Method for decomposing vulcanized rubber

Abstract

To provide a method for decomposing a complex microorganism system capable of achieving the decomposition of a vulcanized rubber at low cost.SOLUTION: There is provided a method for decomposing a vulcanized rubber including: an acclimatization step of bringing a complex microorganism group containing unvulcanized polyisoprene-degrading bacteria into contact with the unvulcanized polyisoprene and acclimatizing the complex microorganism group to obtain an acclimatized complex microorganism group; and a vulcanized rubber decomposition step of bringing the acclimatized complex microorganism group into contact with the vulcanized rubber to decompose the vulcanized rubber. The acclimatization step preferably includes a treatment step in which natural rubber wastewater containing an unvulcanized polyisoprene-degrading bacteria is acclimatized by contact with an unvulcanized polyisoprene. It is more preferable to carry out the contact between the complex microorganism group and the unvulcanized polyisoprene in aerobic conditions during the acclimatization step. There is also provided a method for producing a complex microorganism group having an ability to decompose the vulcanized rubber, which comprises acclimatizing the complex microorganism group containing unvulcanized polyisoprene-degrading bacteria by allowing them to come into contact with unvulcanized polyisoprene.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for decomposing vulcanized rubber. [Background technology]

[0002] The manufacturing process of rubber products generally involves a process in which polymers such as polyisoprene are cross-linked by covalent bonds using sulfur. In addition, many compounding agents, such as reinforcing materials, accelerators for cross-linking reaction formation, and plasticizers to improve processability, are added to realize the product's functions and performance, so there are complex interactions in rubber materials, including covalent bonds and reaction intermediates. Due to the complex interactions in the materials mentioned above, it is difficult to reuse rubber, including material recycling and chemical recycling. In reality, most rubber materials, including tires, are incinerated as thermal recycling after collection. Some recycled materials are available on the market by shearing the molecules physicochemically, but their functions and performance are inferior to the virgin materials mentioned above, so the products that can be used and the amount of compounding are limited.

[0003] On the other hand, the existence of microorganisms (rubber decomposition bacteria) capable of decomposing rubber has been reported. For example, Patent Document 1 describes that the actinomycete BS-GS2 strain belonging to Nocardia Takedensis was pre-cultured by adding vulcanized rubber as a carbon source to the medium, and the ability to decompose natural rubber was confirmed in the subsequent culture. Non-Patent Document 1 describes that since natural rubber decomposition bacteria accumulate on the surface of rubber chunks accumulated in a natural rubber wastewater treatment system, these rubber chunks can be used as an inoculum source for natural rubber decomposition bacteria. Patent Document 2 describes that when the supernatant obtained by centrifuging a culture solution of the actinomycete BS-HA1 strain of the Nocardia genus was added to a chloroform solution of polyisoprene rubber (IR) (unvulcanized polyisoprene) and cultured, the molecular weight of the rubber decreased after the culture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-247241 A [Patent Document 2] JP 2009-13284 A [Non-patent literature]

[0005] [Non-Patent Document 1] Tanikawa et al. (2022) Environmental Biotechnology Society Annual Conference 2022, O-01 Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques described in Patent Documents 1 and 2 involve the cultivation of a single microbial species, and although they are primarily used in the production of food and pharmaceuticals, it is difficult to put them to practical use in the decomposition of waste materials due to cost issues. In addition, techniques using a single microbial species require normal cultivation while avoiding contamination, which makes the operation for control complicated.

[0007] Generally, microbial technologies used at the industrial level for waste treatment use a complex microbial system that grows in the environment, such as activated sludge. Although the technology described in Non-Patent Document 1 uses a complex microbial system, the report confirmed the ability to decompose unvulcanized polyisoprene, and makes no mention of vulcanized rubber. Therefore, an object of the present invention is to provide a decomposition method using a multi-microbial system that can inexpensively decompose vulcanized rubber. [Means for solving the problem]

