Novel microorganism with plastic degradation activity and use thereof

Abstract

The present invention relates to a novel microorganism with plastic degradation activity. The microorganism of the present invention can degrade plastics synthesized from petroleum-based compounds such as polyethylene (PE), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polyurethane (PU), and polyvinyl chloride (PVC) and convert same into low-molecular-weight materials, and is excellent in degrading plastics or plastic metabolic intermediates, and thus can be used in a pretreatment process for recycling plastics.

Description

Novel microorganisms with plastic-degrading activity and their uses

[0001] The present invention relates to a novel microorganism capable of decomposing various plastics and a method for decomposing plastics using the same.

[0002] Plastics have become an indispensable industrial material in modern society. Their high strength and elasticity, light weight, low production costs, and ease of use have made them widely used in various industries for the past 50 years. Plastic production has increased significantly, from 234 million tons in 2000 to 460 million tons in 2019. Furthermore, during the same period, plastic waste generation more than doubled, from 156 million tons to 353 million tons. According to a UN report, plastic production is expected to reach 800 million tons by 2035 and 1.6 billion tons by 2050. Of this, more than two-thirds (76%) will be disposed of as waste. Only 9% of this waste will be recycled, 12% will be incinerated, and 79% will be landfilled.

[0003] Landfilling is the most economical and common method for processing plastic waste, but it requires extensive landfill sites. While high-temperature incineration can reduce waste accumulation, it generates toxic compounds like dioxins and carbon monoxide during combustion, causing further environmental pollution. Physical and chemical recycling, while environmentally friendly, are limited due to limitations such as the low efficiency of the separation / sorting process and the economic viability of recycled plastic.

[0004] Furthermore, environmental pollution caused by the influx of plastic not only threatens the ecosystem and human health, but also incurs additional costs for waste disposal and pollution recovery, and thus, there is an active trend of improvement and research on plastic waste disposal methods.

[0005] As an example of research on plastic-decomposing microorganisms, Korean Patent No. 10-0350928 discloses a novel microorganism, Klebsiella pneumoniae CJ-PVA a (Accession No. KFCC-11126), which grows well under aerobic conditions and has improved polyvinyl alcohol decomposition ability, and a method for treating wastewater containing polyvinyl alcohol using the same (Patent Document 1). In addition, Korean Patent No. 10-0513931 discloses Microbacterium barkeri LC (Accession No. KCCM 10507) and a method for biologically decomposing polyvinyl alcohol using the same (Patent Document 2).

[0006] However, the above plastic-decomposing microorganism is a technology limited to the decomposition of polyvinyl alcohol, which has high surface activity and natural decomposition, and is difficult to apply to the decomposition of plastics synthesized from other petroleum compounds, so there is a disadvantage in that it is difficult to utilize it as a microbial species or combination that decomposes various types of plastics.

[0007] In the above circumstances, the inventors of the present invention have made extensive research efforts to find novel microorganisms capable of decomposing various plastics.

[0008] As a result, the present invention was completed by isolating a novel microorganism capable of decomposing various plastics.

[0009] The purpose of the present invention is to provide a Rhodococcus yunnanensis repla5 strain having plastic decomposition activity, deposited under accession number KACC 81286BP.

[0010] Another object of the present invention is to provide a method for decomposing plastic, comprising a step of culturing plastic with Rhodococcus yunnanensis repla5 strain, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme deposited under accession number KACC 81286BP.

[0011] Another object of the present invention is to provide a composition for decomposing plastic, comprising Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme.

[0012] Another object of the present invention is to provide a method for decomposing a plastic metabolic intermediate, which comprises a step of culturing a plastic metabolic intermediate with a Rhodococcus yunnanensis repla5 strain, a strain culture solution, a strain lysate, or a strain-derived plastic-decomposing enzyme deposited under accession number KACC 81286BP.

[0013] Another object of the present invention is to provide a composition for decomposing a plastic metabolic intermediate, comprising the Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, a strain culture solution, a strain lysate, or a strain-derived plastic decomposing enzyme.

[0014] Another object of the present invention is to provide a composition for promoting plastic oxidation, comprising Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme.

[0015] Hereinafter, the present invention will be described in detail.

[0016] One aspect of the present invention is a Rhodococcus yunnanensis repla5 strain having plastic decomposition activity, deposited under accession number KACC 81286BP.

