Microflora and application thereof in biodegradation of polyurethane plastic

Abstract

The invention provides a flora and an application of the flora in biodegradation of polyurethane plastics. The flora is prepared from raoultella ornithinolytica, klebsiella pneumoniae, coxakella rhizogenes and achromobacter xylosoxidans. According to the method, the polyurethane degrading flora is screened from the collected soil sample, the flora can efficiently degrade waterborne polyurethane and thermoplastic polyurethane elastomers with large chemical structure difference at the same time to degrade polyurethane plastic, the process is greatly simplified, the operation cost is reduced, traditional landfill incineration is replaced, green circulation of polyurethane is assisted, and the method has the advantages of being environmentally friendly and environmentally friendly. The method has important practical significance for solving the problem of environmental pollution caused by polyurethane waste and promoting green cyclic utilization of polyurethane materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microbial technology and environmental biotechnology, and particularly relates to a bacterial flora and application thereof in biodegradation of polyurethane plastics. BACKGROUND

[0002] As a kind of synthetic polymer material with excellent performance, polyurethane has been widely used in many fields such as construction, automobile, electronics, medical treatment and packaging due to its good mechanical strength, chemical corrosion resistance, elasticity and processing adaptability. Among them, waterborne polyurethane (Imprial DLN) has a growing demand in the fields of coatings, adhesives and leather finishing because it uses water as a dispersion medium, greatly reducing the use of organic solvents and meeting the environmental protection trend. Thermoplastic polyurethane elastomer (TPU) has high elasticity like rubber and processability like plastic, and can be processed by thermoplastic molding process without crosslinking, so it is widely used in pipe materials, films, shoe soles and medical consumables. It is estimated that its consumption will reach about 900,000 tons by 2026, with a compound annual growth rate of about 10% in the next five years.

[0003] With the rapid increase in the use of polyurethane materials, the problem of waste disposal has become increasingly prominent. At present, the traditional disposal methods of polyurethane waste mainly include landfill, incineration and physical recycling. However, these disposal methods have significant limitations: in landfill disposal, polyurethane materials have stable structure and strong biodegradation resistance, and can remain in the natural environment for decades or even hundreds of years, causing long-term soil occupation and environmental pollution; although incineration can achieve waste volume reduction, it may release toxic and harmful gases such as dioxins and cyanide during the process, posing a threat to the atmospheric environment and human health; although physical recycling is relatively environmentally friendly, it is limited by material degradation and impurity introduction, and the mechanical properties of the recycled products usually decrease significantly, which can only be used for low-value-added products, making it difficult to achieve high-value recycling, and cannot solve the degradation problem of disposable polyurethane products (such as medical dressings and packaging materials) after use.

[0004] From the material structure, the polyurethane molecular main chain is composed of rigid urethane groups (-NH-CO-O-) and flexible polyol segments, and the chemical stability of the urethane group is high, which further enhances the anti-biodegradation performance. Existing research shows that the biodegradation of polyurethane mainly depends on the enzymes secreted by fungi and bacteria to destroy its molecular structure. Fungi degrade polyurethane mainly by attaching to the surface of polyurethane material, destroying the material structure by mycelial growth, and secreting enzymes such as hydrolase, urease and protease to degrade the polyurethane molecular chain. In contrast, when bacteria degrade polyurethane, a water-soluble intracellular enzyme is first produced to connect the bacterial cell membrane and the polyurethane material, and then an extracellular enzyme is secreted to destroy the polyurethane substrate, and the macromolecules are decomposed into small molecules that can be directly metabolized by bacteria.

[0005] However, the existing degradation strains have obvious limitations. Most of the reported strains can only degrade polyurethane simulators (such as water-based polyurethane dispersion Impranil DLN), and have limited ability to degrade actual polyurethane plastic films. For example, although a variety of Cladosporium 、 Aspergillus and Penicillium fungi can degrade Impranil DLN, the number of strains that can effectively degrade real polyurethane plastics is small. Therefore, in the face of the pressure of waste disposal brought by the wide application of water-based polyurethane and thermoplastic polyurethane elastomer, and the limitations of existing degradation technology, developing a strain that can simultaneously and efficiently degrade water-based polyurethane and thermoplastic polyurethane elastomer, adapt to various environmental conditions, and has high degradation efficiency, is of great practical significance and urgent technical need to solve the environmental pollution problem of polyurethane waste and promote the green recycling of polyurethane materials. It is also the core background and starting point of the development of this patent technology. SUMMARY

[0006] The present application is to solve the technical difficulty that the existing technology cannot simultaneously degrade water-based polyurethane and thermoplastic polyurethane elastomer efficiently in the field of polyurethane waste disposal, and to provide a polyurethane degrading strain with wide application range, high degradation efficiency and strong environmental adaptability, in order to break through the limitations of traditional polyurethane waste disposal methods and promote the green recycling of polyurethane materials.

[0007] The present application provides a strain capable of degrading polyurethane, which is composed of Pseudomonas raoultii (Pseudomonas raoultii) decomposing ornithine, Raoultella ornithinolytica Klebsiella pneumoniae (Klebsiella pneumoniae), Klebsiella pneumoniae Kosakia rhizicola (Kosakia rhizicola), and Kosakonia radicincitans Acidovorax xylosoxidans (Acidovorax xylosoxidans). Achromobacter xylosoxidans The present application also provides a use of the strain, which is for degrading water-based polyurethane. ​

[0008] The application also provides the use of the bacterial flora in degrading thermoplastic polyurethane elastomer.