[0008] The present invention provides the following [1] to

[10] . [1] A method for decomposing vulcanized rubber, comprising: an acclimation step in which a suspension, dispersion or solution containing a complex microbial community including unvulcanized rubber-decomposing bacteria is brought into contact with unvulcanized rubber to acclimate the rubber, thereby obtaining a treatment liquid containing an acclimated complex microbial community; and a vulcanized rubber decomposition step in which the treatment liquid containing the acclimated complex microbial community is brought into contact with vulcanized rubber to decompose the vulcanized rubber. [2] The method according to [1], wherein the suspension, dispersion, or solution further contains natural rubber latex. [3] The method according to [2], wherein the suspension, dispersion, or solution further comprises an acid and / or ammonia. [4] The method according to any one of [1] to [3], wherein the suspension, dispersion, or solution is natural rubber wastewater. [5] The method according to any one of [1] to [4], wherein the unvulcanized rubber decomposing bacterium is an unvulcanized rubber decomposing bacterium belonging to the genus Nocardia, Streptomyces, Gordonia, Rhodococcus, or Xanthomonas. [6] The method according to any one of [1] to [5], wherein the complex microbial community further comprises bacteria of the genus Microbacterium. [7] The method according to any one of [1] to [6], wherein the unvulcanized rubber is a rubber agglomerate in natural rubber wastewater. [8] The method according to any one of [1] to [7], wherein at the start of the vulcanized rubber decomposition process, the complex microbial consortium further comprises one or more types of bacteria selected from the group consisting of bacteria of the genus Spirosoma, the genus Pedobacter, the genus Paucibacter, the genus Elizabethkingia, the genus Bradyrhizobium, the genus Flavisoribacter, and the genus Prosthecobacter. [9] The method according to any one of [1] to [8], wherein the vulcanized rubber decomposition step is carried out for a period of 50 days or more.

[10] A method for producing a complex microbial consortium having the ability to decompose vulcanized rubber, comprising contacting a suspension, dispersion or solution containing a complex microbial consortium including unvulcanized rubber-decomposing bacteria with unvulcanized rubber for acclimatization. Effect of the Invention

[0009] According to the present invention, by using a microbial flora acclimatized in a specific environment, it is possible to provide a method for decomposing hard rubber using a complex microbial community, rather than a single microbial species. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a rubber wastewater treatment system used in the examples. [Diagram 2]2 is a graph showing the change over time in soluble COD in the examples and comparative examples. In FIG. 2, the open circles, black diamonds, black squares, and open squares represent the results of Example 1, Comparative Examples 1, 2, and 3, respectively. [Diagram 3] FIG. 3 is a photograph of a cross section of a vulcanized rubber sheet after 60 days of culture in Example 1, observed by SEM. [Figure 4] FIG. 4 is a photograph of a cross section of a vulcanized rubber sheet after 60 days of culture in Comparative Example 1, observed by SEM. [Diagram 5] FIG. 5 is a photograph of a cross section of a vulcanized rubber sheet on the 132nd day of culture in Example 1, observed by SEM. [Figure 6] FIG. 6 is a photograph of a cross section of a vulcanized rubber sheet on the 132nd day of culture in Comparative Example 1, observed by SEM. [Figure 7] Figure 7 is a graph showing the results of bacterial flora analysis and their changes over time in Example 1 and Comparative Example 2. In Figure 7, Day 0, 60, and 168 respectively represent the results at the start of culture, day 60, and day 168 in Example 1. Furthermore, Day 60(C) represents the results on day 60 of culture in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [1. How to disassemble vulcanized rubber] The method for decomposing vulcanized rubber includes an acclimatization step and a vulcanized rubber decomposition step.

[0012] [Acclimatization process] The acclimation step is a step of acclimating a complex microbial consortium including unvulcanized rubber-degrading bacteria by contacting the complex microbial consortium with unvulcanized rubber, thereby obtaining an acclimated complex microbial consortium having the ability to decompose vulcanized rubber.

[0013] -Complex microbial group- The complex microbial community containing unvulcanized rubber decomposition bacteria is a complex microbial community containing at least unvulcanized rubber decomposition bacteria. The unvulcanized rubber decomposition bacteria may be any microorganism capable of decomposing unvulcanized rubber, and examples of the unvulcanized rubber include various unvulcanized rubbers such as polyisoprene, hydrogenated polyisoprene, polybutadiene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene ternary copolymer, and silicone, with polyisoprene being preferred. Examples of the unvulcanized rubber decomposition bacteria include unvulcanized rubber (e.g., unvulcanized polyisoprene) decomposition bacteria belonging to the genus Nocardia, Streptomyces, Gordonia, Rhodococcus, and Xanthomonas. The complex microbial community contains at least one type of unvulcanized polyisoprene decomposition bacteria, and may contain a combination of two or more types.

