Xanthan Production Research Articles

Xanthomonas campestris pv. campestris secretes the endoglucanases ENGXCA and ENGXCB: construction of an endoglucanase-deficient mutant for industrial xanthan production.

Xanthomonas campestris pv. campestris secretes at least two cellulose-degrading endoglucanases. One of these endoglucanases is encoded by the engXCA gene of X. c. pv. campestris 8400 that was previously characterized by Gough et al. [Gene (1990) 89: 53-59]. An additional endoglucanase encoded by the engXCB gene was identified in X. c. pv. campestris 8400 and FC2. The engXCB gene product that was grouped into the endoglucanase family E contains a putative N-terminal signal peptide, suggesting a secretion by the type II secretion system. The ENGXCB protein contributed approximately 8% to the cellulase activity in xanthan preparations. Deletion of engXCA and engXCB resulted in a fivefold reduction of the cellulose-degrading activity in xanthan preparations. The cellulase activity determined in xanthan preparations of the engXCA-engXCB mutant was only slightly higher than the activity found in preparations that were subjected to heat treatment. Mutations in engXCA and engXCB did not affect the growth rate and xanthan production of X. c. pv. campestris FC2 under several cultivation conditions. The engXCA-engXCB deletion mutant is markerless, which makes this mutant a valuable strain for xanthan production and approaches aimed at inactivating further genes encoding extracellular enzymes.

The effect of olive mill wastewaters variability on xanthan production.

Xanthan production by Xanthomonas campestris from several olive mill wastewaters (OMW) was investigated. Maximum xanthan production of 4 g l(-1) was obtained in media with 50% OMW as sole source of nutrients. OMW storage decreased effluent quality for xanthan production. The range of effluent concentration for X. campestris growth and xanthan production varied depending on OMW extraction Wastewaters from press and two-phase extraction methods required higher dilution rates (< 10%) than those from the three-phase extraction method (50%). Nitrogen supplementation improved xanthan production in press and two-phase OMW. Factors affecting wastewaters composition, namely, waste storage, time of olive harvesting, and method for oil extraction, were found to influence xanthan production in shake-flask cultures. Conditions for xanthan production from OMW should be optimized in accordance with the nature of the waste material.

Xanthomonas campestris strain selection for xanthan production from olive mill wastewaters

Four Xanthomonas campestris strains were tested in olive mill wastewaters (OMW) for xanthan production. Differences among strains were found in the range of tolerance to OMW concentration and xanthan amount obtained. X. campestris NRRL B-1459 S4LII was chosen by its capability for xanthan production from 50–60% OMW as the sole nutrient source.

Formulação de meios de cultivo à base de soro de leite para a produção de goma xantana por X. Campestris C7L

A goma xantana é um polissacarídeo microbiano de grande significado comercial especialmente para a indústria de alimentos. O objetivo deste trabalho foi avaliar a produção de xantana em diferentes meios de cultura à base de soro de leite utilizando o isolado Xanthomonas campestris C7L. Dentre as formulações testadas o meio de soro de leite integral produziu maior viscosidade e concentração final de xantana. Um sistema combinando soro integral (0,35% de proteína) e soro filtrado (0,18%de proteína) foi proposto. Na primeira fase em soro integral a produção de xantana foi de 13g/L e 45% de rendimento,enquanto que na segunda fase utilizando-se soro filtrado obteve-se um total de 28g/L de xantana e 75% de rendimento. O rendimento geral do processo foi de 55% e a viscosidade final do meio atingiu 18000cP. As soluções de xantana produzidas em soro de leite apresentaram comportamento pseudoplástico e tixotrópico característicos deste tipo de polímero. O isolado C7L demonstrou capacidade de produzir gomas de alta viscosidade e qualidade em soro de leite, constituindo uma alternativa promissora para a produção industrial de goma xantana a partir deste subproduto.

