Campestris B100 Culture Grown in Minimal Medium with a Specific Focus on Nutrient Consumption and Xanthan Biosynthesis

Xanthan, a bacterial polysaccharide, is widespread in industrial applications, particularly as a food additive. However, little is known about the process of xanthan synthesis on the proteome level, even though Xanthomonas campestris is frequently used for xanthan fermentation. A label-free LC-MS/MS method was employed to study the protein changes during xanthan fermentation in minimal medium. According to the reference database, 2416 proteins were identified, representing 54.75 % of the proteome. The study examined changes in protein abundances concerning the growth phase and xanthan productivity. Throughout the experiment, changes in nitrate concentration appeared to affect the abundance of most proteins involved in nitrogen metabolism, except Gdh and GlnA. Proteins involved in sugar nucleotide metabolism stay unchanged across all growth phases. Apart from GumD, GumB, and GumC, the gum proteins showed no significant changes throughout the experiment. GumD, the first enzyme in the assembly of the xanthan-repeating unit, peaked during the early stationary phase but decreased during the late stationary phase. GumB and GumC, which are involved in exporting xanthan, increased significantly during the stationary phase. This study suggests that a potential bottleneck for xanthan productivity does not reside in the abundance of proteins directly involved in the synthesis pathways.

xanthanase

A new strain of xanthan-degrading bacteria identified as Cohnella sp. has been isolated from a xanthan thickener for food production. The strain was able to utilize xanthan as the only carbon source and to reduce the viscosity of xanthan-containing medium during cultivation. Comparative analysis of the secretomes of Cohnella sp. after growth on different media led to the identification of a xanthanase designated as CspXan9, which was isolated after recombinant production in Escherichia coli. CspXan9 could efficiently degrade the β-1,4-glucan backbone of xanthan after previous removal of pyruvylated mannose residues from the ends of the native xanthan side chains by xanthan lyase treatment (XLT-xanthan). Compared with xanthanase from Paenibacillus nanensis, xanthanase CspXan9 had a different module composition at the N- and C-terminal ends. The main putative oligosaccharides released from XLT-xanthan by CspXan9 cleavage were tetrasaccharides and octasaccharides. To explore the functions of the N- and C-terminal regions of the enzyme, truncated variants lacking some of the non-catalytic modules (CspXan9-C, CspXan9-N, CspXan9-C-N) were produced. Enzyme assays with the purified deletion derivatives, which all contained the catalytic glycoside hydrolase family 9 (GH9) module, demonstrated substantially reduced specific activity on XLT-xanthan of CspXan9-C-N compared with full-length CspXan9. The C-terminal module of CspXan9 was found to represent a novel carbohydrate-binding module of family CBM66 with binding affinity for XLT-xanthan, as was shown by native affinity polyacrylamide gel electrophoresis in the presence of various polysaccharides. The only previously known binding function of a CBM66 member is exo-type binding to the non-reducing fructose ends of the β-fructan polysaccharides inulin and levan.

Preliminary Assessment of Polysaccharide-Based Emulgels Containing Delta-Aminolevulinic Acid for Oral Lichen planus Treatment

Photodynamic therapy using delta-aminolevulinic acid is considered a promising option in the treatment of oral lichen planus. In the present work, three emulgel compositions prepared from natural polysaccharide gums, tragacanth, xanthan and gellan, were preliminarily tested for oromucosal delivery of delta-aminolevulinic acid. Apart from cytotoxicity studies in two gingival cell lines, the precise goal was to investigate whether the presence of the drug altered the rheological and mucoadhesive behavior of applied gelling agents and to examine how dilution with saliva fluid influenced the retention of the designed emulgels by oromucosal tissue. Ex vivo mucoadhesive studies revealed that a combination of xanthan and gellan gum enhanced carrier retention by buccal tissue even upon dilution with the saliva. In turn, the incorporation of delta-aminolevulinic acid favored interactions with mucosal tissue, particularly formulations comprised of tragacanth. The designed preparations had no significant impact on the cell viability after a 24 h incubation in the tested concentration range. Cytotoxicity studies demonstrated that tragacanth-based and gellan/xanthan-based emulgels might exert a protective effect on the metabolic activity of human gingival fibroblasts and keratinocytes. Overall, the presented data show the potential of designed emulgels as oromucosal platforms for delta-aminolevulinic acid delivery.

Evaluation of Oromucosal Natural Gum-Based Emulgels as Novel Strategy for Photodynamic Therapy of Oral Premalignant Lesions

Photodynamic therapy (PDT) recently has been shown as a promising option in the treatment of premalignant lesions of the soft oral tissues. Effective delivery of photosensitizer is challenging due to poor drug adherence to the oromucosal epithelium. In the present work, emulgels composed of natural polysaccharide gums (tragacanth, xanthan and gellan) were evaluated as novel oromucosal platforms of delta-aminolevulinic acid (ALA) for PDT. Apart from mucoadhesive and textural analysis, the specific steps involved studies on drug penetration behavior and safety profile using a three-dimensional human oral epithelium model (HOE). All designed emulgels presented greater mucoadhesiveness when compared to commercial oromucosal gel. Incorporation of ALA affected textural properties of emulgels, and tragacanth/xanthan formulation with greater hardness and cohesiveness exhibited a protective function against the mechanical tongue stress. Permeability studies revealed that ALA is capable of penetrating across oromucosal epithelium by passive transport and all formulations promoted its absorption rate when compared to a commercial topical product with ALA. Importantly, the combination of tragacanth and xanthan profoundly enhanced photosensitizer retention in the buccal epithelium. Tested samples performed negligible reduction in cell viability and moderately low IL-1β release, confirming their non-irritancy and compatibility with HOE. Overall, the presented findings indicate that tragacanth/xanthan emulgel holds promise as an oromucosal ALA-carrier for PDT strategy.

Effect of basil seed and xanthan gum on physicochemical, textural, and sensory characteristics of low-fat cream cheese

This study aims to produce fat-reduced cream cheese using the different levels (0.25%-0.5%) of basil seed and xanthan gum by a RSM method. The basil seed, xanthan gum, and fat levels did not significantly influence the cream cheese's pH and acidity. With the fat reduction, textural properties were lost; for example, hardness, gumminess, and adhesiveness increased, and cohesiveness decreased. In addition, low-fat cream cheese's sensory score (taste, mouthfeel, and overall acceptance score) was lower. However, adding basil seed and xanthan gum could improve water holding capacity (WHC), hardness, gumminess, cohesiveness, adhesiveness and scores of mouthfeel, and overall acceptance. Basil seed gum had a better impact than xanthan on fat-reduced cream cheese properties among the two gums. In general, results showed that adding 0.5% basil and 0.5% xanthan into cream cheese could manufacture a product with a reduced-fat level (19.04%). At the same time, its physicochemical, sensory, and textural attributes were similar to cream cheese with high fat (24%). In addition, the price of the obtained product was lower.

Production of Bacterial Exopolysaccharides: Xanthan and Bacterial Cellulose

Recently, degradable biopolymers have become increasingly important as potential environmentally friendly biomaterials, providing a wide range of applications in various fields. Bacterial exopolysaccharides (EPSs) are biomacromolecules, which due to their unique properties have found applications in biomedicine, foodstuff, textiles, cosmetics, petroleum, pharmaceuticals, nanoelectronics, and environmental remediation. One of the important commercial polysaccharides produced on an industrial scale is xanthan. In recent years, the range of its application has expanded significantly. Bacterial cellulose (BC) is another unique EPS with a rapidly increasing range of applications. Due to the great prospects for their practical application, the development of their highly efficient production remains an important task. The present review summarizes the strategies for the cost-effective production of such important biomacromolecules as xanthan and BC and demonstrates for the first time common approaches to their efficient production and to obtaining new functional materials for a wide range of applications, including wound healing, drug delivery, tissue engineering, environmental remediation, nanoelectronics, and 3D bioprinting. In the end, we discuss present limitations of xanthan and BC production and the line of future research.

