Method for decomposing urethane, method for producing water-absorbing material, and method for producing sound-absorbing material

Abstract

To provide a method for decomposing urethane through microbial activity, which allows the process to be simplified and shortened.SOLUTION: A urethane decomposition method according to an embodiment of the present invention includes a step in which, in a culture medium to culture microorganisms having urethane decomposition ability, the microorganisms are exposed to a urethane-containing target material. The culture medium contains saccharides and amino acids.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for decomposing urethane, a method for producing a water-absorbing material, and a method for producing a sound-absorbing material.

Background Art

[0002] Polyurethane is a polymer having a urethane bond and is also called a urethane resin. Polyurethane has material properties that are prone to degradation of physical properties due to hydrolysis by moisture, or the influence of ultraviolet rays, heat, microorganisms, etc. However, polyurethane has been modified so that it is difficult to decompose, and the material has evolved into a structure that is resistant to hydrolysis and less affected by microorganisms, and is still used in various fields.

[0003] Since polyurethane has a crosslinked structure, it cannot be melted and reused as a material like a thermoplastic resin. For this reason, it is disposed of as thermal recycling or landfill, and almost no reuse as a material is performed.

[0004] Currently, in order to avoid this problem, research is being conducted in various fields on reuse as a material using the decomposition action of environmentally friendly microorganisms, chemical recycling, and biodegradability. However, it takes time and effort to find effective decomposing bacteria. In addition, chemical recycling and biodegradability also have major technical problems, and there are almost no cases leading to practical application.

[0005] As a method for decomposing polyurethane using the decomposition action of microorganisms, for example, the methods described in Japanese Patent No. 6489542 (Patent Document 1) and Japanese Patent No. 6439971 (Patent Document 2) are known. These patent documents describe using strain C13a (actinomycetes) belonging to the genus Streptomyces as a microorganism having urethane-decomposing ability. In addition, it is described that before allowing a microorganism having urethane-decomposing ability to act and proceed with decomposition, the material to be treated containing urethane is pretreated with an unsaturated fatty acid such as oleic acid.

[0006] In particular, Patent Document 2 describes that by allowing the above-mentioned microorganisms to act on urethane with independent bubbles, fine cavities are formed in the foam cells. Then, by changing the independent foam cells into a cell structure in which they are connected due to the action of microorganisms, new properties such as water absorbency, water retention, and sound absorption can be imparted to the urethane material. This technology has attracted attention as a technology for recycling urethane with independent bubbles as a new material (NPORUS (NPORUS is a registered trademark of Nippon Plast Co., Ltd.)).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] It is considered that the mechanism of urethane decomposition by microorganisms is due to the fact that urethane-decomposing enzymes such as esterase, lipase, and hydrolase released during the growth process of microorganisms act as catalysts to promote the urethane decomposition reaction.

[0009] The pretreatment of urethane with unsaturated fatty acids such as oleic acid, which is patented in the prior art, improves the adhesion of urethane-decomposing bacteria to urethane. The pretreatment agent used in the pretreatment penetrates into the urethane and swells the urethane, improving the adsorptivity of microorganisms, and the decomposition action of microorganisms acts uniformly inside the urethane to obtain a high decomposition effect. As a result, fine cavities are formed in which the independent foam cells of urethane are connected. In this prior art, how to adsorb microorganisms on the surface of urethane and grow them using urethane as a nutrient source is an important point in optimizing the decomposition conditions. And the pretreatment of the material to be treated with unsaturated fatty acids (such as oleic acid) has a great effect in promoting the decomposition of urethane.

[0010] The decomposition process of urethane according to the prior art is illustrated in Fig. 13. As shown in Fig. 13, among all the processes of primary crushing, pretreatment, decomposition treatment, washing, and drying, the pretreatment process and the decomposition treatment process account for 76% of the processing time. Therefore, in the prior art, in order to reduce the man-hours of urethane decomposition and the manufacturing cost of new material, simplification of the pretreatment process and the decomposition treatment process is required.

[0011] Therefore, an object of the present invention is to provide a method for decomposing urethane that can simplify and shorten the process in a method for decomposing urethane by the action of microorganisms.

Means for Solving the Problems

[0012] The method for decomposing urethane according to an embodiment of the present invention is having a step of allowing a material to be treated containing urethane to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, and is a method for decomposing urethane.

[0013] The method for manufacturing a water-absorbing material according to an embodiment of the present invention is having a step of allowing a material to be treated containing foamed urethane having closed cells to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, and is a method for manufacturing a water-absorbing material.