[0014] The complex microbial community may contain microorganisms other than unvulcanized rubber decomposing bacteria (hereinafter, sometimes referred to as other microorganisms). Examples of other microorganisms include bacteria of the genera Microbacterium, Spirosoma, Pedobacter, Paucibacter, Elizabethkingia, Bradyrhizobium, Flavisolibacter, Prosthecobacter, Alicycliphilus, Sediminibacterium, Singulishaera, Chitinophaga, etc. The complex microbial community preferably contains at least one other type of microorganism, more preferably contains a combination of two or more types, and preferably contains at least Microbacterium genus bacteria.

[0015] The complex microbial community includes two or more kinds of microorganisms. Examples of the two or more kinds of microorganisms include a combination of two or more kinds of unvulcanized rubber decomposition bacteria, and a combination of one or more kinds of unvulcanized rubber decomposition bacteria and one or more kinds of other microorganisms. The abundance ratio of each of the bacteria constituting the complex microbial community may vary during the acclimation process. At least at the start of the vulcanized rubber decomposition process, it is preferable that the abundance ratio of one or more kinds of bacteria selected from the genus Spirosoma, the genus Pedobacter, the genus Paucibacter, the genus Elizabethkingia, the genus Bradyrhizobium, the genus Flavisolibacter, and the genus Prosthecobacter is higher than the abundance ratio of other bacteria, and it is more preferable that the abundance ratio of each of these bacteria is higher than the abundance ratio of other bacteria.

[0016] -Unvulcanized rubber- The unvulcanized rubber to be contacted with the complex microbial community may be either natural or synthetic rubber, but natural rubber is preferred. The unvulcanized rubber may be either natural or synthetic rubber as long as it is unvulcanized, and examples of such unvulcanized rubber include polyisoprene, hydrogenated polyisoprene, polybutadiene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, silicone, and other various unvulcanized rubbers, with polyisoprene (either natural or synthetic rubber) being preferred. As the unvulcanized rubber, it is preferred to use rubber agglomerates formed in natural rubber (e.g. polyisoprene rubber) wastewater. Rubber agglomerates are the cause of problems such as clogging of pipes, reactors, and other equipment in the rubber industry, and can be reused, which is efficient from the standpoint of operation, economy, and the environment. The rubber agglomerates in natural rubber wastewater are usually polyisoprene. Rubber agglomerates from natural rubber wastewater can be obtained, for example, by extracting the rubber components from the natural rubber wastewater, or by filling a plurality of core rubbers (unvulcanized rubber) of predetermined shapes into a reaction tank of any device (for example, the device in FIG. 1 ) and passing natural rubber wastewater through it, thereby causing the rubber in the wastewater to adhere to the surface of the core rubber.

[0017] -Liquid containing a complex microorganism community- An example of a contact method is to add the complex microbial community to a solvent and contact the unvulcanized rubber as a suspension, dispersion, or solution (hereinafter, suspension, dispersion, or solution may be collectively referred to as a liquid). The solvent is usually an aqueous solvent (e.g., water, alcohol), preferably water. When preparing the suspension, dispersion, or solution, stirring may be performed as necessary.

[0018] The liquid containing the complex microbial community may further contain other components such as natural rubber latex, acid (e.g., organic acid such as acetic acid, propionic acid, formic acid, etc.), ammonia, etc., and preferably contains at least natural rubber latex, which allows acclimatization to proceed efficiently.

[0019] As a liquid containing a complex microbial community, natural rubber wastewater can be used. Since natural rubber wastewater contains a complex microbial community, by using it, the preparation of raw materials can be easily and efficiently performed at low cost, and waste liquid treatment in the rubber industry can be omitted and reused, which is also preferable from an environmental perspective. In this specification, natural rubber wastewater is waste liquid remaining after separating and extracting rubber components such as latex from sap collected from a raw material plant (rubber tree) in the extraction of natural rubber. It is presumed that the complex microbial community is mixed in during the process of separation and extraction. For example, the mixture may be a mixture of microorganisms attached to tools (e.g., collection, storage, and transport containers such as knives and cups, especially tools that have been used for a long time) used in tapping sap containing rubber components such as latex, a mixture of microorganisms contained in water used for dilution as necessary during processing, or a mixture of microorganisms in the environment. Natural rubber wastewater usually contains unseparated latex, and often contains acids such as ammonia and organic acids (e.g., acetic acid, propionic acid) used in the separation and extraction. The natural rubber wastewater may be subjected to anaerobic treatment before being subjected to the acclimation step, which can remove methane gas derived from organic acids.

