JP3584340B2 - Method for producing purified xanthan gum - Google Patents

Description

【００２６】
実施例４、比較例２
実施例１と同様に発酵および加熱処理を行った。次に発酵液に対して０〜０．１重量％になるようにポリリン酸（ポリリン酸ナトリウム：和光純薬製）水溶液を添加した。次の酵素処理を実施例１と逆の順序で行った。
すなわち、温度５５℃に保温した状態で、１０％硫酸水溶液を添加してｐＨ６．５に調整し、発酵液に対して３ｐｐｍのリゾチーム（リゾチーム太陽：太陽化学製）を添加し、攪拌しながら、１時間処理を行った。次に、温度５５℃に保温した状態で、２０％水酸化ナトリウム水溶液を添加してｐＨ８．５に調整し、発酵液に対して３００ｐｐｍのアルカリプロテアーゼ（ビオプラーゼ：ナガセ生化学製）を添加し、攪拌しながら２時間処理を行った。なお、処理中、１時間後の時点でｐＨ８．５に再度調整した。
酵素処理の終了後、発酵液をｐＨ７．０に調整してから、実施例１と同様の処理によってキサンタンガムの回収を行なった。
その結果を表２に示す。なお、分析方法は実施例１におけるものと同様である。
なお、熱処理とリゾチーム処理だけでは、十分な精製効果が得られなかった。
【００２７】
【表２】

【００２８】
実施例５、比較例３
種菌（１０^１０コ／ｍｌ）２ｍｌを下記Ｄからなる培地液の入った５Ｌ発酵槽に接種し、ｐＨ６．５〜７．５、３０℃にて２４時間通気を伴いながら１段目の前培養を行った後、この培養液を下記Ｅからなる培地液の入った２００Ｌ発酵槽に植菌して、１段目と同様の操作条件で２段目の前培養を行い、その後この培養液を下記Ｆからなる培地液の入った２０００Ｌ発酵槽に植菌して、ｐＨ６．５〜７．５、３０℃にて４８時間の通気発酵を行い、キサンタンガム含有の発酵液を得た。この後、２０００Ｌ発酵槽内でｐＨ１１に調整し、５５℃で９０分間加熱処理した。その後、温度５５℃に保温した状態で、１０％硫酸水溶液を添加してｐＨ８．５に調整し、発酵液に対して０．１重量％になるようにポリリン酸（ポリリンサン５−Ａ：武田薬品工業製）水溶液を添加した。その後、温度５５℃、ｐＨ８．５を保持した状態で、発酵液に対して３００ｐｐｍのアルカリプロテアーゼ（ビオプラーゼ：ナガセ生化学製）を添加し、攪拌しながら２時間処理を行った。次に、温度５５℃に保温した状態で、１０％硫酸水溶液を添加してｐＨ６．５に調整し、発酵液に対して３ｐｐｍのリゾチーム（リゾチーム太陽：太陽化学製）を添加し、攪拌しながら、１時間処理を行った。
【００２９】
Ｄ．
前培養（１段目）の培地成分
グルコース ５ｇ／Ｌ
ポリペプトン ５．２ｇ／Ｌ
酵母エキス ２．６ｇ／Ｌ
ＮａＣｌ ９ｇ／Ｌ
水 ３Ｌ
Ｅ．
前培養（２段目）の培地成分
グルコース ５ｇ／Ｌ
ポリペプトン ５．２ｇ／Ｌ
酵母エキス ２．６ｇ／Ｌ
ＮａＣｌ ９ｇ／Ｌ
水 １３０Ｌ
Ｆ．
本培養の培地成分
グルコース ５０ｇ／Ｌ
ポリペプトン ２ｇ／Ｌ
ＫＨ_２ ＰＯ_４ ２ｇ／Ｌ
ＭｇＳＯ_４ ・７Ｈ_２ Ｏ ０．５ｇ／Ｌ
微量成分 １ｍｌ／Ｌ
水 １１７０Ｌ
その結果を表３に示す。なお、分析方法は実施例１におけるものと同様である。
【００３０】
比較例３
キレート剤を添加しない他は実施例５と同様にして、発酵、酵素処理、キサンタンガムの回収を行なった。その結果を表３に示す。なお、分析方法は実施例１におけるものと同様である。
【００３１】
【表３】

【００３２】
比較例４、５
キレート剤として、発酵液に対して０．１〜１．０重量％のＥＤＴＡ−Ｎａ（和光純薬製）を添加した他は実施例１と同様にして、発酵、酵素処理、キサンタンガムの回収を行った。その結果を表４に示す。なお、分析方法は実施例１におけるものと同様である。
【００３３】
比較例６、７
キレート剤として、発酵液に対して０．１〜０．２重量％のピロリン酸（ピロリン酸ナトリウム：和光純薬製）を添加した他は実施例１と同様にして、発酵、酵素処理、キサンタンガムの回収を行った。
その結果を表４に示す。なお、分析方法は実施例１におけるものと同様である。
【００３４】
比較例８
キレート剤として、発酵液に対して０．１重量％のトリポリリン酸（トリポリリン酸ナトリウム：和光純薬製）を添加した他は実施例１と同様にして、発酵、酵素処理、キサンタンガムの回収を行った。その結果を表４に示す。なお、分析方法は実施例１におけるものと同様である。
【００３５】
比較例９
