Xanthan gum


Xanthan Gum Fermentations. Though xanthan gum fermentations become very viscous, the oxygen demand at this stage in a batch fermentation appears to be rather low and hot rate limiting. Bulk blending and pH control is of more significance (56). Stirred bioreactors are therefore preferable using large impeller to tank diameter ratios.  [c.336]

Although there are hundreds of different products and as many companies producing them, relatively few products rank ia aimual worldwide sales above 50,000,000. Included in this small group are the antibiotics, bacitracin, cephalosporins, erythromycin, gentamicins, kanamycin, neomycins, penicillins, tetracycline, tylosin, and some newer additions the enzymes amylases, diagnostic enzymes, glucose isomerase, rennet and proteases citric and gluconic acids ethanol vitamin B 2 amino acids, MSG, L-lysine, L-tryptophan, t.-phenylalanine, L-aspartic acid and miscellaneous substances, eg, ergot alkaloids, L-sorbose for vitamin C synthesis, xanthan gum, and insulin. Setting aside the tremendous volume of potable ethanol produced by fermentation, the nearly 470,000 t of MSG and approximately 325,000 t of citric acid produced per year represent the top end of the volume scale (Table 4). Fermentation product sales in the United States are presented in Table 5. The 1992 U.S. market share by sales volume for the top 10 fermentation companies is as follows  [c.183]

Xanthan Gum. Xanthan gum [11138-66-2] is produced by industrial fermentation of a carbohydrate under aerobic conditions by culturing the  [c.443]

Other Gums. GeUan gum, the first to receive FDA approval for food use since xanthan gum in 1968, is produced from Pseudomonas elodea by a pure culture fermentation process (88). In the United States, geUan gum received approval in November 1992 for use in all foods when a standard of identity does not preclude its use. In Japan, geUan gum is used in geUed desserts and jelUes and approval is pending ia Canada and Europe (87). Ghatti gum [9000-28-6] tragacanth gum [9000-65-1J, and karaya gum [9000-36-6] are also used, but not as frequendy as the others.  [c.444]

Solutions of gum tragacanth have extremely high viscosity, and the viscosity is stable over a wide pH range to about pH 2 (46). For this reason and because of its stabilizing and emulsifying properties, gum tragacanth was once widely used in food products (47). However, in many appheations it has been increasingly replaced by propylene glycol alginate and more recently, xanthan gum. Gum tragacanth is compatible with other plant hydrocoUoids as weU as proteins and carbohydrates. Primary food appheations include confectionery and icings, dressings and sauces, oil and flavor emulsions, frozen desserts and bakery fillings. The gum is used widely for the preparation of pharmaceutical emulsions and jeUies and also in the cosmetic industry in face and hair lotions.  [c.434]

Guar gum is compatible with other common plant gums, starch, and water-soluble proteins such as gelatin, except for the synergistic viscosity increases given by blends with xanthan gum (55). The presence of salts, water-miscible solvents or low molecular weight sugars can affect the hydration rate. Small amounts of borate, however, cross-link the guar to form mbbery gels (56). These gels can be reversed by adjusting the pH to the acid ranges.  [c.435]

Concentrations above 0.3% form a gel with borate which is reversible upon the subsequent addition of mannitol (a sequestrant for borate) or of acid. Usefiil combinations are formed with carrageenan (63) and xanthan gum (64) and agar. In many appHcations, it is used in combination with these gums at considerable cost savings.  [c.435]

Structure nd Conformation. As subsequendy found for all microbial polysaccharides, the primary stmcture consists of regular repeating units. Each unit contains five sugars two glucose units, two mannose units, and one glucuronic acid unit. The main chain of xanthan gum is built up of P-D-glucose units linked through the 1- and 4-positions, ie, the chemical stmcture of the main chain of xanthan gum is identical to the chemical stmcture of ceUulose. A three-sugar side chain is linked to the 3-position of every other glucose residue in the main chain (78). About half of the terminal D-maimose residues contain a pymvic acid residue linked to the 4- and 6-positions. The distribution of these pymvate groups is unknown. The nonterminal D-maimose unit in the side chain contains an acetyl group at position 6.  [c.436]