[0014] The method for manufacturing a sound-absorbing material according to an embodiment of the present invention is In a culture medium for culturing a microorganism having urethane-degrading ability, a step of allowing a material to be treated containing foamed urethane having independent bubbles to act on the microorganism is included. The culture medium contains saccharides and amino acids. It is a method for manufacturing a sound-absorbing material.

Effect of the Invention

[0015] According to the present invention, in a method for decomposing urethane by the action of a microorganism, it is possible to provide a urethane decomposition method capable of simplifying the steps and shortening the time.

Brief Description of the Drawings

[0016]

Figure 1

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Figure 12

Figure 13

Mode for Carrying Out the Invention

[0017] In order to improve the urethane-decomposing ability of microorganisms having urethane-decomposing ability (hereinafter, also simply referred to as "microorganisms" or "urethane-decomposing bacteria"), the present inventors attempted to improve the urethane-decomposing ability by improving the growth property of microorganisms in a culture medium rather than the adsorptivity of microorganisms to urethane. Two effects are expected for this. 1) By increasing the growth of urethane-decomposing bacteria, the amount of decomposing enzymes released increases, improving the urethane-decomposing ability. 2) The growth rate of urethane-decomposing bacteria becomes faster, the time until the logarithmic phase is reached is shortened, and the expression of urethane-decomposing ability is accelerated.

[0018] In addition, Patent Documents 1 and 2 above disclose that an inorganic salt medium (YES-G0 medium) having the composition shown in Table 1 below is used for culturing urethane-decomposing bacteria. This inorganic salt medium is a culture medium capable of enhancing the adsorptivity and colonization of urethane-decomposing bacteria to urethane.

[0019]

Table 1

[0020] The inventors first conducted various studies on culture media capable of improving the growth of urethane-degrading microorganisms. Then, they further examined whether the urethane-degrading ability could also be improved by using a culture medium capable of improving the growth of urethane-degrading microorganisms.

[0021] As a result, it was found that it is effective to use a culture medium containing saccharides and amino acids in order to enhance the growth of urethane-degrading microorganisms and further improve the urethane-degrading ability.

[0022] <Method for Degrading Urethane> That is, the method for degrading urethane according to an embodiment of the present invention includes a step of allowing a material to be treated containing urethane to act on the microorganism in a culture medium for culturing a urethane-degrading microorganism, and the culture medium contains saccharides and amino acids. The saccharides added to the culture medium are not particularly limited, and examples thereof include soluble starch and glucose. The amino acids added to the culture medium are not particularly limited, and examples thereof include peptone and casamino acids.

[0023] Examples of the culture medium that can be used in the method for degrading urethane according to an embodiment of the present invention include the R2A culture medium having the composition shown in Table 2 below.

[0024]

Table 2

[0025] As described above, the R2A culture medium contains nutrients such as casamino acids, peptone amino acids, and glucose, and can enhance the growth and urethane-degrading ability of urethane-degrading bacteria.

[0026] In the method for decomposing urethane according to an embodiment of the present invention, the microorganism used may be any microorganism having urethane-decomposing ability. For example, it may be any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas.

[0027] Examples of the microorganism having urethane-decomposing ability and belonging to the genus Streptomyces include the microorganism (Streptomyces C13a strain) identified by the accession number FERM BP-21770. The microorganism was deposited on February 12, 2009, at the Patent Microorganisms Depositary, National Institute of Advanced Industrial Science and Technology (1-1-1 Higashi, Tsukuba Central 6, Tsukuba, Ibaraki) under the accession number FERM P-21770. Also, on January 18, 2017, a request for transfer to an international deposit based on the Budapest Treaty was made, and it was deposited at the Patent Microorganisms Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusa Kamatari, Kisarazu, Chiba) under the accession number FERM BP-21770. In addition, mutants of the Streptomyces C13a strain can be used in the present invention as long as they have urethane adsorption and decomposition ability equivalent to this. Specifically, for example, S. albogriseolus (NBRC12834), S. thermoluteus (NBRC14269), and S. viridodiastaticus (NBRC13106) can be preferably used.

[0028] Examples of the microorganism having urethane-decomposing ability and belonging to the genus Sinomonas include the microorganism (Sinomonas atrocyanea ES2231 strain) identified by the accession number NITE P-03613. The microorganism was deposited under the above accession number at the Patent Microorganism Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusa Kamashima, Kisarazu-shi, Chiba-ken) on February 24, 2022. In addition, mutants of the Sinomonas atrocyanea ES2231 strain can also be used in the present invention as long as they have urethane adsorption and degradation ability equivalent to this.