キレート剤として、発酵液に対して０．１重量％のクエン酸（クエン酸ナトリウム：和光純薬製）を添加した他は実施例１と同様にして、発酵、酵素処理、キサンタンガムの回収を行った。その結果を表４に示す。なお、分析方法は実施例１におけるものと同様である。
【００３６】
【表４】

【００３７】
【発明の効果】
本発明によって、固有の粘度を損なうことなく、透光度が良好で黄色成分を低減した、精製度の高いキサンタンガムを得ることができる。[0001]
[Industrial applications]
The present invention relates to a method for producing xanthan gum having good light transmittance and high purity.
[0002]
[Prior art]
In general, water-soluble viscous polysaccharides include dextran, xanthan gum, welan gum, ramzan gum, plutane, scleroglucan, gellan gum, etc., and are widely used in various industries such as food, paint, papermaking, cosmetics, and oil recovery. Its demand is increasing. In particular, xanthan gum has excellent thickening properties, emulsion stability, salt resistance, enzyme resistance, and other properties, and its use in industrial applications as a useful additive is expanding.
[0003]
Conventionally, xanthan gum has been prepared by using microorganisms belonging to the genus Xanthomonas such as X. campestris , carbon sources such as glucose, molasses and starch, water-soluble nitrogen sources such as peptone and yeast extract, magnesium salts, and phosphorus. It is obtained by aerobically culturing in a medium containing acid ions and other trace components. Usually, it is produced by culturing, sterilizing, precipitating with lower alcohols such as ethanol and isopropyl alcohol, and drying. The method for producing xanthan gum is described in U.S. Pat. Nos. 3,020,206, 3,251,479, 3,391,060, 3,433,708 and 3,333. Nos. 594,280, 4,282,321 and 3,659,026.
[0004]
Xanthan gum, as a production microorganism instead of Xanthomonas campestris, other known Xanthomonas bacteria such Xanthomonas Karotate (X.carotate), Xanthomonas Inkanae (X.incanae), Xanthomonas Begoniae (X.begoniae), Xanthomonas Papaberikora (X.papavericola), using the Xanthomonas Tran cell soo (X.translucens), Xanthomonas Basukuroniumu (X.vasculorum) and Xanthomonas Hederae (X.hederae), can be performed xanthan gum production.
