FR2646857A1 - PROCESS FOR OBTAINING AS GENTLE FORM POLYSACCHARIDES FORMED BY BACTERIA OF THE GENUS XANTHOMONAS OR ARTHROBACTER - Google Patents

Abstract

In a process in which a liquid is added to the fermentation medium to precipitate the polysaccharides, they are separated, washed with an organic liquid which advantageously also serves as a precipitation liquid, they are separated and then dried, they are carried out in bulk separating the polysaccharide particles after washing, they are kept in motion with the addition of water and, preferably continuing to keep them in motion, they are then dried. Application of coarse and fluid particles: regulator of the flow properties of aqueous systems.

Description

The invention relates to a method for obtaining, in granular form and

  flowing or fluid, polysacoharides formed by bacteria of the genus X.anthomonas or

  Arthrobacter, a process in which polysaccharides are precipitated

  by adding a liquid precipitation agent to the fermentation medium, the polysaccharides are separated,

  wash them with an organic washing liquid that is used

  advantageously also as a liquid precipitating agent

  tation, they are separated and then dried.

  Such methods are known and are described, but without constituting in any way the object of the invention,

  for example in the AT-330-121 patent.

  The polysaccharides formed by the fermentation of Xanthomonas and Arthrobacter are exopolysaccharides; products formed by bacteria of the genus Xanthomonas are called xanthan and constitute a product obtained from

  large industrial scale which, because of its

  the rheological system, serves as a regulator of

  aqueous systems and stabilizer for emulsions and suspensions. Its great thermostability, its resistance

  in a wide pH range and extraordinary compatibility

  nally high salts with xanthan have opened up a wide range of industrial applications. This is how xanthan formed by fermentation of x.anthomonas campestris is allowed as a thickener and stabilizer

in food products.

  Industrially, xanthan is produced by

  aerobic fermentation of a fermentation broth containing

  glucose. After depletion of the carbon source, the mixture or slurry containing xanthan is pasteurized and the xanthan is precipitated by addition of an organic liquid, in most cases an alcohol

  lower such as isopropanol. When using iso-

  propanol, the concentration causing precipitation is between 45 and 60% by weight of alcohol. The concentration of precipitation is influenced by the content of the mixture

  or porridge in electrolytes and this concentration

  may be lowered by the addition of salts before

  cipitation. Then the precipitated and separated xanthan is taken up, but not dissolved, in an organic liquid

  suitable for the pursuit of his purification. customarily

  the washing liquid is identical to the liquid used

  for precipitation and so it is also

  of the cases, isopropanol. After separation of xanthan la-

  V-é and thus purified, this xanthan is dried and crushed.

  In its usual commercial form, xanthan is a fluid or "flowing" powdery product. Since the fluidity of the powder is determined by the structure of the individual particles, it is desired to obtain particles with a grain-like appearance, whereas the fibrous and downy particles create difficulties during grinding, packaging and

finally during the metered addition.

  AT-330 121 relates to the problem of

  & obtain xanthan with grainy particles and.

  not fibrous and this prior patent proposes, to solve this problem, to use a washing liquid whose organic proportion should not be beyond a certain range (because it would give a fibrous structure) and should not to be below a certain range (because this would give a sticky product), this range being determined by tests. Thus, it is stated for an isopropanol / water system as a washing liquid that the isopropanol content should exceed 8 to 25% by weight of the isopropanol content just to dissolve xanthan; for a tert-butanol / water system, a range of 9 to 28% by weight is indicated. The usual azeotropic distillates, that is to say 87.8% of isopropanol or 96.5% of tert-butanol, expressly prove, according to patent AT 330 121, to be unsuitable washing liquids. for obtaining a grainy structure. These

  Alcohols must always be diluted with water.

  As a result, however, the washing liquid can not be used directly and without precautions as a liquid precipitating agent because

  liquid has a low alcohol concentration.

  The liquid precipitating agent as well as the washing liquid must then undergo a preparation treatment.

  to be able to play their respective roles well.

  It has just been found that even when washing liquids with a high content of organic constituents are used in a desired manner, and although a fibrous structure of xanthan is first formed, it is possible to to obtain a final product grainy and "flowing"

or fluid.

  The process according to the invention is characterized in that, after washing, the particles of the polysaccharide are roughly separated from the washing liquid, are kept in motion with the addition of water and advantageously with the continuation of the keeping in motion - they are then dried. Advantageously, the particles are then added to

  polysaccharide up to about 40%, in particular 8 a.