Properties. Xanthan gum is a cream-colored powder that dissolves in either hot or cold water to produce solutions with high viscosity at low concentration. These solutions exhibit pseudoplasticity, ie, the viscosity decreases as the shear rate increases. This decrease is instantaneous and reversible. Solutions, particularly in the presence of small amounts of electrolyte, have exceUent thermal stabiHty, and their viscosity is essentially constant over the range 0 to 80°C. They are not affected by changes in pH ranging from 2 to 10.  [c.436]

Xanthan gum dissolves in acids and bases, and under certain conditions, the viscosity remains stable for several months. Xanthan gum has exceUent StabiHty and compatibUity with high concentrations of many salts, eg, 15% solutions of sodium chloride and 25% solutions of calcium chloride (79).  [c.436]

The most unusual property of xanthan gum is the reactivity with galactomaimans, such as guar gum and locust bean gum (80,81). The xanthan gum-locust bean gum combination at low gum concentration (less than 0.1%) has a significantly higher viscosity in solution than would be expected on the basis of the viscosity of the individual components. At higher gum concentrations (greater than 0.2%), a cohesive, thermoreversible gel is formed. Xanthan gum—guar gum combinations provide higher than expected viscosities, but do not form a gel.  [c.436]

Health nd Safety Factors. The toxicological and safety properties of xanthan gum have been extensively investigated (82). On the basis of these studies, the EDA issued a food additive order in 1969 that allowed the use of xanthan gum in food products without specific quantity limitations.  [c.436]

Uses. The unique properties of xanthan gum make it suitable for many appHcations for the food, pharmaceutical, and agricultural industries (79).  [c.436]

Solutions of welan are very viscous and pseudoplastic, ie, shear results in a dramatic reduction in viscosity that immediately returns when shearing is stopped, even at low polymer concentrations (230). They maintain viscosity at elevated temperatures better than xanthan gum at 135°C the viscosity half-life of a 0.4% xanthan gum solution is essentially zero, whereas a welan gum solution has a viscosity half-life of 900 minutes (230). The addition of salt to welan solutions slightly reduces viscosity, but not significantly. It has excellent stabiUty and theological properties in seawater, brine, or 3% KCl solutions  [c.299]

Applications. The high heat tolerance and good salt compatibiUty of welan gum indicate its potential for use as an additive in several aspects of oil and natural gas recovery. Welan also has suspension properties superior to xanthan gum, which is desirable in oil-field drilling operations and hydraulic fracturing projects. It is compatible with ethylene glycol, and a welan—ethylene glycol composition that forms a viscous material useful in the formulation of insulating materials has been described (244).  [c.299]

Many of its rheological properties, such as the production of highly viscous solutions at low concentrations, and excellent long-term stabiUty at elevated temperature and salt concentrations, are similar to those of xanthan gum. In a study of 140 synthetic and native biopolymers, scleroglucan was found to be the most thermostable in a synthetic North Sea brine at 90°C for extended time periods (319). A strategy to improve the dispersibiUty and filterabiUty of scleroglucan preparations utilized a precipitant to form a coagulum, followed by the addition of a surfactant prior to drying and grinding the dried mixture was reportedly easier to dissolve than dried native material (320). A problem with native scleroglucan is that the polymer readily adsorbs to rock, which can lead to pore plugging and reduced flow (312).  [c.301]

Xanthan gum has several desirable physical properties that explain the wide appHcation range developed for this polysaccharide (6,24). The viscosity of xanthan gum solutions is highly pseudoplastic. Relatively low concentrations of the biopolymer produce highly viscous solutions that maintain viscosity over wide ranges of temperature and pH. Mono- and divalent cations enhance the stabiUty of solution viscosity to exposure to elevated temperatures (340). The addition of salt to solutions of xanthan results in essentially stable solution viscosity from pH 1.5 to 13 salt also increases the yield value, ie, suspending power, of xanthan gum solutions (230). There is a surprisingly small effect on viscosity over a relatively large range of salt concentrations even though xanthan gum is a polyelectrolyte. At a polysaccharide concentration of approximately 0.35%, there is essentially no change in solution viscosity between 0.01 and 1% KCl. At concentrations of polysaccharide lower than 0.35%, the presence of salt slightly lowers the viscosity, whereas at concentrations higher than 0.35% gum, the presence of salt results in a slight increase in viscosity (230).  [c.302]