[0005]
As a method for purifying xanthan gum, it is generally known to remove undissolved components such as cell residue during fermentation and water-insoluble unconsumed nitrogen components by using centrifugation or cake filtration. Since the fermentation liquid has a high viscosity, a dilution step with water and a concentration step are required, which is not practical in terms of cost and operation.
[0006]
On the other hand, a purification method for treating a fermentation solution with an enzyme for the purpose of lysing or solubilizing cell residue or removing microgels is known, and many proposals have been made.
For example, as an enzyme treatment method for lysing and solubilizing cell residue, US Pat. No. 3,966,618 and US Pat. No. 4,010,071 disclose a method using an acidic protease and a neutral protease. U.S. Pat. No. 4,119,491 discloses a method of removing proteases from a polymer aqueous solution by contacting with a siliceous solid after protease treatment, and EP 39,962 discloses a β-1,3-glucanase. A method using a complex enzyme having an activity and a protease activity, and a method using an enzyme having a nuclease activity in US Pat. No. 4,729,958 have been proposed, but no sufficient effect has been obtained.
[0007]
Further, as an enzyme treatment method for removing microgel, US Pat. No. 4,431,734 discloses an enzyme treatment method using polysaccharase and protease, and US Pat. No. 4,904,586 discloses a polygalase. A method using a combination of an enzyme having cutulonase activity and an enzyme having protease activity, and a purification method using cellulase are proposed in US Pat. No. 4,416,990, but no sufficient effect has been obtained.
[0008]
As a treatment method using a cell wall lysing enzyme, lysozyme, N-acetylmuramyl-L-alanine amidase and peptidase are simultaneously added to Japanese Patent No. 1,318,520 (Japanese Patent Publication No. 60-44919). A way to do this has been proposed. These enzymes are known as cell wall lysing enzymes, but they do not act directly on Gram-negative bacteria, and surprisingly, they are not sufficiently effective despite the need for long-term treatment .
[0009]
All of these methods of treating with an enzyme can omit complicated steps such as dilution and concentration compared to conventional purification methods such as filtration and centrifugation, and are economically and operationally advantageous purification methods. is there. However, good purified xanthan gum has not been obtained because cell debris is not sufficiently solubilized by the enzyme, that is, the activity of the enzyme is not sufficiently extracted, or no suitable enzyme is used. That's why.
[0010]
Japanese Patent Application Laid-Open No. 5-292895 provides a method in which a heat treatment is performed under a specific condition, followed by a treatment with an alkaline protease and lysozyme. In this way, good purified xanthan gum has been obtained. As described above, the enzyme treatment method is suitable as a method for purifying a xanthan gum fermented liquid by selecting a suitable enzyme and performing the enzyme treatment under suitable conditions.
[0011]
It is important to perform the treatment with the enzyme under suitable conditions such as temperature and pH in order to obtain the activity of the enzyme. Furthermore, it is presumed that under conditions suitable for using the enzyme, it is possible to increase the enzyme activity and promote the decomposition by increasing the affinity between the enzyme and the substrate, thereby increasing the enzyme activity and obtaining a better purified xanthan gum. Reached.
[0012]
As a method for purifying a xanthan gum fermentation liquid, use of a chelating agent has not been proposed. However, it is generally known that lysozyme obtains lytic activity against gram-negative bacteria by damaging the outer membrane with a chelating agent such as EDTA-Na (sodium ethylenediaminetetraacetate). However, even if some chelating agents including EDTA-Na were coexisted in the xanthan gum fermented solution and the enzyme treatment was performed, only xanthan gum with low light transmittance was obtained.
[0013]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for obtaining better purified xanthan gum, that is, xanthan gum with high transparency when used as an aqueous solution, by increasing the activity conditions of lysozyme which is a cell wall lysing enzyme.
[0014]
[Means for Solving the Problems]
The method for producing xanthan gum according to claim 1, wherein the fermentation solution containing xanthan gum is heated at an initial pH of 9 to 12.5 and a temperature of 45 to 70 ° C for 30 minutes or more, and then polyphosphoric acid is added to the fermentation solution. , Followed by treatment with an enzyme to solubilize the microbial cells in the fermentation broth.