  % and particularly preferably 10 to 15% water,

in relation to their dry weight.

  In other words, the xanthan fibers are moistened or wetted before drying, trying to obtain as even a distribution as possible of the quantity of water added, which implies the obligation of a

intensive mixing.

  The total amount of water should not be added all at once, to avoid the formation of clumps or lumps. Advantageously, water is added, preferably continuously, in a time period of up to 1 hour and in particular in a time period of up to 10 to 30 minutes. It is accepted that, in the process according to the invention,

  a beginning of dissolution then an agglomeration

  tion of xanthan fibers. We get a final product

  granular, flowing freely and easy handling.

  By keeping the material moving, we avoid the

formation of fairly large aggregates.

  Since, during the subsequent drying, the agent of

2646857-

  Washing still present evaporates, that is to say that

  H20 concentration increases punctually, it is advan-

  tagged to keep the material moving also during

drying.

  In an extremely favorable way, the wetting of the

  washed material takes place in the dryer itself, in particular

  bind in a drum dryer, whose drum then rotates. A preferred form of implementation of the washing / drying treatment according to the invention can be described as follows:

  the precipitated xanthan is taken up in isopro-

  panol obtained by industrial distillation (approximately 87% isopropanol) and the xanthan is washed well with stirring at room temperature. The residence time is 10 A min. The amount of isopropanol is then 10 to 100 times, advantageously 45 to 55 times, the amount of xanthan. After this washing operation, xanthan has a fibrous structure and, after its separation from the

  washing solution, it is introduced into a drum drier.

  bour, operating under vacuum. In order to achieve intensive mixing of the product, this dryer is equipped with a spinning device. Before the beginning of the drying, the water is sprayed into the dryer, under intense mixing, on the fibrous xanthan. To avoid the formation of clumps or lumps, the water must be

  be finely divided. This is achieved by a slow addi-

  With nozzles during high mixing. The time spent adding is between 10 and 30 minutes. The amount of water added is 8 to 30%, preferably 15%, of the amount of dry substance placed in the dryer. If too little water is added, the product remains fibrous. Too much water causes the

  forming grains difficult to grind. The subsequent drying

  With continued intense mixing, this takes place in the usual manner under vacuum, and must ensure the presence of a sufficiently low residual isoppopanol content in the final product (content less than 500 ppm or 500 ppm). Before the addition of water, the polysaccharide particles / wash agent phase is separated, for example by expression, an amount of washing liquid such that there is then a dry matter content representing at least about 40%,

  advantageously from 50 to 55% of the mass. The drying itself

  even takes place in a range of temperature ranging from 50 to

  OC, advantageously between 60 and 80 OC, and advantageously

  with the application of depression. In particular,

  applies a residual vacuum of about 100 mbar.

  By keeping the material under intense movement with the addition of water, it is transformed using the

  device for spinning the fibers into spherical particles

  c. Since, during drying, the volatile isopropanol starts first during this drying, the higher water content of the dry matter facilitates the beginning of dissolution of the

  xanthan fibers. This also results in

  xanthan particles having a denser, granular structure.

  As the isopropanol should not be diluted for washing, this way of operating has the particular advantage that the solution used for the washing does not require regeneration but can be used directly, a favorable thing for the cost price of total operations , for the precipitation of xanthan from the mixture or the slurry. We

  can save operating costs and

  which would otherwise be necessary for a regeneration

  washing liquid. Only one installation

  purification and recovery of isopropanol.

  The cost-effective use of the washing solution for precipitating xanthan from the mixture or slurry is made possible by the high concentration of isopropanol in the solution.

  washing. For a given quantity of mixture or mixture

  For a given concentration for precipitation, the amount of alcohol to be regenerated depends on the isopropanol concentration of the precipitation agent. Like the elevation

  the concentration of isopropanol in the precipitating agent

  tation leads to a decrease in the amount of iso-

  panol to regenerate thus decreases the costs of regeneration.

  All the operations of the process are equally

the following practical example.