[0029] Examples of microorganisms having urethane degradation ability and belonging to the genus Pseudomonas include, for example, the microorganism specified by the accession number NITE P-03612 (Pseudomonas hibiscicola MS4102 strain). The microorganism was deposited under the above accession number at the Patent Microorganism Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusa Kamashima, Kisarazu-shi, Chiba-ken) on February 24, 2022. In addition, mutants of the Pseudomonas hibiscicola MS4102 strain can also be used in the present invention as long as they have urethane adsorption and degradation ability equivalent to this.

[0030] The above Sinomonas atrocyanea ES2231 strain and Pseudomonas hibiscicola MS4102 strain are microorganisms selected by the present inventors from soil and also have degradation ability against thermoplastic polyurethane containing a urea bond.

[0031] The material to be treated used in the method for degrading urethane according to the embodiment of the present invention is not particularly limited as long as it contains urethane. Examples of the material to be treated include, for example, urethane, particularly waste (waste liquid) and soil containing polyurethane. The above urethane means a compound in which an amino group and an alcohol group are dehydrated and condensed via a carbonyl, that is, a carbamic acid ester. The urethane to be decomposed in the present invention includes all urethanes having a urethane bond in their molecular structure, from low molecules such as ethyl carbamate to polymers such as polyurethane.

[0032] The above-mentioned polyurethane is a polymer polymerized by urethane bonds and is used in paints, adhesives, urethane foams, textile products, shoes, automotive parts, building materials, etc. Further, polyurethanes include various types such as linear to branched ones, those containing crosslinks, elastomers, foams, etc., and can be roughly classified into ester-based and ether-based ones. The urethane or polyurethane contained in the material to be treated that is the target of decomposition in the present invention is not particularly limited, but it is desirable to use urethane with a relatively large particle size such that the state where it becomes transparent as a result of adsorption and decomposition by microorganisms can be visually confirmed because it is turbid due to its large particle size. In the case where the material to be treated, such as waste urethane foam, is too large, it is preferable to grind it to an appropriate size before allowing the microorganisms to act.

[0033] The method of allowing the microorganisms to act on the material to be treated is not particularly limited, and it may be such that the material to be treated and the microorganisms come into contact in the above-mentioned culture medium. For example, a method of adding the material to be treated to the culture medium in which the microorganisms are being cultured and continuing the culture of the microorganisms as it is can be mentioned. Further, the material to be treated may be added to a culture medium that does not contain the microorganisms, and the microorganisms may be newly inoculated here to start the culture.

[0034] The time for allowing the microorganisms to act on the material to be treated is not particularly limited, and it may be carried out such that the urethane is sufficiently decomposed in consideration of the urethane content in the material to be treated and the amount of microorganisms to be allowed to act. The longer the time for allowing the microorganisms to act, the more the decomposition of the urethane progresses, but if too much time is taken, the cost for decomposing the urethane becomes high, so it is preferable to set an appropriate time. For example, in conventional Patent Documents 1 and 2, it is described that the material to be treated is allowed to act on microorganisms for about several days to several weeks. In contrast, in the urethane decomposition method according to the embodiment of the present invention, the time for allowing the material to be treated to act on microorganisms can be about 12 hours to 24 hours. Thereby, the urethane-decomposing ability of the microorganisms can be stabilized. Further, if the urethane decomposition method according to the embodiment is carried out under suitable conditions, the time for allowing the material to be treated to act on microorganisms can also be about 6 hours.

[0035] The temperature at which the microorganism acts on the material to be treated may be a temperature suitable for the growth of the microorganism and the decomposition of urethane. For example, it can be about 20°C to 40°C. Note that the temperature at which the microorganism acts on the material to be treated may be appropriately selected according to the type of the microorganism. For example, when the microorganism is Streptomyces C13a strain, the decomposition efficiency is high and optimal when it acts at 40°C. Also, when the microorganism is Sinomonas atrocyanea ES2231 strain, the decomposition efficiency is high and optimal when it acts at 30°C.

[0036] Note that in the methods described in conventional Patent Documents 1 and 2, the material to be treated is pre-treated with an unsaturated fatty acid such as oleic acid before allowing the microorganism to act on it. In contrast, in the urethane decomposition method according to the embodiment of the present invention, as shown in the examples described later, it is not necessary to perform pre-treatment with an unsaturated fatty acid. This is considered to be due to the difference that in the conventional method, the microorganism is made to easily adsorb to the urethane which is the material to be treated and the urethane is used as a nutrient source, while in the urethane decomposition method according to the embodiment of the present invention, the microorganism is grown with the nutrients contained in the culture medium, and the urethane is decomposed by the action of the urethane-decomposing enzyme generated in the process.

