bundles upon cooling. Subsequently they bound with LBG clusters, constructing a xanthan-like 3D gel network. However, in LBG-rich system, LBG chains gradually dissociated from clusters and associated into helical structure during cooling ("dissociation-association" process), forming an LBG-like "sea-island" structure. With further cooling, LBG continued to undergo "dissociation-association" process, along with specifically binding by xanthan chains (helical structure or thick bundles), generating thick grid contour lines and larger sparse gel network. The enthalpy change values indicated that with the decrease of xanthan content, synergistic binding extent was increased and then decreased, reaching the maximum at LBG: xanthan ratio of 7:3. This was responsible for the increment of G ′, gel hardness, and capacity to accumulate energy for the weak shear-induced structure for LBG/xanthan SIGs. This study serves to facilitate the design and production of SIGs with the requisite performance characteristics. [Display omitted] • "3D" network structure was generated in xanthan-rich system. • Sparse network with larger grid was formed in LBG-rich system. • Ratio of 7:3 (LBG: xanthan) was a well-defined stoichiometry for synergistic bind. • Higher association extent caused higher gel strength of LBG/xanthan SIGs. [ABSTRACT FROM AUTHOR]

In this paper, a novel ionogel with semi-interpenetrating poly (ionic liquids)/xanthan gum (PIL/XG) polymer network (semi-IPN) was prepared by using a simple one-pot method. The structure and the pressure sensing performance have been systematically investigated. It was found that introducing a low content (0.3–3.1 wt%) of XG significantly promoted the mechanical performance of ionogels with little effect on the ionic conductivity. The optimized PIL/XG containing 2.2 wt% XG exhibited high compression strength (761.0 kPa) and ionic conductivity (0.63 S/m at 25 °C). Such ionogels showed a liner response (0–100 kPa) and high sensitivity value of 6.86 kPa−1 in a capacitive mode. Meanwhile, as a resistive sensor, PIL/XG exhibited a wide response range to dynamic pressure ranges with stable repeatability. Furthermore, this ionogel exhibited excellent bactericidal properties against both gram-positive bacteria and gram-negative bacteria. This research provides a potential approach for developing ionogels based on semi-IPN with pressure-sensitive and anti-bacterial properties. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, xanthan/polyacrylic acid hydrogels were prepared to improve their physical and physico-chemical properties with the aim of using them in different applications (food or pharmaceutical). The optimal concentration of crosslinking agent for which the hydrogel structure can be in its most stable form was also determined. The stability and stiffness of xanthan/polyacrylic acid/calcium based hydrogels were optimized by a centered face design response surface design. The hydrogels were characterized by studying the swelling profiles and the rheological properties. It was found that the stiffness of hydrogels depended mainly on the fraction of xanthan in the mixture. The physical cross-linking of hydrogels by calcium ions had a double impact on the hydrogels. At low calcium concentration, it behaved as a matrix stabilizer where the rigidity of the hydrogels increased with the increase in the concentration of xanthan, and the swelling rate reaches 78.9% without any erosion of the matrices. However, at high concentrations of calcium, it behaved as a destabilizer and caused phase separation at the microscopic scale. This, led to erosion of hydrogels at low concentrations of xanthan, and therefore their elastic limit was relatively low. The release of diclofenac from the optimal hydrogel composition was modeled by the Korsmeyer–Peppas model. [ABSTRACT FROM AUTHOR]

The synergistic interaction gels of locust bean gum (LBG) /xanthan show great potential for application in the food industry, such as 3D printing and taste/texture simulation. Including 1, 2-propanediol (PDO) significantly promoted the gel-related properties of LBG/xanthan gels. The synergistic interaction between LBG and xanthan was enhanced with the presence of small amounts of PDO (≤ 20 %) due to the dehydration effect of PDO and the resulting promotion of the molecular association. As a result, this further improved the gel network and the gel strength (G ' value and gel hardness). However, more significant amounts of PDO (20 %–40 %) imposed adverse effects with the weakened gel structure and the reduced strength, which was related to the excessive hydration effect and the decreased association of LBG with xanthan. These findings favor the design and development of the synergistic interaction gels with the improved gel structure, gelling temperature, and mechanical strength. [Display omitted] • The presence of 1, 2-propanediol (PDO) postponed the phase transition of xanthan. • Small amounts of PDO enhanced the binding of locust bean gum (LBG) and xanthan. • Small amounts of PDO improved the microstructure and the strength of LBG/xanthan gels. • More significant amounts of PDO caused the excessive self-association of LBG. [ABSTRACT FROM AUTHOR]

Motivated by sustainability and environmental protection, great efforts have been paid towards water purification and attaining complete decolorization and detoxification of polluted water effluent. Textile effluent, the main participant in water pollution, is a complicated mixture of toxic pollutants which seriously impact human health and the entire ecosystem. Developing effective materials for potential removal of the water contaminants is urgent. Recently, cryogels have been applied in wastewater sectors due to their unique physiochemical attributes(e.g. high surface area, lightweight, porosity, swelling-deswelling, and high permeability). These features robustly affected the cryogel's performance, as adsorbent material, particularly in wastewater sectors. This review serves as a detailed reference to the cryogels derived from biopolymers and applied as adsorbents for the purification of textile drainage. We displayed an overview of: the existing contaminants in textile effluents (dyes and heavy metals), their sources, and toxicity; advantages and disadvantages of the most common treatment techniques (biodegradation, advanced chemical oxidation, membrane filtration, coagulation/flocculation, adsorption). A simple background about cryogels (definition, cryogelation technique, significant features as adsorbents, and the adsorption mechanisms) is also discussed. Finally, the bio-based cryogels dependent on biopolymers such as chitosan, xanthan, cellulose, PVA, and PVP, are fully discussed with evaluating their maximum adsorption capacity. [Display omitted] [ABSTRACT FROM AUTHOR]

• Xanthan, with many applications, has been identified in the aerobic granule matrix. • Xanthan gum market is estimated at USD 987.7 million. • Xanthan yields of 4.28–30.64 g/L have been obtained from different wastewaters. • C/N ratio, feeding regime, substrate type, OLR, HRT, & SRT may impact xanthan yield. • Research also needed on xanthan extraction and purification protocol. Aerobic granular sludge (AGS) provides the opportunity to recover resources such as phosphorus, alginate-like exopolysaccharides, polyhydroxyalkanoates, tryptophan, etc. Recently, xanthan, a versatile biopolymer with applications in the food, oil, geotechnical, and biomedical industries, has been identified in the aerobic granule matrix. The production of xanthan from waste is encouraged because conventional processes for its production are costly and require specialized laboratories. This paper presents an overview of xanthan recovery potential from AGS systems. Xanthan yields of 20.92 g/L and 30.64 g/L have been reported for blended wastewaters from different stages of white and rose wine production processes, respectively. Additionally, xanthan yield in the range of 4.28–15.56 g/L have been obtained from confectionary and brewery wastewaters. Currently, there is lack of information in the scientific literature on the factors that govern xanthan biosynthesis in AGS systems. Factors such as substrate type, carbon-to-nitrogen ratio, feeding strategy, hydrodynamic shear force, organic loading rate, hydraulic retention time, solids retention time, and feast/famine period require optimization for simultaneous efficient wastewater treatment and high xanthan biosynthesis. Moreover, quorum sensing and quorum quenching approaches require exploration for xanthan biosynthesis. Further research is also needed on the development of xanthan extraction and purification protocols from aerobic granules. [Display omitted] [ABSTRACT FROM AUTHOR]