[0015]
The method for producing xanthan gum according to claim 2 is the method according to claim 1, wherein the step of treating with the enzyme for solubilizing the microbial cells in the fermentation solution comprises: 10 to 500 ppm of alkaline protease, pH 6 to 10 and temperature of 40 to 65 ° C. for 30 minutes or more, and then (B) 0.5 to 100 ppm of lysozyme to the fermentation broth. , A pH of 5.5 to 8.0 and a temperature of 25 to 60 ° C for 30 minutes or more, or the step (A) after the step (B). Features.
[0016]
In the present invention, the activity of lysozyme is increased by adding polyphosphoric acid during the treatment of the xanthan gum fermented liquor with lysozyme, thereby obtaining a highly purified xanthan gum, that is, a highly transparent xanthan gum when prepared as an aqueous solution. be able to.
[0017]
Prior to the addition of polyphosphoric acid, the xanthan gum-containing fermentation liquor is subjected to a heat treatment at an initial pH of 9 to 12.5, preferably pH 10 to 12, at a temperature of 45 to 70 ° C, preferably 50 to 60 ° C for 30 minutes or more. If the pH is less than 9, the solubilization of bacteria may not be achieved efficiently, which is not preferable. When the pH is higher than 12.5, the coloring of the fermentation liquor and the viscosity properties of the product may be adversely affected, which is not preferable. If the temperature is lower than 45 ° C., the solubilization of the bacterium in the treatment with the enzyme may not be achieved efficiently, which is not preferable. If the temperature is higher than 70 ° C., the coloring of the fermentation liquid and the viscosity properties of the product may be adversely affected, which is not preferable. A treatment time of at least 30 minutes is sufficiently effective, but a heat treatment of at least 2 hours is not preferable because productivity may be reduced. Without this pretreatment, the effect of the treatment with the enzyme may not be exhibited or it may take a long time to exhibit the effect, which is not preferable.
[0018]
After the heat treatment, polyphosphoric acid is added. If polyphosphoric acid is added before heat treatment, polyphosphoric acid may be decomposed, and a sufficient effect may not be exerted. Polyphosphoric acid is added at 0.01 to 1% by weight, preferably 0.05 to 0.2% by weight, based on the xanthan gum fermented solution at a pH of 6 to 9.5 and a temperature of 65 ° C or lower. If the content is less than 0.01% by weight, the sufficient effect of polyphosphoric acid is not exhibited, which is not preferable. If the amount is more than 1% by weight, the bacteriolysis effect does not increase so much, which is not preferable in terms of cost. If the temperature is higher than 65 ° C., polyphosphoric acid may be decomposed, and a sufficient effect may not be exerted. If the pH is less than 6, the chelating effect of polyphosphoric acid may not be sufficiently exhibited, which is not preferable. If the pH is higher than 9.5, polyphosphoric acid may be decomposed, and a sufficient effect may not be exhibited.
[0019]
The treatment with the enzyme is carried out in two stages: alkaline protease and lysozyme. The treatment with the alkaline protease is performed at a pH of 6 to 10, preferably 7.5 to 9.0, a concentration of 10 to 500 ppm, a temperature of 40 to 65 ° C, and preferably 50 to 60 ° C, for 30 minutes or more. If the pH is lower than 6, the activity of the alkaline protease may deteriorate, which is not preferable. If the pH is higher than 10, the physical properties of the product may deteriorate, which is not preferable. When the concentration is less than 10 ppm, the action of the alkaline protease is not sufficiently exhibited, which is not preferable. If the concentration is more than 500 ppm, only the amount of the enzyme used increases, but the bacteriolysis effect does not increase so much, which is not preferable in terms of cost. When the temperature is lower than 40 ° C., the action of the alkaline protease is not sufficiently exhibited, which is not preferable. If the temperature is higher than 65 ° C., the activity of the alkaline protease may deteriorate, which is not preferable. If the treatment time is less than 30 minutes, the action of the alkaline protease is not sufficiently exhibited, which is not preferable.