[0037] In the method for decomposing urethane according to an embodiment of the present invention, since pretreatment of the material to be treated with unsaturated fatty acids is unnecessary, the time and cost required for decomposing the material to be treated containing urethane can be significantly reduced. Of course, the method for decomposing urethane according to an embodiment of the present invention does not exclude performing pretreatment with unsaturated fatty acids, and depending on the properties of the microorganisms used, etc., pretreatment with unsaturated fatty acids may be performed.

[0038] The material to be treated decomposed by the action of microorganisms as described above can be pulverized very easily compared to the material to be treated before decomposition. Urethane having closed cells before the action of microorganisms is difficult to pulverize, and treatments such as freezing and solidifying are required. On the other hand, when microorganisms are allowed to act on the material to be treated, fine cavities are formed in the cells, and many portions serving as fracture initiation points appear when pulverizing. For this reason, even if it is an elastomer, it can be easily pulverized at room temperature by using a centrifugal type pulverizer. After allowing microorganisms to act and further pulverizing the material to be treated to an appropriate size, it can be used as a material for synthesizing new urethane or as a material for use as a water-absorbing material or a sound-absorbing material.

[0039] <Method for manufacturing a water-absorbing material> The method for manufacturing a water-absorbing material according to an embodiment of the present invention includes a step of allowing a material to be treated containing foamed urethane having closed cells to act on the microorganisms in a culture medium for culturing microorganisms having urethane-decomposing ability, and the culture medium contains saccharides and amino acids. As the microorganisms having urethane-decomposing ability, for example, any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas can be used. The microorganisms used in the method for manufacturing a water-absorbing material, the culture medium, and the method of allowing microorganisms to act on the material to be treated can adopt the same configuration as the method for decomposing urethane.

[0040] As described above, in the method for decomposing urethane according to the embodiment of the present invention, a water-absorbing material can be produced by using a material to be treated containing foamed urethane having closed cells as the material to be treated. This is because, by allowing microorganisms to act on the material to be treated, fine cavities are formed in the closed cells of the foamed urethane, and at least some of the bubbles of the foamed urethane are connected to form a structure.

[0041] Generally, a foamed resin having independent bubbles has the bubbles partitioned by walls and contains air in the bubbles, and gases and liquids cannot pass through the inside. On the other hand, when at least some of the bubbles are connected by fine cavities of about several microns (1 μm to 5 μm) by allowing microorganisms to act, liquids such as moisture can be absorbed inside the bubbles. At this time, the liquid such as moisture is absorbed into the connected bubbles by capillary action. And the absorbed liquid such as moisture becomes difficult to be released by surface tension. For this reason, the material to be treated on which microorganisms have acted has improved water absorption and water retention properties and can be used as a water-absorbing material.

[0042] The water-absorbing material thus obtained can be used, for example, for planters for plant cultivation and humidity control materials. Due to the effect of excellent water retention, it can be preferably used for plant cultivation and can also be applied to greening on the rooftops of buildings. Note that it is possible to use the material to be treated after allowing microorganisms to act as a water-absorbing material as it is, or it is also possible to mold them into a desired shape and use them. When processing into a desired shape, for example, it may be performed by a method such as adding a binder such as an isocyanate prepolymer to the material to be treated after allowing microorganisms to act or its pulverized product and heating and pressing while blowing steam. In addition, the material to be treated after allowing microorganisms to act can also be finely pulverized. For this reason, by using the pulverized product obtained by pulverization into fine powder, it is also possible to process into a more complex shape and it can be utilized in various fields.

[0043] <Method for manufacturing sound-absorbing material> The method for manufacturing a sound-absorbing material according to an embodiment of the present invention includes a step of allowing a treated material containing foamed urethane having closed cells to act on a microorganism having urethane-degrading ability in a culture medium for culturing the microorganism, and the culture medium contains saccharides and amino acids. As the microorganism having urethane-degrading ability, for example, any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas can be used. In the method for manufacturing a sound-absorbing material, it is possible to adopt the same configuration as the urethane decomposition method for the microorganism used, the culture medium, and the method of allowing the microorganism to act on the treated material.

[0044] As described above, a sound-absorbing material can be manufactured by using, as a treated material, a treated material containing foamed urethane having closed cells in the urethane decomposition method according to an embodiment of the present invention. This is because, by allowing a microorganism to act on the treated material, fine cavities are formed in the closed cells of the foamed urethane, and at least a part of the bubbles of the foamed urethane are connected.

