Use of pseudomonas aeruginosa in degrading polypropylene plastic and method for degrading polypropylene plastic

Abstract

The application relates to the technical field of microbial degradation, and discloses application of pseudomonas aeruginosa in degrading polypropylene plastic and a method for degrading polypropylene plastic. The pseudomonas aeruginosa is preserved in the China General Microbiological Culture Collection Center, and the preservation number is CGMCC NO: 27456. The pseudomonas aeruginosa has high degradation efficiency and high degradation rate on polypropylene plastic, and has a good market application prospect.

Description

Technical Field

[0001] This invention relates to the field of microbial degradation technology, specifically to the application of Pseudomonas aeruginosa in the degradation of polypropylene plastics and methods for degrading polypropylene plastics. Background Technology

[0002] While plastic products bring convenience to people's lives and agriculture, excessive use of plastic products can also lead to environmental pollution and ecological damage. In particular, with the large-scale use of agricultural mulch film, these discarded plastic films accumulate in the soil and are difficult to degrade due to the inability to collect and dispose of them effectively.

[0003] Currently, the primary method for processing all plastics, including polypropylene, is still incineration for power generation (accounting for approximately 42% of total plastic production), with a recycling rate of only about 35% and 23% still disposed of through landfill. Incineration for power generation produces substances such as dioxins. Sulfur dioxide and large amounts of carbon dioxide and other pollutants and greenhouse gases are emitted. Landfilling plastics requires a large area and, under high temperatures and direct sunlight, releases toxic and harmful substances such as plasticizers and heavy metal ions that pollute groundwater and soil. Furthermore, incompletely degraded plastics transform into microplastics. Microplastics can absorb other toxic and harmful substances and enter the human body or other organisms through the food chain, causing a series of diseases or ecological disasters.

[0004] Microbial treatment of plastic pollution is currently the most environmentally friendly and economical method, but it has not yet been widely adopted due to its long treatment cycle, slow rate, and limited source. Currently, the bacteria that degrade plastics all originate from microbial communities in landfill sites or water bodies where microplastics accumulate. Furthermore, the degradation rates for untreated polypropylene plastics (the highest degradation rate for starch-doped polypropylene plastic films within 120 days is only 19% (Journal of Applied Polymer Science, 2019)) and microplastics (the highest degradation rate for polypropylene microplastics within 40 days is only 6.4% (Marine Pollution Bulletin, 2018)) are relatively low.

[0005] The aforementioned bacterial strains cannot meet the requirements for rapid treatment, which greatly limits the promotion and application of microbial treatment for polypropylene plastic pollution. Therefore, it is necessary to provide a degrading bacterium with high efficiency and high degradation rate for polypropylene plastic films and polypropylene microplastics. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing polypropylene plastic degrading bacteria, which have low degradation efficiency and low degradation rate.

[0007] To achieve the above objectives, the inventors of this invention conducted numerous screening experiments and identified a *Pseudomonas aeruginosa* strain exhibiting high degradation efficiency and rate for polypropylene plastics. Therefore, a first aspect of this invention provides the application of *Pseudomonas aeruginosa* XJ16 in the degradation of polypropylene plastics. This *Pseudomonas aeruginosa* strain is deposited at the China General Microbiological Culture Collection Center (CGMCC) under accession number CGMCC NO: 27456.

[0008] A second aspect of the present invention provides a method for degrading polypropylene plastic, the method comprising: contacting the aforementioned Pseudomonas aeruginosa XJ16 as described in the first aspect with the polypropylene plastic to degrade the polypropylene plastic.

[0009] The *Pseudomonas aeruginosa* XJ16 provided by this invention achieves a degradation rate of up to 23.5% for polypropylene plastic film doped with carbon powder and up to 11.1% for polypropylene microplastics within 120 days. It can be used to treat large quantities of waste polypropylene plastic film and polypropylene microplastics, alleviating the current situation of few degrading bacteria and low degradation efficiency for polypropylene plastic film and polypropylene microplastics, and has good market application prospects.

[0010] Biological Preservation

[0011] The *Pseudomonas aeruginosa* strain of this invention was deposited on May 25, 2023, at the China General Microbiological Culture Collection Center (Address: No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postcode: 100101) (abbreviation of depositary institution: CGMCC), with accession number CGMCC: 27456. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] As previously stated, the first aspect of the present invention provides the application of Pseudomonas aeruginosa XJ16 in the degradation of polypropylene plastics, which is deposited at the China General Microbiological Culture Collection Center, with accession number CGMCC NO: 27456.