This study presents new drug delivery systems based on xanthan, unmodified or modified by esterification with oleic acid, and alginate for controlled release of bioactive substances with anti-inflammatory (piroxicam) and antifungal properties (ketoconazole). The mechanical properties of the developed drug carriers showed that their compressive strength was affected by the encapsulation of the bioactive principles. When ketoconazole was added into the xanthan/alginate matrix, an increment in the mechanical strength was recorded (66.68% compression). The release of the active principles from the materials was best described by the Korsmeyer-Peppas model, with non-Fickian or Fickian diffusion (the values of the exponent of release are between 0.29 and 0.75), depending on the composition of the polymeric matrix. The release rate constant presents smaller values for the materials based on chemically modified xanthan (between 0.89 and 20.11) as compared with materials based on the unmodified form (between 4.27 and 25.00). All materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The designed systems prove to have antimicrobial and anti-inflammatory activity. The findings make prone these biomaterials for the manufacture of transdermal drug delivery systems. [ABSTRACT FROM AUTHOR]

Peanut shells were incorporated in polymeric matrix of chitosan/xanthan/acrylic acid to form Cs/ XN/AAc-PS composite by using gamma irradiation. It was found that 10 kGy irradiation dose is sufficient to crosslinking the network structure and increasing with irradiation dose up to 30 kGy. A decrease in gel content was observed at 40 kGy. The gel content was found to be increased with increasing AAc content. The swelling percentage decreases by increasing of AAc content and irradiation dose except at 40 kGy. Characterization the composite was performed by Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and dynamic light scattering. The adsorption performance of Cs/XN/AAc-PS composite towards the removal of Ni2+ and Co2+ was investigated. The adsorption capacity was found to be enhanced with increasing the temperature, initial metal ion concentration and pH. The highest adsorption capacity values for Ni2+ and Co2+ by Cs/XN/AAc-PS composite are 6.84 and 3.73 mmol/g at pH 6 and initial concentration 150 mg/L, respectively. The maximum capacity was done at the adsorbent dosage of 0.1 g [ABSTRACT FROM AUTHOR]

• Semi-contineous production of X. campestris xanthan in biofilm reactor was studied. • SEM showed high immobilzation of cells on stainless-steel and polyethylen supports. • Xanthan recovery in the biofilm reactor with stainless-steel support was increased. • High elasticity of the xanthan produced using Xanthomonas campestris was observed. Semi-continuous production of xanthan gum using self-immobilized Xanthomonas campestris cells in biofilm reactors was studied. Fermentation was carried out using two different designs of biofilm reactor equipped with a) stainless-steel support (SSS) and b) polyethylene support (PES). Fermentation was performed in three cycles with refreshing the media at the beginning of each: cycle 1, 0−27 h; cycle 2, 27−54 h; and cycle 3, 54–78.5 h. Results showed that the glucose consumption and the pH reduction in the PES biofilm reactor was faster compared to the SSS biofilm reactor. Scanning electron microscopy showed that the SSS was capable to immobilize more cells during the growth of X. campestris. The maximum concentration of xanthan gum in the SSS biofilm reactor obtained after 27 h (3.47 ± 0.71 g/L), while the maximum concentration of xanthan in the PES biofilm reactor obtained after 78.5 h (3.21 ± 0.68 g/L). Thermal stability analysis of xanthan using differential scanning calorimetry showed the presence of two fractures attributed to dehydration and degradation of polymer. The thermogram represented both endothermal and exothermal behaviour of xanthan polymer. Furthermore, the functional groups and molecular structure of the xanthan produced in this study was evaluated using Fourier transform infrared spectrometry and also proton nuclear magnetic resonance. in addition, the surface tension of (0.2 %, w/v) xanthan gum solution was in a range of 52.16–56.5 mN/m. Rheological analysis of xanthan showed that the G′ values were higher than the G″ in all frequencies demonstrating a relatively high elasticity of the produced xanthan gum. [ABSTRACT FROM AUTHOR]

Lutein is a hydrophobic carotenoid with diverse bioactivities. For encapsulating the molecule in a novel method, we prepared two emulsions from xanthan and propylene glycol alginate at the ratios of 3:7 and 4:6. The instability index and particle size of the emulsions were determined using a stability analyzer and laser particle size analyzer. The influence of crystallization on the emulsions was observed under a polarizing microscope. The effects of centrifugal force and storage on the lutein emulsions were analyzed by measuring the changes in absorbance. The results showed that the emulsion fabricated by xanthan and propylene glycol alginate at the ratio of 4:6 was highly stable, and crystals were dispersed when xanthan and propylene glycol alginate existed. These results revealed that the hydrophobicity and absorption kinetics of emulsifiers would determine the stability of emulsion when the viscosity of emulsifiers reached a certain value, and the stability of emulsions would affect the stability of lutein in the emulsions. Unlabelled Image • Compound polysaccharide was used as an emulsifier for preparing emulsions. • Lutein, encapsulated in O/W emulsions, exhibited good stability. • The crystallization of the oil phase affected the stability of emulsions. • The relationship between the stability of emulsions and lutein was exhibited. [ABSTRACT FROM AUTHOR]

Stabilizers are routinely added during cream cheese manufacture to help prevent syneresis during storage. We investigated how different types of stabilizers affected the texture, rheology, and sensory properties of cream cheese. Cream cheeses were manufactured with 0.33% xanthan gum (XG), locust bean gum (LBG), guar gum (GG), or a combination (CBN) of these 3 stabilizers (0.11% of each). Rheological properties of solutions of the individual stabilizers and their combination (equal amounts) were also determined under conditions similar to the aqueous phase of cream cheese (0.6% gum, 1.8% NaCl, and pH 5). Dynamic small amplitude rheological properties of the cream cheeses were measured during heating from 5 to 80°C at the rate of 1°C/min and cooling at the same rate (because most cream cheese is hot packed/filled before cooling). Measured rheological parameters included storage modulus (G′) and loss tangent. Hardness of cream cheeses was determined by texture profile analysis. Quantitative spectrum descriptive sensory analysis was also performed. Distinct differences were observed between the rheological properties of solutions of the individual stabilizers and the CBN containing all the stabilizers. Results showed that CBN solution formed a strong, thermally reversible gel due to synergistic interaction between stabilizers, whereas XG solution formed a weak gel that was not greatly affected by temperature. Solutions of LBG and GG behaved rheologically as entangled polymer solutions. In the high-temperature (>35°C) region, cream cheeses made with XG and CBN showed higher G′ values compared with other cream cheeses. The G′ values were higher for XG- and CBN-stabilized cream cheeses than LBG- and GG-stabilized cream cheeses at several temperature regions during the cooling cycle. The CBN-stabilized cream cheeses had higher hardness values than the cream cheeses manufactured with the individual stabilizers. Differences were observed between the sensory attributes of cream cheeses stabilized with CBN and those made with individual stabilizers. At low temperatures, the higher hardness and G′ values of CBN-stabilized cream cheeses could be due to synergistic interaction between XG and galactomannans. The higher elasticity of XG-stabilized cream cheeses at high temperatures could be due to its higher thermal stability. This study showed that the stabilizers added during manufacture of cream cheese affected its texture, rheological, and sensory properties. [ABSTRACT FROM AUTHOR]