Investigation of the influence of xanthan on mozzarella cheese characteristics focusing on its antimicrobial effect

Objective

This study was designed to show the effect of adding different levels of microbial (lab-produced) and commercial xanthan (CX) for 30 days on the sensory, chemical, and microbiological parameters of mozzarella cheese (MC).

Materials and Methods

The production of xanthan was done in Garcia-Ochoa's medium. The sensory evaluation of the examined MC was achieved through a tabulated scorecard. The Gerber method was used for the determination of MC fat%. The mean counts of staphylococci [colony forming unit (CFU)/gm], coliforms (most probable number/gm), fungi (CFU/gm), and mesophilic bacteria (CFU/gm) were estimated in different fortified cheeses. Also, mean counts of Escherichia coli O157 and Staphylococcus aureus in artificially contaminated MC were determined.

Results

The microbial xanthan (MX) had a significant (p < 0.05) effect on the sensory parameters of the examined samples with its concentration (0.0007%) after 20 days of storage. The MX (0.0005%) and CX (0.0002%) had a significant effect on moisture, fat in dry matter, and protein percentage of MC throughout the storage period. The high meltability degree of MC was observed in samples with both types of xanthan (0.0002%) at the end of storage.

Conclusion

Both types of xanthan at all concentrations had a significant reducing effect on E. coli O157 and S. aureus in all samples from 10 to 30 days of storage. Xanthan has accepted attentiveness and offers beneficial and safe characteristics that improve its adaptability in MC. In the Middle East, this survival trial of E. coli O157 and S. aureus in the MC supplemented by xanthan is considered a scarce exploratory investigation.

Ice-Templated and Cross-Linked Xanthan-Based Hydrogels: Towards Tailor-Made Properties

The use of polysaccharides with good film-forming properties in food packaging systems is a promising area of research. Xanthan gum (XG), an extracellular polysaccharide, has many industrial uses, including as a common food additive (E415). It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. Nevertheless, XG-based polymer films have some disadvantages, such as poor mechanical properties and high hydrophilic features, which reduce their stability when exposed to moisture and create difficulties in processing and handling. Thus, the objective of this work was to stabilize a XG matrix by cross-linking it with glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, or epichlorohydrin below the freezing point of the reaction mixture. Cryogelation is an ecological, friendly, and versatile method of preparing biomaterials with improved physicochemical properties. Using this technique, XG-based cryogels were successfully prepared in the form of microspheres, monoliths, and films. The XG-based cryogels were characterized by FTIR, SEM, AFM, swelling kinetics, and compressive tests. A heterogeneous morphology with interconnected pores, with an average pore size depending on both the nature of the cross-linker and the cross-linking ratio, was found. The use of a larger amount of cross-linker led to both a much more compact structure of the pore walls and to a significant decrease in the average pore size. The uniaxial compression tests indicated that the XG-based cryogels cross-linked with 1,4-butanediol diglycidyl ether exhibited the best elasticity, sustaining maximum deformations of 97.67%, 90.10%, and 81.80%, respectively.

Genomic and phenotypic insight into Xanthomonas vesicatoria strains with different aggressiveness on tomato

Xanthomonas vesicatoria is one of the causal agents of bacterial spot, a disease that seriously affects the production of tomato (Solanum lycopersicum) and pepper (Capsicum annum) worldwide. In Argentina, bacterial spot is found in all tomato producing areas, with X. vesicatoria being one of the main species detected in the fields. Previously, we isolated three X. vesicatoria strains BNM 208, BNM 214, and BNM 216 from tomato plants with bacterial spot, and found they differed in their ability to form biofilm and in their degree of aggressiveness. Here, the likely causes of those differences were explored through genotypic and phenotypic studies. The genomes of the three strains were sequenced and assembled, and then compared with each other and also with 12 other publicly available X. vesicatoria genomes. Phenotypic characteristics (mainly linked to biofilm formation and virulence) were studied in vitro. Our results show that the differences observed earlier between BNM 208, BNM 214, and BNM 216 may be related to the structural characteristics of the xanthan gum produced by each strain, their repertoire of type III effectors (T3Es), the presence of certain genes associated with c-di-GMP metabolism and type IV pili (T4P). These findings on the pathogenicity mechanisms of X. vesicatoria could be useful for developing bacterial spot control strategies aimed at interfering with the infection processes.

Exopolysaccharides Producing Bacteria: A Review

Bacterial exopolysaccharides (EPS) are essential natural biopolymers used in different areas including biomedicine, food, cosmetic, petroleum, and pharmaceuticals and also in environmental remediation. The interest in them is primarily due to their unique structure and properties such as biocompatibility, biodegradability, higher purity, hydrophilic nature, anti-inflammatory, antioxidant, anti-cancer, antibacterial, and immune-modulating and prebiotic activities. The present review summarizes the current research progress on bacterial EPSs including their properties, biological functions, and promising applications in the various fields of science, industry, medicine, and technology, as well as characteristics and the isolation sources of EPSs-producing bacterial strains. This review provides an overview of the latest advances in the study of such important industrial exopolysaccharides as xanthan, bacterial cellulose, and levan. Finally, current study limitations and future directions are discussed.

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G') was significantly greater than the viscous modulus (G″) for the entire frequency range.

Xanthan-Based Materials as a Platform for Heparin Delivery

Heparin (Hep), with its anticoagulant activity, antiangiogenic and apoptotic effects, and growth factor binding, plays an important role in various biological processes. Formulations as drug delivery systems protect its biological activity, and limit the potential side effects of faulty administration. The objective of this study was to develop novel xanthan-based materials as a delivery carrier for heparin. The materials exhibited remarkable elastic behavior and toughness without any crack development within the network, which also support their application for tissue engineering. It was found that all materials possessed the ability to control the release of heparin, according to the Korsmeyer-Peppas release model. All Hep-containing materials caused significant exchanges of the activated partial thromboplastin time (aPTT) and prothrombin time (PT) parameters, indicating that formulated natural/natural synthetic polymeric networks conserved heparin's biological activity and its ability to interrupt the blood coagulation cascade. The obtained results confirmed that developed materials could be carriers for the controlled release of heparin, with potential applications in topical administration.

Edible Xanthan/Propolis Coating and Its Effect on Physicochemical, Microbial, and Sensory Quality Indices in Mackerel Tuna (Euthynnus affinis) Fillets during Chilled Storage

Worldwide aquaculture production is increasing, but with this increase comes quality and safety related problems. Hence, there is an urgent need to develop potent technologies to extend the shelf life of fish. Xanthan gum is commonly used in the food industry because of its high-water solubility, stability of its aqueous solutions in a wide pH range, and high viscosity. One of its modern food applications is its use as a gelling agent in edible coatings building. Therefore, in this study, the effect of xanthan coating containing various concentrations (0, 1, 2%; w/v) of ethanolic extract of propolis (EEP) on physicochemical, microbial, and sensory quality indices in mackerel fillets stored at 2 °C for 20 days was evaluated. The pH, peroxide value, K-value, TVB-N, TBARS, microbiological and sensory characteristics were determined every 5 days over the storage period (20 days). Samples treated with xanthan (XAN) coatings containing 1 and 2% of EEP were shown to have the highest level of physicochemical protection and maximum level of microbial inhibition (p < 0.05) compared to uncoated samples (control) over the storage period. Furthermore, the addition of EEP to XAN was more effective in notably preserving (p < 0.05) the taste and odor of coated samples compared to control.

