JP2002210307A - Flocculant and flocculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a flocculant showing flocculation activity of high efficiency by small charging quantity by physically reforming the structure of γ- polyglutamic acid. SOLUTION: The flocculant contains radiation crosslinked product of γ- polyglutamic acid or its salt as a main component and is obtained by the radiation crosslinking of safe γ-polyglutamic acid especially produced by γ- polyglutamic acid producing bacteria. Further, the flocculant can be also obtained by irradiating a cultured fluid, which is obtained by culturing γ- polyglutamic acid producing bacteria, with radiation. The radiation crosslinked product of γ-polyglutamic acid or its salt with a mol.wt. of 10,000,000 or more has especially high flocculation activity. Since γ-polyglutamic acid itself is also food, the safety of the flocculant is ensured and the flocculant can be safely put to practical use not only in wastewater treatment but also in a field of food processing, the fermentation industry, tap water treatment or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flocculant used in the field of water supply, food production, fermentation industry, sewage treatment, wastewater treatment and the like, and more particularly to γ-polyglutamic acid or γ-polyglutamic acid. The present invention relates to a flocculant or a flocculant containing a radiation crosslinked polyglutamate as a main component, exhibiting high-efficiency flocculating activity when introduced into a small amount of a liquid to be treated, and having no harm to the environment and organisms, particularly to the human body.

[0002]

2. Description of the Related Art Conventionally, as a flocculant used for sewage treatment and the like, a synthetic polymer flocculant such as polyacrylamide has been frequently used. However, it has been pointed out that this flocculant is hard to be decomposed when released into the environment and thus tends to accumulate in the environment, and that the monomer is toxic.

[0003] Therefore, this synthetic polymer flocculant is only used for sewage treatment and is not a flocculant that can be used very much in the fields of water supply, food industry, fermentation industry and the like. Also, in the trend of environmental purification, a new coagulant which is safer for sewage treatment is being studied.

Under these circumstances, Japanese Patent Application Laid-Open No. 8-257306 discloses
Has proposed a flocculant comprising γ-polyglutamic acid. This γ-polyglutamic acid is a substance known as a stringing component of natto, in other words, it is itself a food. Therefore, this γ-polyglutamic acid is not harmful to the human body, and is also an extremely safe substance that is biodegradable by bacteria.

[0005] The discovery that this safe γ-polyglutamic acid has agglutinating activity is extremely revolutionary in the agglutination field. Since γ-polyglutamic acid is a food itself, it can be used as a flocculant not only in sewage treatment but also in fields ingested by the human body such as waterworks, food industry, and fermentation industry.

[0006] Since γ-polyglutamic acid is biodegradable, even if released into the environment, it is biodegraded by bacteria into water and carbon dioxide and is not accumulated in the environment. In addition, even if γ-polyglutamic acid remains in tap water, food, and fermented products, it is harmless to the human body and is extremely safe.

[0007]

Although γ-polyglutamic acid has such excellent properties, it has been disclosed in
Judging from Japanese Patent No. 57306, there are still insufficient points in the amount of coagulant and coagulation activity.

[0008] In particular, FIG. 2 of the aforementioned publication discloses that the aggregation activity peaks when the concentration of γ-polyglutamic acid is around 20 mg / L. This means that 20 mg of γ-polyglutamic acid must be added to 1 liter of the liquid to be treated. Since γ-polyglutamic acid is still expensive at present, if a large amount of liquid to be treated has to be aggregated as in the treatment of sewage, the cost of the aggregation treatment will increase.

Further, according to FIG. 2, even when the concentration of γ-polyglutamic acid is set to 20 mg / L, the aggregation activity reaches only about 4. In this publication, the aggregation activity is 1
/ OD550, more specifically, an amount defined by 1 / sample value−1 / blank value. The sample value is the OD ₅₅₀ of the supernatant after aggregation, and the blank value is the OD ₅₅₀ of the unaggregated liquid, ie, the contaminated liquid. Where OD
₅₅₀ means l when light having a wavelength of 550 nm is used.
It is an optical density defined by og ₁₀ (I ₀ / I).

