Composition for converting radioactive substance into non-radioactive substance and a method of preparing the composition

Abstract

The present invention relates to a composition for transmuting a radioactive substance into a non-radioactive substance using complex microorganisms and a method for preparing the composition.

Claims

1. A composition for transmuting a radioactive substance into a non-radioactive substance, comprising a mixed culture of microorganisms comprising: a radiation-resistant microorganism selected from the group consisting of Deinococcus sp., and Bacillus sp.; a yeast selected from the group consisting of Cryptococcus sp., Saccharomyces sp. and Trichosporon sp.; a fungus selected from the group consisting of Irpex sp. and Phanerochaete sp.; a photosynthetic bacteria species selected from the group consisting of Rhodobacter sp.; Chlorobium sp., Chromatium sp., Rhodospirillum sp., and Rhodopseudomonas sp.; and a green algae selected from the group consisting of Trebouxia sp., Stichococcus sp., Eliptochloris sp. and Coccomyxa sp; wherein each of the microorganisms is present at a concentration of 0.5×10.sup.2 CFU/ml to 2.5×10.sup.10 CFU/ml.

2. The composition according to claim 1, wherein the radiation-resistant microorganism is selected from the group consisting of Deinococcus radiodurans, Bacillus safensis and Bacillus pumilus; the yeast is selected from the group consisting of Saccharomyces boulardii, Saccharomyces servazzii, Saccharomyces cerevisiae, Trichosporon cutaneum and Trichosporon loubieri; the fungus is selected from the group consisting of Irpex lacteus, Irpex hydnoides, Phanerochaete chrysosporium and Phanerochaete sordida; the photosynthetic bacterial species is selected from the group consisting of Rhodobacter sphaeroides and Rhodobacter capsulatus; and the green algae is selected from the group consisting of Coccomyxa viridis and Stichococcus sp.

3. The composition according to claim 1, wherein the microorganisms are present in a total amount of 0.05% by weight to 60% by weight, based on the weight of the composition.

4. The composition according to claim 1, wherein the radioactive substance is cesium (Cs), uranium, iodine, strontium, iridium, radium or plutonium.

5. The composition according to claim 1, further comprising an environmentally acceptable carrier.

6. The composition according to claim 1, wherein the composition is used to dispose of radioactive waste or to treat soil, groundwater or wastewater, contaminated with radioactive substances.

7. A method for preparing the composition for transmuting a radioactive substance into a non-radioactive substance as set forth in claim 1, the method comprising: culturing the radiation-resistant microorganisms, the yeast, the fungi, the photosynthetic bacteria, and the green algae in culture medium individually or at least partially together; and mixing the cultured microorganisms to form the composition.

8. The method according to claim 7, wherein the microorganisms are cultured at a temperature of 20° C. to 40° C. for 12 hours to 7 days.

9. The method according to claim 7, wherein the cultured microorganisms are mixed with stirring.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a photograph showing samples prepared by adding a radioactive substance (Cs-137) at a concentration of 50,000 becquerels to compositions comprising complex microorganisms in Experimental Example 1.

(2) FIG. 2 is a photograph showing a sample holder designed to keep the position of a composition in place relative to detectors such that the intensities of radiation from the composition are observed with time.

(3) FIG. 3 shows the count rates of gamma rays from .sup.137Cs as a radioactive isotope during 49 days of storage of samples prepared by adding the radioactive substance to a composition comprising complex microorganisms in Example 2.

(4) FIG. 4 shows the count rates of gamma rays from .sup.137Cs as a radioactive isotope during 49 days of storage of samples prepared by adding the radioactive substance to a composition comprising complex microorganisms in Example 1.

(5) FIG. 5 photographically shows the viability and growth of microorganisms after samples (10 ml each) contaminated with .sup.137Cs following radioactivity testing for ˜60 days were diluted 10.sup.4-fold with sterile physiological saline and were added to solid media (NA, MRS, TSA, PDA) supplemented with different nutrients depending on the strain types in order to determine whether or not the complex strains added at the initial stage of testing were viable.

(6) FIG. 6 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 1.

(7) FIG. 7 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 2.

(8) FIG. 8 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 3.

(9) FIG. 9 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 4.

(10) FIG. 10 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 5.

(11) FIG. 11 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 6.

(12) FIG. 12 graphically shows the count rates of gamma rays per second after contact of a composition comprising only one microorganism with cesium in Comparative Example 7.

MODE FOR INVENTION

(13) The present invention will be described in more detail with reference to the following examples. However, these examples are provided for illustrative purposes only and the present invention is not limited thereto.

Example 1

Preparation of Composition Comprising Complex Microorganisms

(14) Rhodobacter capsulatus as a photosynthetic bacterial species was cultured in Van Niel's yeast medium supplemented with K.sub.2HPO.sub.4 (1 g), MgSO.sub.4 (0.5 g), and yeast extract (10 g). The medium was sterilized under high temperature (121° C.) and pressure conditions for 15 min and was allowed to cool to 30° C. Two or three platinum loops of the cultured colonies were inoculated into a solid plate medium under aseptic conditions. Then, the inoculated medium was incubated for 2-3 days with a supply of light from a tungsten lamp while maintaining the temperature at 26° C. under anaerobic conditions, giving a culture solution having a concentration of 1˜9×10.sup.7 viable cells/mL.

