JPS60227692A - Concentration and collection of xanthane gum - Google Patents

Abstract

PURPOSE:Cell bodies are removed from the fermentation mixture of xanthane gum and the solution is subjected to concentration by ultrafiltration, then the concentrate is mixed with a specific mixed solution to effect precipitation of xanthane gum whereby the titled gum of high purity is recovered by use of a reduced amount of solvents. CONSTITUTION:Cell bodies are removed from the fermentation mixture for xanthane gum and the solution is concentrated by means of an ultrafiltrator which contains PS hollow fibers of 1-500mum pore diameter, as the flow rate is increased with increase in concentration, to give 1-5% clear concentrate (A). In the meantime, (a) 10-90 volumes of 0.05-1% of aqueous hydrochloride of a divalent metal such as Ca, Mg, or Zn are combined with (b) 90-10 volumes of an aqueous organic solvent such as methanol to prepare a precipitation solution (B). Then, component A and component B are mixed so that the pH becomes 11-13, forcibly stirred to form fluffy precipitates. The precipitates are subjected to removal of liquids by applying mechanical force such as screw press, then directly crushed or crushed after drying to give the titled gum.

Description

[Detailed description of the invention] The present invention relates to a method for recovering xanthan gum.

Xanthan gum is Xanthomonas campestris (X
It is a polysaccharide obtained by fermentation of anthomonas campestris). This polysaccharide is used as an excipient in food processing, as a thickener, and as a water retention agent. It is also useful as a viscosity regulator for oil drilling.

The crude fermentation liquor of xanthan gum is a highly viscous coagulated aqueous solution containing bacterial cells and insoluble residual layers, soluble salts and organic compounds, and 0.5 to 5 weight - of xanthan gum.

A typical method for recovering xanthan gum is to dilute this crude fermentation liquid with water to make the viscosity as low as 500 centivoids (hereinafter abbreviated as eps) or less to facilitate the removal of insoluble matter. Next, a monovalent metal salt such as potassium chloride is added to the disinfecting solution, and an aqueous organic solvent such as methanol or inopropyl alcohol is added in an amount of 1.5 to 2.5 times the amount of the disinfecting solution to precipitate xanthan gum. It is being collected. This dilution method using an aqueous organic solvent requires a large amount of solvent, and the cost of recovery equipment and recovery energy account for a large portion of the total cost of xanthan gum.

For this purpose, a method is used in which isopropyl alcohol is added to the fermentation crude liquid in advance, below the precipitate lid, and heated to around 100C, filtered and sterilized. No.), or add and mix a disinfectant solution to an aluminum salt aqueous solution to pH 1.
A method has been proposed in which the temperature is maintained at 5.5 to 4.5 and then gelled and recovered (Japanese Patent Application Laid-Open No. 51-18795).

In the first method, the amount of solvent is reduced because there is no dilution with water, but thermal deterioration due to heating and impurities such as salts and low-molecular organic substances (glucose, etc.) contained in the fermentation crude liquid are included in the gum at the time of precipitation. It has drawbacks such as discoloration and odor.

Furthermore, since the gel obtained by the second method has a large liquid content and low gel strength, it is difficult to remove the liquid by mechanical stress. Moreover, the gum obtained by this method has a high salt content and is water-insoluble, so its uses are extremely limited.

As a result of various studies with the aim of drastically reducing the amount of solvent and obtaining gum with high purity, the present invention has been developed by concentrating diluted sterilizing solution while removing low molecular weight impurities through ultrafiltration, and using a small amount of viscous P solution. By mixing the divalent metal salt with a small amount of an aqueous organic solvent, water, and a mixed aqueous solution of d6, and preferably adjusting the pH to a range of 11 to 13, a strong solid that can be stress-deliquified with a very small amount of solvent can be obtained. It was discovered that a precipitate with a high temperature can be obtained, leading to the present invention.

That is, the present invention is comprised of the following three requirements.

(1) The diluted sterilizing solution is clarified and concentrated by ultrafiltration. (
2) A mixed solution consisting of a divalent metal salt, an aqueous organic solvent, and water is used as a precipitation solution. (31 fl) and (2) are thoroughly mixed.

Its pH is preferably 11-13. This method allows a highly pure gum to be obtained with a small amount of solvent.