Therefore, when the aggregation activity is 4, 1 / l
og ₁₀ (I ₀ / I) = 4, so that I = I ₀ /1.8=
0.55I ₀ is obtained. That is, when the aggregation activity is 4,
Transmitted light amount I have shown that attenuated to about 1/2 of the incident light intensity I _0. In other words, it shows that the light is still turbid enough to reduce the light amount by half even after the aggregation treatment.
This indicates an insufficient cohesive strength of γ-polyglutamic acid.

In the case where the coagulation activity is determined, kaolin is used as a pollutant component. Kaolin is a clay-like substance that also naturally causes self-aggregation when the initial concentration is high. The publication discloses that the concentration of the kaolin suspension being measured is 5 g / L, which indicates that the kaolin suspension is in a very high concentration cloudy state. In other words, even if the agglutinating activity is 4 under the highest conditions, if self-aggregation occurs during the measurement,
It is conceivable that the actual agglutination activity will be less than 4.

In order to accurately measure the agglutinating activity, it is necessary to use a low-concentration solution even if kaolin is used.
Furthermore, in order to perform accurate measurement, it is necessary to conduct a flocculation experiment using low-concentration polluted water in nature as a liquid to be treated.

Accordingly, an object of the present invention is to provide a more efficient aggregating activity with a smaller amount of aggregating agent, in other words, a lower aggregating agent concentration, by physically modifying the structure of γ-polyglutamic acid. It is to provide a flocculant and a flocculation method.

[0014]

According to the first aspect of the present invention, a γ-
An aggregating agent comprising a radiation crosslinked product of polyglutamic acid or γ-polyglutamate as a main component.

The invention of claim 2 relates to γ-polyglutamic acid or γ-polyglutamic acid produced by a γ-polyglutamic acid-producing bacterium.
An aggregating agent comprising a radiation crosslinked polyglutamate as a main component.

A third aspect of the present invention is an aggregating agent comprising a radiation cross-linked body obtained by irradiating a culture obtained by culturing a γ-polyglutamic acid producing bacterium as a main component.

A fourth aspect of the present invention is an aggregating agent comprising a radiation crosslinked γ-polyglutamic acid or γ-polyglutamate having a molecular weight of 10,000,000 or more as a main component.

The invention of claim 5 is characterized in that at least one kind of metal ion selected from aluminum, calcium, iron and magnesium is added to a radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate. It is a flocculant.

The invention according to claim 6 is the invention wherein the radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate is 0.1 to 0.1%.
This is a coagulation method characterized by adding to a liquid to be treated to a concentration of 10 mg / L.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a flocculant and a flocculation method according to the present invention will be described in detail.

The present inventors have conducted intensive studies with the aim of increasing the efficiency of agglutinating activity. As a result, γ-polyglutamic acid or γ-polyglutamic acid
The present invention has been completed by discovering that a radiation cross-linked product obtained by irradiating a polyglutamate shows more efficient aggregation activity than γ-polyglutamic acid.

Γ-polyglutamic acid is a kind of linear polypeptide, and its aggregation mechanism is not yet known in many respects. Compared to the fact that general inorganic metal ions exert a cohesive force due to cationicity, the idea that γ-polyglutamic acid structurally has a positive polar group, and this positive polar group exerts an aggregating action Has also been proposed. But the fact is not clear.

The present inventors have discovered for the first time that the radiation crosslinked product obtained by irradiating this γ-polyglutamic acid or γ-polyglutamate exhibits a more efficient cohesive force. However, the aggregation mechanism of the radiation crosslinked product is still unknown.

The radiation cross-linked product is formed by cross-linking chain long molecules of γ-polyglutamic acid or γ-polyglutamate, so that a large number of large bag-like spaces are formed inside. According to the imagination of the present inventors, it is thought that the liquid to be treated is absorbed in the bag-shaped space, and that pollutants are absorbed and accumulated in the bag-shaped space. Not. In particular, there is an urgent need to elucidate the mechanism for selectively absorbing pollutants.