Effect of agave fructans on xanthan rheology: Impact on sodium caseinate emulsion properties

The influence of agave fructans (AF) (1-10%) and xanthan (from 0.03% to 0.25%) in combination with sodium caseinate (SC) at 1% on the rheological and physicochemical properties of aqueous phases and emulsions was evaluated. Steady-state flow behavior, particle size distribution, and stability studies were used to characterize the systems. The aqueous systems displayed the shear-thinning behavior characteristic of xanthan solutions; however, this behavior was modified by the presence of SC and AF due to interactions between AF-SC and AF-xanthan based on predominant hydrogen bonding because of the hydroxyl groups on AF. In emulsions, an increase in viscosity due to the effect of the AF concentration reflects a probable association of fructan aggregates on the surface of SC particles that reinforce the interfacial layer of SC, while xanthan contributes to an increase in the viscosity of the continuous phase, which effectively prevents coalescence and floc formation even at higher concentrations, despite the possible existence of a depletion flocculation effect attenuated by the interaction between AF-SC and AF-xanthan. PRACTICAL APPLICATION: These results can be of use, in an important way, in the design of stable functional emulsions in which there is an application for agave fructans recognized as dietary fiber, also considering their peculiar way of interacting with xanthan favoring its stabilizing functionality.

Understanding relations between rheology, tribology, and sensory perception of modified texture foods

The aim of this work was to examine relations between instrumental and sensory parameters in a texture modified food matrix, with and without saliva. Nine pureed carrot samples (eight thickened and a control) were developed with starch (0.4 and 0.8% wt/wt), xanthan (0.2 and 0.4% wt/wt) or starch-xanthan blends that met International Dysphagia Diet Standardisation Initiative (IDDSI) Level 4 guidelines using fork and spoon tests. Rheological and tribological tests were conducted on the food and simulated bolus prepared by adding fresh stimulated saliva to the food (1:5, saliva:food) to mimic oral processing. Perceived sensory properties were identified using a temporal dominance of sensations (TDS) test (n = 16) where panelists were given a list of nine attributes. The area under the curve was extracted from TDS curves for each attribute/sample and this was correlated with rheological (viscosity at 10 s^-1 , G', G″, and tan δ at 1 Hz) and tribological (friction coefficient in three regimes) data. The viscosity of the control sample decreased after adding hydrocolloids (except Starch_0.8%) and with saliva incorporation. G' and G″ either increased or were similar for xanthan and blends and decreased for starch-thickened samples. Hydrocolloid addition increased friction for all samples and was higher with saliva addition. Sensory results showed that samples with starch were perceived as thick and grainy while xanthan was perceived as smooth and slippery. A greater number of sensory attributes correlated with viscoelastic parameters compared to friction coefficients. Correlations were highest with the saliva added samples, further highlighting the importance of including saliva during instrumental testing.

Food Xanthan Polysaccharide Sulfation Process with Sulfamic Acid

Xanthan is an important polysaccharide with many beneficial properties. Sulfated xanthan derivatives have anticoagulant and antithrombotic activity. This work proposes a new method for the synthesis of xanthan sulfates using sulfamic acid. Various N-substituted ureas have been investigated as process activators. It was found that urea has the greatest activating ability. BBD of xanthan sulfation process with sulfamic acid in 1,4-dioxane has been carried out. It was shown that the optimal conditions for the sulfation of xanthan (13.1 wt% sulfur content) are: the amount of sulfating complex per 1 g of xanthan is 3.5 mmol, temperature 90 °C, duration 2.3 h. Sulfated xanthan with the maximum sulfur content was analyzed by physicochemical methods. Thus, in the FTIR spectrum of xanthan sulfate, in comparison with the initial xanthanum, absorption bands appear at 1247 cm-1, which corresponds to the vibrations of the sulfate group. It was shown by GPC chromatography that the starting xanthan gum has a bimodal molecular weight distribution of particles, including a high molecular weight fraction with Mw > 1000 kDa and an LMW fraction with Mw < 600 kDa. It was found that the Mw of sulfated xanthan gum has a lower value (~612 kDa) in comparison with the original xanthan gum, and a narrower molecular weight distribution and is characterized by lower PD values. It was shown by thermal analysis that the main decomposition of xanthan sulfate, in contrast to the initial xanthan, occurs in two stages. The DTG curve has two pronounced peaks, with maxima at 226 and 286 °C.

Glimepiride-Loaded Nanoemulgel; Development, In Vitro Characterization, Ex Vivo Permeation and In Vivo Antidiabetic Evaluation

Glimepiride (GMP), an oral hypoglycemic agent is extensively employed in the treatment of type 2 diabetes. Transdermal delivery of GMP has been widely investigated as a promising alternative to an oral approach but the delivery of GMP is hindered owing to its low solubility and permeation. The present study was designed to formulate topical nanoemulgel GMP system and previously reported solubility enhanced glimepiride (GMP/βCD/GEL-44/16) in combination with anti-diabetic oil to enhance the hypoglycemic effect. Nanoemulsions were developed using clove oil, Tween-80, and PEG-400 and were gelled using xanthan gum (3%, w/w) to achieve the final nanoemulgel formulations. All of the formulations were evaluated in terms of particle size, zeta potential, pH, conductivity, viscosity, and in vitro skin permeation studies. In vivo hypoglycemic activity of the optimized nanoemulgel formulations was evaluated using a streptozocin-induced diabetes model. It was found that a synergistic combination of GMP with clove oil improved the overall drug permeation across the skin membrane and the hypoglycemic activity of GMP. The results showed that GMP/βCD/GEL-44/16-loaded nanoemulgel enhanced the in vitro skin permeation and improved the hypoglycemic activity in comparison with pure and marketed GMP. It is suggested that topical nano emulsion-based GMP gel and GMP/βCD/GEL-44/16 could be an effective alternative for oral therapy in the treatment of diabetes.

Efficacy of Xanthan-Based Chlorhexidine Gel on the Levels of Interleukin-1β in Chronic Periodontitis: An Interventional Study

Aims and Objectives:

Xanthan-based chlorhexidine gel (Chlosite®) is a local drug delivery system that exposes the sub-gingival bacteria to the effects of chlorhexidine (CHX) for a prolonged time. Hence, the study aimed at evaluating the clinical efficacy of the subgingival application of Chlosite gel as an adjunctive to mechanical scaling and root planing (SRP) and at evaluating the salivary interleukin (IL)-1β level to substantiate the clinical efficacy of xanthan-based CHX gel.

Materials and Methods:

A total number of 40 patients with chronic periodontitis in the age group of 30–50 years were enrolled in this interventional study. The patients were assigned to group A, in which only SRP was done, and group B, in which SRP along with the subgingival application of Chlosite gel was done. Periodontal parameters and salivary IL-1β level were evaluated, and the data obtained were statistically analyzed by using paired and unpaired “t” tests.

Results:

The results obtained showed a statistically significant reduction in the mean gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL), and salivary IL-1β values in both the groups from baseline to 30 days. There was a statistically significant reduction in GI, in group B when compared with group A, after the treatment. Salivary IL-1β value in group B was slightly lower when compared with group A after the treatment, but it was not statistically significant.

Conclusions:

The xanthan-based CHX gel is therapeutically effective when used as an adjunct to SRP. The study also indicated that salivary IL-1β can be used as a reliable biomarker.