[0045] Generally, the sound-absorbing effect of a sound-absorbing material is exerted by absorbing the vibration energy of sound and converting it into thermal energy. The treated material after allowing the microorganism to act as described above can be easily pulverized into a powder. And the pulverized material, in addition to the fact that the pulverized material itself is an elastomer and is easy to absorb energy, is refined, so that the pulverized material itself macroscopically vibrates, and it is considered that an excellent sound-absorbing effect is exerted by the synergistic effect of these two phenomena.

[0046] The sound-absorbing material obtained in this way can be preferably used, for example, as a sound-absorbing and heat-insulating material for a refrigerator or a vending machine. Also, similar to the water-absorbing material obtained as described above, it is possible to use the treated material after allowing the microorganism to act as a sound-absorbing material in its original state, or it is also possible to mold them into a desired shape and use them.

[0047] The method for decomposing urethane, the method for manufacturing a water-absorbing material, and the method for manufacturing a sound-absorbing material according to embodiments of the present invention include the aspects described below. (1) A step of allowing a material to be treated containing urethane to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, A method for decomposing urethane. (2) The microorganism includes any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas, The method for decomposing urethane according to (1) above. (3) The microorganism belonging to the genus Streptomyces is the Streptomyces C13a strain identified by the accession number FERM BP-21770, The method for decomposing urethane according to (2) above. (4) The microorganism belonging to the genus Sinomonas is the Sinomonas atrocyanea ES2231 strain identified by the accession number NITE P-03613, The method for decomposing urethane according to (2) above. (5) The microorganism belonging to the genus Pseudomonas is the Pseudomonas hibiscicola MS4102 strain identified by the accession number NITE P-03612, The method for decomposing urethane according to (2) above. (6) The saccharides are saccharides containing soluble starch and / or glucose, The method for decomposing urethane according to any one of (1) to (5) above. (7) The amino acids are amino acids containing peptone and / or casamino acids, The method for decomposing urethane according to any one of (1) to (6) above. (8) A step of allowing a material to be treated containing foamed urethane having independent bubbles to act on the microorganism in a culture medium for culturing a microorganism having urethane-degrading ability, The culture medium contains saccharides and amino acids, Method for producing a water-absorbing material. (9) The microorganism includes any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas, The method for producing a water-absorbing material according to (8) above. (10) A step of allowing a material to be treated containing foamed urethane having independent bubbles to act on the microorganism in a culture medium for culturing a microorganism having urethane-degrading ability, The culture medium contains saccharides and amino acids, Method for producing a sound-absorbing material. (11) The microorganism includes any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas, The method for producing a sound-absorbing material according to (10) above.

Example

[0048] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0049] [Evaluation of microbial growth] (Microorganism) As microorganisms having urethane-degrading ability, a microorganism specified by the accession number FERM BP-21770 (strain: Streptomyces C13a) and a microorganism specified by the accession number NITE P-03613 (strain: Sinomonas atrocyanea ES2231) were used.

[0050] (Culture medium) As a culture medium for implementing the urethane decomposition method of the present invention, R2A medium "Dai-go" (with the composition described in Table 2 above) manufactured by Shioya MS Co., Ltd. (sold by Fujifilm Wako Pure Chemical Corporation) was used. For comparison, the YES-G0 medium prepared as follows was used. KH2PO4 solution and Na2HPO4 solution with the concentrations shown in Table 3 below were prepared, and 10 mL and 40 mL of each were mixed to obtain Solution A. Also, other Solution B, Solution C, and Solution D were solutions with the compositions shown in Table 3 below. After preparation, Solution A to D were sterilized under the conditions of 121 °C for 20 minutes. Into a 3 L Erlenmeyer flask, 20 mL of Solution A, 4.0 g of gelatin, 970 mL of distilled water, and 0.5 g of (NH4)2SO4 were added and mixed, and sterilized under the conditions of 121 °C for 20 minutes. After cooling, 10 mL of Solution B, 0.1 mL of Solution C (10-fold concentration), and 2 mL of Solution D were added to this 3 L Erlenmeyer flask respectively to prepare the YES-G0 medium.