• Columns: xanthan solutions consistent at 89 % recovery, regardless of density. • 2D tanks: densified xanthan showed radial invasion, 5x recovery vs. pure xanthan. • Simulations: near-zero gravity number essential to avoid density-driven flow issues. • Evaluation of density driven two-phase flow in confined multilayer 2D system. • Simulations: increasing K upper /K lower leads to fast breakthrough in multilayer system. Polymer solutions aid DNAPL (Dense Non Aqueous Phase Liquid)-contaminated soil remediation but are impacted by gravity and viscous forces. This study assesses the interplay between buoyancy and viscous forces in influencing the distribution of DNAPL and the invading phase, by introducing a densified brine (NaI) biopolymer (xanthan) solution as remediation fluid. A matrix of experiments was conducted, encompassing rheological measurements, multiphase flow tests in 1D-columns and 2D-tanks. Numerical modeling was used to assess polymer and DNAPL propagation under different conditions. NaI addition maintains xanthan's shear-thinning yet lowers mid-range shear viscosity 2.6 times. Confined column tests show similar 89 % performance for viscous polymer solutions regardless of density. Unconfined tests mimicking real sites reveal non-densified viscous polymer solution yield mere 0.09 recovery due to density-driven flow. Densified polymer attains radial invasion, boosting recovery to 0.46 with 1.21 aspect ratio. Numerical simulations aligned with experiments, suggesting a near-zero gravity number is necessary to prevent density-driven flow problems. The multiphase flow experiments in confined multilayer system are performed and using the numerical modeling the effects of the permeability contrast and dimensions of the layers on the shape of front are analyzed. [ABSTRACT FROM AUTHOR]

The periosteum is a membrane that surrounds bones, providing essential cellular and biological components for fracture healing and bone repair. Tissue engineered scaffolds able to function as periosteum substitutes can significantly improve bone regeneration in severely injured tissues. Efforts to develop more bioactive and tunable periosteal substitutes are required to improve the success of this tissue engineering approach. In this work, a chemical modification was performed in chitosan, a polysaccharide with osteoconductive properties, by introducing phosphate groups to its structure. The phosphorylated polymer (Chp) was used to produce chitosan-xanthan-based scaffolds for periosteal tissue engineering. Porous and mechanically reinforced matrices were obtained with addition of the surfactant Kolliphor® P188 and the silicone rubber Silpuran® 2130A/B. Scaffolds properties, such as large pore sizes (850–1097 μm), micro-roughness and thickness (0.7–3.5 mm in culture medium), as well as low thrombogenicity compared to standard implantable materials, extended degradation time and negligible cytotoxicity, enable their application as periosteum substitutes. Moreover, the higher adsorption of bone morphogenetic protein mimic (cytochrome C) by Chp-based formulations suggests improved osteoinductivity of these materials, indicating that, when used in vivo , the material would be able to concentrate native BMPs and induce osteogenesis. The scaffolds produced were not toxic to adipose tissue-derived stem cells, however, cell adhesion and proliferation on the scaffolds surfaces can be still further improved. The mineralization observed on the surface of all formulations indicates that the materials studied have promising characteristics for the application in bone regeneration. [ABSTRACT FROM AUTHOR]

• The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed. • Sodium silicate as coagulant was added and its accelerating mechanism for the retarding effect of xanthan in cement paste was investigated. • Established a "suppression-excitation" system of cement slurry. The effect of polyhydroxy xanthan on the corresponding hydration process of cement and regulation mechanism was discussed, then sodium silicate as coagulant was added into the xanthan-retarded cement paste and its accelerating mechanism for the retarding effect of xanthan was investigated. The results indicate that due to chemisorption between hydrophilic hydroxyl and carboxyl and calcium ions, the core-shell construction of xanthan-cement to a certain extent hinders the hydration process of cement particles, adding sodium silicate in the cement-added xanthan significantly inhibits the retardation of the xanthan, shortens the setting time of the retarding cement, improves the compressive strength of the retarded cement, and to some extent promotes the hydration of C 3 A. The early hydration of C 3 A, C 3 S and sodium silicate rapidly formed a large amount of C-S-H, which was bound with the ettringite skeleton to promote coagulation hardening of the cement slurry, further established a "suppression-excitation" system between xanthan and sodium silicate in cement slurry. [ABSTRACT FROM AUTHOR]

• The effect of alkyl grafted xanthan derivatives chain stiffness on the stabilization on O/W emulsions was investigated. • A series of xanthan hydrophobic derivatives was prepared under ordered and disordered conformation • Stiff Hydrophobically Modified Xanthan permitted long term stabilization of emulsions with flexible ones did not. • Amphiphilic xanthan under disordered conformation stabilizes O/W emulsion when alkyl length brings gel-like viscoelastic properties • The Oil-in-Water emulsions stabilization by Hydrophobically Modified Xanthan is mainly governed by aqueous continuous phase rheology The impact of xanthan chemical modification under both ordered and disordered conformations on oil-in-water (O/W) emulsion stabilization was investigated. While both hydrophobically modified xanthan (HMX) are able to stabilize the O/W interface, a dramatic difference was observed macroscopically. When HMX ord (ordered conformation) could produce stable emulsions at concentrations down to 0.2% w/w, HMX dis (disordered conformation) led to unstable systems mostly by creaming whatever the concentration studied. Moreover, in the case of HMX dis , the role of the grafted chain length was investigated and two different behaviors were observed depending on the grafting unit. It was demonstrated that the cornerstone of these emulsion stability was the rheological properties of the continuous phase which was governed by two main factors: the partitioning of HMX dis between the interface and the continuous phase and the viscosifying ability of the polymer, the latter being directly linked to the backbone stiffness. [ABSTRACT FROM AUTHOR]

Xanthan gum, whose structure determines its physicochemical properties, is an important microbial polysaccharide. Currently, marketed xanthan products are produced by wild-type strains followed by post-fermentation separation or chemical modification, which are complicated and labor-intensive. In the present study, we designed eight polysaccharides containing uniformly distributed repeating units and different rheological properties based on natural xanthan skeleton and according to the relationship between property and structure. The customized polysaccharides were produced in Xanthomonas campestris CGMCC 15155 using marker-less gene knockout and gene overexpression methods. The results showed that their different homogeneous primary structures determined their specific secondary structures and rheological properties, especially the terminal mannose, the pyruvyl group, and the acetyl group attached to the internal mannose of the side chain. Polysaccharides lacking a terminal mannose, such as xanthan XdM-0 and XdM-A, had reduced zero-shear viscosity and modulus values. The internal acetyl group of the side chain stabilized the helix structure (e.g., in XG-A0), while the pyruvate group had the opposite effect (e.g., in XG-AP and XG-0P). The eight xanthan variants provide a promising theoretical foundation to further study the structure-activity relationship of xanthan and will help to construct xanthan-containing block copolymers. Unlabelled Image • Eight polysaccharides based on the xanthan gum skeleton were customized. • The polysaccharides contained uniformly distributed repeating unit structures. • The polymers showed different secondary structures and rheological properties. • The terminal mannose of xanthan affected the advanced structure and property. • The internal acetyl significantly stabilized the conformation of xanthan. [ABSTRACT FROM AUTHOR]