Effect of Intake of Food Hydrocolloids of Bacterial Origin on the Glycemic Response in Humans: Systematic Review and Narrative Synthesis

Diabetes mellitus is a chronic condition characterized by increased blood glucose levels from dysfunctional carbohydrate metabolism. Dietary intervention can help to prevent and manage the disease. Food hydrocolloids have been shown to have favorable properties in relation to glycaemic regulation. However, the use of food hydrocolloids of bacterial origin to modulate glucose responses is much less explored than other types of hydrocolloids. We, therefore, carried out the first review examining the impact of intake of food hydrocolloids of bacterial origin (as a direct supplement or incorporated into foods) on glycemic response in humans. Fourteen studies met the inclusion criteria. They used either xanthan gum, pullulan, or dextran as interventions. There was a wide variation in the amount of hydrocolloid supplementation provided and methods of preparation. Postprandial blood glucose responses were reduced in half of the studies, particularly at higher intake levels and longer chain hydrocolloids. When xanthan gum was added to the cooking process of muffins and rice, a significant reduction in postprandial blood glucose was observed. The use of these hydrocolloids is potentially effective though more research is needed in this area.

Development and Evaluation of Rifampicin Loaded Alginate-Gelatin Biocomposite Microfibers

Various systematic phases such as inflammation, tissue proliferation, and phases of remodeling characterize the process of wound healing. The natural matrix system is suggested to maintain and escalate these phases, and for that, microfibers were fabricated employing naturally occurring polymers (biopolymers) such as sodium alginate, gelatin and xanthan gum, and reinforcing material such as nanoclay was selected. The fabrication of fibers was executed with the aid of extrusion-gelation method. Rifampicin, an antibiotic, has been incorporated into a biopolymeric solution. RF1, RF2, RF3, RF4 and RF5 were coded as various formulation batches of microfibers. The microfibers were further characterized by different techniques such as SEM, DSC, XRD, and FTIR. Mechanical properties and physical evaluations such as entrapment efficiency, water uptake and in vitro release were also carried out to explain the comparative understanding of the formulation developed. The antimicrobial activity and whole blood clotting of fabricated fibers were additionally executed, hence they showed significant results, having excellent antimicrobial properties; they could be prominent carriers for wound healing applications.

Polyacrylamide Grafted Xanthan: Microwave-Assisted Synthesis and Rheological Behavior for Polymer Flooding

Application of polymer-flooding systems in secondary and tertiary oil recovery represents a real challenge for oil industry. In this work, our main objective is to explore possibilities of making use of xanthan-g-polyacrylamide for polymer flooding in a particular Devonian oilfield of medium salinity. The graft polymer was synthesized by using microwave-assisted graft copolymerization reaction of acrylamide on xanthan. The synthesized copolymer with optimized grafting parameters has been characterized by Infrared Spectroscopy and Thermal Analysis (DSC). Rheological analysis by steady shear and oscillatory flow experiments have been subsequently performed for xanthan and grafted xanthan under reservoir conditions. In steady shear, as expected the grafted polymer solutions flow as shear-thinning materials and apparent viscosity showed good fits with Cross's model. The viscosity losses due to salinity or temperature are more controlled for the grafted xanthan compared to pristine xanthan. When the grafted polymer concentration is increased to 2000 ppm the losses were halved. In oscillatory shear, the copolymer solutions followed a global behavior of semi-dilute entangled systems; furthermore, all dynamic properties were influenced by the brine salinity. Compared to xanthan, the elastic properties of xanthan-g-polyacrylamide solutions have been significantly improved in saline media and the losses in elasticity of grafted polymer solutions are lower.

pH-Dependent Gelation of a Stiff Anionic Polysaccharide in the Presence of Metal Ions

Cross-linking of polysaccharides by metal ions provides polymer gels highly required by industrial applications. In this article, we study the rheological properties and microstructure of solutions of a stiff anionic polysaccharide xanthan cross-linked by chromium (III) ions, and we demonstrate that their properties are highly sensitive to the preparation pH. Stable gels are obtained in a wide range of pH from 2.4 to 7.8. The maximum elastic modulus is observed for the gels made at pH 6.3, and by freeze-fracture transmission electron microscopy it is shown that they are characterized by the most dense network structure. However, out of this pH interval, no gelation is observed. At low pH (< 2.4) it is due to high protonation of carboxylic groups of xanthan preventing their interaction with chromium ions, and to the disappearance of oligomeric ions, which are effective in cross-linking. At high pH (> 7.8) the absence of gelation is caused by the transformation of reactive chromium ions into insoluble chromium hydroxide. At the same time, for the gels initially formed at pH 6.3, subsequent change of pH to strongly acidic (1.4) or basic (8.9) medium does not affect appreciably their properties, meaning that chromium cross-links are stable once they are formed. These observations open a reliable route to produce polysaccharide gels with required mechanical properties in a wide pH range where they initially cannot be prepared. It is also shown that the increase of pH to 6.3 of the initially ungelled solution prepared at pH 1.5 results in gelation. This effect offers a facile way for delayed gelation of polysaccharides, which is especially required by oil industry.

Clinically Relevant Insulin Degludec and its Interaction with Polysaccharides: A Biophysical Examination

Protein polysaccharide complexes have been widely studied for multiple industrial applications and are popular due to their biocompatibility. Insulin degludec, an analogue of human insulin, exists as di-hexamer in pharmaceutical formulations and has the potential to form long multi-hexamers in physiological environment, which dissociate into monomers to bind with receptors on the cell membrane. This study involved complexation of two negatively charged bio-polymers xanthan and alginate with clinically-relevant insulin degludec (PIC). The polymeric complexations and interactions were investigated using biophysical methods. Intrinsic viscosity [η] and particle size distribution (PSD) of PIC increased significantly with an increase in temperature, contrary to the individual components indicating possible interactions. [η] trend was X > XA > PIC > A > IDeg. PSD trend was X > A > IDeg > XA > PIC. Zeta (ζ)- potential (with general trend of IDeg < A < XA < X ≈ PIC) revealed stable interaction at lower temperature which gradually changed with an increase in temperature. Likewise, sedimentation velocity indicated stable complexation at lower temperature. With an increase in time and temperature, changes in the number of peaks and area under curve were observed for PIC. Conclusively, stable complexation occurred among the three polymers at 4 °C and 18 °C and the complex dissociated at 37 °C. Therefore, the complex has the potential to be used as a drug delivery vehicle.

Assessment of simultaneous addition of sucrose and xanthan effects on the thermal, pasting, and rheological behavior of corn starch

Thermal, pasting, and rheological properties of starch-based systems are the key characteristics for its processing. This study aimed to investigate the main and interactive effects of sucrose and xanthan on the thermal, pasting, and rheological behavior of corn starch. A central composite design (CCD) was used to evaluate the effect of simultaneous addition of sucrose and xanthan on some processing properties of starch-based systems. The results showed that besides the xanthan and sucrose effects (p < .001), the interactions played a significant role in all considered properties of corn starch except the flow behavior index (p < .05). Adding xanthan and sucrose increased the transition temperatures and the enthalpy change (ΔH) of the starch gelatinization, while they increased all pasting properties except setback viscosity. Statistical analysis results revealed the synergistic effects due to adding xanthan and sucrose on the thermal and pasting properties of starch. These were ascribed to the first- and second-order interaction effects (p < .05). Regression models proposed for prediction of all considered properties of the starch-based mixtures in the range of selected factors (R² > 0.88). The Fourier-transform infrared (FTIR) spectra revealed an increase in hydrogen bonding by increasing xanthan and sucrose. Since the formation of hydrogen bonds between mixture components could be affected the considered properties of the starch pastes. PRACTICAL APPLICATIONS: Starch-based foods are the most frequently consumed kind of foods in the developing countries, which provide a great deal of energy, and nutrients in a healthy diet. Therefore, the production of these kinds of food products is of great importance. The gelatinization, pasting, and rheological properties of starch-based foods are imperative aspects in its processing. These properties show differences according to the presence of other ingredients such as hydrocolloids and sweeteners. Since the addition of xanthan as hydrocolloid and sugar as a common sweetener in starch-based foods, affect optimal processing condition. Knowing the effects of the hydrocolloid and sweetener addition on thermal, pasting, and rheological properties of starch systems, help to improve the process and finding optimal process conditions for the production of sauces, baby foods, bread, confectionery, etc.