[0051]

Table 3

[0052] (Culture) -Streptomyces C13a- Streptomyces C13a was inoculated into 100 mL of R2A medium or YES-G0 medium and cultured with shaking to obtain a preculture solution. The culture conditions at this time were 40 °C, 140 rpm, and 7 days. Subsequently, 1 mL of each of the preculture solutions obtained above was added to 100 mL of R2A medium or YES-G0 medium respectively, and cultured with shaking at 40 °C and 140 rpm. 12 hours and 24 hours after the start of the culture, 10 mL of the culture broth was collected and added to a test tube each time, centrifuged at 4000 rpm for 10 minutes, and the supernatant was removed with a pipette. Then, it was placed in a thermostat at 100 °C for 24 hours, dried thoroughly, and the dry weight of the bacterial cells was measured with an electronic balance. The results are shown in Figure 1.

[0053] -Sinomonas atrocyanea ES2231- In the same manner as in the case of using the above Streptomyces C13a, the growth properties of Sinomonas atrocyanea ES2231 were also evaluated in R2A medium and YES-G0 medium. For Sinomonas atrocyanea ES2231, the evaluation was carried out by changing the culture temperature to 20 °C, 30 °C, and 40 °C, respectively. Note that the growth property of the bacterium was evaluated by the change in absorbance (OD660). The results are shown in FIGS. 2 and 3.

[0054] As shown in FIGS. 1 and 2, in both cases, it was found that the R2A medium had a shorter induction period for the start of bacterial growth and an increased growth rate. Also, the culture temperature was most stable at 30 °C. It is considered that the decomposition effect is enhanced by acting urethane on viable cells with vitality before reaching the stationary phase with a constant growth rate and a saturated state.

[0055] The states of the culture vessels 24 hours after starting the culture of Streptomyces C13a are shown in FIGS. 4 and 5. As shown in FIG. 4, when the YES-G0 medium was used, the bacteria were easily aggregated and grew in the form of spherical algae about 1 mm to 2 mm in the culture solution. On the other hand, as shown in FIG. 5, when the R2A medium was used, the bacteria were finely dispersed in the culture solution and grew in a suspended state. This difference in the growth state of the urethane-decomposing bacteria is also considered to affect the urethane-decomposing ability. That is, it is considered that the urethane-decomposing ability is made uniform and the urethane-decomposing ability is stabilized when the urethane-decomposing bacteria are finely dispersed.

[0056] [Example 1] (Material to be treated) As the material to be treated, a waste material of foamed urethane used for the steering of an automobile, which was pulverized into a size of about 5 mm square, was used. The pulverization of waste urethane foam was carried out using a cutting mill SM300 manufactured by Varder Scientific Co., Ltd. (formerly Retche Co., Ltd.). (Microorganism) As the microorganism having urethane-degrading ability, the microorganism (strain: Streptomyces C13a) specified by the accession number FERM BP-21770 was used. (Culture medium) R2A medium "Digo" (having the composition described in Table 2 above) manufactured by Shiotani MS Co., Ltd. (sold by Fujifilm Wako Pure Chemical Corporation) was used. (Degradation of urethane) In the same manner as the evaluation of the growth property of the above microorganism, 1 mL of the preculture solution and the above material to be treated were added to 100 mL of R2A medium, and the treatment (culture) was carried out at 30 °C and 140 rpm for 24 hours. The preculture was also carried out at 30 °C. After washing and drying the material to be treated after 24 hours, the weight was measured, and the degradation rate was evaluated by comparing with the weight of the material to be treated before the action of the microorganism. The results are shown in Fig. 6.

[0057] [Example 2] In Example 1, the degradation of urethane was carried out in the same manner as in Example 1, except that unsaturated fatty acid was allowed to act on the material to be treated by the following method as a pretreatment before allowing the microorganism to act on the material to be treated. The results are shown in Fig. 6. (Unsaturated fatty acid) As the unsaturated fatty acid, oleic acid (manufactured by Wako Pure Chemical Industries, Ltd., grade: Wako special grade) was used. (Pretreatment) A solution prepared by diluting the oleic acid prepared above to a concentration of 10% (W / W) with 99% ethanol was prepared and added to a 100 mL Erlenmeyer flask. About 4 g to 5 g of the material to be treated was placed in the above 100 mL Erlenmeyer flask to completely immerse the material to be treated, covered with aluminum foil, and treated at room temperature for 1 hour. After the treatment time elapsed, the Erlenmeyer flask was washed with tap water and distilled water, and further distilled water was added for ultrasonic cleaning. The material to be treated was taken out from the Erlenmeyer flask and further washed with distilled water. Then, it was dried sufficiently (overnight) at 40 °C and sterilized under the conditions of 121 °C for 20 minutes.

[0058] [Comparative Example 1] In Example 2, urethane decomposition was carried out in the same manner as in Example 2 except that the R2A medium was replaced with the YES-G0 medium. The results are shown in Fig. 6.