Highlights • First thorough rheological characterization of in-vivo engineered xanthan variants. • Higher impact of pyruvylation than acetylation on rheological properties of xanthan. • Position of acetylation affects rheological properties of xanthan. • Acetylation of xanthan plays significant role in thermostability of its rheological properties. Abstract Xanthan is an extensively studied viscosifying agent discovered in 1961. Acetylation and pyruvylation have a major influence on its rheological properties and the effect of these groups on the conformation and rheological properties of xanthan have been studied for decades. However, these studies rely mainly on chemical modifications and therefore the degree of pyruvylation and acetylation as well as regioselectivity of deacetylation cannot be controlled. Here, we present an in-depth rheological characterization of natural xanthan and seven xanthan-variants, with defined acetylation and pyruvylation patterns created via genetic modification of Xanthomonas campestris LMG 8031. By that approach xanthan-variants with defined acetylation and pyruvylation patterns in their most natural state due to the mild production conditions were obtained. It was possible to link the defined substituent patterns to their corresponding rheological properties to give novel structure-function relationship insights of xanthan-variants in salt-free environments and in the presence of mono- and divalent cations. [ABSTRACT FROM AUTHOR]

The dynamic properties of water and polymer molecules in xanthan hydrogels at different polymer mass fractions were investigated through the combination of conventional and fast-field cycling NMR relaxation to obtain the information about dynamics in different time scales. The results showed that water dynamics were faster in diluted than in concentrated hydrogels. However, the type of polymer-chain dynamics did not change for xanthan fractions from 0.1 to 0.5, although they slowed at higher xanthan fractions as the system approached transition to the glass state. The addition of the nonionic small drug molecules pentoxifylline did not change the dynamics in the hydrogels, but they were affected by the medium pH. The water and polymer-chain dynamics were faster in the hydrogels for the neutral than the acid medium. These differences resulted in slower swelling and thinner and more rigid hydrogel layer of the matrix tablet in the acid medium that was less susceptible to erosion. Consequently, pentoxifylline release from xanthan tablets in acid medium is dominated by drug diffusion. At neutral pH, the molecular mobility is greater, which resulted in rapid and extensive swelling of the hydrogel, leading to erosion-dominated drug release. [ABSTRACT FROM AUTHOR]

Abstract The effect of Basil Seed Gum (BSG) on native and pre-gelatinized corn starch and flour gels was evaluated. With this purpose, the hydration, pasting, rheological, textural and microstructural properties of the mixed gels were analyzed. Xanthan was used as a comparison, as it presents comparable high zero shear viscosity to BSG. The presence of BSG led to greater water binding capacity and greater water absorption index of the starch and flours compared to the free-gum systems. In general BSG substantially increased the peak and final viscosities of the pastes, also leading to a raise in the viscoelasticity (G' and G") and hardness of the final gels, native or treated (pregelatinized starch and extruded flour). A more opened microstructure—compared to a homogeneous and dense matrix of the control native starch gels— with strands and a spider-like network of BSG across the pockets was detected. On the other hand, xanthan showed the opposite effect, decreasing the peak and final viscosities of the native systems, delaying the gelatinization process, and also leading to weaker gels of reduced viscoelasticity with opened honeycomb-like microstructures. However, for pregelatinized flour and starch the effect of xanthan was minimal. Graphical abstract Image 1 Highlights • Basil Seed Gum (BSG) and xanthan showed opposite behavior during starch gelation. • BSG led to a high water binding and absorption capacity of starch and flours. • BSG resulted in stronger gels in all native and pregelatinized systems. • Opened structures with strands (BSG) and honeycomb-like ones (xanthan) were observed. [ABSTRACT FROM AUTHOR]

Highlights • MNPs/ACS analysis is used to measure viscoelasticity of glycerol and xanthan. • The method enables viscoelasticity analysis at high oscillation frequencies. • Results for glycerol agree well with oscillatory shear rheological measurements. • For xanthan, agreement between the two methods is better at high concentrations. Abstract We show results of nanorheological studies of different concentrations of xanthan (non-Newtonian fluid) in water using magnetic nanoparticles (MNPs) together with the AC susceptibility (ACS) vs frequency method. For comparison we also show the ACS response for different concentrations of glycerol in water (Newtonian fluid). The ACS response is measured, and the data is modelled using dynamic magnetic models and different viscoelastic models. We study the ACS response (in-phase and out-of-phase ACS components) at different concentrations of xanthan in water (up to 1 wt% xanthan) and with a constant concentration of MNPs. We use MNP systems that show Brownian relaxation (sensitive to changes in the environmental properties around the MNPs). ACS measurements are performed using the DynoMag system. The Brownian relaxation of the MNP system peak is shifting down in frequency and the ACS response is broadening and decreases due to changes in the viscoelastic properties around the MNPs in the xanthan solution. The viscosity and the storage moduli are determined at each excitation frequency and compared with traditional macroscopic small amplitude oscillatory shear rheological measurements. The results from the traditional rheological and nanorheological measurements correlate well at higher xanthan concentration. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Xanthan and chitosan entangle their chains along the films' preparation. • The layer-by-layer technique permits to explore the interaction between the film components. • The interaction among xanthan, chitosan and calcium ion makes stable films in buffers with different pH. • Films containing calcium and phosphate ions precipitate hydroxyapatite inside the film due to the pH increase. • Films with hydroxyapatite allow the attachment and growth of MG63 cells. Abstract Mineralized films are interesting biomaterials to repair bone defects. They can be easily shaped into bone defect and be permeated by body fluids as well as allow cell proliferation. Xanthan and chitosan films mineralized with hydroxyapatite prepared and characterized in this work showed an improved film stability and controlled swelling degree when dipped in different pH buffers. The layer-by-layer technique used in the film's preparation associated with the behaviour at different pH allowed to explore separately each interaction – polysaccharide-polysaccharide and polysaccharide-ions. The entanglement between polysaccharides, the interaction of the oppositely charged polysaccharides ionic groups (amine for chitosan and carboxylate for xanthan) and the interaction with Ca2+ ions confers a pH-responsive behaviour to the films. The mineralization with in situ hydroxyapatite formation resulted in an additional stability in the mineral phase. It has lower crystallinity similar to bone mineral as confirmed by X-Ray diffractogram. The films that were dipped in calcium phosphate solution during their production had positive results with in vitro cell adhesion test using MG63 cells culture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal-doped CQDs were clustered from xanthan biopolymer and metal (Pd & Ag). • CQDs, Pd@CQDs & Ag@CQDs exhibited with size of 7.5, 21.0 & 11.7 nm, respectively. • The catalytic activity of CQDs enhanced significantly after metal doping. • Catalytic performance followed the order of Pd@CQDs ≫ Ag@CQDs > CQDs. • Value of t 1/2 decreased from 256.4 min for CQDs to 55.9 min for Pd@CQDs. Carbon quantum dots (CDs) ingrained form biopolymers as photostable, biocompatible, and nontoxic fluorescence nanostructures, are superiorly applicable in different scientific disciplines. Attributing to their optoelectronic characters, CDs were interestingly exploited in environmental remediation as a catalyst under the effect of UV-light. However, the Current work represents a unique investigation for the superiority of metal-doped CDs (Pd@CDs & Ag@CDs ingrained from xanthan biopolymer) in catalytic discoloration of methylene blue (MB) under the effect of daylight. Geometrical features and mean size of CDs (7.5 nm), Pd@CDs (21.0 nm) & Ag@CDs (11.7 nm) were investigated via microscopic images and Zetasizer data. Additionally, CDs & Ag@CDs & Pd@CDs were exhibited with an observable peak at 220 nm and a broad band at 290 nm, to affirm the conjugative composition for all the nucleated dots. Catalytic performance of the prepared dots for reductive discoloration of MB in day light was followed the order of Pd@CDs > Ag@CDs ≫ CDs. Reduction percent was estimated to be 40 % for CDs, however after metal doping, the reduction percent was greatly enhanced to be 77 % and 83 %, for Ag@CDs & Pd@CDs, respectively. Kinetic studies showed that, the half time for discoloration of MB was decreased from 68.5 min with exploitation of CDs to 30.9 and 22.6 min, using Ag@CDs & Pd@CDs, respectively. [ABSTRACT FROM AUTHOR]