[0014] The *Pseudomonas aeruginosa* strain of this invention, with accession number CGMCC NO: 27456, was obtained from an oil reservoir environment and purified by streak plating. The colonies of this *P. aeruginosa* are pale yellow with a moist surface. Total RNA was extracted from strain XJ16, and 16S5 RNA gene sequence analysis was performed. Comparison with the DNA sequence database (Genbank) confirmed that this bacterium is *Pseudomonas aeruginosa*. This *P. aeruginosa* strain is deposited at the China General Microbiological Culture Collection Center, accession number CGMCC NO: 27456.

[0015] The *Pseudomonas aeruginosa* strain provided by this invention can produce a large number of live *P. aeruginosa* cells after culturing. It should be noted that this invention does not have specific requirements for the culturing method, as long as it enables the *P. aeruginosa* to proliferate; for example, a 103... 7 The inoculum of live Pseudomonas aeruginosa was inoculated into R2A liquid medium at a CFU / mL inoculum and cultured at 30-40℃ for 12-48 hours to obtain the culture solution.

[0016] It should be noted that the present invention does not impose any particular limitations on the culture conditions of *Pseudomonas aeruginosa*. Those skilled in the art can select appropriate conditions based on known techniques. The present invention provides a specific embodiment, which should not be construed as a limitation of the invention. For example, the composition of the R2A liquid culture medium used for culture can be: 0.5 g / L yeast extract; 0.25 g / L tryptone; 0.75 g / L peptone; 0.5 g / L glucose; 0.5 g / L soluble starch; 0.3 g / L K₂HPO₄; 0.024 g / L MgSO₄; 0.3 g / L sodium pyruvate; the remainder being water, pH = 7. The inorganic salt culture medium used for cultivation can consist of: 3 g / L KNO3; 3 g / L Na2HPO4; 0.5 g / L MgSO4; 12 g / L Na2EDTA·2H2O; 10 g / L Na2SO4; 5 g / L FeSO4·7H2O; 0.5 g / L CuSO4·5H2O; with the remainder being water, pH=7.

[0017] As previously described, a second aspect of the present invention provides a method for degrading polypropylene plastic, the method comprising: contacting Pseudomonas aeruginosa XJ16 with the polypropylene plastic to degrade the polypropylene plastic.

[0018] Preferably, the polypropylene plastic is a polypropylene microplastic and / or a polypropylene plastic film doped with carbon powder.

[0019] More preferably, the particle size of the polypropylene microplastics is 100-1000 μm, more preferably 780-920 μm. The inventors of this invention have discovered that when the particle size of the polypropylene microplastics is 780-920 μm, it exhibits higher degradation efficiency.

[0020] More preferably, the thickness of the polypropylene plastic film is 0.1-2.0 mm, and more preferably 1.0-1.1 mm.

[0021] It should be noted that the present invention does not impose any particular limitation on the content of carbon powder in the polypropylene plastic film doped with carbon powder, and can use various commercially available polypropylene plastic films doped with carbon powder.

[0022] According to a preferred embodiment, the amount of *Pseudomonas aeruginosa* XJ16 used is 0.3-2.3 L of OD relative to 1 g of the polypropylene plastic. 600 The bacterial suspension has an OD value of 0.1-2.5. Particularly preferably, the amount of *Pseudomonas aeruginosa* XJ16 used is 0.3-2.3 L relative to 1 g of the polypropylene plastic. 600 Bacterial solution with a value of 0.5-2.0.

[0023] According to another preferred embodiment, the contact conditions include: being carried out under stirring conditions, with a stirring speed of 100-250 rpm, preferably 120-150 rpm; and a temperature of 20-45°C, preferably 30-40°C.

[0024] The present invention will be described in detail below through examples.

[0025] In the following examples, unless otherwise specified, all raw materials used were commercially purchased.

[0026] In this invention, the degradation rate of polypropylene plastic = (weight of polypropylene plastic before degradation - weight of polypropylene plastic after degradation) / weight of polypropylene plastic before degradation × 100%.

[0027] Polypropylene plastic film doped with carbon powder: sourced from the Bamboo Research and Development Center of the National Forestry and Grassland Administration.

[0028] Preparation example: Preparation of Pseudomonas aeruginosa bacterial suspension

[0029] Pseudomonas aeruginosa strain with accession number CGMCC NO: 27456 was inoculated into R2A liquid medium sterilized at 121°C for 20 min, and cultured on a shaker at 120 rpm and 35°C for 24 h to obtain a seed culture. The obtained seed culture was then inoculated into 100 mL of inorganic salt medium at a volume ratio of 2% to obtain OD. 600 The bacterial solution has a value of 0.7.

[0030] Example 1

[0031] A polypropylene plastic film (0.5 cm in length and width, and 1 mm in thickness) doped with carbon powder (49.6 ± 0.1 mg) was added to 100 mL of the bacterial culture obtained in the preparation example. The film was then cultured on a shaker at 120 rpm and 35 °C for a total of 28 days. Every 7 days, the carbon-doped polypropylene plastic film was removed, dried at 65 °C to constant weight, and weighed. This experiment was repeated in triplicate.