[0020]
The treatment with lysozyme is performed at a pH of 5.5 to 8.0, preferably 6.5 to 7.5, a concentration of 0.5 to 100 ppm, a temperature of 25 to 60 ° C, and preferably 50 to 60 ° C, for 30 minutes or more. If the pH is lower than 5.5 or higher than 8.0, the activity of lysozyme is not sufficiently exhibited, which is not preferable. When the concentration exceeds 100 ppm, only the amount of the enzyme used is increased, but the bacteriolysis effect is not so high, which is not preferable in terms of cost. When the temperature is lower than 25 ° C., the action of lysozyme is not sufficiently exhibited, which is not preferable. If the temperature is higher than 60 ° C., the activity of lysozyme may deteriorate, which is not preferable. The order of the alkali protease treatment and the lysozyme treatment may be any order, but the treatment with the lysozyme after the treatment with the alkaline protease is more preferable in that the pH of the fermented solution can be efficiently adjusted.
[0021]
【Example】
Examples 1 to 3, Comparative Example 1
2 ml of an inoculum (Xanthomonas campestris) (ATCC 55298) was inoculated into a 500 ml flask containing 100 ml of a medium solution comprising the following A, and the first stage culture was carried out at an initial pH of 7.0 at 30 ° C for 24 hours with shaking culture. After that, 10 ml of this culture solution was inoculated into a 500 ml flask containing 90 ml of a medium solution comprising the following B, and precultured in the second stage under the same operating conditions as the first stage. Three of them, 300 ml in total, are inoculated into a 5 L fermenter containing 2.7 L of a medium solution composed of the following C, and subjected to aeration fermentation at pH 6.5 to 7.5 at 30 ° C. for 48 hours to contain xanthan gum. A fermented liquid was obtained.
[0022]
A.
Pre-culture (first stage) medium component glucose 5g / L
Polypeptone 5.2 g / L
Yeast extract 2.6 g / L
NaCl 9g / L
100 ml of water
B.
Preculture (2nd stage) medium component glucose 5g / L
Polypeptone 5.2 g / L
Yeast extract 2.6 g / L
NaCl 9g / L
90 ml of water
C.
Medium component of main culture glucose 50g / L
Polypeptone 4g / L
KH ₂ PO ₄ 2g / L
_{MgSO 4 · 7H 2 O 0.5g /} L
Trace component 1ml / L
2.7L of water
[0023]
The enzymatic treatment thereafter was performed by dispensing 300 g of the fermented liquid into a beaker. The fermentation liquor was adjusted to pH 11 and heat-treated at 55 ° C. for 90 minutes. Next, an aqueous solution of polyphosphoric acid (sodium polyphosphate: manufactured by Wako Pure Chemical Industries) was added so as to be 0 to 0.2% by weight based on the fermentation liquid. Thereafter, while maintaining the temperature at 55 ° C., a 10% aqueous sulfuric acid solution was added to adjust the pH to 8.5. An aqueous suspension containing 300 ppm of alkaline protease (Bioprase: manufactured by Nagase Biochemicals) based on the fermentation solution was added to the pH-adjusted fermentation solution after removing the adsorbent with a 0.4 μm microfilter, followed by stirring. For 2 hours. During the treatment, the pH was again adjusted to 8.5 one hour later. Next, while maintaining the temperature at 55 ° C., the pH was adjusted to 6.5 by adding a 10% aqueous sulfuric acid solution, and 3 ppm of lysozyme (Lysozyme Taiyo: manufactured by Taiyo Kagaku) was added to the fermentation broth. The treatment was performed for 1 hour with stirring.