The present invention will be explained in more detail below. Diluting the crude gum fermentation liquid is important in the sense of facilitating the removal of insoluble matter and lowering the concentration of dissolved impurities, but the amount of solvent used depends on the amount of fermentation liquid. For,
If diluted, the amount used will increase accordingly. As a result of various studies, we have discovered that the method to resolve these contradictory demands is to concentrate the diluted sterilizing solution. However, concentration by methods such as evaporation, dialysis, freezing, and reverse osmosis results in concentration of impurities as well, which is contrary to the purpose of the present invention. Only the concentration by ultrafiltration used in the present invention concentrates only macromolecules such as gum, and salts, low-molecular organic substances, etc. are permeated and removed together with water, which is a suitable purpose for the present invention.

As the degree of concentration increases, the amount of solvent used decreases, but on the other hand, the gum precipitation operation becomes difficult, so a concentration range of 1 to 5 t is appropriate, preferably 2 to 4 t. The pore size of the membrane used for ultrafiltration should naturally be selected depending on the molecular weight of the gum to be concentrated and the molecular weight of the impurities to be removed, but a commercially available pore size in the range of 1 to 500 mμ is usually sufficient to achieve the purpose. The shape of the membrane may be either a flat plate or a hollow fiber, but from the viewpoint of processing speed, it is preferable to
A hollow fiber shape is preferred. As the material of the membrane, membranes made of polystyrene, polyacrylonitrile, polyamide, polyolefin, phenol-aldehyde, urea-aldehyde, and copolymers mainly composed of these can be used.

It should be noted that xanthan gum disinfectant solution is a high viscosity solution of 500 to 600 cps, even if it is a diluted solution.
When highly concentrated, it reaches 40,000 to 60,000 cps. A characteristic of this gum is that it has thixotropy, which shows a significant decrease in viscosity under shear stress. Therefore, it is desirable to maintain the flow rate above a certain level while gradually increasing the flow rate as the degree of concentration increases. When the flow rate decreases or stops, the viscosity becomes high and clogging occurs.
The result is 5-.

Next, regarding the composition of the precipitate, using only an aqueous organic solvent has the effect of reducing only the concentration ratio, but by creating a mixed aqueous solution with a divalent metal salt, the amount of solvent used can be significantly reduced. Furthermore, by adjusting the pH'i to 11 to 16 when mixing the gum concentrate and the precipitate,
Furthermore, it has been found that the amount of solvent used can be reduced.

For example, for 1 volume of 0.5% disinfectant solution, 2 to 2.5 volumes of inpropyl alcohol are required;
Concentrate well to 0.25 volume of concentrate.

The amount of isopropyl alcohol used at this time is 0.5~
It becomes 0.625 volume, which has a reduction effect of 1/4. Next, using a mixed aqueous solution of 50 volumes of 0.5% calcium chloride aqueous solution and 50 volumes of isopropyl alcohol, the amount required to precipitate 0.25 volume of the 2-thigam concentrate is 0.25-0.
375 volumes is enough. That is, 1 for a 0.5-th diluted solution.
/8 reduction. Furthermore, during mixing, p Hf 12.
When maintained between 0 and 12.5, precipitates can be obtained using 0.125 to 0.25 volumes, allowing for a 6-1/16th reduction. Comparing this in unit weight of xanthan gum, it is actually 1/64 (-(0,125/2
．． 0)÷(2,010,5)).

In addition to calcium, preferred divalent metals that can be used in the precipitation solution of the present invention include hydrochloric acid, sulfuric acid, and nitrates of magnesium and zinc. Also, when using these metals, the pH to be maintained is 1
1 to 13, preferably 12. for calcium salts.
0-12.5, 12.5-15.0 for magnesium salts
and 12.5 to 15.0 for zinc salts. If the pH is too high, hydroxides will be formed, and if the pH is too low, the reduction effect will be small.

The amount of metal salt used is substantially sufficient if it is the amount necessary for bonding with the carboxylic acid of xanthan gum, but usually 0.05
It can be carried out in a concentration range of 1 to 1. -valent metals have no or very small reduction effect, and trivalent metals have a reduction effect, but form a water-insoluble gel, which is contrary to the purpose of the present invention. In addition to inpropyl alcohol, methanol, ethanol, acetone, butanol, etc. can be used as the aqueous organic solvent. The mixing ratio of the metal salt aqueous solution and the aqueous organic solvent varies depending on the concentration of the gum to be treated, but is usually 1.
0 to 90 volumes to 90 to 10 volumes, preferably 5
0-70 volume vs. 50-30 volume.