[0059] The results of Example 1 and Example 2 using the R2A medium showed the same resolution as Comparative Example 1 under the conventional conditions, whether or not there was pretreatment. Thus, it was confirmed that the urethane decomposition method according to the embodiment of the present invention has the same decomposition effect as the conventional method without performing pretreatment with unsaturated fatty acids. That is, the urethane decomposition method according to the embodiment of the present invention does not require pretreatment with unsaturated fatty acids, so that the time required for urethane decomposition can be significantly shortened.

[0060] It is presumed that this is due to a change in the growth property of urethane-decomposing bacteria due to the difference in the culture medium. As described above, the conventional conditions used an inorganic salt medium (YES-G0 medium). This was for the purpose of improving the adsorptivity of urethane-decomposing bacteria to urethane and improving the urethane decomposition ability by growing urethane-decomposing bacteria using urethane as a nutrient source. Therefore, under the conventional conditions, pretreatment with unsaturated fatty acids was effective for improving the adsorptivity of urethane-decomposing bacteria. In contrast, in the urethane decomposition method according to an embodiment of the present invention, by using a culture medium containing a nutrient source such as an R2A medium, it aims to improve the growth property of urethane-decomposing bacteria in the culture medium. For this reason, as shown in the above growth property evaluation, it has been confirmed that the induction period of the growth of urethane-decomposing bacteria is shortened and the growth rate in the logarithmic phase is also increased. In addition, the morphology of urethane-decomposing bacteria during growth is not aggregated in the conventional spherical alga shape but is finely dispersed in a suspended state. It is considered that such a difference in the growth property of urethane-decomposing bacteria in the culture medium may affect the urethane-decomposing ability.

[0061] [Example 3] In Example 1, urethane was decomposed in the same manner as in Example 1 except that the time for allowing microorganisms to act on the material to be treated was 6 hours. The results are shown in FIG. 7.

[0062] [Example 4] In Example 2, urethane was decomposed in the same manner as in Example 2 except that the time for allowing microorganisms to act on the material to be treated was 6 hours. The results are shown in FIG. 7.

[0063] As shown in FIG. 7, when using the R2A medium, it was confirmed that even when the decomposition treatment time was 6 hours without pretreatment (Example 3), the decomposition ability was equivalent to that of the conventional conditions (Comparative Example 1). That is, it was confirmed that by using the R2A medium, an equivalent decomposition effect to the conventional conditions can be obtained in a short time without performing pretreatment with unsaturated fatty acids. This means that in order to obtain a decomposition effect equivalent to that of the conventional method for decomposing urethane, the time for allowing microorganisms to act can be reduced from 24 hours to 6 hours, which is one-fourth. This phenomenon is considered to be caused by the difference in the growth property of urethane-decomposing bacteria due to the aforementioned R2A medium.

[0064] (Observation of the cross-section of the material to be treated) The state of the material to be treated before allowing microorganisms to act, and the material to be treated after urethane decomposition according to Example 1 and Example 3 were observed with a microscope. The results are shown in FIGS. 8, 9, and 10, respectively. As a result, as shown in FIGS. 9 and 10, it was confirmed that fine cavities with a diameter of about 1 μm to 10 μm were formed on the wall surface of independent bubbles in the material to be treated after the action of microorganisms. In addition, it was observed that these fine cavities penetrated into the interior of the cells. Such fine cavities were not observed in the material to be treated (not subjected to the action of microorganisms) shown in FIG. 8. Thus, when decomposing the material to be treated while culturing microorganisms using R2A medium, the formation of fine cavities could be confirmed even when the decomposition time was 6 hours and 24 hours without performing pretreatment with unsaturated fatty acids. Therefore, it can be said that there is a urethane decomposition effect equivalent to that obtained when decomposition is carried out by the methods described in Conventional Patent Documents 1 and 2.

[0065] [Example 5] In Example 1, urethane was decomposed in the same manner as in Example 1, except that the microorganism used was replaced with the microorganism specified by the accession number NITE P-03613 (strain: Sinomonas atrocyanea ES2231).

[0066] [Example 6] In Example 2, urethane was decomposed in the same manner as in Example 2, except that the microorganism used was replaced with the microorganism specified by the accession number NITE P-03613 (strain: Sinomonas atrocyanea ES2231).

[0067] [Example 7] In Example 3, urethane was decomposed in the same manner as in Example 3, except that the microorganism used was replaced with the microorganism specified by the accession number NITE P-03613 (strain: Sinomonas atrocyanea ES2231).

