JPH10204103A - Novel polysaccharide having specific viscosity characteristic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polysaccharide which has a specified molecular weight and constituents and, upon a change in a concentration, not only changes in its viscosity but also changes in its state from a viscous solution to a gel state by culturing bacteria of the genus Pseudomonas in a nutrient medium and recovering it from the culture. SOLUTION: Polysaccharide-producing bacteria of the genus Pseudomonas are cultured in a nutrient medium, and the polysaccharide is collected from the culture. The bacteria cultured may be those of any species and strain so far as they belong to the genus Pseudomonas and produce a polysaccharide. The polysaccharide produced by this method has a molecular weight of about 1,600,000 when determined by high-performance liquid chromatography using a gel filtration column and has constituents comprising glucose residues and mannose residues in a 1:1 molar ratio. A 0.5w/v% aqueous solution of this polysaccharide is a viscous solution at a temp of 5-10 deg.C, whereas its 1w/v% aqueous solution is in a gel state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel polysaccharide having adjustable viscosity properties and a method for producing the same using bacteria.

[0002]

2. Description of the Related Art Conventionally, polysaccharides derived from microorganisms, such as xanthan gum and levan, have been used as additives for foods, cosmetics, feeds and the like, and further as industrial materials, based on their unique physical properties. For example, xanthan gum can be obtained from the bacterium Xanthomonas campestris ( Xanthomona gum).
s campestrics ) is a high-molecular-weight polysaccharide that is produced outside the cells.
It is a polysaccharide having a side chain consisting of one glucuronic acid and two mannoses in a chain of 4-β-D-glucoside bonds. The aqueous solution behaves almost as a non-Newtonian viscous liquid near room temperature, and is relatively stable to heat, alkalis, and acids. Specifically, xanthan gum has been used for the purpose of improving the viscosity properties of foods and cosmetics by utilizing such properties.

[0003]

As described above, conventional polysaccharides such as xanthan gum are used in various fields based on their viscosity characteristics. However, although these polysaccharides can generally change the degree of viscosity by a change in concentration, they maintain an intermediate property (sol) between a fluid viscous region and a solidified (gelled) region. It was difficult to do. Further, the solidification stability and the pH stability at high temperatures were not always satisfactory.

[0004] Therefore, in view of the recent technical background in which food forms have been diversified, for example, not only the degree of viscosity can be changed by a change in concentration, but also a viscous solution changes to a gelled state. It would be desirable to provide a polysaccharide that can vary up to.

[0005]

Means for Solving the Problems The present inventors have studied the growth and products of various microorganisms in various media, and found that bacteria belonging to the genus Pseudomonas have both a thickening property and a gelling ability. To produce polysaccharides. This polysaccharide is not yet described in the prior art literature.

Therefore, according to the present invention, the above-mentioned problems are solved.
(A) a molecular weight of about 1.6 million as measured by high performance liquid chromatography using a gel filtration column;
(B) as constituents glucose and mannose residues in a molar ratio of 1: 1 and (C) at 5 ° C. to 10 ° C. a 0.5% (weight / volume) aqueous solution is However, the problem can be solved by providing a polysaccharide whose viscosity property can be adjusted, wherein an aqueous solution of 1 (weight / volume)% is in a gel state.

According to the present invention, there is also provided a method for efficiently producing the polysaccharide. Pseudomonas Specifically this method is capable of producing said polysaccharide body (Pseudo
monas ) The bacterium is cultured in a nutrient medium, and the polysaccharide is collected from the culture.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The polysaccharide according to the present invention has the above-mentioned characteristics (A) to (C). The viscosity characteristics of the solution are as follows. That is, at normal room temperature, the polysaccharide is about 0.5 to about 1.0.
(Weight / volume)% aqueous solution is in the form of a viscous solution,
An aqueous solution of about 2 (weight / volume)% is in a gel state.
Furthermore, an aqueous solution of about 3% (weight / volume) of the polysaccharide is
It becomes a gelled state even at a higher temperature. Further, the gel state once formed in this manner can be kept in a stable state even after incubation at 100 ° C. for 30 minutes. Moreover, the gelled state is stable over a wide range from acidic to alkaline, for example, at room temperature,
The gelled state is maintained even under strongly acidic (0.5 N hydrochloric acid) conditions.