Example:

  By aerobic fermentation of a nutrient solution

  containing glucose (40 g / l), a solution inoculated

  Xanthomonas campestris, a fermentation broth

  tion. The fermentation is stopped when the residual sugar content is less than 0.1%. The fermentation broth is pasteurized and xanthan is continuously precipitated by the addition of about 86% by weight isopropanol. Precipitation takes place in a container with a volume of 100 liters, equipped with a stirrer A turbine, in which is introduced by parallel pumping the mixture or mixture, and

  about 86% by weight isopropanol. Simul-

  With the help of a pump, the xanthan is precipitated with the alcohol / water mixture in which it is suspended. The

  ratio of the amount of mixture or slurry to the amount

  alcohol is determined by the corresponding concentration

  from precipitation to about 50% by weight of isopropanol. To ensure intense contact between the mixture and the isopropanol, the turbine stirrer is rotated at 1000 rpm. Then the xanthan fibers are separated from the liquid which covers them, the fibers are suspended in 50 times their amount of isopropanol (86% by weight) and, with vigorous stirring (rotary turbine stirrer at 1000 rpm ), the fibers are washed for 10 min. Precipitation as well as washing occur at about 20 ° C. The fibrous xanthan thus washed is separated using a fine-meshed sieve and is manually expressed. a) Subsequent treatment carried out differently from that of the invention: 30 kg of the wet product (this amount corresponds to about 15 kg of xanthan dry substance) are introduced into an industrial drier / drum operating under vacuum. The drum dryer is equipped with a device

  of spin for the thorough mixing of the dry matter.

  After the application of the depression, heat is

  running the spin device (running at 300 rpm) until reaching a final temperature of * C and a residual vacuum of 100 mbar. The dried xanthan has a solids content (or solids content) of about 93% and has a fibrous or fluffy structure. The product to be milled (grain size such that 95% of the grains are less than 180 Vm) has a bulk density of 0.41. The appended FIG. 1 shows, at a magnification of times, the appearance of the crushed product, consisting of xanthan fibers after their washing with 86% isopropanol and their drying, without the addition of water at the beginning of drying. The crushed product represented in FIG.

  therefore does not correspond to the product of the invention.

  b) Treated Product According to the Invention: The drum dryer is charged by operating as

  indicated in a). Then the test device is started.

  rage (rotating at 300 rpm) and is projected by spraying

  sation, using a nozzle in about 10 min,

  2 1 of water on the xanthan kept in motion. The opera-

  Drying takes place as described in a). The humid

  residual density is around 7%, the iso-

  residual propanol is below 500 millionths

(less than 500 ppm).

  FIG. 2 shows, with a magnification of 50 times, the grains of the xanthan powder which are obtained after washing with 86% propanol and adding 13% of water, (relative to the dry substance). xanthan) before the start of drying. The grains obtained after grinding have a higher bulk density than the dried product without the addition of water and they flow better. The apparent density is after grinding (which gives grains

  95% of which are less than 180 pm) at an average value of about

0.7.

Claims (9)

  1. Process for obtaining, in granular and fluid form, polysaccharides formed by bacteria of the genus Xanthomonas or Arthrobacter, process in which the polysaccharides are precipitated by the addition of a liquid precipitation agent to the fermentation medium, they are separated, they are washed with an organic washing liquid which advantageously also serves as a precipitation liquid, is separated and then dried, characterized in that, after washing, the particles are roughly separated off   polysaccharide from the washing liquid, they are   keeps in motion with addition of water and, preferably continuing to keep them in motion, they are then dried. 2. Method according to claim 1, characterized in that one adds to the polysaccharide particles up to   approximately 40%, in particular 8 to 30% and in particular   preferably 10 to 15% of water, based on their dry weight.   3. Process according to claim 1 or 2, characterized   in that the water is added, preferably continuously, over a period of up to 1 hour and in particular between 10 minutes and 30 minutes.   4. Method according to any one of the claims   1i to 3, characterized in that the addition of water takes place in   a drum dryer, whose drum rotates.   5. Process according to any one of the claims   1 to 4, characterized in that azeotropic technical distillates of alcohols having a low molecular weight, in particular ethanol, isopropanol or tert.-butanol, or mixtures thereof, are used as the washing liquid. these alcohols, and preferably isopropanol about 87.8 t by volume.   6. Process according to any one of the claims   1 to 5, characterized in that the amount of washing liquid used is tenfold, advantageously   to 55 times the amount of polysaccharides.   7. Process according to any one of the claims   1 to 6, characterized in that the washing liquid is separated   so that before the addition of water the polysaccharide substrate   Ridique has a dry matter content (or a solids content) of at least 40%, and which preferably represents feels 50 to 55 * of the mass.   8. Process according to any one of the claims   1 to 7, characterized in that the drying is carried out in a   range of temperature ranging from 50 & 120 * C, advantageously- between 60 and 80 ° C.   9. Process according to any one of the claims   1 & 8, characterized in that the drying is carried out with the application of a vacuum, advantageously by applying   a residual vacuum corresponding to about 100 mbar.