As the γ-polyglutamic acid according to the present invention, those produced by various production methods are used. Examples of the production method include a culture method using a microorganism and a chemical synthesis method. When synthesized by a chemical synthesis method, sewage treatment is mainly performed from the viewpoint of safety.

In the microorganism culture method, bacteria such as Bacillus subtilis, Bacillus anthracis, Bacillus megaterium, Bacillus natto and the like can be used. It is. This strain produces .gamma.-polyglutamic acid having a molecular weight of hundreds of thousands to several millions and has a relatively large molecular weight, so that a crosslinked product can be efficiently produced by radiation.

The γ-polyglutamic acid produced by microorganisms is a natural product that is harmless to humans and animals, and has a great feature of being biodegradable, as it has been eaten as a main component of natto sticky substance since ancient times. In other words, this γ-polyglutamic acid is excellent not only in that it has biodegradability, but also has no harm even if it is eaten accidentally, and conversely becomes a nutrient. Therefore, it is suitable as a raw material for a flocculant in the field of water supply, food, and fermentation as well as wastewater treatment.

The γ-polyglutamic acid produced by the microorganism is a linear γ-peptide having no branch and is a copolymer of L-glutamic acid and D-glutamic acid, that is, a heteropolymer. Γ-polyglutamic acid having this heteropolymer structure is most suitable as a raw material of the flocculant according to the present invention.

The γ-polyglutamic acid produced by a microorganism is obtained by inoculating a microorganism in a liquid medium containing required nutrients, culturing the mixture at a required temperature for a required time, and isolating γ-polyglutamic acid from the culture solution. A solid medium may be used. As a flocculant, not only γ-polyglutamic acid alone,
A culture containing γ-polyglutamic acid obtained by precipitation from the culture solution or the culture solution itself may be used. Furthermore, a solid medium can be used as a flocculant.

As the chemically synthesized γ-polyglutamic acid, polymers having various structures such as a homopolymer of L-glutamic acid, a homopolymer of D-glutamic acid, and a mixture of both homopolymers are produced. These chemically synthesized γ-polyglutamic acids also serve as the raw material for the flocculant according to the present invention.

The γ-polyglutamate used in the present invention is formed as a salt by a neutralization reaction between γ-polyglutamic acid and a basic compound. γ-polyglutamic acid and a basic compound are dissolved in a solvent such as water at room temperature, and efficiently produced by stirring with heating. Examples of the basic compound include hydroxides of alkali metals and alkaline earth metals, such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and organic basic compounds such as amines. There is.

Under the reaction conditions of γ-polyglutamic acid and a basic compound, the heating temperature is preferably 5 to 100 ° C.
If the temperature is less than 5 degrees, the reaction will be slow. If it exceeds 100 degrees, water, which is a kind of solvent, will boil and the reaction may not be stable.
Further, the pH is preferably in the range of neutral to basic, particularly pH.
Is preferably in the range of 5 to 10. Further, the amount of γ-polyglutamic acid and the basic compound is suitably a stoichiometric reaction amount without excess or deficiency.

The γ-polyglutamic acid or γ-polyglutamate used in the present invention preferably has a molecular weight of several hundred thousand to several million. In the case of microbial production, its molecular weight ranges from several hundred thousand to several million. Even in the case of chemical synthesis, those polymerized to hundreds of thousands or more are suitable. If the molecular weight of the raw material molecules is small, the molecular weight of the radiation crosslinked product will be small, making it unsuitable as a flocculant.

In the present invention, the above-mentioned γ-polyglutamic acid or γ-polyglutamate is crosslinked with radiation to produce a crosslinked product having a molecular weight of 10,000,000 or more. γ-polyglutamic acid is represented by (—NH (COOH) CH—CH ₂ —CH ₂ —
CO-) _n , and the subscript n gives the degree of polymerization. Depending on the degree of polymerization n, a molecular weight of several hundred thousand to several million suitable as a raw material is given.