The inadequate existence of practical techniques for water purification poses a prominent and widespread global environmental challenge. This study aims to clarify the efficacy of xanthan application in the photocatalytic removal of nadolol, pindolol, and cefoperazone from water reservoirs. Under the influence of a simulated solar light source, xanthan exhibited significant degradation rates for pindolol (77%) and cefoperazone (91%). In contrast, nadolol's degradation efficiency was notably lower (10%). These findings suggest that the molecular structure can substantially influence the efficiency of the purification process. Computational analyses were conducted to gain a more profound understanding of the implications of molecular structure. [Display omitted] • Biosynthesized xanthan in efficient photocatalytic water purification. • Effective emulsion stabilization and environmental remediation. • Computational analysis via DFT: RDG surface and quantum-molecular descriptors. • Paving the way for sustainable environmental cleanup strategy applications. [ABSTRACT FROM AUTHOR]

Soft contact tribology has emerged as a useful technique for understanding the lubrication behaviour of foods and pharmaceutical systems. While this field developed by adapting techniques used to characterise lubrication of oils, such as using the PCS instruments Mini-Traction Machine (MTM) that consists of a ball rolling/sliding against a rotating plate, methodologies have also emerged using rheometers with tribocell attachments in pure sliding configurations. Our hypothesis is that soft-contact tribology is strongly dependent on the contact mechanics, and as such the measurement from ball-to-pin contact in rheo-tribocell should differ from the ball-to-disc contact in a Mini-Traction Machine (MTM) even at a similar relative speed and contact pressure. We find that when lubricated using Newtonian fluids, the rheo-tribocell results are comparable to the MTM. However, when the lubricant is a multiphase fluid (emulsion, polymer solution) with non-Newtonian rheology, tribological behaviour measured from two devices differs markedly. We interpreted such inconsistency according to the geometrical difference in soft tribological contact, and conclude that a universal relationship cannot be derived between the devices. We highlight that Hertzian contact (assumed in Stribeck-Hersey analysis) is not universally valid in soft tribological contacts, and that it is necessary to consider the mechanics and geometry of the tribological contact when analysing the results. This also makes it hard to compare measurements and conclusions obtained from the different devices. • Friction of Newtonian fluids measured in the rheo-tribocell follow a Stribeck curve. • Starvation may be present for shear-thinning fluids in the rheo-tribocell. • The Hertzian assumption, valid for the MTM, is absent from the rheo-tribocell. • MTM data cannot be used to interpret rheo-tribocell valid data interpretation. • A cautious approach is required when commissioning new tribology measurement systems. [ABSTRACT FROM AUTHOR]

Abstract During the progress of xanthan from a recent discovery to its present status as a well-established food hydrocolloid, some investigations have indicated that the ordered structure, which underlies most of the practical applications of xanthan, is a single helix stabilised by ordered packing of sidechains along the polymer backbone, giving first-order kinetics for the disorder–order transition. Others favoured a coaxial double helix, whose formation causes a doubling of molecular weight and mass per unit length. It is proposed here that both interpretations are correct, and that ordering is a 2-stage process: formation of single helices followed, under favourable conditions, by enthalpically-driven conversion to coaxial double helices. Comparison of recent evidence from atomic force microscopy with models from analysis of X-ray fibre diffraction data suggests that the most likely coaxial arrangement is an antiparallel 5 1 double helix. Graphical abstract Image Highlights • Rapid progress of xanthan from recent discovery to major food hydrocolloid. • Accompanying evidence of both single-helix and double-helix structures. • Proposed interpretation in terms of 2-stage process of conformational ordering. • Stage 1: coil–single helix transition; stage 2: conversion to 5 1 double helices. [ABSTRACT FROM AUTHOR]

Abstract Collagen-based materials are probably among the most used class of biomaterials in tissue engineering and regenerative medicine. Although collagen is often privileged for providing a suitable substrate on which cells can be cultured or a matrix in which cells can be dispersed, its mechanical properties represent a major limitation for clinical translation and even for handling of the obtained regenerated tissue. In this work, the combination of polysaccharides chitosan (Ch) and xanthan gum (X) was investigated as an alternative for scaffolds for soft tissue engineering. Moreover, in an attempt to reach a compromise between obtaining highly porous biomaterials while maintaining appropriate mechanical properties, a surfactant (Kolliphor® P188, K) was added to Ch-X matrices to generate pores, while silicone rubber (Silpuran® 2130A/B, S) was used to balance their mechanical properties. Addition of K (10 or 25% w/w) increased the porosity and pore-dimensions, while addition of S improved by up to 156% and 85% the elastic moduli and the elastic behavior of Ch-X-based scaffolds, under both compressive and tensile loads, respectively, at 50% strain. Relaxation tests confirmed that these materials do have a viscoelastic behavior. The presence of S increased thickness and microscale surface roughness and did not affect liquid uptake and stability, thrombogenicity, biodegradation and cytotoxicity of polysaccharide-based scaffolds. In conclusion, this work shows that Ch-X-S porous blends constitute suitable scaffolds for soft tissue engineering. Highlights • Chitosan-xanthan based materials were investigated for application in soft tissue engineering. • Porous matrices were obtained by adding different proportions of surfactant (Kolliphor® P 188). • Mechanical properties were improved after addition of a silicone liquid rubber (Silpuran 2130 A/B®). • Silicone improved the elastic moduli of Ch-X-based scaffolds, under compressive and tensile loads. • Ch-X-Silicone porous blends constitute suitable scaffolds for soft tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract The sensitivity of microorganisms to low pH can be utilized in food protection by preparing coatings based on macromolecular acids. Due to limited diffusivity of macromolecules low pH occurs primarily at the surface, while the interior parts of the food remain unaffected. This principle is demonstrated using food approved alginic acid in various types of coatings (aqueous, emulsions, dispersions, dry coating) on a wide range of foods including meat, fish, chicken, shrimp and boiled rice. Significant delay or inhibition of the natural flora is generally demonstrated, particularly when exposed to 'temperature abuse'. Specifically, we show that the coatings reduce or inhibit regrowth of pathogens (Bacillus cereus , B. weihenstephanensis , Listeria monocytogenes serotype 1 and Staphylococcus aureus). In special cases like boiled rice, alginic acid may largely replace acetic acid for acidification and preservation, as demonstrated studying regrowth of added spores of B. cereus. Most formulations allow easy removal prior to further processing (cooking, frying). Temporary side effects such as 'acid cooking' obtained for high acid concentrations on sensitive surfaces (e.g. salmon) disappear during processing, recovering the normal taste and texture. The coating is hence suitable for a large variety of foods. Highlights • Food coating formulations containing macromolecular alginic acid developed • Provide low surface pH for extended periods without affecting interior parts • Protect against external microbial contamination, including pathogens • Increase shelf-life by suppressing natural microbial growth and preventing regrowth • Applicable to a range of foods [ABSTRACT FROM AUTHOR]