[0009] As described above, the polysaccharide according to the present invention exhibits, in addition to thickening properties, extremely unique physical properties not found in known xanthan gum, levan and the like.
It could be widely used in fields such as feed.

[0010] The polysaccharide according to the present invention can be efficiently produced by a method of culturing Pseudomonas bacteria in a nutrient medium, which is another embodiment of the present invention. The Pseudomonas bacterium belongs to the genus Pseudomonas and can be used irrespective of its species and strain as long as it can produce the polysaccharide. However, among them, the bacteria isolated from the soil of Tottori City, Tottori Prefecture as ethanol-assimilating bacteria by the present inventors, were sent to the Institute of Biotechnology, National Institute of Advanced Industrial Science and Technology on January 7, 1997. Pseudomonas stutzeri BL deposited and assigned accession number FERM P-16025
58 strains are particularly preferred.

As a nutrient medium for producing the polysaccharide of the present bacterium,
In general, it can grow Pseudomonas bacteria,
Any medium containing a carbon source, a nitrogen source, yeast extract and metal salts may be used.

Usually, glucose, fructose, sucrose, glycerol, vegetable oils, ethanol, propanol, butanol and the like can be used as carbon sources. The most preferred carbon source is ethanol and is used at a starting concentration of 0.1-8% (v / v), preferably 1-4% (v / v). Ethanol is added at the beginning of the culture or during the culture.

As a nitrogen source, peptone, yeast extract,
An amino acid mixture, an inorganic ammonium salt, ammonia or the like can be used at 0.05 to 5%, preferably 0.1 to 2%.

As the inorganic metal salt, potassium or magnesium phosphate or sulfate is 100 to 1,500 mg / l.
The calcium, zinc, iron and manganese sulfates, hydrochlorides or phosphates can be used in the range of 1 mg to 100 mg / l for each component.

Trace elements such as vitamins are added to yeast extract at a concentration of 0.1%.
It can be added at a rate of 0.5 to 1 g / l.

The cultivation is usually performed for 1 to 10 days under aerobic conditions such as shaking culture or deep aeration stirring culture. The culture temperature is 15 to 45 ° C, preferably 25 to 37 ° C.
H is 7 to 12, preferably 9 to 10. After completion of the culture, the viscosity is reduced by appropriate dilution, the bacteria are removed by centrifugation, membrane filtration, or the like, followed by freeze-drying, spray-drying, and heat-vacuum drying to provide the polysaccharide according to the present invention.

The above strain BL58, which is a preferred strain according to the present invention, has the following mycological properties:
Pseudomonas Sutsutsueri (Pseudomonas stutzeri)
Was identified.

(Bacteriological Properties) The results of examining the taxonomic properties of strain BL58 based on the description in Bergey's Manual of Systematic Bacteriology, Volume 1 (1984) are shown below. .

[0019] Properties Physical and morphological properties Colony morphology Colony morphology, wavy green, creamy, bumpy, opaque, low convex 2 mm in diameter Motility + sporulation-Gram stain-Physiological properties Growth temperature (37 ° C) + (41 ° C) + (45 ° C.) + catalase + oxidase + urease + glucose fermenting - NO ₃ reduction - indole production - acid from glucose - arginine dihydrolase - esculin hydrolysis - gelatin hydrolysis - beta-galactosidase - glucose assimilation + arabinose assimilation - Mannose assimilation-Mannitol assimilation-N-acetylglucosamine assimilation-Maltose assimilation + Gluconic acid assimilation + Capric acid assimilation + Adipic acid assimilation-Malic acid assimilation + Citric acid assimilation + Phenyl acetate assimilation-Cytochrome oxidase + Alkaline of maleic acid culture solution + Tween 80 - Starch + Phenylalanine deaminase + As a result, we identified BL58 strain as described above.