(15) Coccomyxa viridis, Eliptochloris sp. and Stichococcus sp. Trebouxia sp. as green algal species were cultured in Bold's basal medium (BBM) supplemented with a mixture of KH.sub.2PO.sub.4 (0.175 g), CaCl.sub.2.2H.sub.2O (0.025 g), MgSO.sub.4.7H.sub.2O (0.075 g), NaNO.sub.3 (0.25 g), K.sub.2HPO.sub.4 (0.075 g), NaCl (0.025 g), Na.sub.2EDTA (0.1 g), KOH (0.062 g), FeSO.sub.4.7H.sub.2O (0.0498 g), H.sub.3BO.sub.3 (0.115 g), MnCl.sub.2.4H.sub.2O (0.00181 g), ZnSO.sub.4.7H.sub.2O (0.000222 g), NaMoO.sub.4.5H.sub.2O (0.00039 g), CuSO.sub.4.5H.sub.2O (0.000079 g), and Co(NO.sub.3).sub.2.6H.sub.2O (0.0000494 g) in 1 liter of purified water. The medium was sterilized under high temperature (121° C.) and pressure conditions for 15 min and was allowed to cool to 25° C. The cultured green algae were collected by scraping with a cell scraper and inoculated into a solid plate medium. Then, the inoculated medium was incubated for 10 days with a supply of light from a fluorescent lamp (3000 lux) while maintaining the temperature at 20-25° C. under aerobic conditions, giving a culture solution having a concentration of 1.0×10.sup.5-1.0×10.sup.6 viable cells/mL.

(16) Saccharomyces servazzii KCCM12157P and Trichosporon loubieri KCTC10876BP as yeast species and Phanerochaete chrysosporium KCCM10725P as a fungal species were cultured in potato dextrose broth (PDB) medium supplemented with potato infusion (200 g) and dextrose (20 g) in 1 liter of purified water. The medium was sterilized under high temperature (121° C.) and pressure conditions for 15 min and was allowed to cool to 30° C. Two or three platinum loops of the cultured yeast were inoculated into a solid plate medium under aseptic conditions. Then, the inoculated medium was incubated for 1 day while maintaining the temperature at 30° C. under aerobic conditions, giving a culture solution having a concentration of 1.0×10.sup.7 viable cells/mL.

(17) Bacillus safensis KCCM12163P and Bacillus pumilus KCCM12165P as radiation-resistant bacterial strains were cultured in Nutrient broth media supplemented with peptone (10 g), beef extract (10 g), and sodium chloride (5 g) in 1 liter of purified water. The medium was sterilized under high temperature (121° C.) and pressure conditions for 15 min and was allowed to cool to 30° C. Two or three platinum loops of the cultured bacterial colonies were inoculated into a solid plate medium under aseptic conditions. Then, the inoculated medium was incubated for 1 day while maintaining the temperature at 30° C. under aerobic conditions, giving a culture solution having a concentration of 1.0×10.sup.7-10.sup.9 viable cells/mL.

(18) Thereafter, the microorganism culture solutions were combined. The combined culture solution was divided into two groups (“Composition 1” and “Composition 2”), each of which had a concentration of 1×10.sup.5-10.sup.9 cfu/ml.

Example 2

Preparation of Composition Comprising Complex Microorganisms

(19) A composition comprising complex microorganisms was prepared in the same manner as in Example 1, except that only four of the five culture solutions were used. The four culture solutions were obtained from Bacillus pumilus KCCM12165P, Saccharomyces servazzii KCCM12157P, Phanerochaete chrysosporium KCCM10725P, and Rhodobacter capsulatus. The composition was divided into two groups (“Composition 1” and “Composition 2”), each of which had a concentration of 1×10.sup.7-10.sup.9 cfu/ml.

Comparative Example 1

Preparation of Composition Comprising Single Microorganism Species

(20) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Bacillus safensis KCCM12163P was used.

Comparative Example 2

Preparation of Composition Comprising Single Microorganism Species

(21) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Rhodobacter capsulatus was used.

Comparative Example 3

Preparation of Composition Comprising Single Microorganism Species

(22) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Phanerochaete chrysosporium KCCM10725P was used.

Comparative Example 4

Preparation of Composition Comprising Single Microorganism Species

(23) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Bacillus pumilus KCCM12165P was used.

Comparative Example 5

Preparation of Composition Comprising Single Microorganism Species

(24) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Saccharomyces servazzii KCCM12157P was used.

Comparative Example 6

Preparation of Composition Comprising Single Microorganism Species

(25) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Trichosporon loubieri KCTC10876BP was used.

Comparative Example 7

Preparation of Composition Comprising Single Microorganism Species

(26) A composition was prepared in the same manner as in Example 1, except that only the culture solution of Stichococcus sp. was used.

