JPH0725772A - Antibacterially active agent from polysaccharide by radiation treatment and production thereof - Google Patents

Abstract

PURPOSE:To provide a method for efficiently producing an oligosaccharide having high antibacterial activity and a low molecular weight polysaccharide in a large scale. CONSTITUTION:The antibacterial agent is obtained by irradiating ionizing radiation onto a polysaccharide. The polysaccharide is, e.g. polygalactosamine. A dose of the ionizing radiation is, e.g. in the range of 0.01-1000Gy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a substance having a high antibacterial activity, which is obtained by decomposing or modifying a polysaccharide by irradiating the polysaccharide with ionizing radiation and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing an antibacterial active substance using a polysaccharide, there is a method for producing a decomposition product such as an oligomer having an antibacterial activity by subjecting various polysaccharides to acid decomposition or enzymatic decomposition.

Among them, the acid decomposition method requires hydrolysis under concentrated conditions such as concentrated hydrochloric acid, and as a result, a large amount of monosaccharide is produced, resulting in poor conversion efficiency and acid resistance. There is a problem that a reactive reaction vessel is required and it is difficult to collect the reagent.

On the other hand, the enzymatic decomposition method can obtain various oligomers under relatively mild conditions as compared with the acid decomposition method. However, it has a drawback that an enzyme suitable for decomposing each polysaccharide is necessary and that the reaction takes a long time. In addition, there are problems that it is difficult to recover the enzyme and that the enzyme is deactivated during the reaction.

[0005]

In view of the above problems,
An object of the present invention is to provide a method for efficiently producing a large amount of oligosaccharides or low molecular weight polysaccharides having high antibacterial activity from polysaccharides.

[0006]

In order to solve the above-mentioned problems, the present inventors have proposed a method for producing an antibacterial active substance from a polysaccharide, which is an alternative to the acid decomposition method or the enzymatic decomposition method, to the polysaccharides with ionizing radiation. It was found that by irradiating with, highly polymerized oligosaccharides having high antibacterial activity can be easily and effectively produced in a short time. The method for producing an antibacterial active substance by irradiation of the present invention is advantageous in that a large amount of sample can be continuously treated in a short time, and further, treatment in either a dry state or a solution state is possible. is there.

The polysaccharide used in the present invention is understood in the broadest sense, and includes all natural products, microbial products and processed products thereof. Examples of polysaccharides of natural products include cellulose, starch, inulin,
Examples thereof include alginic acid, carrageenan, laminarin, porphyran, and fucodine contained in algae such as chitin, chitosan, xylan, and pectin. On the other hand, examples of polysaccharides produced by microorganisms include polygalactosamine, nanman, pullulan, and the like, lentinan produced by basidiomycete, and sizofiran. These polysaccharides may be used alone or as a mixture. In the present invention, it is particularly preferable to use polygalactosamine or chitosan as the polysaccharide.

In the present invention, the ionizing radiation for irradiating the polysaccharide includes α rays, β rays, γ rays, electron rays, X rays and ultraviolet rays. Practically, it is convenient to use γ rays, electron rays or X rays. The dose of ionizing radiation is preferably in the range of 0.01 to 1000 kGy. No effect was observed below 0.01 kGy, and 1
This is because if it is 000 kGy or more, the decomposition proceeds too much and the activity is lost.

The antibacterial activity referred to in the present invention means the property of killing or suppressing the growth of microorganisms such as bacteria and filamentous fungi.

When irradiating the polysaccharide with ionizing radiation, the polysaccharide is prepared in a dry, suspension or aqueous solution state. When the polysaccharide is in a dry state, the dose of ionizing radiation to be applied is preferably a high dose of about 100 to 1000 kGy. Irradiation with radiation in a dry state is advantageous from the viewpoint of easy mass treatment. When the polysaccharide is in the form of an aqueous solution, the dose of ionizing radiation to be applied is 0.
A dose as low as 01 to 10 kGy is sufficient. Irradiation in an aqueous solution state is advantageous from the viewpoint of requiring a low dose.
When the polysaccharide is in a suspended state, it is desirable that the dose be in between. The required irradiation dose also differs depending on the atmosphere (eg, nitrogen, oxygen, etc.) during irradiation. As described above, irradiation of a relatively high dose is required when the polysaccharide is in a dry state, but in such a case, the irradiation process can be completed in a short time by using a high dose rate electron accelerator. .

Irradiation of polysaccharides causes various changes in their chemical structure. For example, the main chain of the polysaccharide is cleaved, and as a result, the viscosity is reduced, the solubility is increased, the three-dimensional structure is changed, and the like due to the reduction in the molecular weight. In addition, side chain changes such as elimination of NH ₂ groups and ring collapse occur.