[0017] The present inventors isolated a strain capable of decomposing plastic from waste polyethylene vinyl and performed 16S rRNA sequence analysis (SEQ ID NO: 1) to identify a pure single strain through subculture, and confirmed that the obtained strain belonged to the genus Rhodococcus. The isolated microorganism was named Rhodococcus yunnanensis repla5 and deposited in the Korean Agricultural Culture Collection (KACC) of the National Institute of Agricultural Sciences on December 7, 2023, and was assigned the accession number KACC 81286BP.

[0018] In the present invention, the "Rhodococcus genus" is a non-spore-forming aerobic bacterium, classified as a nocardia-type actinomycete containing mycolate. The Rhodococcus genus is composed of genetically and physiologically diverse bacteria, but can be isolated and utilized from soil or seawater, performs various enzymatic functions, and has a unique cell wall structure. The Rhodococcus cell wall contains mycolic acid, like that of Mycobacteria, Nocardia, and Corynebacteria. Mycolic acid, a long-chain lipid in the cell envelope, facilitates the intracellular uptake of hydrophobic substrates. Furthermore, the ability to metabolize hydrophobic substrates enables the production of surfactants. These compounds thus produced attach cells to hydrophobic phases, increase interfacial tension, and disperse hydrophobic substrates. The substrates present in the growth medium change the fatty acid composition of the biomembrane lipids, thereby altering the fluidity of the cell envelope. Therefore, changes in the fatty acid composition play an important role in the resistance of Rhodococcus cells to toxic chemicals. Rhodococcus strains form biofilms on carriers, increasing their resistance to toxic chemicals. The genus Rhodococcus is resistant to and decomposes xenobiotic toxicity and exists in areas contaminated with aromatic compounds. Rhodococcus decomposes benzene, toluene, xylene, biphenyl, polycyclic aromatics, phenol, PCBs, aniline, ether, pesticides, etc., and also acts as a desulfurizing bacterium.

[0019] In the present invention, the plastic may be at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE), but is not limited thereto.

[0020] The polyethylene terephthalate mentioned above is a relatively high-density saturated polyester resin that can be crystalline or amorphous thermoplastic. Amorphous polyethylene terephthalate has high transparency but low tensile strength and poor sliding properties, making it primarily used for bottles and packaging. Crystalline polyethylene terephthalate, on the other hand, has high hardness, rigidity, and strength, as well as excellent sliding properties and wear resistance, making it a popular choice for Ensinger's semi-finished products for machining.

[0021] The above polyvinyl chloride is similar to polypropylene, but has one hydrogen atom replaced by one chlorine atom. In the case of polyvinyl chloride, rather than the main carbon chain of polyvinyl chloride, the plasticizers (e.g., bis-2-ethylhexyl phthalate, dioctyl adipate, etc.) included during production are mainly studied, and are partially decomposed by bacteria and fungi collected from various environments, converting them into low-molecular-weight substances.

[0022] The above polystyrene is structurally similar to polyethylene terephthalate (PET) and HDPE / LDPE, but due to the structural characteristics of the monomer, it has higher hydrophobicity, so it hardly hydrolyzes, and it is known to have the slowest decomposition rate in the natural environment among the generally classified plastics. Polystyrene is a thermoplastic plastic that is lightweight and has no taste or odor, so it is used in household goods, toys, electrical insulators, radio and television cases, packaging materials, etc. Polypropylene is polymerized from propylene obtained from petroleum and is widely used in bottles, containers, etc.

[0023] The polypropylene mentioned above is a polymer obtained by polymerizing propylene through Ziegler-Natta polymerization or metallocene-catalyzed polymerization. Polypropylene has a methyl group (CH3) attached to every other carbon atom in the polyethylene molecular chain, forming a regularly arranged, short branched structure. While it has a relatively simple molecular structure linked by carbon bonds, similar to polystyrene, the methyl group contained in each bond makes it difficult to hydrolyze.

[0024] The above polyurethane is based on the urethane bond (-NHCOO-) through the polymerization reaction of isocyanate and polyol, and various diols are sometimes added as chain extenders. Basically, the urethane bond itself is known to be vulnerable to microbial attack, but since the polyester or polyether bonds present within the polyol, such as PCL or polyethylene glycol, account for the absolute majority of the polymer structure, the biodegradation of urethane is primarily determined by the type and degree of these bonds whether or not it is decomposed by microorganisms. Polyester urethane can be decomposed relatively easily than polyether urethane by hydrolases such as ester hydrolase, and it is known that numerous fungi and bacteria can decompose it.