Experimental Example 1

Measurement of Intensities of Radiation from Solutions Containing Cs-137 and the Compositions

(27) 100 ml of each of Compositions 1 and 2 prepared in Example 1 and Compositions 1 and 2 prepared in Example 2 was mixed with 400 ml of a liquid sample of Cs-137 (half-life: (30.05±0.08) year, 0.1 M HCl aqueous solution, 50 kBq on Mar. 3, 2018, 0.159 mL). 500 ml of the resulting sample was irradiated with light at 12-h intervals while shaking at ˜120 rpm in a shaking incubator at 25° C. Radioactivities from the sample were measured at 24-h intervals. The sample was closed with a lid made of air-permeable, hydrophobic silicon with less water evaporation. The sample including the complex microorganisms and the radioactive isotope was placed on a shaker (DAIHAN Scientific model SHO-2D) and was shaken continuously at ˜100 RPM except for ˜30 min for radiation intensity measurement. The laboratory temperature was maintained at 21-25° C. without artificial temperature control over the entire experimental period. In the laboratory, fluorescent lamps remained turned on during the experiment and turned off after 6 p.m.

(28) Two p-type high-purity Ge detectors with relative efficiencies of ˜70% were used to measure radiation intensities. A detection part of each of the Ge detectors is encapsulated in a structure surrounded by a shield to shield gamma rays from the outside. The shield is lined with a 10 cm thick lead plate and a 2 mm thick copper plate. The detector is installed in a vertical cooling system. A sample (or beam source) holder is used to observe the intensities of radiation from the sample with time. The sample holder is designed such that the position of the sample is kept in place relative to the detector. The sample holder is made of an acrylic cylinder and a plate. The sample holder fixes the vertical position of the sample relative to the bottom of the shield. The inner diameter of the cylinder is adapted to the outer diameter of an Erlenmeyer flask containing the sample to fix the horizontal position of the sample. The holder is spaced a distance from the outer periphery of the detector. The detector is fitted into the holder such that the center of the cylinder of the holder coincides with the center of the detector. To this end, the holder is made by cutting an acrylic resin into a doughnut shape. The distances between the upper sides of the detectors and the bottom of the Erlenmeyer flask containing the sample are ˜5 mm and ˜55 mm (FIG. 2).

(29) After contact of the complex microorganisms with cesium for a total of 49 days, the count rates of gamma rays per second were measured. The results are shown in FIGS. 3 and 4.

(30) Trend lines were plotted based on the above experimental results. When calculated using the trend lines, the effective initial half-life was estimated to be 39 days from the increased count rates of gamma rays from the radioactive isotope .sup.137C with a half-life of 30 years (from April 12 to April 17) and the effective elimination half-life was estimated to be 87 days from the decreased count rates (from April 18 to May 31).

(31) These results support the assumption that the increased count rates of gamma rays at the initial stage are due to the decay of Cs-173 and the decreased count rates of gamma rays are because the microorganisms directly biotransmuted Cs-137 into stable isotopes Ba-137 or Ba-138 without accelerating radioactive decay.

(32) After contact of the composition including only one microorganism with cesium in each of Comparative Examples 1-7, the count rates of gamma rays per second were measured. The results are shown in FIGS. 6-12. No significant decrease in the count rate of gamma rays was observed when only one microorganism was used, unlike when the complex microorganisms were used.

Experimental Example 2

Determination of Transmutation in Solutions Containing Cs-137 and the Compositions

(33) To determine whether transmuAtation occurred, cesium was treated with the microorganisms, as in Experimental Example 1. After storage for 60 days, the solutions were sampled. The concentrations of .sup.137Ba and .sup.138Ba in the samples were analyzed using a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). The results are shown in Table 1.

(34) TABLE-US-00001 TABLE 1 Bal37 Bal38 Sample Concentration RSD Concentration RSD No. name (μg/L) (%) (μg/L) (%) 1 Control 0.1741 1.64 0.124 0.50 2 D 17.196 0.80 17.034 0.83 3 DX 23.974 0.47 23.838 0.35 D: Composition of Example 2 including the complex microorganisms + average cesium concentration; DX: Composition of Example 1 including the complex microorganisms + average cesium concentration; Control: Cesium-containing composition

(35) As can be shown from the results in Table 1, the concentrations of .sup.137Ba and .sup.138Ba in D and DX were ˜100-140 times and ˜142-194 times higher than those in the control containing only cesium without complex microorganisms. These results demonstrate that the radioactive substance .sup.137Cs can be transmuted into non-radioactive substances .sup.137Ba and .sup.138Ba by the complex microorganisms.

Experimental Example 3

Determination of Viabilities of the Microorganisms in Solutions Containing Cs-137 and the Compositions

(36) To determine the viabilities of the microorganisms, cesium was treated with the microorganisms, as in Experimental Example 1. After storage for 60 days, the solutions were sampled. 10 ml of each of the samples was diluted 10.sup.4-fold with sterile physiological saline. The viability and growth of the strains in solid media (NA, MRS, TSA, PDA) supplemented with different nutrients depending on the strains were observed (see FIG. 5).

(37) These results concluded that even when contaminated with a high concentration (50,000 becquerels) of radioactive .sup.137Cs, the complex microorganisms added at the initial stage remained viable at a high concentration (>1×10.sup.5 cfu/ml).