[0020]

EXAMPLES The present invention will be described in more detail with reference to Examples.

Example 1: Isolation of strain BL58 5 ml of a 0.1 g soil sample collected from soil in Tottori City, Tottori Prefecture
And suspended in a culture medium shown in Table I below at 30 ° C. for 5 days with shaking culture. 0.1 ml of this culture is inoculated into 5 ml of the same fresh medium and cultured with shaking at 30 ° C. for 5 days. This operation 3
After repeated enrichment culture, ethanol-assimilating microorganisms are isolated by forming colonies on an agar plate medium of the same composition. BL58 strain was selected as the strain having the highest polysaccharide productivity among these obtained microorganisms. Therefore,
The production of the polysaccharide of the invention is also possible with other microorganisms obtained by the present specific method.

Table I: Medium C ₂ H ₅ OH 3% (v / v) (NH ₄ ) ₂ SO ₄ 1.5 g / l (NH ₄ ) ₂ SO ₃ 1.5 g / l NH ₄ NO ₃ 1.5 g / l KH _{2 PO 4 1.5g / l K 2} HPO 4 0.67g / l MgSO 4 · 7H 2 O 0.3g / l CaCl 2 · 2H 2 O 0.01g / l ZnSO 4 · 7H 2 O 0.01g / l FeSO 4 · 7H 2 _{O 0.01g / l MnSO 4 · 7H} 2 O 0.001g / l yeast extract 0.5 g / l as can be seen from the medium composition of table I, BL58 strain, those obtained from natural soil samples as ethanol utilizing bacteria It is. According to the above method using such a specific medium, those skilled in the art can easily obtain a strain that can be used in the present invention.

Example 2 Conditions for Polysaccharide Production by the BL Strain The medium composition of Table I used in Example 1 for the isolation of the BL58 strain was B
It is also suitable for the production of polysaccharide by strain L58. Hereinafter, an example in which the BL58 strain is cultured in a medium based on such a medium composition will be described. In the examples, “% (v / v)” and “% (w / v)” in the case of displaying percentages mean (volume / volume)% and (weight / volume)%, respectively.

From the slant storage medium, the amount of one platinum loop
The cells were inoculated in a Sakaguchi flask containing ml of medium (ethanol 1% (v / v)) and cultured at 30 ° C. for 24 hours. 1 ml of this culture was inoculated into the same medium containing ethanol (3% (v / v)) and cultured at 30 ° C. The results obtained when the initial medium pH was 7 to 11 are shown in FIG. The growth was fast at pH8, but no increase in viscosity due to polysaccharide production was observed.
On the other hand, when the pH is 9 or more, an induction period for growth is observed, but the viscosity of the culture solution is remarkably increased, and the pH is 10 to 10.
Under the conditions of 11, the culture solution was completely gelled. This strain produced polysaccharide efficiently only under alkaline conditions.

Next, the influence of the concentration of ethanol in the medium was examined. FIG. 2 shows the results obtained by examining the growth with the initial ethanol concentration varied from 1 to 8% (v / v), and FIG. 3 shows the amount of polysaccharide produced (expressed as the total amount of sugars).

When the concentration of ethanol as a carbon source is 1-2%
In (v / v), the BL58 strain grew rapidly, but as the ethanol concentration was increased, the induction period of growth became longer, and no growth was observed at an ethanol concentration of 7% (v / v) or more. Up to an ethanol concentration of 4% (v / v), the production of polysaccharide also tends to increase.
At ５5% (v / v), the culture gelled, indicating high polysaccharide production. When the ethanol concentration was 5% (v / v) or more, the production amount of polysaccharide decreased.