Depending on the biocompatibility of Xanthan, polyvinyl alcohol and the antibacterial efficiency of zinc oxide nanoparticles (ZnO), a series of (Xanthan-polyvinyl alcohol)/ZnO nanocomposite hydrogels were prepared as wound dressing using eco-friendliness 60 Co γ-ray irradiation facility. ZnO nanoparticles were characterized using X-ray diffraction, UV–vis spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis. The size of ZnO nanoparticles was ranged between 15 and 25 nm. The presence of ZnO nanoparticles reconstructed the internal structure of the hydrogel network which aid in a homogenous porous structure as indicated by scanning electron micrographs. Such adequate porosity along with the presence of ZnO nanoparticles controls the fluid uptake ability, water retention and water vapor transmission rate. The fluid uptake ability in pseudo-extracellular fluid and water ranged between (554–664%) and (1281–1603%), respectively. After exposure to air for 6 h, ZnO dressings kept about 50–65% of their water content which makes them more suitable for moderate exudating wounds. Water vapor transmission rate ranged between 167 and 184 (g/(m 2  h) which is sufficient to keep wound's surface moist. ZnO dressings show an efficient microbial barrier potency and profound antimicrobial activity against Staphylococcus aureus , Escherichia coli and Candida albicans . In vitro cytotoxicity and haemolytic potency evaluation showed their biocompatibility. [ABSTRACT FROM AUTHOR]

In this work, we report the potential application of cold plasma technology for tailoring the functional properties of hydrocolloids. On treating xanthan gum in solid phase with atmospheric air cold plasma, we observed an increase in the viscosifying ability at low shear rates, and emulsion stabilizing activity of the gum, without affecting the colour or the basic polysaccharide backbone. The observed changes have potential benefits for salad-dressing and instant dry soup formulations. [ABSTRACT FROM AUTHOR]

Scale formation is a serious problem in water systems where it causes process fouling and interruption. Guar and xanthan gums are naturally occurring and environmentally safe carbohydrate polymers. In an attempt to investigate their antiscaling effect, Monte Carlo (MC) simulation method was employed to screen their tendency to adsorb on growing scale crystals. This study was performed on calcite (CaCO 3 ) and anhydrite (CaSO 4 ) crystals. Molecules of both polymers show a tendency to adsorb on both salts. Adsorption tendency of gum polymers on both minerals is expressed in terms of the values of adsorption energy calculated from Monte Carlo simulation method. The effect of polymerization degree and the number of water molecules on both adsorption energy and deformation energy is involved. MC observations indicate that Xanthan demonstrates a higher tendency for adsorption on calcite surface than guar while guar shows a higher tendency for adsorption on anhydrite. [ABSTRACT FROM AUTHOR]

The gelation properties and structure characteristics of tara gum blended with κ-carrageenan or xanthan were respectively investigated by texture analysis, dynamic rheology and morphological observation. Results indicated that tara gum, a non-gelling polysaccharide, could form thermo-reversible gels in the case of mixture of κ-carrageenan or xanthan, the melting and gelling points were elevated with increasing mixture concentration. There was a synergistic interaction in the two blend systems, which was directly observed by scanning electron microscope or atomic force microscope. The maximum gel strength occurred when blend ratio and blending temperature of the two blends (tara gum-κ-carrageenan, tara gum-xanthan) were 2:8, 80 °C; 4:6, 60 °C respectively. Besides, appropriate amount of salt ions could significantly enhance the gel strength of tara gum-κ-carrageenan blend gel, which could be weakened by excess salt ions. While salt ions had no obvious enhancing effect in the gelation of tara gum-xanthan blend system. The understanding of gelation properties and gelling mechanism is beneficial for the diversified and value-added application of tara gum in food and chemical industries. [ABSTRACT FROM AUTHOR]

Rheology-controlling agents are of importance for numerous products in a variety of industries. Replacement of synthetic chemicals with natural additives is desired in light of current environmental awareness and limited fossil resources. This study investigates the rheological features of Paenan, an exopolysaccharide produced by Paenibacillus polymyxa . Paenan exhibits highly shear-thinning flow behavior at concentrations ≥0.1% in 0.5% NaCl. Because of its pronounced intermolecular network, it forms stable, weak gels, thereby delivering elasticity as well as thixotropy. Application-relevant flow behavior is obtained with 60–65% less polymer as compared to the benchmark commercial products Xanthan and Gellan. In mixtures with surfactants (sodium lauryl ether sulfate, cetrimonium chloride, cocamidopropyl betaine, or lauryl glucoside), Paenan displays outstanding compatibility with every class of surfactant, making it superior to the partially incompatible Xanthan and Gellan. The weak-gel character of Paenan/surfactant systems is retained with three out of four surfactants, rendering Paenan highly interesting for various applications. [ABSTRACT FROM AUTHOR]

Similar to gluten, zein can form a viscoelastic network upon hydration and shear. This makes zein a promising protein to develop gluten-free bakery products. In this study, the effect of addition of different hydrocolloids (hydroxypropyl methylcellulose (HPMC), guar and xanthan gum), and the inclusion of pregelatinized starch (PG starch) and lactic acid (LA) on zein-corn starch dough and bread properties was examined. The addition of HPMC, and to a lesser extent guar gum, significantly changed the viscoelastic zein dough properties and resulted in bread samples with improved loaf volume and sensory properties. Scanning electron microscopy revealed the formation of a continuous fine foam-like structure in the zein-starch dough when HPMC and guar gum were added. This finer structure translated in a lower dough stiffness and resistance to deformation, and a higher degree of deformation characterized by lower complex moduli and increased creep compliance values. Xanthan gum addition, conversely, had an adverse effect on zein bread loaf volume which was attributed to potential weak repulsion between xanthan and zein molecules. In addition, the amount of α-helix and β-sheet secondary structures in bread samples was altered upon hydrocolloid and PG starch addition and played a role in bread crumb hardness. Overall, the zein bread with HPMC showed textural properties most similar to gluten bread. This research sheds light on different structure levels of zein-based gluten-free recipes as affected by inclusion of hydrocolloids, PG starch and LA, and provides a sound basis for the rational development of zein-based gluten-free breads. [Display omitted] • Zein forms a viscoelastic fibrillar network upon hydration and shear. • Zein-starch (Z-S) systems hold promise for gluten-free bread production. • Hydrocolloid addition alters the viscoelastic dough properties of Z-S recipes. • Hydrocolloid characteristics strongly determine protein structure in Z-S recipes. • Molecular built and microstructure of hydrocolloid Z-S dough relate to loaf quality. [ABSTRACT FROM AUTHOR]