Studies on xanthan production from Xanthomonas campestris

Xanthan is an heteropolysaccharide produced by Xanthomonascampestris. Xanthan gum fermentation by a local isolate of X. campestris using different carbon sources was studied. The production of polysaccharide was influenced by the carbon source used. The production of the xanthan was 15.654 g/l with synthetic medium. Production of xanthan at various temperatures ranging between 25 °C and 40 °C was studied. The growth and production was maximum between 25–30 °C. Xanthan production was maximum at pH 7.0–7.5.

Oxygen transfer and uptake rates during xanthan gum production.

Oxygen uptake rate and oxygen mass transfer rate have been studied during xanthan gum production process in stirred tank bioreactor. Empirical equations for the oxygen mass transfer coefficient have been obtained taking into account several variables such as air flow rate, stirrer speed and apparent viscosity. Oxygen uptake rate evolution in the course fermentation has been measured, obtaining an equation as a function of biomass concentration, including overall growth and non growth-associated oxygen uptake. A metabolic kinetic model has been employed for xanthan gum production description including oxygen mass transfer and uptake rates. The results point out that this model is able to describe adequately not only oxygen dissolved evolution, but also of the production of xanthan and substrate consumption. Also, the influence of several parameters (k(L)a, air flow rate and dissolved oxygen) in the evolution of the key compounds of the system have been studied. The results of the simulation shown that an increasing of dissolved oxygen concentration favor the xanthan gum production.

Xanthan gum: production, recovery, and properties

Xanthan gum is a microbial polysaccharide of great commercial significance. This review focuses on various aspects of xanthan production, including the producing organism Xanthomonas campestris, the kinetics of growth and production, the downstream recovery of the polysaccharide, and the solution properties of xanthan.

Effect of virulence and serial transfers of Xanthomonas campestris on xanthan gum production

The virulence of six Xanthomonas campestris isolates was evaluated using the percentage of lesion area of leaves Brassica oleraceae host plant, compared to diameter of colonies, xanthan production and gum viscosity. In terms of virulence, the isolates belonged to two statistically different groups: isolates B, UPF and C7 showed values between 52 and 69%, while isolates CF, C and strain B-1459 gave 0-30% of lesion area. Final xanthan concentration, gum viscosity and colony diameter did not correlate with virulence calculated by percentage of lesion area, showing that this parameter is not a good criterium for selection of potential xanthan producer isolates. Serial transfers of X. campestris isolates host plant did not show a significant effect on in vitro production of xanthan or on viscosity levels, suggesting that the increasing interaction between plant and bacteria did not stimulate the increase xanthan production and viscosity.

Xanthan production from whey treated with immobilized lactase

Xanthan production from whey treated with immobilized lactase

Xanthan production by solid state fermentation

Xanthomonas campestris strains were cultivated on a variety of solid substrates in order to evaluate their ability to produce the exopolysaccharide xanthan. The solid substrates used were agro-industry wastes or by-products, including spent malt grains, apple pomace, grape pomace, and citrus peels, which can be obtained at a very low cost. With most substrates, xanthan yields were comparable to those obtained from conventional submerged cultivation. The basic characteristics of the process were studied on solid substrates prepared by impregnating the inert support (spent malt grains) with a solution of nutrients. Fermentations were performed on the laboratory scale either under static conditions or in rotating cultures. The production conditions were optimized so as to achieve polymer yields ranging from 32.9 to 57.1 g l −1, as referred to the liquid volume impregnating the various substrates. The products were analysed by NMR spectroscopy, revealing a composition consistent with that of commercial xanthan.

Xanthan gum and ethanol production by Xanthomonas campestris and Zymomonas mobilis from peach pulp

The wild type of Xanthomonas campestris and a mutant strain of Zymomonas mobilis CP4, tolerant to sucrose up to 40% (w/v), were used to produce either xanthan gum or ethanol, respectively, from peach pulp supplemented with different salts. Both bacteria grew well (2.7 mg/ml for X. campestris and 1.45 mg/ml for Z. mobilis) in fine peach pulp and the production of xanthan gum or ethanol was 0.1–0.2 g/l or 110 g/l, respectively.

Xanthan gum production by Xanthomonas campestris w.t. fermentation from chestnut extract.