(Effects of Various Carbon Sources) FIG. 4 shows the effects of alcohols and saccharides as carbon sources on the polysaccharide production of strain BL58. This bacterium used 0.5% (v / v) propanol or butanol as a carbon source, but did not grow on methanol. In addition, this bacterium is 3% (w / v)
Glycerol, glucose and fructose as carbon sources, but not lactose. In the production of polysaccharides, 0.5% (v
Although the increase in the viscosity of the culture solution was observed also in the concentration of / v), the increase in the viscosity of the culture solution was hardly observed with other alcohols. On the other hand, in the production of polysaccharides using carbohydrates as a carbon source, 3% (v / v) ethanol and 3% (w / v) glucose and fructose were completely gelled in the culture solution in the target ethanol. In the case of, only an increase in the viscosity of the culture solution was observed, and it did not lead to gelation.

Example 3: Preparation of polysaccharide preparation and its characteristics The BL58 strain was cultured in a total of 10 Sakaguchi flasks containing 100 ml of the medium shown in Table I above (30 ° C., 5 days, initial p
H10.0), distilled water was added to the gelled culture solution for dilution, and the centrifuged supernatant was dialyzed against distilled water. The polysaccharide was prepared as a freeze-dried preparation of the dialysate. Subsequent analysis shows the results using the lyophilized polysaccharide preparation.

(Chemical Structure of Polysaccharide) The molecular weight of the polysaccharide produced by the BL58 strain was measured by high performance liquid chromatography using a gel filtration column of Shodex GS-710 (trademark). As a result, the molecular weight of the polysaccharide produced by the BL58 strain was estimated to be about 1.6 million.

The constituents of the present polysaccharide consisted of glucose and mannose at a ratio of 1: 1 and contained trace amounts of organic acids. The composition of the present polysaccharide was analyzed using the following method.

1% (w / v) of polysaccharide was converted to 2N TFA
(Trifluoroacetic acid) in the presence of acid hydrolysis (100 ° C.,
After 12 hours), the decomposition product was analyzed using thin-layer chromatography and high performance liquid chromatography. The results of the thin layer chromatography are shown in FIG.

The effects of polysaccharide concentration and temperature on gelation were investigated. Polysaccharide solutions having a concentration of 0.5 to 3.0% (w / v) were prepared, and gelation was observed at each concentration. 1%, 2% and 3
% (W / v) aqueous solution of polysaccharide at 10 ° C., 30
It was completely solidified up to 55 ° C. and the gel state could be maintained. Also, by adjusting the polysaccharide concentration, the gelation temperature was shown to be finely controlled. The results are shown in Table II.

[0033] (Organic solvent dispersing effect) 1% (w / v) aqueous solution of polysaccharide derived from BL58 strain was mixed with ethanol and acetone at a ratio of 1: 1
And the effect on gelation was examined. Ordinary microbial polysaccharides precipitate with organic solvents. However, no precipitation was observed in the polysaccharide produced by strain BL58 even in the presence of 50% ethanol or acetone, and rather, the organic solvent was dispersed in the polysaccharide solution to promote gelation.

(Gelification Effect of Metal Ions) After adding various metal salts to a 1% (w / v) solution of polysaccharide derived from BL58 strain, the effect of addition of metal salts on gelation was examined. The addition of the divalent metal salt promoted the gelation of the polysaccharide. In particular, Mn ions were effective for gelation under low temperature conditions.

(Stability of polysaccharide) A 3% (w / v) solution of polysaccharide derived from BL58 strain forms a stable gel. Therefore,
The stability under acidic and alkaline conditions was studied. pH 3.
At 0 to 11.0, a stable gel was formed, but when the pH was adjusted to 3.0 or 11.0 and the mixture was boiled, the gel became a liquefied state.

Example 4: Stability of the gel derived from the polysaccharide of the present invention Using the polysaccharide prepared in Example 3, the temperature stability of the gel was examined. Xanthan gum and levan used were products of Sigma Chemical Co., USA. 3% or 5% (w / v) of each polymer sample in distilled water
And kept at 50 to 100 ° C. for 30 minutes, and the observed results are shown in Table III. The polysaccharide according to the present invention is 50 to 10
Although the gelled state was maintained at 0 ° C., xanthan gum was paste-like, and levan only exhibited a viscous solution.