[0025] The polyethylene described above is made by the polymerization of ethylene and is composed solely of carbon-hydrogen chains, making it very stable. Like other plastics, it is known to not decompose for decades after landfill. Polyethylene decomposes through oxidation, creating functional groups such as hydroxyl (-OH) and carbonyl (C=O), and breaking carbon-carbon bonds to produce intermediate substances (fatty acids) with relatively low molecular weights. Polyethylene is a thermoplastic, lightweight and flexible, making it a versatile plastic used in everything from industrial materials to daily necessities. High-density polyethylene (HDPE) is impact-resistant and cold-resistant, and is primarily used to make shopping bags and pipes. Low-density polyethylene (LDPE) has branched polymers, making it lower in density than linear HDPE, but has good elasticity and is easy to process.

[0026] In the present invention, “plastic decomposition activity” means activity capable of decomposing plastic and plastic metabolic intermediates.

[0027] In the present invention, "plastic degradation" refers to the decomposition of high molecular weight substances constituting plastic into low molecular weight intermediate substances or intermediates that can be metabolized through the metabolic pathway of microorganisms. In order to metabolize plastics composed of heavy structures, they must be decomposed into monomer units with small molecular weights (Mw ~500), and monomers are utilized for microbial metabolism in various forms. Among various monomers, hydrocarbon structural substances ([CnHn]n) are mainly metabolized through the fatty acid degradation pathway (β-oxidation pathway), and metabolism can occur step by step in the order of alkane, alcohol, aldehyde, and fatty acid.

[0028] According to an embodiment of the present invention, it was confirmed that the Rhodococcus yunnanensis repla5 strain can decompose various types of plastics by decomposing polyethylene at a decomposition rate of about 3.04%, polystyrene at a decomposition rate of about 15.39%, polypropylene at a decomposition rate of about 5.0%, polyethylene terephthalate at a decomposition rate of about 7.82%, and polyurethane at a decomposition rate of about 3.29% (Example 3-1).

[0029] Another aspect of the present invention is a method for decomposing plastic, comprising a step of culturing plastic with Rhodococcus yunnanensis repla5 strain, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme deposited under accession number KACC 81286BP.

[0030] In the present invention, the plastic may be at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE), but is not limited thereto.

[0031] In the present invention, the culturing may be performed by inoculating the Rhodococcus yunnanensis repla5 strain into a medium having a pH of 5 to 9, pH 5 to 8, pH 5 to 7, pH 6 to 9, pH 6 to 8, or pH 6 to 7, but is not limited thereto.

[0032] If the strain is grown at a pH outside the range of pH 5 to 9, the strain may not be cultured well.

[0033] In the present invention, the cultivation may be performed at a temperature of 10 to 40°C for 7 to 60 days after inoculating the Rhodococcus yunnanensis repla5 strain into a medium containing plastic as a carbon source, and preferably, it may be performed at a temperature of 25 to 40°C for 10 to 60 days, but is not limited thereto.

[0034] If cultured at a temperature higher or lower than the above-mentioned culture temperature, the strain may not be cultured properly. In addition, if cultured for a shorter time than the above-mentioned culture time, the culture may be terminated before the plastic decomposition activity is sufficiently manifested. If cultured for a longer time than the above-mentioned culture time, the plastic decomposition efficiency may be low relative to the culture time.

[0035] In the present invention, the medium composition, culture temperature, and culture time can be changed depending on the type of plastic to be decomposed, and when the Rhodococcus yunnanensis repla5 strain and a plastic or a plastic metabolic intermediate are cultured together under conditions in which these conditions are combined as process parameters, a specific plastic can be relatively decomposed to a large extent or all plastics can be decomposed into low-molecular-weight substances that can be reused.

[0036] The plastic added to the above medium may be in the form of finely divided flakes, powder, or thin film to increase contact with the Rhodococcus yunnanensis repla5 strain or strain culture solution, strain lysate, or strain-derived plastic-degrading enzyme.

[0037] According to an embodiment of the present invention, when Rhodococcus yunnanensis repla5 and plastic powder (LDPE) were supplied as a carbon source, an increase in oxygen elements on the surface of the plastic and the formation of CO bonds and carbonyl groups (C=O) were confirmed. In addition, it was confirmed that hydroxyl groups (OH) and carbonyl groups (C=O) were formed on the chemical functional groups on the surface of the plastic. In addition, the hydroxyl groups (OH) shown in the FT-IR analysis can be seen as hydroxyl groups bonded to the plastic in the form of C-OH, considering that the CO bonds confirmed in the XPS were shown, and it was confirmed that Rhodococcus yunnanensis repla5 can oxidize plastic (Example 3-2).