Improvement of gluten-free bread and cake properties using natural hydrocolloids: A review

The main wheat component responsible for bread and cake quality is gluten. Celiac disease is an autoimmune digestive disease that is caused by the digestion of gluten, and the only treatment of this disease is a gluten-free diet. Various gluten-free formulations (composite and wheatless flours) have applied gums (as gluten substitutes) to mimic the viscoelastic properties of gluten. In the bakery products, gums have been used to improve dough performance, bread and cake characteristics, textural and sensorial quality, and extension the products shelf life. This paper reviews the effect of the most common and new hydrocolloids (balangu seed, wild sage seed, basil seed, cress seed, xanthan, guar, starch carrageenan, methylcellulose, carboxy methyl cellulose, hydroxyl propyl methyl cellulose, and locust bean gums) on the rheological, physicochemical, textural, and quality characteristics of gluten-free breads and cakes. Gums affect gelatinization and retrogradation of starch through a strong association of amylose with gum, resulting in a decrease in the retrogradation of starch. Gums addition increased volume and porosity of the breads and cakes and resulted in softer products.

Water-Erodible Xanthan-Acrylate-Polyurethane Antifouling Coating

Biopolymer xanthan (Xn) and its functionalized polymer xanthan acrylate (XnAc) were used to improve the antifouling properties of synthesized waterborne polyurethane (WBPU) coatings, namely, WBPU-Xn and WBPU-XnAc. XnAc was synthesized by functionalization of xanthan (Xn) using polyacrylic acid. Coating hydrophilicity, adhesive strength, and erosion all varied with the Xn and XnAc contents. A moderate erosion rate was recorded only for the WBPU-XnAc coating. A good antifouling property for longer time was found in the WBPU-XnAc coating using zinc pyrithione as a biocide in the field test.

Effect of common and new gums on the quality, physical, and textural properties of bakery products: A review

Hydrocolloids (gums) have a good functional characteristic such as emulsifying, gelling, solubility, and textural improvement. In the bakery products, hydrocolloids were used to improving dough performance, bread and cake characteristics, sensorial quality, and extension the products shelf life. Several studies reported the potential use of hydrocolloids in breads, biscuits, cakes, and pasta formulation. The present review summarized the effect of the most common and new hydrocolloids (xanthan, guar, Arabic, carrageenan, karaya, alginate, acacia, methylcellulose, carboxy methyl cellulose, hydroxyl propyl methyl cellulose, locust bean, balangu seed, wild sage seed, basil seed, and cress seed gums) on the rheological, physicochemical, textural, and quality characteristics of bakery products. Gums addition improved volume and porosity of the breads and cakes. Gums influence on the gelatinization and retrogradation of starch and decreased the retrogradation of starch. In the bakery products, hydrocolloids were used to improving mixing and increasing the shelf life of the products through moisture preservation and avoidance of syneresis in some frozen foods. This study summarized the influence of the most common and new hydrocolloids on the rheological, physicochemical, textural, and quality characteristics of bakery products. Addition of seeds gum to the breads, biscuits, cakes, and pasta formula led to an increase in the viscosity of the batter. Also, the firmness of bakery products showed that they became softer with increasing gum levels.

Biopolymers interaction elaborating using viscoelastic relaxation spectra, network parameters, and thermodynamic properties

Herein, oscillatory rheological measurements were performed to study the interaction behavior of xanthan gum-sage seed gum blends at different ratios (SSG-XG: 1-0, 3-1, 1-1, 1-3, 0-1), from the dynamic viscosity behavior, relaxation spectrum, fracture properties, network parameters, and thermodynamic points of view at the temperature range of 10-90°C. Then, the coefficient of the interaction of four parameters, which were obtained from the clustering technique and Han curves, were used to investigate the interaction behavior quantitatively. At 90°C, SSG showed 2.01 extent of loss modulus overshoot, which was the highest value among different gum dispersions at different temperatures, while XG showed strain softening behavior. At 10 and 90°C, SSG and 1-1 SSG-XG showed the highest spreadability reflected by the slope of loss tangent after flow point stress (tan δ_AF ) of 0.52 and 0.40, respectively. The high values of ψ parameter, which represented the Gibbs free energy change, of both 1-3 and 3-1 SSG-XG blends and the lowest entropy value of 1-3 SSG-XG, suggested that the role of entropy change in incompatibility behavior of 1-3 SSG-XG was higher than that of 3-1 SSG-XG blend. With the increase in temperature from 10 to 70°C, the XG Euclidean distance from SSG decreased, while it increased from 70 to 90°C and showed the highest Euclidean distance with XG at 10°C (3.92) and 90°C (4.05). Interaction coefficients and Han curves results showed that all blends were incompatible with the lowest antagonistic behavior for 1-1 SSG-XG dispersion at 50°C. Often, a mixture of hydrocolloids, especially xanthan gum and a galactomannan, are employed in processed foods to modify their rheological properties and cut the cost. The synergistic/non-synergistic effect of biopolymers mixture, which is invaluable from the practical and economical points of view, seems to be mainly induced by their thermodynamic status of interaction. Our former study showed that the thermodynamic indices of mixing could be probed by mechanical parameters. On the other hands, we found that the mechanical properties of materials are highly temperature dependent. Therefore, in this study, to better investigate the effect of temperature on the biopolymers interaction, first we classified all the thermodynamic and mechanical properties (relaxation spectrum, fracture properties, and network parameters) of hydrocolloids into four classes, then one parameter was selected randomly from each class. The selected parameters were employed to investigate the synergistic/non-synergistic effect at all temperature ranges by determining the interaction coefficient and decide on the best interaction temperature.

Characterizing the Dynamic Textural Properties of Hydrocolloids in Pureed Foods-A Comparison Between TDS and TCATA

Pureed foods, a compensatory diet for dysphagia, require the incorporation of hydrocolloids in order to be swallowed safely. The effect of hydrocolloid addition on textural dynamics of pureed foods has not yet been investigated. Starch and xanthan were added to levels that allowed products to meet the criteria of the International Dysphagia Diet Standardization Initiative. Nine pureed carrot matrices made with two concentrations of starch, xanthan, and their blends were characterized for textural evolution using two dynamic sensory techniques: Temporal Dominance of Sensations (TDS) and Temporal Check-All-That-Apply (TCATA). Each test, with four replications, was conducted with 16 panelists. Results indicate that purees were divided into two groups based on sensory responses--grainy and smooth were the primary differentiating attributes for these two groups. Grainy was associated with starch-added samples, while samples with xanthan (alone and in blends) were smooth and slippery. For both groups, thickness was perceived during the first half of processing, adhesiveness in the second half of oral processing, and mouthcoating was perceived toward the end of processing. A comparison of results from these tests showed that both TDS and TCATA gave similar information about texture dynamics and product differentiation of pureed foods.