There are two methods for mixing the gum concentrate and precipitating liquid and precipitating them: adding the gum liquid to the precipitating liquid and forcibly stirring to precipitate it into a fine cotton-like shape, or extruding it through pores and spinning it to precipitate it into a fiber-like form. Depending on the purpose, any method can be employed, such as dropping it dropwise through pores and precipitating it in the form of beads.

The precipitate is removed by mechanical stress using a pressure leaf filter, centrifuge, screw press, compression, or the like.

Next, a washing operation may be performed depending on the intended use of the product, or the product can be obtained by directly drying and pulverizing.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Example 1 (Ultrafiltration step) 4 tons of xanthan gum fermented crude liquid (gum concentration 2.5%) and 1 part of water
6t was added and the whole was diluted to 2Ql. The viscosity of the diluted liquid at this time was 580 cps (B-type rotational viscometer, 25
U, 30 rpm, rotor 43) and ivy.

First, insoluble impurities such as bacterial cells were removed using a centrifuge, and the P solution was collected. The light transmittance of the p liquid was 54.8% when distilled water was taken as 10% (Shimadzu spectrophotometer, U
V-120-02, 560 nm).

Next, an ultrafilter [Asahi Kasei Co., Ltd., model ACL-10]
50, hollow fiber membrane inner diameter 1,4111 m, 200 pieces, effective membrane area 0.1771', module diameter 42 ml11
．． Module length 34511m, molecular weight cut off 13000
．． Concentration was performed using a membrane material (polyacrylonitrile) to obtain a clear 2.5% viscous concentrate, and Table 1 shows the concentration conditions and results. The impurity removal effect is evident by the light transmittance and ash content. The color of the liquid changed from yellow-brown to white-yellow.

9- Table 1 *1 Measured after diluting to 115%.

*2 Add each solution to methanol, vacuum dry the precipitate at 60C for 40 hours, take 500 Da into a crucible,
Ash at 500C, add a few drops of concentrated hydrochloric acid, and then heat at 800C.
The remaining amount was weighed and expressed in terms of weight.

-10- (Recovery process) The 2.5% gum concentrate obtained in the ultraviolet filtration process was mixed with the following various precipitating liquids, and the state of gum precipitation, the amount of precipitating liquid and solvent used was compared with the conventional method. The results are shown in Table 2 for comparison.

Precipitation solution A: 100 Thimethanol B: 5% calcium chloride aqueous solution pH adjusted to 11.0 C: 1% aluminum sulfate aqueous solution pH 5.6 to 3.9D
: 1% calcium chloride aqueous solution 65 volume + methanol 35 volume mixture p) 1.5.0-6.5 E: D mixture pH adjusted to 12.0-12°5 Table 2 Note that the gel obtained in C was insoluble in water, but the other precipitates completely dissolved when returned to water.

The above results show that it is difficult to remove the precipitate using salt alone. Furthermore, it is difficult to precipitate with methanol. It is necessary to use it in combination with a metal salt, but if the pH is not adjusted to the alkaline side, many lids are used for the precipitation solution, and a hard precipitate that can be sufficiently removed cannot be obtained. Only in the present invention, a precipitate that can be well deliquified can be obtained with a small amount of solvent used.

Example 2 For 1 volume of 1 t gum concentrate obtained by ultrap-filtration, 0
．． Comparison was made of the lid used for a mixed solution of 60 volumes of 6% aqueous calcium chloride solution and 40 volumes of inpropyl alcohol, the precipitation state when the pH was changed, and the usage ratio of Inglobil alcohol. The results are shown in Table 3.

Table 3: If the pH is not adjusted to 12-16 even after using salt and solvent, the amount used is too large or the precipitate is weak, usually
Its functions include filtration and deliquification.

-15-

Claims (1)

[Claims] The xanthan gum fermentation sterilization solution is concentrated by ultrafiltration, and the concentrated liquid is mixed with a mixed solution consisting of a divalent metal salt, an aqueous organic solvent, and water to precipitate and recover. Concentration recovery method.