[0024]
To perform the analysis, the fermentation liquor was collected after the fermentation, after the heat treatment, after the first step of the enzyme treatment, and after each step after the second step of the enzyme treatment, and the turbidity of the treatment liquid was measured. Further, the xanthan gum-containing fermented liquor after completion of the enzyme treatment was mixed with 1.5% by weight of 85% isopropyl alcohol to precipitate and separate xanthan gum, followed by blowing and drying. Thereafter, a 1% by weight aqueous solution of the obtained solid xanthan gum was prepared, and the light transmittance, yellowness and viscosity were measured.
[0025]
Table 1 shows the above results. In addition, each analysis method is as shown below.
Treatment liquid turbidity: Measured by visible light at 660 nm after diluting the liquid 7-fold.
Light transmittance: Measured by transmittance in the visible light region using a quartz cell having a layer length of 2 cm.
Yellowness: Measured using an SM color computer (manufactured by Suga Test Instruments Co., Ltd.).
Viscosity: Measured with a Brookfield viscometer (30 rpm).
[Table 1]

[0026]
Example 4, Comparative Example 2
Fermentation and heat treatment were performed in the same manner as in Example 1. Next, an aqueous solution of polyphosphoric acid (sodium polyphosphate: manufactured by Wako Pure Chemical Industries, Ltd.) was added so as to be 0 to 0.1% by weight based on the fermentation liquid. The following enzyme treatment was performed in the reverse order of Example 1.
That is, while keeping the temperature at 55 ° C., a 10% aqueous solution of sulfuric acid is added to adjust the pH to 6.5, and 3 ppm of lysozyme (Lysozyme Taiyo: manufactured by Taiyo Kagaku) is added to the fermentation solution, and while stirring, The treatment was performed for one hour. Next, while maintaining the temperature at 55 ° C., the pH was adjusted to 8.5 by adding a 20% aqueous sodium hydroxide solution, and 300 ppm of an alkaline protease (Bioplase: manufactured by Nagase Biochemical) was added to the fermentation broth. The treatment was performed for 2 hours with stirring. During the treatment, the pH was adjusted again to 8.5 after 1 hour.
After completion of the enzyme treatment, the fermentation liquor was adjusted to pH 7.0, and xanthan gum was recovered by the same treatment as in Example 1.
Table 2 shows the results. The analysis method is the same as that in the first embodiment.
The heat treatment and the lysozyme treatment alone did not provide a sufficient purification effect.
[0027]
[Table 2]

[0028]
Example 5, Comparative Example 3
2 ml of the inoculum (10 ¹⁰ cells / ml) is inoculated into a 5 L fermenter containing a medium solution comprising the following D, and the first-stage preculture is performed at pH 6.5 to 7.5 at 30 ° C. with aeration for 24 hours. After that, this culture was inoculated into a 200-L fermenter containing a medium solution comprising the following E, and precultured in the second stage under the same operating conditions as in the first stage. The culture was inoculated into a 2000-L fermenter containing a medium solution composed of the following F, and subjected to aeration fermentation at pH 6.5 to 7.5 at 30 ° C for 48 hours to obtain a fermented solution containing xanthan gum. Thereafter, the pH was adjusted to 11 in a 2000 L fermenter, and heat treatment was performed at 55 ° C. for 90 minutes. Thereafter, while keeping the temperature at 55 ° C., a 10% aqueous sulfuric acid solution is added to adjust the pH to 8.5, and polyphosphoric acid (polylinsan 5-A: Takeda) is adjusted to 0.1% by weight based on the fermentation liquor. An aqueous solution (manufactured by Yakuhin Kogyo) was added. Thereafter, while maintaining the temperature at 55 ° C. and the pH at 8.5, 300 ppm of an alkaline protease (Bioprase: manufactured by Nagase Biochemical) was added to the fermentation liquor, and the mixture was treated for 2 hours with stirring. Next, while maintaining the temperature at 55 ° C., a 10% aqueous sulfuric acid solution was added to adjust the pH to 6.5, and 3 ppm of lysozyme (Lysozyme Taiyo: manufactured by Taiyo Kagaku) was added to the fermentation solution, and the mixture was stirred. The treatment was performed for one hour.