Impact of Different Gums on Textural and Microbial Properties of Goat Milk Yogurts during Refrigerated Storage

In this study, the impact of seven different gums on textural and microbiological properties of goat milk yogurt during refrigerated storage was investigated. The results showed that yogurt containing xanthan and locust bean gums had enhanced firmness, consistency, cohesiveness, and viscosity during four weeks of storage compared to the control and yogurt fortified with other gums (p < 0.05). The addition of gums also helped to maintain the microbial viability of the yogurt culture and the probiotic Bifidobacterium spp. This study thus demonstrated that these gums could be used in the production of goat milk yogurt with enhanced textural properties.

Nanohybrid hydrogels designed for transbuccal anesthesia

BACKGROUND

Local anesthesia in dentistry is by far the most terrifying procedure for patients, causing treatment interruption. None of the commercially available topical formulations is effective in eliminating the pain and phobia associated to the needle insertion and injection.

MATERIALS AND METHODS

In this work we prepared a nanostructured lipid-biopolymer hydrogel for the sustained delivery of lidocaine-prilocaine (LDC-PLC) for transbuccal pre-anesthesia. The lipid was composed of optimized nanostructured lipid carriers (NLC) loaded with 5% LDC-PLC (NLC/LDC-PLC). The biopolymer counterpart was selected among alginate, xanthan (XAN), and chitosan matrices. The XAN-NLC hydrogel presented the most uniform aspect and pseudoplastic rheological profile, as required for topical use; therefore, it was selected for subsequent analyses. Accelerated stability tests under critical conditions (40°C; 75% relative humidity) were conducted for 6 months, in terms of drug content (mg/g), weight loss (%), and pH.

RESULTS

In vitro LDC-PLC release profile through Franz diffusion cells revealed a bimodal kinetics with a burst effect followed by the sustained release of both anesthetics, for 24 hours. Structural analyses (fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy) gave details on the molecular organization of the hybrid hydrogel, confirming the synergic interaction between the components. Safety and efficacy were evaluated through in vitro cell viability (3T3, HaCat, and VERO cells) and in vivo antinociceptive (tail-flick, in mice) tests, respectively. In comparison to a control hydrogel and the eutectic mixture of 5% LDC-PLC cream (EMLA®), the XAN-NLC/LDC-PLC hybrid hydrogel doubled and quadrupled the anesthetic effect (8 hours), respectively.

CONCLUSION

Considering such exciting results, this multifaceted nanohybrid system is now ready to be further tested in clinical trials.

Synergistic interactions between konjac-mannan and xanthan/tragacanth gums in tomato ketchup: Physical, rheological, and textural properties

In this research, simultaneous contribution of konjac-mannan (0.3%), xanthan (0.3%), and tragacanth (0.3%) gums in tomato ketchup was investigated comparing the physicochemical, rheological, texture, and sensory properties with the control sample containing 0.3% xanthan gum. Samples selected through viscosity and syneresis evaluation of the nine prepared samples were analyzed by color, flow behavior, frequency sweep, particle size, texture, and sensory experiments. Results indicated that increasing xanthan concentration did not have any significant effect on the apparent viscosity while considerable improvement was observed in the physical stability of ketchups containing konjac-mannan/xanthan ascribed to smaller particles with larger contact surfaces encouraging gel network formation. Highest a* and a*/b* was observed for konjac-mannan/xanthan (0.075%/0.225%) in which formation of hydrated gel granules of gums intensifies light diffraction due to the decreased particle size. This synergistically formed viscous three-dimensional gel network is responsible for the highest cohesiveness and gumminess of the same sample between the ketchup formulations containing two gums. Organoleptic properties of ketchup samples containing konjac-mannan/xanthan showed no significant difference with the control sample. PRACTICAL APPLICATIONS: Development of modern food technologies along with the lifestyle changes over the past few decades and grown public awareness of the relevance between health and nutrition have considerably increased the consumption of ready meals containing low-fat and fiber-rich functional condiments. Ketchup is a popular sauce thickened with tomato pulp powder, potato or corn starch, modified starch, and severally available hydrocolloids such as carboxymethyl cellulose, xanthan, guar, and locust bean gum. In this research work, mixtures of konjac-mannan and xanthan/tragacanth hydrocolloids are used to produce new ketchups with improved physical and rheological properties and lower prices.

Improvement of viability of probiotic bacteria, organoleptic qualities and physical characteristics in kefir using transglutaminase and xanthan

BACKGROUND

Using kefir as a probiotic food carrier has many benefits. At the same time, it is considered an appropriate product for the dairy industry. The aim of this study was to evaluate the effect of xanthan gum and transglutaminase enzyme on the viability of probiotics and the organoleptic qualities and physicochemical characteristics of kefir.

METHODS

Three levels of transglutaminase enzyme (50, 100 and 150 ppm), and xanthan gum (0.05%, 0.1% and 0.2%) were used. Sensory and physicochemical properties and viability of probiotic bac- teria were measured over 2 weeks of storage at 4&deg;C.

RESULTS

By increasing the amounts of xanthan gum and transglutaminase, the viscosity of the samples was increased and syneresis was reduced significantly (P < 0.05). The kefir sample containing 150 ppm enzyme and 0.2% gum had the highest number of probiotic bacteria. Moreover, the highest organoleptic scores were found for this sample.

CONCLUSIONS

It can be concluded that adding 150 ppm transglutaminase and 0.2% xanthan improved the vi- ability of probiotics and the physical and organoleptic characteristics of kefir.

Application of Polysaccharide-Based Hydrogels as Probiotic Delivery Systems

Polysaccharide hydrogels have been increasingly utilized in various fields. In this review, we focus on polysaccharide-based hydrogels used as probiotic delivery systems. Probiotics are microorganisms with a positive influence on our health that live in the intestines. Unfortunately, probiotic bacteria are sensitive to certain conditions, such as the acidity of the gastric juice. Polysaccharide hydrogels can provide a physical barrier between encapsulated probiotic cells and the harmful environment enhancing the cells survival rate. Additionally, hydrogels improve survivability of probiotic bacteria not only under gastrointestinal track conditions but also during storage at various temperatures or heat treatment. The hydrogels described in this review are based on selected polysaccharides: alginate, κ-carrageenan, xanthan, pectin and chitosan. Some hydrogels are obtained from the mixture of two polysaccharides or polysaccharide and non-polysaccharide compounds. The article discusses the efficiency of probiotic delivery systems made of single polysaccharide, as well as of systems comprising more than one component.

Use of hydrophilic natural gums in formulation of sustained-release matrix tablets of tramadol hydrochloride

The objective of this work was to develop matrix sustained-release tablets of highly water-soluble tramadol HCl using natural gums (xanthan [X gum] and guar [G gum]) as cost-effective, nontoxic, easily available, and suitable hydrophilic matrix systems compared with the extensively investigated hydrophilic matrices (ie, hydroxypropyl methylcellulose [HPMC]/carboxymethyl cellulose [CMC] with respect to in vitro drug release rate) and hydration rate of the polymers. Matrix tablets of tramadol (dose 100 mg) were produced by direct compression method. Different ratios, of 100∶0, 80∶20, 60∶40, 20∶80, 0∶100 of G gum (or X):HPMC, X gum:G gum, and triple mixture of these polymers (G gum, X gum, HPMC) were applied. After evaluation of physical characteristics of tablets, the dissolution test was, performed in the phosphate buffer media (pH 7.4) up to 8 hours. Tablets with only X had the highest mean dissolution time (MDT), the least dissolution efficiency (DE₈%), and released the drug following a zero-order model via swelling, diffusion, and erosion mechanisms. Guar gum alone could not efficiently control the drug release, while X and all combinations of natural gums with HPMC could retard tramadol HCl release. However, according to the similarity factor (f ₂), pure HPMC and H₈G₂ were the most similar formulations to Topalgic-LP as the reference standard.