[0038] The plastic decomposition method according to the present invention can be applied as a pretreatment process for plastic recycling.

[0039] Another aspect of the present invention is a composition for decomposing plastic, comprising Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme.

[0040] In the present invention, since the Rhodococcus yunnanensis repla5 strain uses plastic as a carbon source, the strain itself, the strain culture solution, the strain lysate, or the strain-derived plastic decomposing enzyme can be used for the purpose of decomposing plastic.

[0041] In the present invention, the plastic may be at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE), but is not limited thereto.

[0042] Another aspect of the present invention is a method for decomposing a plastic metabolic intermediate, comprising a step of culturing a plastic metabolic intermediate with a Rhodococcus yunnanensis repla5 strain, a strain culture solution, a strain lysate, or a strain-derived plastic-decomposing enzyme, deposited under accession number KACC 81286BP.

[0043] In the present invention, the plastic metabolic intermediate may be at least one selected from the group consisting of an alkane, an alcohol, an aldehyde, and a fatty acid, but is not limited thereto.

[0044] Another aspect of the present invention is a composition for decomposing a plastic metabolic intermediate, comprising a Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, a strain culture solution, a strain lysate, or a strain-derived plastic decomposing enzyme.

[0045] In the present invention, since the Rhodococcus yunnanensis repla5 strain uses plastic as a carbon source, the strain itself, the strain culture solution, the strain lysate, or the strain-derived plastic decomposition enzyme can be used for the purpose of decomposing plastic metabolic intermediates.

[0046] Another aspect of the present invention is a composition for promoting plastic oxidation, comprising Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme.

[0047] In the present invention, the composition for promoting plastic oxidation can promote a catalytic action by oxidation in relation to the decomposition of plastic, which is a polymer material, and the catalytic action can promote the formation of a microbial biofilm (hydrophilic) and a depolymerization reaction by increasing the hydrophilicity of the surface of the plastic, which is hydrophobic.

[0048] According to an embodiment of the present invention, Rhodococcus yunnanensis repla5 corroded a plastic surface by biodegradation and formed a microbial biofilm of the repla5 strain on the plastic surface (Example 2-3).

[0049] The present invention relates to a novel microorganism having plastic decomposition activity, and the microorganism of the present invention can decompose plastics synthesized from petroleum compounds such as polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE) and convert them into low-molecular substances, and is excellent in decomposing plastics or plastic metabolic intermediates, and can be used in a pretreatment process for recycling plastics.

[0050] Figure 1 shows the results of confirming the number of viable cells after culturing Rhodococcus yunnanensis repla5, a strain with plastic decomposition activity, in a minimal medium with added plastic powder.

[0051] Figure 2 shows the results of confirming the degree of corrosion (b) and the presence or absence of biofilm formation (c) after culturing Rhodococcus yunnanensis repla5 in a minimal medium with added plastic film.

[0052] Figure 3 shows the results of analyzing the changes in chemical functional groups after culturing Rhodococcus yunnanensis repla5 in a minimal medium with added plastic film using X-ray photoelectron spectroscopy.

[0053] Figure 4 shows the results of analyzing the changes in chemical functional groups after culturing Rhodococcus yunnanensis repla5 in a minimal medium with added plastic film using an X-ray Fourier transform infrared spectroscopy.

[0054] Figure 5 shows the results of analyzing the change in surface hydrophilicity using a contact angle meter after culturing Rhodococcus yunnanensis repla5 on a minimal medium with added plastic film.

[0055] Hereinafter, one or more specific examples will be described in more detail through examples. However, these examples are provided for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0056]

[0057] Example 1: Isolation of plastic-degrading microorganisms

[0058] 1-1. Isolation of plastic-decomposing microorganisms

[0059] A strain with plastic-decomposing ability was isolated from discarded polyethylene waste vinyl in rural soil environments.

[0060] Specifically, waste vinyl made of polyethylene was supplied as the sole carbon and energy source to microorganisms with potential plastic decomposition capacity and cultured with shaking at 25 ℃, 180 rpm, and aerobic conditions for approximately 60 days. The minimal medium composition was as follows: pH 6.51, 0.7 g NH2PO4, 0.7 g K2HPO4, 0.7 g MgSO4·7H2O, 1.0 g NH4NO3, 0.005 g NaCl, 0.002 g FeSO4·7H2O, 0.002 g ZnSO4·7H2O, 0.001 g MnSO4·H2O, per 1 L of distilled water. After cultivation, one strain that grew using polyethylene as a carbon source was isolated through a pure separation method.