[0029]
D.
Pre-culture (first stage) medium component glucose 5g / L
Polypeptone 5.2 g / L
Yeast extract 2.6 g / L
NaCl 9g / L
3L of water
E. FIG.
Preculture (2nd stage) medium component glucose 5g / L
Polypeptone 5.2 g / L
Yeast extract 2.6 g / L
NaCl 9g / L
130L water
F.
Medium component of main culture glucose 50g / L
Polypeptone 2g / L
KH ₂ PO ₄ 2g / L
_{MgSO 4 · 7H 2 O 0.5g /} L
Trace component 1ml / L
Water 1170L
Table 3 shows the results. The analysis method is the same as that in the first embodiment.
[0030]
Comparative Example 3
Fermentation, enzyme treatment, and collection of xanthan gum were performed in the same manner as in Example 5 except that no chelating agent was added. Table 3 shows the results. The analysis method is the same as that in the first embodiment.
[0031]
[Table 3]

[0032]
Comparative Examples 4 and 5
Fermentation, enzyme treatment, and xanthan gum recovery were performed in the same manner as in Example 1 except that 0.1 to 1.0% by weight of EDTA-Na (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a chelating agent to the fermented liquid. went. Table 4 shows the results. The analysis method is the same as that in the first embodiment.
[0033]
Comparative Examples 6 and 7
Fermentation, enzymatic treatment, xanthan gum in the same manner as in Example 1 except that 0.1 to 0.2% by weight of pyrophosphoric acid (sodium pyrophosphate: manufactured by Wako Pure Chemical Industries) was added to the fermentation solution as a chelating agent. Was collected.
Table 4 shows the results. The analysis method is the same as that in the first embodiment.
[0034]
Comparative Example 8
Fermentation, enzyme treatment, and collection of xanthan gum were performed in the same manner as in Example 1 except that 0.1% by weight of tripolyphosphoric acid (sodium tripolyphosphate: manufactured by Wako Pure Chemical Industries) was added to the fermentation solution as a chelating agent. Was. Table 4 shows the results. The analysis method is the same as that in the first embodiment.
[0035]
Comparative Example 9
Fermentation, enzyme treatment, and collection of xanthan gum were performed in the same manner as in Example 1 except that 0.1% by weight of citric acid (sodium citrate: manufactured by Wako Pure Chemical Industries) was added to the fermentation solution as a chelating agent. Was. Table 4 shows the results. The analysis method is the same as that in the first embodiment.
[0036]
[Table 4]

[0037]
【The invention's effect】
According to the present invention, highly purified xanthan gum having good light transmittance and reduced yellow component can be obtained without impairing the inherent viscosity.

Claims (2)

After heat-treating the fermented liquor containing xanthan gum at an initial pH of 9 to 12.5 and a temperature of 45 to 70 ° C. for 30 minutes or more, polyphosphoric acid is added to the fermented liquor. A method for producing xanthan gum, which comprises performing an enzyme treatment to solubilize cells. The treatment step with the above enzyme for solubilizing the microbial bacteria in the fermentation liquor comprises (A) adding 10 to 500 ppm of an alkaline protease to the fermentation liquor, adjusting the pH to 6 to 10 and the temperature to 40 to 65 ° C. And then (B) 0.5 to 100 ppm of lysozyme is added to the fermented liquor, the pH is set to 5.5 to 8.0 and the temperature is 25 to 60 ° C. for 30 minutes or more. The method for producing xanthan gum according to claim 1, wherein the step (A) is performed after the step (B).