Enhancement of levodopa stability when complexed with β-cyclodextrin in transdermal patches

Levodopa is a promising candidate for administration via the transdermal route because it exhibits a short plasma half-life and has a small window of absorption in the upper section of the small intestine. The aim of this study was to prepare stable levodopa transdermal patches. Both xanthan gum and Carbopol 971 polymers were selected with ethylcellulose constituting the backing layer of the prepared patches. The effect of adding β-cyclodextrin on the prepared patches was investigated. The uniformity in thickness, weight and content of the studied patches was acceptable. Physicochemical characterization revealed that there was no interaction between levodopa and the applied polymer. The results proved that levodopa precipitated as an amorphous form in carbopol patches. Controlled drug release was achieved for all the tested patches over a 6 h period. However, increased permeation was achieved for the carbopol patches. Although cyclodextrin did not enhance levodopa permeation, the stability study confirmed that levodopa stability was enhanced when complexed with β-cyclodextrin. The cumulative amount of drug released from carbopol patches is slightly higher than that of xanthan patches. The optimal stability was achieved in the carbopol/levodopa:β-cyclodextrin patch. The levodopa-β-cyclodextrin complex was successfully characterized using X-ray diffraction, NMR analysis and molecular dynamics simulations. In conclusion, carbopol/levodopa:β-cyclodextrin patches can be considered as a promising stable and effective transdermal drug-delivery system.

Binding of the substrate UDP-glucuronic acid induces conformational changes in the xanthan gum glucuronosyltransferase

GumK is a membrane-associated glucuronosyltransferase of Xanthomonas campestris that is involved in xanthan gum biosynthesis. GumK belongs to the inverting GT-B superfamily and catalyzes the transfer of a glucuronic acid (GlcA) residue from uridine diphosphate (UDP)-GlcA (UDP-GlcA) to a lipid-PP-trisaccharide embedded in the membrane of the bacteria. The structure of GumK was previously described in its apo- and UDP-bound forms, with no significant conformational differences being observed. Here, we study the behavior of GumK toward its donor substrate UDP-GlcA. Turbidity measurements revealed that the interaction of GumK with UDP-GlcA produces aggregation of protein molecules under specific conditions. Moreover, limited proteolysis assays demonstrated protection of enzymatic digestion when UDP-GlcA is present, and this protection is promoted by substrate binding. Circular dichroism spectroscopy also revealed changes in the GumK tertiary structure after UDP-GlcA addition. According to the obtained emission fluorescence results, we suggest the possibility of exposure of hydrophobic residues upon UDP-GlcA binding. We present in silico-built models of GumK complexed with UDP-GlcA as well as its analogs UDP-glucose and UDP-galacturonic acid. Through molecular dynamics simulations, we also show that a relative movement between the domains appears to be specific and to be triggered by UDP-GlcA. The results presented here strongly suggest that GumK undergoes a conformational change upon donor substrate binding, likely bringing the two Rossmann fold domains closer together and triggering a change in the N-terminal domain, with consequent generation of the acceptor substrate binding site.

Systems Biology of Microbial Exopolysaccharides Production

Exopolysaccharides (EPSs) produced by diverse group of microbial systems are rapidly emerging as new and industrially important biomaterials. Due to their unique and complex chemical structures and many interesting physicochemical and rheological properties with novel functionality, the microbial EPSs find wide range of commercial applications in various fields of the economy such as food, feed, packaging, chemical, textile, cosmetics and pharmaceutical industry, agriculture, and medicine. EPSs are mainly associated with high-value applications, and they have received considerable research attention over recent decades with their biocompatibility, biodegradability, and both environmental and human compatibility. However, only a few microbial EPSs have achieved to be used commercially due to their high production costs. The emerging need to overcome economic hurdles and the increasing significance of microbial EPSs in industrial and medical biotechnology call for the elucidation of the interrelations between metabolic pathways and EPS biosynthesis mechanism in order to control and hence enhance its microbial productivity. Moreover, a better understanding of biosynthesis mechanism is a significant issue for improvement of product quality and properties and also for the design of novel strains. Therefore, a systems-based approach constitutes an important step toward understanding the interplay between metabolism and EPS biosynthesis and further enhances its metabolic performance for industrial application. In this review, primarily the microbial EPSs, their biosynthesis mechanism, and important factors for their production will be discussed. After this brief introduction, recent literature on the application of omics technologies and systems biology tools for the improvement of production yields will be critically evaluated. Special focus will be given to EPSs with high market value such as xanthan, levan, pullulan, and dextran.

Gamma scintigraphic evaluation of floating gastroretentive tablets of metformin HCl using a combination of three natural polymers in rabbits

The present research was aimed at formulating a metformin HCl sustained-release formulation from a combination of polymers, using the wet granulation technique. A total of 16 formulations (F1–F16) were produced using different combinations of the gel-forming polymers: tamarind kernel powder, salep (palmate tubers of Orchis morio), and xanthan. Post-compression studies showed that there were no interactions between the active drug and the polymers. Results of in vitro drug-release studies indicated that the F10 formulation which contained 5 mg of tamarind kernel powder, 33.33 mg of xanthan, and 61.67 mg of salep could sustain a 95% release in 12 hours. The results also showed that F2 had a 55% similarity factor with the commercial formulation (C-ER), and the release kinetics were explained with zero order and Higuchi models. The in vivo study was performed in New Zealand White rabbits by gamma scintigraphy; the F10 formulation was radiolabeled using samarium (III) oxide (¹⁵³Sm₂O₃) to trace transit of the tablets in the gastrointestinal tract. The in vivo data supported the retention of F10 formulation in the gastric region for 12 hours. In conclusion, the use of a combination of polymers in this study helped to develop an optimal gastroretentive drug-delivery system with improved bioavailability, swelling, and floating characteristics.

Nanostructured gellan and xanthan hydrogel depot integrated within a baghdadite scaffold augments bone regeneration

Controlled delivery of biological cues through synthetic scaffolds to enhance the healing capacity of bone defects is yet to be realized clinically. The purpose of this study was development of a bioactive tissue-engineered scaffold providing the sustained delivery of an osteoinductive drug, dexamethasone disodium phosphate (DXP), encapsulated within chitosan nanoparticles (CN). Porous baghdadite (BD; Ca₃ ZrSi₂ O₉ ) scaffolds, a zirconia-modified calcium silicate ceramic, was coated with DXP-encapsulated CN nanoparticles (DXP-CN) using nanostructured gellan and xanthan hydrogel (GX). Crosslinker and GX polymer concentrations were optimized to achieve a homogeneous distribution of hydrogel coating within BD scaffolds. Dynamic laser scattering indicated an average size of 521 ± 21 nm for the DXP-CN nanoparticles. In vitro drug-release studies demonstrated that the developed DXP-CN-GX hydrogel-coated BD scaffolds (DXP-CN-GX-BD) resulted in a sustained delivery of DXP over the 5 days (78 ± 6% of drug release) compared with burst release over 1 h, seen from free DXP loaded in uncoated BD scaffolds (92 ± 8% release in 1 h). To estimate the influence of controlled delivery of DXP from the developed scaffolds, the effect on MG 63 cells was evaluated using various bone differentiation assays. Cell culture within DXP-CN-GX-BD scaffolds demonstrated a significant increase in the expression of early and late osteogenic markers of alkaline phosphatase activity, collagen type 1 and osteocalcin, compared to the uncoated BD scaffold. The results suggest that the DXP-releasing nanostructured hydrogel integrated within the BD scaffold caused sustained release of DXP, improving the potential for osteogenic differentiation. Copyright © 2015 John Wiley & Sons, Ltd.