[0020] The amount of ammonia contained in the liquid containing a complex microbial community is preferably 100 mg / L or more, preferably 200 mg / L or more. The upper limit is preferably 500 mg / L or less, preferably 400 mg / L or less. Therefore, the amount of ammonia contained in the liquid containing a complex microbial community is preferably 100 to 500 mg / L, preferably 200 to 400 mg / L.

[0021] The amount of organic acid contained in the liquid containing a complex microbial community is not particularly limited, but is usually 1000 to 8000 mg / L, and preferably 2000 to 5000 mg / L. For example, when the organic acid contains acetic acid, its content is not particularly limited, but is usually 500 to 4000 mg / L, and preferably 1000 to 2000 mg / L in the liquid containing the complex microbial community. When the organic acid contains propionic acid, its content is not particularly limited, but is usually 500 to 4000 mg / L, and preferably 1000 to 3000 mg / L in the liquid containing the complex microbial community.

[0022] -Contact treatment- The contact can be carried out, for example, by filling a reaction vessel (reactor: e.g., flow-type) provided with openings for inflow and outflow with unvulcanized rubber, injecting a suspension, dispersion or solution containing a complex microbial community into the reaction vessel using pressure or the like, and passing the liquid through the reaction vessel, and repeating this process multiple times as necessary. The packing density of the unvulcanized rubber is preferably 10 to 40%, more preferably 25 to 35%, of the effective volume of the reaction vessel. From the viewpoint of contact efficiency, the unvulcanized rubber to be packed is preferably a plurality of unvulcanized rubber chunks (e.g., particle size of about 1 to 20 cm, preferably about 2 to 10 cm).

[0023] Contact between the microbial complex and the unvulcanized rubber is preferably carried out under aerobic conditions, which allows the coagulation and decomposition of the rubber to proceed and allows for efficient acclimatization.

[0024] The soluble chemical oxygen demand (COD), biochemical oxygen demand (BOD), and suspended solids (SS) of the liquid containing the complex microbial community immediately before contacting with the unvulcanized rubber are not particularly limited, but examples are as follows. The COD is usually 2000 mg / L or less, preferably 1500 mg / L or less. The lower limit is usually 10 mg / L or more, preferably 20 mg / L or more. The BOD is not particularly limited, but is usually 5000 mg / L or less, preferably 4000 mg / L or less. The lower limit is usually 100 mg / L or more, preferably 1000 mg / L or more. The SS is usually 1500 mg / L or less, preferably 1000 mg / L or less. The lower limit is usually 100 mg / L or more, preferably 200 mg / L or more. This makes it easier to adjust the COD of the reaction liquid after the acclimation step, and the subsequent steps can be carried out efficiently.

[0025] In this specification, COD can be measured using a kit manufactured by HACH Co., Ltd. Furthermore, BOD and SS can be measured in accordance with the Sewerage Testing Method.

[0026] The treatment time for the contact treatment is not particularly limited as long as the complex microbial community is acclimatized, but is usually 12 to 60 days, preferably 15 to 50 hours, and more preferably 20 to 40 hours. The temperature condition is not particularly limited, and the treatment can be performed at room temperature (for example, 15 to 35°C, preferably 18 to 30°C).

[0027] After the contact treatment, a treatment liquid can be obtained from the recovered water (a solution containing unvulcanized rubber (its aggregates)). If necessary, the recovered water may be subjected to post-treatment such as ultrasonic treatment before collection of the treatment liquid (treatment such as separation of the rubber component). The liquid after the contact treatment contains microorganisms, and there are cases where microorganisms are attached to the unvulcanized rubber and its aggregates. By ultrasonic treatment, these microorganisms can be suspended in the liquid, and a treatment liquid containing a larger amount of microorganisms can be obtained. For ultrasonic treatment, a commercially available ultrasonic cleaner or the like can be used.