Most of the irradiated polysaccharides are of high molecular weight. It goes without saying that such high molecular weight compounds have antibacterial activity, but even those having a low molecular weight, for example, those having a molecular weight of 10,000 or less,
Has antibacterial activity.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to these Examples.

[0014]

Example 1 Chitosan was used as a polysaccharide. Electron beam of 100 kGy (Sample 1) and 5 on dry chitosan
Irradiation with 00 kGy (Sample 2) was performed. The irradiated chitosan was dissolved in a 0.5% acetic acid aqueous solution, and then the pH of the solution was adjusted to 6.0 to obtain a 0.1% chitosan aqueous solution. For comparison, a chitosan aqueous solution was obtained by the same procedure using chitosan which was not irradiated with an electron beam (control 1).

E. coli culture medium (Nutrient Bro
The above chitosan solution was added to th) to increase the growth rate of Escherichia coli at Otake Bioscanner OT-BS-16.
Was measured by turbidity measurement. The result is shown in FIG. Growth of E. coli was somewhat delayed in Control 1 compared to a blank sample containing no chitosan. The delay in the growth of E. coli was significant in Sample 1, and the growth of E. coli was not observed in Sample 2 during the 47-hour culture. As described above, an increase in antibacterial activity was observed by chitosan irradiated with ionizing radiation.

Further, a membrane for molecular weight fractionation was used to obtain a molecular weight of 1
When less than 10,000 decomposition products were separated and the same experiment was conducted, an increase in antibacterial activity was also observed in the low molecular weight fraction of chitosan irradiated with ionizing radiation.

[0017]

Example 2 Using the same method as in Example 1, aqueous chitosan solutions of Sample 1 and Sample 2 and Control 1 were obtained.

Each of the above chitosan solutions was added to an agar medium of Fusarium oxysporum, which is a type of filamentous fungus, and the growth rate thereof was observed. The results are shown in Table 1.

[0019]

[Table 1] As is clear from the above results, Fusarium oxyspor was added to the medium supplemented with chitosan irradiated with ionizing radiation.
The growth of um was greatly inhibited.

[0020]

Example 3 Chitosan was dissolved in water to prepare a 0.0125% dilute aqueous solution. This aqueous solution was irradiated with γ rays at various doses under air equilibration. For comparison, a chitosan aqueous solution not irradiated with γ-ray was used as a control.

Each of the above chitosan solutions was added to the culture solution of Escherichia coli, and the growth rate of Escherichia coli was measured by turbidity. The result is shown in FIG.

As is apparent from FIG. 2, 0.05-0.
A significant increase in antibacterial activity was observed at doses in the 2 kGy range. The antibacterial activity was reduced at doses of 0.2 kGy or more.

Therefore, it was found that by irradiating the polysaccharide in an aqueous solution state with ionizing radiation, the antibacterial activity can be effectively increased at a dose much lower than that in the dry state.

[0024]

Example 4 Chitosan was dissolved in water to prepare a 0.1% aqueous solution. While aeration with nitrogen or oxygen, γ
The rays were irradiated at various doses. For comparison, a chitosan aqueous solution not irradiated with γ-ray was used as a control.

Each of the above chitosan solutions was added to the culture solution of Escherichia coli, and the growth rate of Escherichia coli was measured by turbidity. The results are shown in FIGS. 3 and 4.

When γ-rays are irradiated while nitrogen is ventilated (FIG. 3), a dose in the range of 0.8 to 1.0 kGy is 68.
The growth of Escherichia coli could be suppressed for more than an hour. on the other hand,
In the case of γ-ray irradiation while ventilating oxygen (Fig. 4),
It was observed that the antibacterial activity reached its maximum at a dose of 0.2 kGy and that the activity decreased at doses higher than that.

[Brief description of drawings]

FIG. 1 is a graph showing the antibacterial activity of chitosan against Escherichia coli when irradiated in a dry state.

FIG. 2 is a view showing the antibacterial activity of chitosan against Escherichia coli when irradiated in a dilute aqueous solution.

FIG. 3 is a diagram showing antibacterial activity against Escherichia coli when an aqueous chitosan solution is irradiated under nitrogen aeration.

FIG. 4 is a diagram showing antibacterial activity against Escherichia coli when a chitosan aqueous solution is irradiated under oxygen aeration.

Claims (4)

[Claims] 1. An antibacterial active substance obtained by irradiating a polysaccharide with ionizing radiation. 2. The antibacterial active substance according to claim 1, wherein the polysaccharide is chitosan or polygalactosamine. 3. The dose of ionizing radiation is 0.01 to 100.
The antibacterial active substance according to claim 1, which is in the range of 0 Gy. 4. A method for producing an antibacterial active substance, which comprises irradiating a polysaccharide with ionizing radiation.