When this γ-polyglutamic acid is irradiated with radiation, CH ₂ is converted to CH— by a dehydrogenation reaction, and the two linear chains of γ-polyglutamic acid are linked via CH-HC, and [(—NH ( _{COOH) CH-CH-CH 2} -CO
-) It is considered to be crosslinked as in _n ] ₂ . When the degree of cross-linking is further increased, [(—NH (COOH) CH—
A radiation crosslinked product having a high molecular weight such as CH—CH ₂ —CO—) _n ] _m is produced. Here, m indicates the degree of crosslinking and gives the number of linear chains of γ-polyglutamic acid to be cross-linked.

By increasing the degree of crosslinking m, γ-
The molecular weight of the radiation crosslinked polyglutamic acid is set to 10,000,000 or more. Since γ-polyglutamic acid is a polypeptide chain, it has a network structure in which a large number of large spaces are formed inside by the connection of —CH—HC—. As previously mentioned,
It is considered that the polluted water is absorbed in these many internal spaces and the pollutants are internally accumulated.

The present invention is characterized in that radiation is used to crosslink γ-polyglutamic acid. When cross-linking is performed by chemical synthesis, high temperatures are required, and as a result, γ-polyglutamic acid as a raw material undergoes thermal denaturation. When radiation crosslinking is used, crosslinking can be performed at a low temperature, so that crosslinking can be realized without altering γ-polyglutamic acid. Therefore, by radiation crosslinking, γ containing no denatured product
-A crosslinked polyglutamic acid can be obtained.

In particular, γ-polyglutamic acid produced by a microorganism is a kind of polypeptide, and it is difficult to employ heat crosslinking, judging from the weak heat of amino acids. Considering that the viscous substance of natto is γ-polyglutamic acid,
You can understand the situation of heat denaturation when natto is heated. Therefore, the present invention is characterized in that radiation crosslinking is used to realize low-temperature crosslinking.

In addition to irradiating γ-polyglutamic acid or γ-polyglutamate alone, the culture solution
Irradiation of a culture, a solid medium, or the like can provide a radiation cross-linked substance of γ-polyglutamic acid or γ-polyglutamate alone or a contaminant of the radiation cross-linked substance. Any of them can be used as the flocculant according to the present invention. In particular, when the culture solution is irradiated with a radiation, a solution containing a radiation crosslinked body is generated, and when added to the liquid to be treated, the handling method and the concentration adjustment are easy.

As radiation for crosslinking, α-rays, β-rays, γ-rays
A line, an X-ray, an electron beam, a neutron beam, a meson beam, an ion beam and the like can be used. Among them, γ-ray,
X-rays and electron beams are preferred. As X-rays, both X-ray tube and non-tube types can be used, and radiated light radiated from an electron ring that has been widely used in recent years can also be used. For the electron beam, a known electron beam irradiation device can be used according to the beam energy.

Gamma rays are excellent in that a radiation source can be used. Cobalt 60, strontium 9
0, zirconium 95, cesium 137, cerium 14
1, ruthenium 177 and the like, but cobalt 60 and cesium 137 are preferable from the viewpoint of half-life and energy.

In the present invention, γ-polyglutamic acid is radiation-crosslinked to obtain a γ-polyglutamic acid having a molecular weight of 10,000,000 or more.
-Produce radiation-crosslinked polyglutamic acid. When the molecular weight is crosslinked to 10,000,000 or more, the aggregation property of the γ-polyglutamic acid cross-linked product increases sharply, and a significantly superior aggregation effect is exhibited as compared with the aggregation property of γ-polyglutamic acid alone.