Table III BP Xanthan gum Levan temperature 3% 5% 3% 5% 3% 5% 50 ° C GGPPSS 60 ° C GGPPSS 70 ° C GGPPSS 80 ° C GGPPSS 90 ° C GGPPSS 100 ° C GGPPSSG : gelled P: paste-like S: low viscosity Example 5: pH stability of the polysaccharide of the present invention The polysaccharide prepared in Example 3, xanthanzam (Sigma Each 3% aqueous solution of Levan (manufactured by Chemical Co., Ltd.) and Levan (manufactured by Sigma Chemical Co.) was adjusted to pH 2 to 11 with 1N hydrochloric acid or 1N sodium hydroxide, and was observed after holding at 25 ° C. for 6 hours. As shown in Table IV, the polysaccharide according to the present invention maintained a stable gel state between pH 2 and 11, and no change in physical properties was observed. Under the same conditions, xanthan gum turned into a paste, and levan turned into a viscous solution and did not gel.

[0038]Table IV pH BP Xanthan gum Leban 2 GPS 3 GPS 4 GPS 5 GPS 6 GPS 7 GPS 8 GPS 9 GPS 10 GPS11 GPS G: Gelled P: Paste S: Low viscosity Next, 3% (w / v) of each polysaccharide solution was strongly acidified (0.5N
Hydrochloric acid, or strongly alkaline (0.5N sodium hydroxide)
Under room temperature or boiling (30 minutes)
Physical property changes were observed. As shown in Table V,
Polysaccharides that become clear form gels at room temperature even in 0.5N hydrochloric acid
Done. Boiling or 0.5N sodium hydroxide aqueous solution
In liquid, it becomes a strong viscous liquid, xanthan zam,
The viscosity was clearly higher than that of

Table V Solution BP Xanthan gum Levan 0.5N HCI Room temperature GPS boiling (30 minutes) VPS 0.5N NaOH Room temperature VPS boiling (30 minutes) VPSG : Gelation V: High viscosity P: Paste S: Low viscosity

[0040]

According to the present invention, by adjusting the concentration of the polysaccharide in the aqueous solution, it is possible to provide a polysaccharide capable of arbitrarily adjusting the viscosity from a low viscosity to a high viscosity and further a gelation state. Such polysaccharide-based gel has high temperature resistance, acid resistance, and alkali resistance, and improves the viscosity and quality of medicines and foods, improves the moisture retention and viscosity of cosmetics, and is applied to toiletry products, construction It can be used to improve materials and apply it to tertiary oil recovery.

[Brief description of the drawings]

FIG. 1 shows the effect of medium pH on the growth of strain BL58.

FIG. 2 is a graph showing the effect of ethanol concentration on the growth of strain BL58.

FIG. 3 is a graph showing the relationship between initial ethanol concentration in a culture medium and polysaccharide production.

FIG. 4. Effect of carbon source on polysaccharide production.

FIG. 5 is a diagram of thin-layer chromatography of an acid hydrolyzate.

Claims (6)

[Claims] (A) a molecular weight of about 1 as measured by high performance liquid chromatography using a gel filtration column;
600,000; (B) as constituents glucose and mannose residues in a 1: 1 molar ratio; and (C) 0.5% (weight / volume)% at 5 ° C. to 10 ° C. The aqueous solution becomes a viscous solution, but 1 (weight / volume)
% Aqueous solution is in a gelled state, the polysaccharide having an adjustable viscosity characteristic. 2. The polysaccharide according to claim 1, which can be produced by a Pseudomonas genus bacterium. 3. The method for producing a polysaccharide according to claim 1 or 2, wherein Pseudomonas ( Ps ) capable of producing the polysaccharide is used.
eudomonas ) A method for producing a polysaccharide, comprising culturing bacteria of the genus in a nutrient medium and collecting the polysaccharide from the culture. 4. The bacterium belonging to the genus Pseudomonas is Pseudomonas stutzeri BL58 strain (FE
RMP-16025). 5. The production method according to claim 3, wherein the nutrient medium contains a carbon source, a nitrogen source, a yeast extract and metal salts. 6. The method according to claim 3, wherein all or a part of the carbon source is ethanol.