[0061]

[0062] 1-2. Microbial identification

[0063] To identify the pure single strain obtained through the third subculture, 16S rRNA sequence analysis was performed, and the obtained strain was confirmed to be a member of the genus Rhodococcus. The isolated microorganism was named Rhodococcus yunnanensis repla5 and deposited in the Korean Agricultural Culture Collection (KACC) of the National Institute of Agricultural Sciences on December 6, 2023, and assigned the accession number KACC 81286BP.

[0064] Hereinafter, the isolated strain of the present invention is referred to as “Repla 5”.

[0065]

[0066] Example 2: Verification of plastic degradation

[0067] 2-1. Evaluation of the plastic resolution of Ripla 5

[0068] The plastic degradation capacity of Repla 5 was evaluated. Low-density polyethylene (LDPE), a plastic powder, was added to a minimal medium, and Repla 5 was inoculated. The medium was shaken and cultured under aerobic conditions (28°C, 130 rpm) for approximately 14 days. After 14 days, the culture medium was harvested, and the viable cell count of Repla 5 was determined as colony-forming units (CFUs).

[0069] As a result of the experiment, the value was approximately 4.0 x 10^6 CFU / mL in D0, but approximately 7.6 x 10^7 CFU / mL in D14, and the error bars represent the standard deviation of the mean value (Fig. 1). It was confirmed that Repla 5 proliferated using plastic powder as a carbon source.

[0070]

[0071] 2-2. Microbial Growth Evaluation of Ripple 5

[0072] The OD600 value of the culture solution of Repla 5 cultured in Example 2-1 was measured, and the results are shown in Table 1 below.

[0073] Incubation period (days) 1 day 2 days 3 days 4 days 5 days 6 days 7 days Repla 50.004± 0.002 0.000± 0.0000.020± 0.004 0.069± 0.005 0.090± 0.004 0.103± 0.003 0.109± 0.005 Control group - 0.001± 0.001 0.000± 0.001 0.000± 0.001 0.000.000± 0.0000.000± 0.0000.001± 0.001 0.003± 0.002

[0074]

[0075] As can be confirmed in Table 1 above, in the control group, no increase in optical density was observed for 7 days, but in the case of Repla 5, the optical density increased due to microbial growth, and it was confirmed that the saturation level was reached after approximately 6 days.

[0076]

[0077] 2-3. Evaluation of biofilm formation by Ripla 5

[0078] To evaluate biofilm formation by Repla 5, plastic film (LDPE) was added to minimal medium, inoculated with Repla 5, and cultured under aerobic conditions (28°C, 130 rpm) with shaking for approximately 14 days. After 14 days, the plastic film was recovered from the culture medium, and the microbial biofilm formed on the surface of the plastic film and the presence of corrosion due to biodegradation were observed using a scanning electron microscope. The results are shown in Fig. 2.

[0079] As a result of the experiment, in the control group without the addition of Repla 5, no microbial biofilm or plastic surface corrosion was observed (Fig. 2A). In contrast, when Repla 5 was cultured for 28 days, the plastic surface was corroded due to biodegradation (Fig. 2B), and a microbial biofilm of Repla 5 was formed on the surface (Fig. 2C).

[0080]

[0081] Example 3. Plastic decomposition using Repla 5

[0082] 3-1. Evaluation of the plastic decomposition rate of Ripla 5

[0083] The plastic degradation capacity of Repla 5 was evaluated by dry weight measurement. Each plastic powder was supplied as the sole carbon source to minimal medium, inoculated with Repla 5, and cultured under aerobic conditions (28°C, 130 rpm) with shaking for 7 days. The plastic degradation rate of the strain was calculated according to Equation 1, and the results are shown in Table 2.

[0084] [Mathematical Formula 1]

[0085] Plastic decomposition rate of Ripla 5 = (AB) / A*100

[0086] (A: Initial plastic mass, B: Residual plastic mass after decomposition)

[0087] Plastic typeInitial mass (g)Mass after decomposition (g)Reduced mass (g)Decomposition rate (%)Standard deviationPolyethylene (PE)0.20060.19450.00613.040.46Polystyrene (PS)0.20020.16940.030815.390.83Polypropylene (PP)0.20010.19010.01005.001.85Polyethylene terephthalate (PET)0.20070.18500.01577.821.13Polyurethane (PU)0.20050.19390.00663.290.31

[0088] As can be confirmed in Table 2 above, the plastic degradation rates (%) of each of the 5-repla plastics were 3.04% for polyethylene, 15.39% for polystyrene, 5.00% for polypropylene, 7.82% for polyethylene terephthalate, and 3.29% for polyurethane.