[0028] -Acclimatized complex microorganism group- The acclimatized complex microbial community contained in the obtained treatment liquid may be a complex microbial community that has undergone an acclimatization step and has the ability to decompose vulcanized rubber, and although there are no particular limitations on the microbial species and number of microbial species, it is preferable that it contains one or more of the unvulcanized rubber decomposition bacteria exemplified in the above "complex microbial community". The acclimatized complex microbial community may further contain one or more of microorganisms other than the unvulcanized rubber decomposition bacteria described in the above "complex microbial community", and among these, it is preferable that it further contains Microbacterium bacteria, and more preferably it further contains one or more bacteria selected from Spirosoma, Pedobacter, Paucibacter, Elizabethkingia, Bradyrhizobium, Flavisoribacter, and Prostecobacter.

[0029] [Vulcanized rubber decomposition process] The vulcanized rubber decomposition step is a step in which the treatment liquid containing the acclimatized complex microbial community prepared in the acclimatization step is brought into contact with vulcanized rubber to decompose the vulcanized rubber.

[0030] The vulcanized rubber is usually polyisoprene vulcanized rubber, and may be natural or synthetic rubber. Examples of vulcanized rubber include vulcanized rubbers made from various rubber raw materials such as polyisoprene, hydrogenated polyisoprene, polybutadiene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene ternary copolymer, and silicone. It is preferable to use vulcanized rubber made from the same rubber raw material as the unvulcanized rubber used in the contact step. The method for producing vulcanized rubber is not particularly limited, and examples include a method in which a rubber raw material (e.g., polyisoprene (natural rubber latex, synthetic polyisoprene)) is appropriately mixed with raw materials such as a reinforcing material, an antiaging agent, and a process oil, and kneading is started, and after kneading at a high temperature, a crosslinking agent such as sulfur, a co-crosslinking agent, a vulcanization accelerator, and a vulcanization aid such as stearic acid are appropriately mixed and further kneaded using an open roll.

[0031] The method of contacting the treatment liquid containing an acclimatized complex microorganism group with vulcanized rubber includes a method in which the acclimatized complex microorganisms and the vulcanized rubber are placed in a culture tank and cultured together. The culture is preferably performed under aerobic conditions with aeration while preventing contamination. For example, a method in which the treatment liquid containing an acclimatized complex microorganism group is poured into a culture tank, the vulcanized rubber is placed therein, a culture stopper is placed, and the mixture is cultured by shaking. The weight ratio of the vulcanized rubber to the treatment liquid is usually 0.01 to 5% by weight, preferably 0.05 to 1% by weight. The speed of the shaking culture is not particularly limited, but is preferably 50 to 200 rpm, more preferably 100 to 150 rpm, for example.

[0032] The SS of the treatment liquid immediately before contact with the vulcanized rubber is not particularly limited, but is usually 5 mg / L or more, preferably 10 mg / L or more, and more preferably 15 mg / L or more. The upper limit is usually 200 mg / L or less, preferably 100 mg / L or less, and more preferably 40 mg / L or less. Therefore, it is usually 5 to 200 mg / L, preferably 10 to 100 mg / L, and more preferably 15 to 40 mg / L. This allows the acclimatized complex microbial community to be efficiently produced by contact with and decomposition of the vulcanized rubber.

[0033] The temperature condition in the decomposition step may be room temperature, for example, 15 to 35° C., and preferably 18 to 30° C. The decomposition step is carried out for, for example, 50 days or more, and more preferably 60 days or more, so that the vulcanized rubber can be sufficiently decomposed.

[0034] [2. Method for producing a complex microbial consortium capable of decomposing vulcanized rubber] By undergoing the acclimation step in the above-mentioned decomposition method, a microbial consortium having the ability to decompose vulcanized rubber can be produced. The resulting microbial consortium can be used to decompose vulcanized rubber. EXAMPLES

[0035] The present invention will now be described with reference to examples, which are not intended to limit the scope of the present invention.

[0036] Example 1 A simulated wastewater simulating the composition of natural rubber wastewater was prepared, and treated using the apparatus of FIG. 1 to obtain treated water. The apparatus A1 of FIG. 1 includes an injection pipe 1 having an injection port 11 and connected to a drainage channel 2, a drainage channel 2 having ports 21 and 22, which are openings intended for sample confirmation and oxygen supply, and an outlet 23, a wastewater tank 3 for accumulating a wastewater sample to be supplied to the drainage channel, and a pump 4 for continuously sending the wastewater sample from the wastewater tank 3 to the drainage channel 2 through a liquid sending pipe 41. The effective volume of the apparatus A1 was 2.4 L (injection pipe 1: 0.5 L + drainage channel 2: 1.9 L). The drainage channel was filled with multiple core rubbers, and the packing density was about 30% of the effective volume of the drainage channel (reactor). The core rubber was natural unvulcanized polyisoprene rubber that had been used for wastewater treatment after 365 days had passed since it was filled in this apparatus, and was in the form of granules with a size of approximately 3 to 6 cm.