The stmcture of xanthan has also been investigated by electron microscopy. A series of micrographs of native and denatured xanthan preparations show stiff, relatively straight rod-shaped stmctures, ranging from 2 to 10 p.m long and 4 nm in diameter (342). Xanthan gum prepared using several methods shows sections of single- and double-stranded stmctures within a single polymer strand (351) apparendy the polymer becomes partiy unwound under the particular conditions used to prepare the sample for analysis. The method of preparation and treatment of the sample is important in determining what stmctural features will be present in the polymer, and treatments exist to change the polymer from one conformation to another. The effect of salt on single- and double-stranded stmctures has been studied (358), and a model for salt-induced extension and dissociation of native xanthan gum involving a two-step mechanism proposed. Lowering the salt concentration results in an extended double-stranded polymer at even lower salt concentrations, dissociation of the double helix into single strands occurs (359).  [c.302]

Production and Utilization. The nutritional requirements of X. campestris have been studied in order to optimize the production of xanthan gum. Fermentations for the industrial production of xanthan gum are done at 28°C, and utilize glucose concentrations from 1—5% (362). Higher glucose concentrations do not result in higher levels of gum biosynthesis. Saccharides such as sucrose, starch, and maltodextrins can also be used for gum production. The use of a completely defined media for gum production has been described (230). It has also been shown that some organic acids including pymvic, succinic, and a-ketoglutaric acids increase the production of xanthan gum. It is necessary to maintain a neutral pH during fermentation in order to obtain maximal yields during polymer biosynthesis the medium becomes acidic, but can be neutralized by the addition of a suitable base.  [c.302]

The unusual rheological properties of xanthan gum have led to its use ia a wide variety of food and industrial appHcations. Uses of xanthan gum in food products have been reviewed (230). It is frequendy the thickener of choice because of its abiUty to maintain solution viscosity (for emulsion stabilization) in salts and acids, such as are found in salad dressings. It has been used extensively in no oil or low oil salad dressing formulations, and has been shown to provide long-term emulsion stabiUty. U.S. FDA Standards of Identity also permit its use in sauces, puddings, bakery and pie fillings, and dry mixes for beverages. Xanthan gum can be mixed with carrageenan and galactomannans such as locust bean gum to improve gelling and stabilization of frozen dairy products and desserts. The synergistic interactions of xanthan gum and the galactomannans can be used in situations where fast gelling time is desirable or to reduce costs of additives (230).  [c.303]

Other industrial uses for xanthan gum include thickening textile and carpet printing pastes, suspending pigments in ceramic glazes to improve glaze dispersion, and ink and clay coating formulations in the printing and paper (qv) industries, respectively (230). Agrochemical producers blend herbicides (qv) and insecticides (qv) with xanthan in order to improve appHcation to plants.  [c.303]

Low molecular weight (1000—5000) polyacrylates and copolymers of acryflc acid and AMPS are used as dispersants for weighted water-base muds (64). These materials, 40—50% of which is the active polymer, are usually provided in a Hquid form. They are particularly useful where high temperatures are encountered or in muds, which derive most of their viscosity from fine drill soHds, and polymers such as xanthan gum and polyacrylamide. Another high temperature polymer, a sulfonated styrene maleic—anhydride copolymer, is provided in powdered form (65,66). AH of these materials are used in relatively low (ca 0.2—0.7 kg/m (0.5—2 lb /bbl)) concentrations in the mud.  [c.180]

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36).  [c.190]

Property Polyacrylamide Xanthan gum  [c.192]

There are a large number of feed additive products classified as generally recogni2ed as safe (GRAS). These are products that have been considered by a group of qualified experts to be safe for the intended use in animal feeds no permission or registration is required for use at recommended levels based on scientific procedures or experience in common use in feed. There must be reasonable evidence to support the safety of such products. Some restrictions are placed on quantity of some products, such as selenium and ethoxyquin. GRAS products include a wide range of materials, ranging from ammoniated cottonseed meal to xanthan gum. A Hst of all GRAS substances for animal feeds is available (7).  [c.147]

In the late 1950s and early 1960s, the possibiHty of producing fermentation gums, under controlled conditions, was investigated. Many polysaccharides produced by microorganisms have been studied, including xanthan gum (71), curdlan [54724-00 ] (72), bioalgin (73), puUulan [9057-02-7] (74), scleroglucan [39464-87 ] (75), and more recendy, geUan, welan, and rhamsan gums (76). To date, only xanthan gum [11138-66-2] has achieved commercial significance.  [c.436]