[0068] [Example 8] In Example 4, urethane was decomposed in the same manner as in Example 4, except that the microorganism used was replaced with the microorganism specified by the accession number NITE P-03613 (strain: Sinomonas atrocyanea ES2231).

[0069] (Water Absorbency Test) For Examples 1 to 8, Comparative Example 1, and the untreated material, a water absorption test was conducted as follows. First, for Examples 1 to 8 and Comparative Example 1, after each culture period elapsed, the bacterial solution was discarded, and the treated material was rinsed with distilled water. Then, ultrasonic cleaning was performed with 99% ethanol. Further, after the treated material was washed with distilled water, it was thoroughly dried at 40 °C (overnight). Each of the dried treated materials obtained as described above was mixed with a binder as an adhesive component. As the binder, a moisture-curing isocyanate prepolymer (manufactured by Token Resin Co., Ltd.) was used. Then, by press molding while passing steam, a disk-shaped molded product with a diameter of 90 cm and a thickness of 20 mm was manufactured. A steam press machine was used for the press molding. From each molded product, three test pieces with a thickness of about 25 mm, a width of about 25 mm, and a length of about 25 mm were cut out respectively, and their dimensions were measured in units of 0.1 mm. After each test piece was dried at 60 °C for 24 hours, it was immersed in a container filled with pure water at room temperature so that the test piece was completely submerged 30 mm below the water surface. The water was gently stirred about once every few hours, and the test piece was allowed to absorb water for 24 hours. After 24 hours elapsed, the test piece was taken out, placed on a sieve inclined at about 45° from the vertical, and left for 30 seconds. Then, their respective masses were measured in units of 0.01 g. This was taken as the water absorption amount, and it was converted per 100 cm 2 of the surface area, and the average of the three points was obtained for evaluation. The results of the water absorption test are shown in Fig. 11.

[0070] (Water retention test) A wire mesh was placed on absorbent cotton so that the test piece and the absorbent cotton did not come into direct contact. Each of the water-absorbed test pieces used in the water absorption test was placed thereon, and the weight after 60 minutes elapsed as time passed was measured. Note that the test piece showing the water absorption amount closest to the average value of the water absorption amounts in the water absorption test was used as the test piece for the water retention test. When measuring, the top and bottom of the test piece were determined, and the measurement was always performed with the same surface facing down. The results of the water retention test are shown in Fig. 12.

[0071] As shown in FIGS. 11 and 12, the test pieces after 6 hours of allowing microorganisms to act on the material to be treated in the R2A culture medium without pretreatment with unsaturated fatty acids showed higher values than the test pieces of Comparative Example 1 under the conventional conditions in both absorption characteristics and water retention characteristics. That is, even when the conditions of the urethane decomposition method were changed, it was confirmed that there were no problems in terms of the material properties of the obtained water-absorbing material, and rather, higher material properties than before could be obtained.

Claims

1. A step of allowing a material to be treated containing urethane to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, A method for decomposing urethane.

2. The microorganism contains any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas, The method for decomposing urethane according to Claim 1.

3. The microorganism belonging to the genus Streptomyces is Streptomyces C13a strain identified by the accession number FERM BP-21770, The method for decomposing urethane according to Claim 2.

4. The microorganism belonging to the genus Sinomonas is Sinomonas atrocyanea ES2231 strain identified by the accession number NITE P-03613, The method for decomposing urethane according to Claim 2.

5. The microorganism belonging to the genus Pseudomonas is Pseudomonas hibiscicola MS4102 strain identified by the accession number NITE P-03612, The method for decomposing urethane according to Claim 2.

6. The saccharides are saccharides containing soluble starch and / or glucose, The method for decomposing urethane according to Claim 1 or 2.

7. The amino acids are amino acids containing peptone and / or casamino acid, The method for decomposing urethane according to Claim 1 or 2.

8. A step of allowing a material to be treated containing foamed urethane having independent bubbles to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, A method for producing a water absorbent material.

9. The microorganism contains any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas, The method for producing a water absorbent material according to Claim 8.

10. A step of allowing a material to be treated containing foamed urethane having independent bubbles to act on the microorganism in a culture medium for culturing a microorganism having urethane-decomposing ability, wherein the culture medium contains saccharides and amino acids, A method for producing a sound-absorbing material.

11. The microorganism contains any one or more microorganisms selected from the group consisting of microorganisms belonging to the genus Streptomyces, microorganisms belonging to the genus Sinomonas, and microorganisms belonging to the genus Pseudomonas. The method for producing a sound-absorbing material according to claim 10.

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