[0032] 50.2±0.1 mg of carbon powder (particle size 430 μm) was added to 100 mL of the bacterial culture obtained in the preparation example, and the culture was carried out by shaking in a shaker at 120 rpm and 35 °C for a total culture time of 28 days. During the period, the carbon powder was taken out every 7 days, dried at 65 °C to constant weight, and then weighed. The experiment was repeated in 3 parallel experiments.

[0033] Example 2

[0034] A polypropylene plastic film (3.0 cm in length and width, and 1 mm in thickness) doped with carbon powder (302.2 ± 0.1 mg) was added to 100 mL of the bacterial culture obtained in the preparation example. The film was then cultured on a shaker at 120 rpm and 35 °C for a total of 120 days. Every 30 days, the carbon-doped polypropylene plastic film was removed, dried at 65 °C to constant weight, and weighed. This experiment was repeated in triplicate.

[0035] 300.6±0.1 mg of carbon powder (particle size 430 μm) was added to 100 mL of the bacterial culture obtained in the preparation example, and the culture was carried out by shaking in a shaker at 120 rpm and 35 °C for a total culture time of 120 days. During the period, the carbon powder was taken out every 30 days, dried at 65 °C to constant weight, and then weighed. The experiment was repeated in 3 parallel experiments.

[0036] Example 3

[0037] 50.6±0.1 mg of polypropylene microplastics (particle size of 850 μm) was added to 100 mL of the bacterial culture obtained in the preparation example, and the culture was carried out by shaking in a shaker at 120 rpm and 35 °C for a total culture time of 28 days. During the period, the polypropylene microplastics were taken out every 7 days, dried at 65 °C to constant weight, and then weighed. The experiment was repeated in 3 parallel experiments.

[0038] Example 4

[0039] 303.6 ± 0.1 mg of polypropylene microplastics (particle size of 850 μm) was added to 100 mL of the bacterial culture obtained in the preparation example, and the culture was carried out by shaking in a shaker at 120 rpm and 35 °C for a total culture time of 120 days. During the period, the polypropylene microplastics were taken out every 30 days, dried at 65 °C to constant weight, and then weighed. The experiment was repeated in 3 parallel experiments.

[0040] Example 5

[0041] 50±0.1 mg of polypropylene microplastics (particle size of 510 μm) was added to 100 mL of the bacterial culture obtained in the preparation example. The culture was carried out by shaking in a shaker at 120 rpm and 35 °C for a total culture time of 28 days. During the period, the polypropylene plastic film doped with carbon powder was taken out every 7 days, dried at 65 °C to constant weight, and then weighed. The experiment was repeated in 3 parallel tests.

[0042] Table 1

[0043]

[0044]

[0045] As can be seen from the results in Table 1, the Pseudomonas aeruginosa provided by the present invention has a high degradation rate for polypropylene plastic films and polypropylene microplastics doped with carbon powder.

[0046] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. Pseudomonas aeruginosa ( Pseudomonas aeruginosa The application of XJ16 in degradable polypropylene plastics is characterized by, The preservation number of the Pseudomonas aeruginosa is CGMCC NO.27456, and the Pseudomonas aeruginosa XJ16 is derived from the oil reservoir environment; the polypropylene plastic is polypropylene microplastic and / or polypropylene plastic film doped with carbon powder.

2. The application according to claim 1, wherein, The particle size of the polypropylene microplastics is 100-1000 μm.

3. The application according to claim 1 or 2, wherein, The thickness of the polypropylene plastic film is 0.1-2.0 mm.

4. A method for degrading polypropylene plastic, characterized in that, The method includes: contacting Pseudomonas aeruginosa XJ16 with polypropylene plastic to degrade the polypropylene plastic; the preservation number of Pseudomonas aeruginosa is CGMCC NO.27456.

5. The method according to claim 4, wherein, The polypropylene plastic is a polypropylene microplastic and / or a polypropylene plastic film doped with carbon powder.

6. The method according to claim 5, wherein, The particle size of the polypropylene microplastics is 100-1000 μm.

7. The method according to claim 5 or 6, wherein, The thickness of the polypropylene plastic film is 0.1-2.0 mm.

8. The method according to any one of claims 4-6, wherein, The amount of *Pseudomonas aeruginosa* XJ16 used relative to 1g of the polypropylene plastic is 0.3-2.3L of OD. 600 Bacterial solutions with a value of 0.1-2.

5.

9. The method according to any one of claims 4-6, wherein, The contact conditions include: being carried out under stirring conditions, with a stirring speed of 100-250 rpm and a temperature of 20-45℃.

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