[0037] The simulated wastewater was prepared to mimic the composition of natural rubber wastewater at natural rubber extraction sites. Normally, ammonia is added to the collected latex, and acid is added to coagulate the rubber, which is then washed, resulting in natural rubber wastewater. Therefore, the simulated wastewater was prepared by adding ammonia, acetic acid, and propionic acid to the natural rubber latex to concentrations of 250 mg / L, 1800 mg / L, and 2000 mg / L, respectively. At the time of inflow, the total COD was 7290±630 mg / L, the total BOD was 302±450 mg / L, and the SS (suspended solids concentration) was 765±167 mg / L. COD was measured using a kit from HACH. BOD and SS were also measured based on the sewerage test method.

[0038] The treatment was carried out according to the following procedure. First, simulated wastewater was stored in a wastewater tank and continuously sent from the inlet of the drainage channel using a liquid transfer pump (wastewater flow rate: 1.9 L / day, room temperature: 25°C). The rubber particle size in the wastewater tended to increase before it passed through port 1, and it was assumed that coagulation would progress, and the rubber particle size tended to decrease after it passed through port 1, and it was assumed that the rubber would be broken down into smaller molecules. An outlet was opened further downstream of port 2 in the drainage channel, and the treated water was led to and stored in a recovery tank. The retention time of the wastewater in the drainage channel was one day.

[0039] The recovered water was further treated with ultrasonic waves to obtain treated water containing rubber components and rubber microorganisms. The ultrasonic treatment was carried out using an ULTRASONIC CLEANER VS-150 (manufactured by AS ONE Corporation) at 50 Hz for 15 minutes (n=2, the same applies to the following comparative examples).

[0040] 250 mL of treated water (SS at the start of immersion of vulcanized rubber sheet: 17.5 mg / L) was collected and placed in a 300 mL flask together with several 10 x 10 x 0.5 mm vulcanized rubber sheets (weight ratio to treated water: about 0.1% by weight). In preparing the vulcanized rubber sheet, the compounding ingredients shown in Table 1 were mixed using a lab plastomill for kneading A (dispersion treatment of compounding ingredients other than stearic acid, sulfur, and vulcanization accelerator into rubber polymer), and an open roll for kneading B (dispersion treatment of stearic acid, sulfur, and vulcanization accelerator). The rubber after kneading B was press-vulcanized at 150 ° C for 20 minutes using a 0.5 mm thick mold and a press machine. The vulcanized rubber was cut with scissors and adjusted to the above size to make a vulcanized rubber sheet.

[0041] A silicon plug was attached to the opening of the flask to ensure ventilation while preventing bacterial contamination from the outside. The flask was cultured at a shaking speed of 120 rpm in an environment adjusted to room temperature (about 20 to about 25°C).

[0042] Comparative Example 1 The procedure was the same as in Example 1, except that activated sludge (SS at the start of the vulcanized rubber decomposition process when the vulcanized rubber sheet immersion began: 22.0 mg / L) collected from a septic tank for domestic wastewater at the Sumitomo Riko Komaki Works was used as is instead of the treated water in Example 1.

[0043] Comparative Examples 2 and 3 The same procedures as in Example 1 and Comparative Example 1 were carried out, except that the culture using the vulcanized rubber sheet was not carried out.

[0044] [Table 1]

[0045] [Table 1 Footnotes] *1 Show Black, manufactured by Showa Cabot Corporation *2 Suncellar CZ-G, Sanshin Chemical Industry Co., Ltd., N-cyclohexyl-2-benzothiazole sulfenamide (CBS) *3 Sulfax, dispersible sulfur, manufactured by Tsurumi Chemical Industry Co., Ltd. *4 Sansen 410 manufactured by Nippon San Oil Co., Ltd.