Xanthomonas campestris w.t. was used for production of xanthan gum in fermentations with chestnut flour for the first time. Fermentations were carried out with either chestnut flour or its soluble sugars (33.5%) and starch (53.6%), respectively, at 28 degrees C and 200 rpm at initial pH 7.0 in flasks. The effect of agitation rate (at 200, 400, and 600 rpm) on xanthan gum production was also studied in a 2-L batch reactor. It was found that xanthan production reaches a maximum value of 3.3 g/100 mL at 600 rpm and 28 degrees C at 45 h.

Use of agricultural wastes for xanthan production by Xanthomonas campestris

Four different acid-hydrolyzed wastes, from melon, watermelon, cucumber and tomato were compared for xanthan production. Growth of Xanthomonas campestris, xanthan biosynthesis, kinetics and chemical composition were investigated. Both growth and xanthan production were dependent on the acid hydrolysate concentrations and available nitrogen. Melon acid hydrolyzed waste was the best substrate for xanthan production. Exopolysaccharide obtained throughout this study was compared to commercial xanthan, showing a very similar chemical composition. Acid hydrolyzed wastes are proposed as a new carbon source for xanthan production.

Xanthan gum biosynthesis and application: a biochemical/genetic perspective.

Xanthan gum is a complex exopolysaccharide produced by the plant-pathogenic bacterium Xanthomonas campestris pv. campestris. It consists of D-glucosyl, D-mannosyl, and D-glucuronyl acid residues in a molar ratio of 2:2:1 and variable proportions of O-acetyl and pyruvyl residues. Because of its physical properties, it is widely used as a thickener or viscosifier in both food and non-food industries. Xanthan gum is also used as a stabilizer for a wide variety of suspensions, emulsions, and foams. This article outlines aspects of the biochemical assembly and genetic loci involved in its biosynthesis, including the synthesis of the sugar nucleotide substrates, the building and decoration of the pentasaccharide subunit, and the polymerization and secretion of the polymer. An overview of the applications and industrial production of xanthan is also covered.

The effect of acid stress on key enzyme activities and growth kinetics in cultures of Xanthomonas campestris

Extracellular polysaccharide production by Xanthomonas campestris was studied under sublethal acid stress. Chemostat cultures were obtained at a dilution rate of 0.05 h 1 and the normal feed was then supplemented with 2.5 mM acetic acid, 1.96 mM pentanoic acid or 1.39 mM octanoic acid. Undissociated acid fractions led to an appreciable loss of biomass formation expressed by the drop in the biomass. X. campestris responded to sublethal acid stress by overproducing xanthan, and an increase in the specific xanthan production and xanthan yield was observed in all cases. The corresponding specific glucose consumption rate increased by a maximum of 45.2% with pentanoic acid. By adding feed containing 2.5 mM acetic acid, the culture biomass immediately started to decrease, falling from 0.145 to 0.103 g litre 1h, 1, whereas the specific xanthan production rate was stimulated from 0.282 gg 1cells h 1 to a maximum 0.325 g g 1cells h 1. Similar behaviour was observed in the pentanoic acid and octanoic acid fermentations. Enhanced activities of the pentose phosphate cycle and xanthan anabolic reactions were observed after acid additions.

Metabolic structured kinetic model for xanthan production

A metabolic structured kinetic model for xanthan gum production is described and fitted to experimental data obtained in a batch stirred tank reactor. The model is able to describe the evolution of biomass, consumption of carbon, nitrogen, dissolved oxygen, and production of xanthan at different temperatures. The description of growth is carried out by means of an unstructured model taking the nitrogen source as the limiting nutrient, employing the logistic equation which fits adequately the experimental data of the increase in biomass concentration as a function of initial concentrations of biomass and nitrogen source. The model proposed is metabolically structured because it takes into account the carbon source metabolism into the cell, describing xanthan production, carbon source, and dissolved oxygen consumption in a structured way according to a reaction network as a simplified scheme of the intracellular metabolism. The limiting nutrient of xanthan production and carbon source consumption is supposed to be dissolved oxygen. The parameter estimation has been performed by fitting to experimental data, employing an integral method coupling a fourth-order Runge-Kutta algorithm to a multiple-response nonlinear regression technique. Runs performed at four different temperatures (25, 28, 31, and 34°C) are fitted and described by the model.