Pickering emulsions stabilized by protein microgel, and hydrocolloid have shown desirable properties to be used as animal fat replacers. However, the potential applications of these structures as animal fat replacers in meat systems formulations have not been explored yet. Therefore, novel Pickering emulsions stabilized by canola proteins microgels and xanthan gum were developed, and their potential as animal fat replacer in meat systems was assessed for the first time. In the present study, 25, 50, 75, and 100% animal fat content were replaced by Pickering emulsion. Moreover, the obtained results revealed that complete fat replacement with canola proteins-based Pickering emulsion in meat emulsion improved its nutritional value by significantly enhancing the percentage of protein, monounsaturated and polyunsaturated fatty acid composition, and reduction of saturated fatty acid content compared to control (100% animal fat). Reformulation with PEs enhanced the meat systems' technological behavior such as emulsion stability and cooking loss, and oxidative stability. Also, significant total color difference (Δ E *) was observed only in samples with 100% fat replacement. Meat systems containing fat replacement ≤50% showed the closest texture parameters to the control sample. This study provides a promising alternative to replace animal fat with plant-based ingredients in meat systems. [ABSTRACT FROM AUTHOR]

The current work was designed to prepare a multifunctional cryogel based on zinc oxide nanoparticles (ZnONPs) loaded xanthan gum (XG) and cationic chitosan (CC) using a facile freeze-drying technique. The ZnONPs was prepared by solid state technique using XG as stabilizing agent. The features of the prepared materials were fully investigated. The results demonstrated that the prepared ZnONPs was smaller than 50 nm and has nearly hexagonal shape. The zeta potential (−41.54 mv) affirmed the well stability of the prepared ZnONPs. The ZnONPs loaded XG/CC composite cryogels exhibited porous morphological structures. The FTIR data also affirmed the chemical interaction between XG, CC and ZnONPs. After ensuring the successful preparation of cryogels, their adsorption efficiency toward reactive yellow 145 (RY145) dye and copper ions (Cu2+) was evaluated. The results displayed that the highest removal of RY145 dye (94%) and Cu2+ (93%) was achieved after 1 hr at pH 2 and 5 using 0.5 g/L and 1.0 g/L, respectively, of ZnONPs-4 @XG/CC cryogel. The kinetic, isotherm and thermodynamic studies revealed that the adsorption was favorable, multilayer, spontaneous, endothermic and mainly physisorption for RY145 and chemisorption for Cu2+. The co-existence of RY145 dye and Cu2+ in a solution decreases the adsorption of each other. The ZnONPs-4 @XG/CC cryogel removed color, aluminum, arsenic, boron, barium, iron, and lead from real textile wastewater sample. Moreover, the antimicrobial activities of nanocomposite cryogel (ZnONPs-4 @XG/CC) revealed highest resistance growth rate (R% = 100%) against both S. aureus and E. coli. Based on these obtained findings, the composite based on ZnONPs loaded XG/CC cryogel can be considered as promising material for an efficient wastewater treatment. • A facile freeze-drying technique was used for cryogel preparation. • Cryogel was formed from zinc oxide nanoparticles (ZnONPs) loaded admixture of both xanthan gum (XG) and cationic chitosan (CC). • The resultant cryogel exhibited porous structure, high surface area. • The results of adsorption study displayed the highest removal of RY145 dye (94%) and Cu2+ ion (93%). • The antimicrobial activities of nanocomposite cryogel revealed highest resistance growth rate (R% = 100%) against both S. aureus and E. coli. [ABSTRACT FROM AUTHOR]

Oil spills represent a serious threat for the ecosystem and human health. Materials with high porosity have been proven to be efficient as oil adsorbents. In this paper, new materials based on xanthan, lignin and their esters have been studied. The novelty of the present work consists in the esterification of lignin through an enzymatically catalyzed reaction. Lignin esters were added into a xanthan matrix to obtain adsorbent materials. FTIR, C13 NMR and XPS analyses have confirmed the success of the lignin esterification reaction. Materials based on xanthan, lignin and their esters were obtained. Their mechanical properties were evaluated. The adsorption of altered argan oil and sunflower oil onto the obtained materials was investigated. Experiments were carried out at different amounts of oil. For the kinetic study, measurements at different contact time were also done. It was found that the studied materials retained over 60% of the total oil quantity. Equilibrium data were well fitted to Henry, Langmuir and Harkin-Jura isotherm models. [Display omitted] • Lignin was esterified through an enzymatic reaction. • Xanthan-lignin based materials were obtained and used as adsorbents. • Kinetic data for all materials were best fitted to the pseudo-second-order model. • Adsorption process followed Henry, Langmuir and Harkin-Jura isotherm models. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interaction energy between xanthan and locust bean gum was analyzed using DFT. • The ordered xanthan with locust bean gum formed a geometry structure. • The disordered xanthan with locust bean gum formed a heterotypic structure. • Electrostatic interaction acted as the key force for geometry structure. • Hydrogen bond maintained the network structure of heterotypic structure. To explore the interaction sites and energies of ordered and disordered xanthan gum with locust bean gum (LBG), we prepared xanthan with different conformations and used it to form synergistic complexes with LBG. The interaction strength between xanthan and LBG was analyzed by analog computation using the density functional theory (DFT) method. Furthermore, the viscoelastic changes of the xanthan-LBG complex in different solutions were analyzed to verify the DFT results. The results showed that the ordered xanthan interacted with LBG through the side chains, with an interaction energy (E Int) of −479.450 kcal/mol. On the other hand, the disordered xanthan and LBG formed gels through backbone-to-backbone interactions, with an E Int of −262.290 kcal/mol. Overall, the study provides insights into xanthan-galactomannan gel formation and a theoretical basis for the broader application of xanthan. [ABSTRACT FROM AUTHOR]

The impact of pH on the physicochemical properties of 10% menhaden oil-in-water (O/W) emulsions containing 2% whey protein isolate (WPI) and 0.1% xanthan (XG)-locust bean gum (LBG) mixtures was investigated. The O/W emulsions containing 0.1% XG-LBG mixtures were compared to emulsions with 0.1% XG and 0.1% LBG. The results indicated that stability is dependent on pH and biopolymer type. At both pH 3 and 5, emulsions containing either XG or XG-LBG mixtures had large particle sizes, viscosity, droplet aggregation, and creaming index, resulting in poor physical stability which can be related to the adsorbed protein-polysaccharide interactions. At pH7, the XG-LBG emulsions showed the greatest resistance to phase separation and resulted in stable emulsions. Lipid oxidation measurements also indicated that XG-LBG mixtures can be used to form stable emulsions at pH 3 and pH 7. These results have significant implications for the development of novel structures containing lipid phases susceptible to lipid oxidation. [ABSTRACT FROM AUTHOR]