In order to crosslink γ-polyglutamic acid to a molecular weight of 10,000,000 or more, it is necessary to irradiate the γ-polyglutamic acid raw material with radiation at an absorbed dose of 1 to 500 kGy.
Below y, crosslinking does not progress easily, and 500 kGy
If it exceeds, the crosslinking proceeds excessively, so that the internal space formed by the network structure of the crosslinked product becomes small, and conversely, the aggregation activity decreases. From the viewpoints of crosslinkability and aggregation activity, the absorbed dose is more preferably 5 to 100 kGy.

Γ-polyglutamic acid and γ-polyglutamic acid per se have the property of not being dissolved in organic solvents such as alcohol and acetone. Further, γ-polyglutamate is soluble in water, but γ-polyglutamic acid is insoluble in water. However, when this is subjected to radiation crosslinking, the surface of the radiation-crosslinked body is modified to have an affinity for water or a water-containing organic solvent such as water-containing alcohol or water-containing acetone.

The present invention has also been made by paying attention to the properties of surface modification of γ-polyglutamic acid and γ-polyglutamate by radiation crosslinking. That is, by being a radiation crosslinked product, both γ-polyglutamic acid and γ-polyglutamate have an affinity for water or a water-containing organic solvent, and specifically, so that they are dissolved in the water to be treated. Become. Although the mechanism of this surface modification is not well understood, the present invention has been made based on this fact.

Therefore, the radiation-crosslinked γ-polyglutamic acid or γ-polyglutamate according to the present invention is dissolved in the water to be treated such as sewage wastewater, tap water, food-containing water, fermentation water, etc. It exerts a flocculating effect as a flocculant.
In other words, pollutants can be coagulated and settled from waste water and tap water to obtain clean water, and foods and fermented products can be obtained from food-containing water and fermented water by coagulation and settling.

Γ-polyglutamic acid or γ according to the present invention
-The radiation crosslinked product of polyglutamate exhibits an effective aggregation effect when added in an amount of about 0.1 to 20 mg per liter of the liquid to be treated. Therefore, the coagulant concentration is 0.1 to
The range is preferably 20 mg / L, more preferably 0.5 to 10 mg / L.
mg / L. At 0.1 mg / L or less, the aggregation effect is reduced, and at 20 mg / L or more, the aggregation effect is slightly reduced and the aggregation cost is too high.

Γ-polyglutamic acid or γ according to the present invention
-Radiation cross-linked polyglutamate exhibits a sufficient coagulation effect even when used alone as a coagulant,
Particularly when used together with metal ions, they exhibit an excellent aggregation effect in synergy with the aggregation effect of metal ions. As metal ions, for example, aluminum, calcium,
One or more metal ions selected from iron, magnesium and the like are selected and added to the water to be treated. When metal ions are added, they are not suitable for fields such as food processing from the viewpoint of safety, and are suitable for treating wastewater having a high pollutant concentration.

[0049]

[Example 1] Production of radiation crosslinked product of γ-polyglutamic acid Bacillus subtilis F-2-01 was selected as a γ-polyglutamic acid-producing bacterium. The liquid medium was placed in a 1 × 10 ³ m ³ container for mass production. The medium composition was configured as follows. Glucose 10% by weight L-glutamic acid 8% by weight Peptone 0.7% by weight Urea 0.68% by weight NaNO3 0.5% by weight KH2PO4 0.24% by weight Purified water

The above strain was inoculated into this liquid medium,
After adjusting H to 7.5, it was kept at a constant temperature of 37 ° C. If the culture is continued for 6 days with aeration and stirring, γ-polyglutamic acid and its salts accumulate in the culture solution. The culture was centrifuged to separate cells from the culture, and the γ-polyglutamic acids were further isolated.

The production amount of γ-polyglutamic acid depends on the culture conditions, but is 5 to 50 (g / g) in the culture solution.
L), which proves that industrial mass production of γ-polyglutamic acids is possible. Also,
The molecular weight of the produced γ-polyglutamic acids is 500,000-
It turned out that it distributed to 2 million.