Xanthan Gum. As a result of a project to transform agriculturally derived products into industrially usefiil products by microbial action, the Northern Regional Research Laboratories of the USDA showed that the bacterium TCanthomonas campestris - noduces a polysaccharide with industrially usefiil properties (77). Extensive research was carried out on this interesting polysaccharide in several industrial laboratories during the eady 1960s, culminating in commercial production in 1964.  [c.436]

Production. Xanthan gum is produced by the microorganism X. campestriSm originally isolated from the mtabaga plant. The gum is produced commercially by culturing X campestris purely under aerobic conditions in a medium containing commercial glucose, a suitable nitrogen source, dipotassium phosphate, and appropriate essential elements. When the fermentation is complete, the gum is recovered from the fermentation broth by precipitation with isopropyl alcohol, and dried, milled, tested, and packed.  [c.436]

Welan has similar properties to xanthan gum except that it has increased viscosity at low shear rates and improved thermal stabiUty and compatibihty with calcium at alkaline pH (90). The increased thermal stabiUty has led to its use as a drilling mud viscosifter especially for high temperature weUs. The excellent compatibihty with calcium at high pH has resulted in its use in a variety of specialized cement and concrete appHcations.  [c.437]

Xanthan gum [11138-66-2] is an anionic heteropolysaccharide produced by several species of bacteria in the genus Aanthomonas A. campestris NRRL B-1459 produces the biopolymer with the most desirable physical properties and is used for commercial production of xanthan gum (see Gums). This strain was identified in the 1950s as part of a program to develop microbial polysaccharides derived from fermentations utilizing com sugar (333,334). The primary  [c.301]

Using a variety of measurement techniques, a relatively wide range of molecular weights have been reported for xanthan gum preparations ( 2-50 X 10 ). Two preparations of native xanthan gum have molecular weights of 13 and 50 x 10 , as determined by light scattering measurements (341). By measuring the contour length of the molecule from electron micrographs, an estimate of 20 x 10 has been made (342). Sedimentation studies have yielded an average value of 7.6 x 10 (343) and a range of values of 4-12 x 10 (344). Using size-exclusion chromatography, average molecular weights of 1.8and2.4x 10 have been measured (345). Low angle laser light scattering has given molecular weight estimations in the range of 4.1-12.2 x 10 (346).  [c.302]

Structure and Conformation. The conformation of the biopolymer in solution has been a subject of debate. Several analytical methods (qv) have shown that the polymer goes through a phase transition at elevated temperatures, which depends on the concentration of salt. Increasing the temperature at low salt concentrations brings about a conformational shift from an ordered state to a disordered, random coil conformation (334). The change is associated with a decrease in solution viscosity and can also be characterized by changes in optical rotation and circular dicroism (347—349), nuclear magnetic resonance (348), and electron microscopy (342,350,351). The transition temperature increases with increasing sodium or calcium ion concentration, as well as with the acetate content of the polysaccharide, and decreases with increasing pymvate content. The transition temperature is apparendy independent of polymer concentration this has been interpreted as evidence that the polymer is a single-stranded helix (352), and this conclusion has been supported by spectroscopic analysis of the polymer in solution (353—355). The crystalline stmcture of xanthan gum has been examined by x-ray diffraction (356) and reported to be a single-stranded helix with a diameter of 2 nm, but the possibiUty that the molecule could form a double-stranded helix has not been ruled out. Evidence that the native stmcture of xanthan is a double-stranded helix has been provided by light-scattering experiments (357). As of this writing, it appears that xanthan generally has a double-hehcal conformation but can be treated in a fashion, eg, prolonged dialysis at low ionic strength, which causes it to assume a single-helical conformation (349).  [c.302]

Studies utilizing enzymes capable of hydrolyzing the ceUulosic backbone chain indicate that the polymer is incompletely substituted with trisaccharide side chains on alternating glucose residues. An excess of glucose in a high molecular weight fragment obtained by hydrolysis of native xanthan gum using a heat-stable xanthanese mixture (360), suggests that this hydrolytic fragment contains ceUulosic regions lacking in side chains. When disordered xanthan gum was hydrolyzed using a fungal ceUulase preparation the product had more glucose than the amount expected if the backbone chain were fuUy substituted (361).  [c.302]