Prosopis ruscifolia (or vinal tree) is an abundant plant from Argentina semiarid areas, whose seeds contain a galactomannan type interesting gum: vinal gum. The aim of this work was to analyze the rheological behavior of vinal gum suspensions and the consequences of its interactions with commercial gums widely employed in the food industry. V inal gum aqueous suspensions were in good agreement with the Cox-Merz rule at concentrations lower or equal to 1% (w/w), which establishes an empirical relationship between complex and apparent viscosity. The flow curves of vinal gum could be defined only by two parameters -Newtonian viscosity (η 0 ) and strain rate ( γ ˙ 0.1 )- and the shear-thinning behavior of vinal gum complied with the generalized curve for other polysaccharides. In mixtures with xanthan gum, vinal gum exhibited a synergistic relationship on its elastic behavior (at a total gum concentration of 1% (w/w)). On the other hand, vinal gum showed no synergism with κ- carrageenan or sodium alginate at the same total concentration of polymer. Apparent viscosity of v inal gum aqueous suspensions showed Arrhenius type dependence with temperature, as other galactomannans. The rheological behavior was not dependent on shear time, and the thickening power of vinal gum was slightly affected by pH and ionic strength changes. The present work provides detailed information on rheological characteristics of a non-traditional galactomannan extracted from an abundant and available source, being a starting point for possible applications of vinal gum as thickening and/or stabilizing agent in food, pharmaceutical, paper, textile, oil and cosmetics industries. [ABSTRACT FROM AUTHOR]

The effects of acid hydrolysis intensity on the physicochemical properties of starch/xanthan gum (XG) system were studied. Waxy corn starch (WCS) was subjected to different concentrations of hydrochloric acid, and crystallization and relative molecular weight analysis were performed. The results revealed that the starch granules became smaller during acid hydrolysis. X-ray diffraction pattern analysis showed that the crystal structure did not change with acid hydrolysis. Evaluation of the properties and digestibility of different acid-thinned starch/XG systems indicated that the viscosity of acid-thinned starch/XG decreased with increased acid hydrolysis intensity. Rheological property measurements indicated that the compound systems were a pseudo-plastic fluid, which is a typical weak gel structure. Finally, we show that the WCS1.0 M/XG has the highest stability of the tested mixtures. We conclude that adjusting the conditions of acid hydrolysis improves the stability and food quality-enhancing properties of starch. [ABSTRACT FROM AUTHOR]

The impact of the chain stiffness on physicochemical properties has been studied by chemical modification of xanthan under both ordered and disordered conformations. Corresponding rheological properties were studied and results showed that amphiphilic xanthan exhibited completely different behaviors depending on its conformation during modification. Xanthan, when modified under ordered conformation, exhibits similar behavior to non-modified one, only the chain relaxation being strongly slowed down. Therefore, the high stiffness of xanthan helices does not allow hydrophobic moieties to associate. Oppositely, xanthan modified under its disordered conformation displayed a chemical gel-like behavior without any relaxation of the chain within the studied frequency range nor with temperature, which is unexpected for this length of alkyl chains. These different viscoelastic properties can be correlated to the regioselectivity of the grafting; the latter can be controlled by the conformation of xanthan during modification, thus by the synthesis conditions. [ABSTRACT FROM AUTHOR]

Xanthan is an extracellular polysaccharide of polyanionic nature widely used in industrial processes as flow modifier. Its characterization in dilute solutions is complicated by the strong tendency to aggregation. We explore the possibility to obtain dilute xanthan solutions without aggregates. We applied some steps of the sample preparation procedures from previous works on xanthan, such as ultrasonication, heating and micro filtration. The influence of this type of treatment on the observed properties of xanthan 0.1 M NaCl aqueous solutions is studied. Renaturalization of xanthan solutions above the overlap concentration does not break the aggregates but, on the opposite, produces the ones that are more resistant to ultrasound. Ultrasonication breaks only large aggregates and at long sonication times brings the risk of the single chain degradation. The best results are provided by a procedure that combines a short ultrasonication time followed by micro filtration but it is impossible to obtain a solution completely free of small aggregates by conventional sample preparation methods. Nevertheless, a significant reduction of large aggregates results in a linear concentration dependence of xanthan reduced viscosity, which allows more confident determination of the intrinsic viscosity. Another advantage of large aggregates removal is a possibility of physical interpretation of xanthan molecular parameters by static light scattering, taking into account its association tendency. [ABSTRACT FROM AUTHOR]

Emulsions are broadly used in pharmaceutics either as intermediate products or as final dosage forms. Such disperse systems are only kinetically stabilized and therefore early detection of physical instability is highly desirable. This work employed diffusing wave spectroscopy (DWS) to study a series of model emulsions that were categorized, based on their composition, as either “simple” or “complex”. DWS data were compared with results of droplet size imaging, apparent viscosity obtained by microfluidics, and near-infrared (NIR) analytical centrifugation. A mathematical model of the droplet mean square displacement (MSD) was modified by us regarding improved fitting of experimental data. Although the emulsions showed different types of instability like creaming and sedimentation, a good rank correlation was found between the DWS parameters and results from the comparative stability methods. Our findings indicate that DWS provides a highly attractive method for stability analysis of pharmaceutical emulsions because it requires only low sample volumes, is rapid and non-invasive. The proposed data modeling provides the means for a better understanding of emulsion microstructure that in turn will help designing quality into pharmaceutical dispersions. [ABSTRACT FROM AUTHOR]

The polysaccharide xanthan which is produced by the γ -proteobacterium Xanthomonas campestris is used as a food thickening agent and rheologic modifier in numerous food, cosmetics and technical applications. Its great commercial importance stimulated biotechnological approaches to optimize the xanthan production. By targeted genetic modification the metabolism of Xanthomonas can be modified in such a way that the xanthan production efficiency and/or the shear-thickening potency is optimized. Using atomic force microscopy (AFM) the secondary structure of single xanthan polymers produced by the wild type Xanthomonas campestris B100 and several genetically modified variations were analyzed. We found a wide variation of characteristic differences between xanthan molecules produced by different strains. The structures ranged from single-stranded coiled polymers to branched xanthan double-strands. These results can help to get a better understanding of the polymerization- and secretion-machinery that are relevant for xanthan synthesis. Furthermore, we demonstrate that the xanthan secondary structure strongly correlates with its viscosifying properties. [ABSTRACT FROM AUTHOR]

Aim The aim of this study was to modify xanthan, a well-known gelling agent, in order to treat sialorrhea, which increases salivary flow due to an excessive stimulus of the salivary reflex. Methods Chemical modification occurs by covalent attachment of l -cysteine (SH) to the polymeric backbone of xanthan (X) via amide bond formation. Safety considerations, water uptake capacity, and erosion were evaluated. Furthermore, mucoadhesiveness on buccal mucosa and vapor uptake studies were performed. In vitro/in vivo correlation of reduce of salivary flow was conducted and drug release of embedded tannin was determined. Results Safety investigations ensured modified X-SH being safe to use. X-SH exposed 1.5-x higher water uptake capacity in comparison to unmodified xanthan. Then, stability of X-SH augmented 5.5-fold in the case of matrix erosion studies. Reduction of salivary flow could be obtained 1.6-fold improved in case of X-SH compared to X. Furthermore, tannin was 1.8-fold controlled released in comparison to unmodified xanthan. Conclusion Taking these findings into consideration, chemical modified xanthan emerged with its distinctive properties as a promising approach in treating sialorrhea. [ABSTRACT FROM AUTHOR]