A 5% by weight aqueous solution of the γ-polyglutamic acid was irradiated with 20 kGy of gamma rays from a cobalt 60 radiation source to produce a γ-polyglutamic acid radiation crosslinked product.
The aqueous solution gelled by this irradiation, and the molecular weight of the γ-polyglutamic acid radiation crosslinked product was estimated to be about 15 million. The gel-like substance was dehydrated to obtain a powder of a γ-polyglutamic acid radiation crosslinked product. This powder was white.

As described above, γ-polyglutamic acid salt is water-soluble, but γ-polyglutamic acid is insoluble in water. It is difficult to show the effect. However, γ
-The radiation crosslinked product of polyglutamic acids has an affinity for water and is soluble in water, so that it can be used as it is as a flocculant.

[Example 2: Coagulation test] In order to purify natural water, a test for purifying polluted water in an outer moat of a castle representing K city was conducted. The polluted water from the outer moat was charged into a test tank of about 27 tons having a volume of 5.4 × 9.0 × 1.3 (m ³ ). 40 g of the γ-polyglutamic acid radiation crosslinked product obtained in Example 1 was charged into this test tank and dissolved by stirring.
The final input concentration was 1.5 mg / L. Thereafter, when the mixture was allowed to stand for 2 hours, a precipitate was visually observed.

After settling for 3 hours from the introduction, the optical density of the purified supernatant water and the contaminated water before settling (O
D) was measured. Since the light having the wavelengths of 500 nm and 700 nm was used, the respective OD values are shown in Table 1.

For comparison with the data of Japanese Patent Application Laid-Open No. 8-257306, 700 nm and 500 nm
Was calculated. Aggregation activity value is given by 1 / OD ₇₀₀ with 1 / OD _500, respectively 1 / sample value -1
/ Blank value. The sample value is the value of the supernatant water, and the blank value is the value of the contaminated water before settling. Therefore,
1 / OD ₇₀₀ = 1 / 0.015 / 1 / 0.065 = 51
Also, 1 / OD ₅₀₀ = 1 / 0.022-1 / 0.072 =
It becomes 32.

While the agglutinating activity value (1 / OD ₅₅₀ ) of the above publication is 4 at the maximum, the agglutinating activity value is 1 in this test.
/ OD ₇₀₀ = 51 and 1 / OD ₅₀₀ = 32, indicating that the agglutinating activity value is increased by a factor of 10 or more in any case. Moreover, the input concentration of the flocculant is 20 mg in the past.
/ L, whereas in this example 1.5 mg / L was sufficient, and it was found that the dosage could be reduced by a factor of 15.

As described above, since γ-polyglutamic acid itself is a safe food, its radiation cross-linked form is also safe, and is a coagulant in the fields that are absorbed by the human body such as food processing, fermentation, and water treatment. Can be used as

Example 3: Aggregation test using cations
In order to observe the aggregation effect when a cation was used in combination as an aggregation aid, 35 g of AlCl ₃ .6H ₂ O was added together with 40 g of the γ-polyglutamic acid radiation crosslinked product of Example 1.
The input concentration of the radiation crosslinked γ-polyglutamic acid was 1.5 mg / L, and the input concentration of aluminum chloride was 1.
It was 3 mg / L. Other test conditions are exactly the same as in Example 2.

Since aluminum ions are added,
The coagulated sediment appeared very quickly, and the coagulant was charged and stirred, and the sedimentation started at the same time, indicating that the immediate effect was extremely high. Let stand for 1 hour and wait for sedimentation to finish.
The optical densities at 00 nm and 500 nm were measured. The results are shown in Table 2.

When the agglutination activity value was determined, 1 / OD ₇₀₀ = 1
/0.012-1/0.065=68 or 1 / OD ₅₀₀
= 1 / 0.019-1 / 0.072 = 39. While the agglutinating activity value (1 / OD ₅₅₀ ) of the above publication is a maximum of 4, the aggregating activity value in this example is 1 / OD ₇₀₀ = 6.
8, 1 / OD ₅₀₀ = 39, indicating that the aggregation activity was 10 times or more. The total input concentration of the γ-polyglutamic acid radiation crosslinked product and aluminum chloride was 2.8 m.
g / L, the input concentration of 20 mg under the highest conditions of the prior art.
/ L can be reduced to 1/7 or less.