Sweetness and other sensory properties of model fruit drinks: Does viscosity have an impact?

BACKGROUND

The impact of thickening agents and viscosity levels on sensory perception was studied in model fruit drinks. Four formulations were prepared that varied in the sweetener blend (erythritol, maltitol and/or steviol glycosides). Locust bean gum and its blends with either xanthan or carrageenan were used to adjust viscosity levels (20, 40, and 70 mPa s). The ranges of viscosity and sweetness level were selected to represent a typical concentration range in commercially available beverages.

RESULTS

An increase in viscosity resulted in significant increases in pulpiness, sliminess and perceived viscosity (P-values ≤ 0.001), which were not dependent on sweeteners or hydrocolloid type. Taste perception remained largely unchanged irrespective of the hydrocolloid used.

CONCLUSION

The impact of viscosity on sweetness and taste perception was much smaller in the concentrations used than has been generally reported. The effect of the type of hydrocolloid on the perception of taste attributes was greater than that of viscosity.

Properties of oil/water emulsions affecting the deposition, clearance, and after-feel sensory perception of oral coatings

The aims of this study were to investigate the influence of (i) protein type, (ii) protein content, and (iii) viscosity of o/w emulsions on the deposition and clearance of oral oil coatings and after-feel perception. Oil fraction (m(oil)/cm(2)(tongue)) and after-feel perception differed considerably between emulsions which do not flocculate under in mouth conditions (Na-caseinate) and emulsions which flocculate under in mouth conditions (lysozyme). The irreversible flocculation of lysozyme stabilized emulsions caused slower oil clearance from the tongue surface compared to emulsions stabilized with Na-caseinate. Protein content had a negative relation with oil fraction for lysozyme stabilized emulsions and no relation for Na-caseinate stabilized emulsions immediately after expectoration. Viscosity differences did not affect oil fraction, although the presence of thickener decreased deposition of oil on tongue. We conclude that after-feel perception of o/w emulsions is complex and depends on the deposited oil fraction, the behavior of proteins in mouth, and thickeners.

Real-time stability testing of air-dried primers and fluorogenic hydrolysis probes stabilized by trehalose and xanthan

A method for conserving primers and differently labeled fluorogenic hydrolysis (i.e., TaqMan) probes at ambient conditions is presented. Primers and hydrolysis probes with four different fluorophore-quencher combinations (6- FAM-BHQ1, HEX-BHQ1, ROX-BHQ650, and Cy5-BHQ2) were mixed with trehalose and xanthan at final concentrations of 56 mM and 2.78 mM, respectively. Mixtures were air-dried at 23°C for 30 min on strips composed of cyclo olefin polymer (COP), a material widely used in the manufacturing of in vitro diagnostic (IVD) test carriers. After one year of storage, the functionality of the primers and fluorophore-quencher combinations was validated by real-time polymerase chain reaction (real-time PCR), confirming their stability when stored in the presence of stabilizers, with the best results achieved using trehalose. This approach could be of great benefit for manufacturing IVD systems, for example, for genotyping applications based on multiplexing using different fluorescent dyes.

Electrostatic interactions of cationic lauric arginate with anionic polysaccharides affect antimicrobial activity against spoilage yeasts

AIMS

To investigate the effect of anionic polysaccharides often used in beverage applications (xanthan and λ-carrageenan) on the antimicrobial efficacy of the cationic surfactant lauric arginate (LAE) against typical spoilage yeasts.

METHODS AND RESULTS

The antimicrobial efficacy of LAE against Saccharomyces cerevisiae, Candida albicans and Zygosaccharomyces bailii in the absence and presence of anionic polysaccharides was assessed by microtitre and macrobroth dilution assays. Combining LAE with either xanthan or λ-carrageenan caused a pronounced decrease in LAE's antimicrobial efficacy, with the minimal inhibitory and lethal concentrations (MIC and MLC) both increasing with increasing polysaccharide concentration. This reduction in antimicrobial efficacy was more pronounced for the addition of λ-carrageenan. To determine the cause of loss of activity, physical properties of solutions were examined. Turbidity and sedimentation measurements indicated that complexes between LAE and anionic polysaccharides had been formed. Electrophoresis measurements showed that complexes had varying electrical charges and dimensions depending on solution composition.

CONCLUSION

Results suggest that electrostatic interactions between LAE and anionic polysaccharides play a major role in complex formation and loss of antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results have important implications for the utilization of LAE as an antimicrobial agent in beverage and food products containing anionic polysaccharides.

Minimal phenotypic test for simple differentiation of Xanthomonas campestris from other yellow-pigmented bacteria isolated from soil

BACKGROUND AND OBJECTIVES

Isolation of Xanthomonas campestris from soil has a wide range of applications from monitoring of phytopathogenic populations in soil to screening of improved xanthan-producing strains. Identification of Xanthomonas campestris and its pathovars requires pathogenicity tests in addition to phenotypic and molecular characterization.

MATERIALS AND METHODS

Thirty phenotypic tests were carried out on 57 yellow-pigmented bacterial isolates obtained from soil of cabbage farms after screening on Selective Xanthomonas (SX) agar and transferring on Yeast Malt agar. Absorption spectra of pigments and capability of biopolymer production were determined for the isolates. Some characteristics of the biopolymer produced and presence of a X. campestris-specific gene marker were investigated for nine putative X. campestris isolates.

RESULTS

The present study introduces a set of simple phenotypic tests including urease, acid production from sucrose, mucoid growth on 5% sucrose, starch hydrolysis, growth in 4% NaCl, motility and utilization of asparagine as sole carbon and nitrogen source for quick and inexpensive tentative identification of Xanthomonas campestris. Validation of these tests was confirmed in 100% of the cases by characterization of bacterial exopolysaccharide as xanthan and production of genus-specific xanthomonadin pigment. Moreover, tracking of hrc gene among putative X. campestris isolates gave positive results in 80% of cases.

CONCLUSION

The Minimal simple phenotypic tests facilitate the screening and differentiation of putative X. campestris isolates from other false bacterial strains isolated from soil on semiselective SX agar.

Crystallization and preliminary crystallographic characterization of GumK, a membrane-associated glucuronosyltransferase from Xanthomonas campestris required for xanthan polysaccharide synthesis

GumK is a membrane-associated inverting glucuronosyltransferase that is part of the biosynthetic route of xanthan, an industrially important exopolysaccharide produced by Xanthomonas campestris. The enzyme catalyzes the fourth glycosylation step in the pentasaccharide-P-P-polyisoprenyl assembly, an oligosaccharide diphosphate lipid intermediate in xanthan biosynthesis. GumK has marginal homology to other glycosyltransferases (GTs). It belongs to the CAZy family GT 70, for which no structure is currently available, and indirect biochemical evidence suggests that it also belongs to the GT-B structural superfamily. Crystals of recombinant GumK from X. campestris have been grown that diffract to 1.9 A resolution. Knowledge of the crystal structure of GumK will help in understanding xanthan biosynthesis and its regulation and will also allow a subsequent rational approach to enzyme design and engineering. The multiwavelength anomalous diffraction approach will be used to solve the phase problem.