[0089] Through this, it was confirmed that Ripla 5 is a strain that can decompose various types of plastics.

[0090]

[0091] 3-2. Evaluation of plastic oxidation using Ripla 5

[0092] Plastics are hydrophobic materials, and to be biologically degraded, they must undergo oxidation to make them hydrophilic. The ability of Repla 5 to oxidize plastic was evaluated by supplying plastic film (LDPE) as the sole carbon source.

[0093] Specifically, plastic powder was added to the minimal medium, and Repla 5 was inoculated and cultured under aerobic conditions (28°C, 130 rpm) with shaking for about 14 days. After 14 days, LDPE was recovered from the culture medium, and oxidation of the plastic was confirmed by XPS (X-ray photoelectron spectroscopy), FT-IR (Fourier-transform infrared spectroscopy), and a contact angle meter, and the results are shown in Figs. 3 to 5.

[0094] XPS analysis results confirmed an increase in oxygen elements on the plastic surface and the formation of CO bonds and carbonyl groups (C=O) (Fig. 3). FT-IR analysis results showed that hydroxyl groups (OH) and carbonyl groups (C=O) were formed on the chemical functional groups on the plastic surface. Considering that the CO bonds confirmed in XPS appeared in the FT-IR analysis, it can be seen that the hydroxyl groups (OH) were bonded to the plastic in the form of C-OH (Fig. 4). This means that Repla 5 can oxidize plastic.

[0095] In addition, through contact angle measurement, the contact angle of the plastic cultured with Repla 5 decreased from 96.65 in the control group to 86.80, and a contact angle less than 90 indicates hydrophilicity. In other words, it was confirmed that the hydrophilicity of the plastic increased when Repla 5 was cultured with LDPE.

[0096] Through this plastic oxidation evaluation, it was confirmed that the Ripla 5 strain can decompose plastic when cultured alone or in mixed culture with other strains, and can also increase the plastic degradation rate.

[0097] [References]

[0098] (Patent Document 1) KR 10-0350928 B1

[0099] (Patent Document 2) KR 10-0513931 B1

[0100] [Accession number]

[0101] Name of depositor: National Institute of Agricultural Sciences, Rural Development Administration, Microbial Bank (KACC)

[0102] Accession number: KACC 81286BP

[0103] Date of acceptance: 20231207

[0104]

Claims

1. Rhodococcus yunnanensis repla5 strain having plastic-decomposing activity, deposited under accession number KACC 81286BP.

2. In paragraph 1, Rhodococcus yunnanensis repla5 strain, wherein the plastic is at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE).

3. A method for decomposing plastic, comprising a step of culturing plastic with Rhodococcus yunnanensis repla5 strain, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme deposited under accession number KACC 81286BP.

4. In paragraph 3, A method for decomposing plastic, wherein the plastic is at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE).

5. A composition for decomposing plastic, comprising Rhodococcus yunnanensis repla5 strain deposited under accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic decomposing enzyme.

6. In paragraph 5, A composition for decomposing plastic, wherein the plastic is at least one selected from the group consisting of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyurethane (PU), and polyethylene (PE).

7. A method for decomposing a plastic metabolic intermediate, comprising a step of culturing a plastic metabolic intermediate with Rhodococcus yunnanensis repla5 strain, strain culture solution, strain lysate or strain-derived plastic-decomposing enzyme deposited under accession number KACC 81286BP.

8. In paragraph 7, A method for decomposing a plastic metabolic intermediate, wherein the plastic metabolic intermediate is at least one selected from the group consisting of an alkane, an alcohol, an aldehyde, and a fatty acid.

9. A composition for decomposing a plastic metabolic intermediate, comprising a strain of Rhodococcus yunnanensis repla5 deposited under the accession number KACC 81286BP, a strain culture solution, a strain lysate or a strain-derived plastic decomposing enzyme.

10. A composition for promoting plastic oxidation, comprising Rhodococcus yunnanensis repla5 strain deposited under the accession number KACC 81286BP, strain culture solution, strain lysate or strain-derived plastic-decomposing enzyme.

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