Addition of a cation can realize high-speed coagulation and precipitation, and since the cation is mixed, it is not suitable as a coagulant in the field of being absorbed by the human body. Therefore, it can be used as a flocculant in wastewater treatment. Moreover, it is a highly active flocculant having a flocculation activity value 100 times or more that of the conventional one.

[0063]

According to the first aspect of the present invention, since the coagulant is mainly composed of a radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate, it can be used not only for treating wastewater, but also for the human body. It does not cause any harm to living organisms and can be used as a flocculant in water supply, food, and fermentation fields. In addition, since the agglutination activity value is extremely high and the amount of the input can be reduced, a highly efficient and inexpensive agglutination effect can be exhibited.

According to the second aspect of the present invention, unlike a chemically synthesized product, it is extremely safe because it mainly contains a radiation cross-linked form of γ-polyglutamic acid or γ-polyglutamate produced by a γ-polyglutamic acid-producing bacterium. It is highly active and can be actively used as a flocculant in the water supply, food, and fermentation fields.

According to the third aspect of the present invention, a culture obtained by culturing γ-polyglutamic acid-producing bacteria is directly irradiated with radiation, so that the operation of isolating γ-polyglutamic acid from the culture is not required, and Γ-polyglutamic acid in the product can be immediately converted to a radiation crosslinked product. Since the radiation-crosslinked culture can be used as a flocculant, it can contribute to a reduction in the production cost of the flocculant. In particular, in the case of a culture solution obtained by culturing in a liquid medium, this culture solution can be used as a stock solution of the flocculant, so that the work of adjusting the aqueous solution at the time of adding the flocculant is omitted and the handling is simplified.

According to the invention of claim 4, the molecular weight is 100
Since the radiation-crosslinked body of γ-polyglutamic acid or γ-polyglutamate having a molecular weight of not less than 100,000 is a main component, the radiation-crosslinked body has water solubility even if γ-polyglutamic acid itself is insoluble in water. When added to treated water, it can be easily dissolved. Therefore, the flocculation treatment operation is easier than that of γ-polyglutamic acid.

According to the invention of claim 5, since one or more metal ions selected from aluminum, calcium, iron and magnesium are added to the radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate, The effect can be exhibited immediately, the time performance of the coagulation effect can be improved, a large amount of water to be treated can be purified, and it can be effectively applied to, for example, wastewater treatment.

According to the sixth aspect of the present invention, the radiation-crosslinked γ-polyglutamic acid or γ-polyglutamate is added to the liquid to be treated so as to have a concentration of 0.1 to 10 mg / L. Compared with a flocculant comprising polyglutamic acid, the amount of the flocculant to be added can be reduced, and a flocculant having a highly efficient flocculant activity value can be provided.

Claims (6)

[Claims] 1. An aggregating agent comprising a radiation-crosslinked γ-polyglutamic acid or γ-polyglutamate as a main component. 2. An aggregating agent comprising as a main component a radiation-crosslinked γ-polyglutamic acid or γ-polyglutamate produced by a γ-polyglutamic acid-producing bacterium. 3. A coagulant comprising, as a main component, a radiation crosslinked body obtained by irradiating a culture obtained by culturing a γ-polyglutamic acid-producing bacterium. 4. An aggregating agent comprising as a main component a radiation crosslinked γ-polyglutamic acid or γ-polyglutamic acid having a molecular weight of 10,000,000 or more. 5. An aggregating agent comprising adding one or more metal ions selected from aluminum, calcium, iron and magnesium to a radiation crosslinked product of γ-polyglutamic acid or γ-polyglutamate. 6. An agglomeration method comprising adding a radiation cross-linked product of γ-polyglutamic acid or γ-polyglutamate to a liquid to be treated in a concentration of 0.1 to 10 mg / L.