[0046] Each sample was collected periodically during the culture, and the COD (chemical oxygen demand) was analyzed using a measuring kit manufactured by HACH. The results of soluble COD up to 200 days after the culture are shown in FIG. 2. In the control without rubber (Comparative Examples 2 and 3) and the activated sludge of domestic water (Comparative Example 1), no increase in soluble COD was observed, whereas in the sample with rubber added (Example 1), an increase was observed, and in particular, a large increase was observed up to the 60th day of the culture. In addition, when the COD increase rate after the 97th day was compared between Example 1 and Comparative Example 1, the Example was about 2.4 times higher (0.226 mg / L and 0.094 mg / L, respectively). These results suggested that in Example 1, the polymer in the vulcanized rubber was degraded from a relatively early stage.

[0047] The rubber in each sample solution of Example 1 and Comparative Example 1 was periodically sampled, and the cross-sections were observed using pyrolysis GC and a scanning electron microscope. As a result, as is clear from the results of the observation of the cross-sections of the surfaces on the 60th and 132nd days of culture, the material in the sample of Example 1 was significantly altered compared to the sample of Comparative Example 1, and the alteration of the material was already observed from the surface to a depth of about 50 μm or more on the 60th day (FIGS. 3 to 6). These results suggested that in Example 1, the polymer in the vulcanized rubber was altered, i.e., decomposed, from the surface layer.

[0048] In addition, DNA was extracted from the culture solution (liquid in which the biofilm on the surface of the vulcanized rubber sheet was suspended in the culture solution) on the 60th day of culture of the sample of Example 1, the 16S rRNA gene was amplified by the PCR method, and the bacterial flora was analyzed using the next-generation sequencer MiSeq (Figure 7). As a result, in the sample to which rubber was added, Microbacterium bacteria and Nocardia bacteria, which are often reported as rubber decomposition bacteria, were frequently detected as early as the 60th day of culture. It was confirmed that these bacteria were dominant even on the 168th day of culture. The abundance ratio of Nocardia genus in Example 1 continued to increase from the early stage of the experiment, which was consistent with the behavior of the COD concentration. On the other hand, in Comparative Examples 2 and 3, in which no vulcanized rubber pieces were added, Nocardia genus was not detected.

[0049] These results show that the method of the present invention is capable of decomposing vulcanized rubber, and is also capable of decomposing hard rubber materials used in automotive parts. [Explanation of symbols]

[0050] A1 Rubber wastewater treatment equipment 1 Injection tube 11 Inlet 2 Drainage channel 21, 22 ports 23 Outlet 3 Wastewater tank 4. Pump 41 Liquid delivery pipe

Claims

1. an acclimation step of contacting unvulcanized rubber with a suspension, dispersion or solution containing a complex microbial community including unvulcanized rubber-degrading bacteria for acclimation to obtain a treatment liquid containing an acclimated complex microbial community; and a vulcanized rubber decomposition step in which a treatment liquid containing an acclimatized complex microbial community is brought into contact with vulcanized rubber to decompose the vulcanized rubber; A method for decomposing vulcanized rubber, comprising:

2. The method of claim 1 , wherein the suspension, dispersion, or solution further comprises natural rubber latex.

3. The method of claim 2 , wherein the suspension, dispersion, or solution further comprises an acid and / or ammonia.

4. The method according to any one of claims 1 to 3, wherein the suspension, dispersion or solution is natural rubber wastewater.

5. The method according to any one of claims 1 to 3, wherein the unvulcanized rubber decomposing bacterium is an unvulcanized rubber decomposing bacterium belonging to the genus Nocardia, Streptomyces, Gordonia, Rhodococcus, or Xanthomonas.

6. The method according to any one of claims 1 to 3, wherein the complex microbial community further comprises bacteria of the genus Microbacterium.

7. The method according to any one of claims 1 to 3, wherein the unvulcanized rubber is a rubber agglomerate in natural rubber wastewater.

8. The method according to any one of claims 1 to 3, wherein at the start of the vulcanized rubber decomposition process, the complex microbial consortium further comprises one or more bacteria selected from the group consisting of bacteria of the genus Spirosoma, the genus Pedobacter, the genus Paucibacter, the genus Elizabethkingia, the genus Bradyrhizobium, the genus Flavisoribacter, and the genus Prostecobacter.

9. The method according to any one of claims 1 to 3, wherein the vulcanized rubber decomposition step is carried out for a period of 50 days or more.

10. A method for producing a complex microbial consortium having the ability to decompose vulcanized rubber, comprising contacting unvulcanized rubber with a suspension, dispersion or solution containing a complex microbial consortium including unvulcanized rubber-decomposing bacteria for acclimatization.

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