Large quantities of xanthan gum are used by the oil and natural gas industry in several aspects of hydrocarbon production (230,349) (see Gas, natural Hydrocarbons Petroleum). The high viscosity achievable at low concentration and the high suspending power efficientiy remove bit cuttings while reducing friction substantially throughout the drill string. Xanthan is compatible with many additives frequendy used to prepare drilling duids, and drilling duids can be made up of fresh, brackish, or salt water and stiU maintain viscosity. It can effectively thicken hydraulic fracture duids that are employed to improve porosity in subterranean formations, where viscosity is required to suspend a propping additive such as sand which is then pumped underground into newly formed fissures. The excellent heat stabiUty and salt compatibiUty frequendy result in its selection over lower cost viscosifiers. Xanthan is also added to solutions pumped underground that are used to displace oil toward a collection well. It improves the sweeping efficiency of these dooding duids enough to make them cost effective.  [c.303]

A wide variety of organic polymers serve a number of useful purposes ia drilling fluids, the most important of which are to iacrease viscosity and control filtration rates (Table 5). These polymers are either natural polysaccharides, eg, s. 2nxh.[9005-25-8] (qv),guar gum, xanthan gum [11138-66-2] and other biopolymers (see Gums Microbialpolysaccharides) or derivatives of natural polymers, eg, cehulose (qv), lignosulfonate, and lignite and synthetic polymers, eg, polymers and copolymers of acryflc acid, acrylonittile, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The most commonly used polymeric viscosity budders are the cehulosics, xanthan gum, and polyacrylamides.  [c.178]

Xanthan gum is a high molecular weight microbial polysaccharide produced by the bacterium 2Canthomonas campestris (48). Commercially xanthan gum is produced by a fermentation (qv) process and precipitation of the gum in alcohol. It is a viscosity builder and suspending agent and can be used in almost any type of water (49). Although xanthan gum solutions support bacterial growth, a preservative is usually not needed unless the solution is to be stored. Because of suspending ability at low concentrations and in electrolyte solutions, xanthan gum is widely used for drilling, workover, and completion fluids. Concentrations range from ca 0.6 to 6 kg/m (0.2—2 lb /bbl). Two other biopolymers, succinoglucan gum [39464-87-4] (50) and welan gum [96949-22-3] (48,51), are also finding some use in drilling fluids at concentrations similar to xanthan gum.  [c.179]

Mobility control agents reduce the mobility ratio. The early mobility control agents were partially hydroly2ed polyacrylamides having molecular weights of 1-5 x 10 and xanthan gum, a biopolymer (75). Virtually all field projects have used polymers from one of these two classes. Variations in polymer molecular weight and stmcture have been made to improve performance properties. Relatively low (100 ppm for fresh water, 1000 ppm or more for saline systems) polymer concentrations can significantly increase injected water viscosity. Adsorption of these polymers on rock can result in a decrease in rock permeability to aqueous fluids (residual resistance). This permeability reduction persists during long periods of water injection. Some polymer field projects have exhibited injected water permeability reductions, attributed to residual resistance effects, that have lasted for more than three years and seven years, respectively, after polymer injection (76).  [c.192]

Each EOR polymer type has important advantages and significant disadvantages (Table 1). When dissolved in more saline waters, xanthan gum produces a higher apparent viscosity than the same concentration of partially hydroly2ed polyacrylamide (78). Xanthan gum is more soluble in saline waters than are polyacrylamides, particularly in injection waters containing divalent metal ions. Xanthan gum also generally adsorbs less on rock surfaces and is substantially more resistant to shear degradation than polyacrylamides (77). However, xanthan gum is also more expensive and the extensional viscosity of the semirigid xanthan molecule is less than that of the flexible polyacrylamide (79). Both polymers cross-link easily in the presence of transition metals.  [c.192]

In addition to the normal problems of completely dissolving particles of water-thickening polymers, xanthan gum contains insoluble residues which decrease polymer injectivity. Various methods of reducing insolubles content and improving xanthan solution injectivity are available (80—87). None appears economically viable. Oxygen scavengers (88) and bactericides (77,89) are commonly used to stabili2e injected polyacrylamide and xanthan gum solutions (90—102).  [c.192]


See pages that mention the term Xanthan gum : [c.986]    [c.1075]    [c.1075]    [c.1075]    [c.178]    [c.438]    [c.444]    [c.430]    [c.301]    [c.303]    [c.179]    [c.184]   
Standard Handbook of Petroleum and Natural Gas Engineering Volume 1 (1996) -- [ c.710 ]