Evidence for a role for the gumB and gumC gene products in the formation of xanthan from its pentasaccharide repeating unit by Xanthomonas campestris.

The biosynthesis of the extracellular polysaccharide xanthan in Xanthomonas campestris pv. campestris is directed by a cluster of 12 genes, gumB-gumM. Several xanthan-deficient mutants of the wild-type strain 8004 have previously been described which carry Tn5 insertions in this region of the chromosome. Here it is shown that the transposon insertion in one of these mutants, strain 8397, is located 15 bp upstream of the translational start site of the gumB gene. EDTA-treated cells of strain 8397 were able to synthesize the lipid-linked pentasaccharide repeating unit of xanthan from the three nucleotide sugar donors (UDP-glucose, GDP-mannose and UDP-glucuronic acid) but were unable to polymerize the pentasaccharide into mature xanthan. A subclone of the gum gene cluster carrying gumB and gumC restored xanthan production to strain 8397 to levels approximately 28% of the wild-type. In contrast, subclones carrying gumB or gumC alone were not effective. These results are discussed with reference to previous speculations, based on computer analysis, that gumB and gumC are both involved in the translocation of xanthan across the bacterial membranes.

Optimal Feeding Profile for Xanthan Gum Production Under N-Limited Conditions

A novel feeding strategy for xanthan gum production under N-limited conditions is introduced. The optimal feeding profile is obtained by using a mixed quality and performance criteria and applying a simple dynamic programming approach for profile optimization. Experimental verification by feedforward control of ammonia supply rate shows an significant increase in process performance.

Production of xanthan gum and ice-nucleating material from whey by Xanthomonas campestris pv. translucens

Xanthomonas campestris pv. translucens IFO13599 could produce xanthan gum (18.5 mg/100 mg, lactose) with lactose as the growth substrate in spite of a low level of β-galactosidase. This productivity corresponded to one-fifth that with glucose. This strain could also produce ice-nucleating material having an ice-nucleating temperature, T50, of −2.8 °C with xanthan gum in the culture broth. We found that this strain produced both materials in whey medium from which the insoluble components had been removed. The production of xanthan with ice-nucleating material reached a maximum after cultivation for 168 h under optimum conditions. Furthermore, the xanthan obtained had a low viscosity because of its variant structure revealed, by TLC and HPLC analyses, to be lacking pyruvic acid. Furthermore, we concluded that this mixture had considerable potential as a regeneratic agent, when compared to other regeneratic agents such as carboxymethylcellulose.

Prediction of xanthan fermentation development by a model linking kinetics, power drawn and mixing

A model for xanthan fermentation which considers the interaction between kinetic and mixing phenomena is described. Fermentation kinetics are represented by expressions reported in the literature. The volume of well-mixed regions or ‘caverns’ can be calculated as a function of the power number and apparent yield stress according to expressions proposed in the literature. A comprehensive data base containing aerated power data was used to predict the power drawn. The model assumes that kinetic changes occur only in well-mixed caverns or ‘actives zones’. The model was able to estimate an agitation rate profile which allowed complete broth mixing during fermentation at a minimum power drawn. The model predictions were able to indicate that the evolution of gum concentration is a function of impeller speed (if insufficient agitation power is drawn) and this is due to a mixing problem. In model-controlled fermentations, the bacterial growth and the xanthan productivity (g/litre h −1) of the process were lower than those obtained in cultures in which the dissolved oxygen tension (DOT) was kept above 10% saturation (DOT-controlled), however, the specific xanthan productivity (g xanthan/g cells h −1) remained unchanged. DOT-controlled culture consumed at least 46% more power than the model-controlled fermentation. When compared at the same xanthan gum concentration, the broths obtained with model-controlled fermentations were more viscous than those obtained with DOT-controlled cultures.