[0009] The application also provides a method for degrading waterborne polyurethane, which is degrading by using the bacterial flora.

[0010] The application screens polyurethane degrading bacterial flora from collected soil samples, which can simultaneously and efficiently degrade waterborne polyurethane (Impranil DLN) and thermoplastic polyurethane elastomer (TPU) with large differences in chemical structure, greatly simplifies the process, reduces the operation cost, replaces the traditional landfill incineration, helps the green recycling of polyurethane, and has important practical significance for solving the environmental pollution problem of polyurethane waste and promoting the green recycling of polyurethane materials. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a standard curve diagram of waterborne polyurethane; Figure 2 is a degradation effect diagram of the A bacterial flora on waterborne polyurethane; Figure 3 is a scanning electron microscope diagram of the A bacterial flora degrading thermoplastic polyurethane elastomer film; Figure 4 is an infrared spectrum diagram of the A bacterial flora degrading thermoplastic polyurethane elastomer film; Figure 5 is a metabolic product detection result diagram of the A bacterial flora degrading thermoplastic polyurethane elastomer film; Figure 6 is a quantitative detection diagram of extracellular enzyme activity of the A bacterial flora. DETAILED DESCRIPTION

[0012] The application will be described in detail below through specific examples and drawings Example 1: Screening of polyurethane degrading bacteria (1) Sample collection The soil samples were collected at a garbage landfill site at the border between Chutang Township and Guanwangmiao Township of Suiping County, Zhumadian City, Henan Province, using a five-point sampling method and were stored in a laboratory refrigerator at 4℃.

[0013] (2) Sample enrichment 2g of soil samples were respectively weighed and added into 30% LB liquid medium for culture at 30℃, so as to rapidly proliferate the microorganisms in the soil which are resistant to pollution environment and have polyurethane degradation potential, thereby laying a foundation for subsequent screening of target functional bacterial flora.

[0014] The above LB (Luria-Bertani) medium: sodium chloride 10g / L, tryptone 10g / L, yeast extract 5g / L, pH 7.5.

[0015] (3) Screening of degrading bacteria The seed liquid in the growth phase described in (2) above was inoculated into an inorganic salt screening medium containing 0.5% aqueous polyurethane, and cultured at 30°C. The residual aqueous polyurethane content in the shake flask was detected by sampling, and the bacterial population with the highest aqueous polyurethane degradation efficiency was screened.

[0016] The inorganic salt screening medium described above: 0.7 g / L K2HPO4, 0.7 g / L KH2PO4, 0.005 g / L NaCl, 0.7 g / L MgSO4·7H2O, 1.34 g / L NH4Cl, 0.002 g / L FeSO4·7H2O, 0.002 g / L ZnSO4·7H2O, 0.001 g / L MnSO4·H2O; 1000 mL distilled water; sterilized at 121°C for 30 min, then 0.5% Impranil DLN was added.

[0017] Example 2: Preparation of TPU film TPU particles were weighed and dissolved in a beaker. Tetrahydrofuran was added in a fume hood, and after the TPU particles were dissolved, the mixture was poured into a glass culture dish and left to stand to allow the tetrahydrofuran to evaporate.

[0018] Example 3: Characterization of TPU surface by scanning electron microscopy (SEM) SEM was used to observe the changes in the surface morphology of the TPU film, and to characterize the degradation effect of the A bacterial population on the TPU film. After 40 days of treatment at 30°C under laboratory shake flask conditions, the polyester TPU film with increased complexity was observed by SEM. As shown in Figure 3 C and D, the TPU material treated with the A bacterial population showed obvious erosion on the surface, and the erosion covered the entire film, including delamination and cracks. In contrast, the surface of the untreated TPU material Figure 3 A and B can be seen to remain smooth and intact, with only mechanical cracks appearing Example 4: Fourier transform infrared spectroscopy (FTIR) analysis of functional group changes in TPU film FTIR absorbs light of different wavelengths according to the functional groups and chemical bond vibrations of the TPU film, and thus analyzes the degradation ability of the A bacterial population, as shown in Figure 4 As shown in -1 , compared with the control group, the experimental group treated with the A bacterial population at 30°C for 40 days showed a significant decrease in C=O stretching vibration at 1727 cm -1 , a slight decrease in urea / polyurethane N-H bending at 1530 cm -1 , and a slight decrease in C-N stretching vibration at 1241 cm -1The increase of O-H and N-H stretching vibration indicated the hydrolysis of ester bond and urethane bond, which confirmed the ability of TPU degradation.

[0019] Example 5 Metabolite detection of TPU film by GC-MS To further clarify the degradation intermediates of TPU material, the soluble compounds released into the supernatant were identified by GC-MS, as shown in Figure 2. Figure 5 As shown in Figure 2, after the treatment of A group, TPU produced 2,4-di-tert-butyl phenol and the breakage of urethane bond; the formation of urethane bond was particularly attributed to the degradation of TPU soft segment, and 2,4-di-tert-butyl phenol was often used as a stabilizer in the synthesis process of TPU material, which indicated that A group had a certain depolymerization effect on TPU film.

[0020] Example 6 Quantitative detection of extracellular enzyme activity of TSY1 strain To determine the enzyme activity of A group, after the incubation of TPU film and no TPU film at 30℃ for 2d, the supernatant was used to evaluate the extracellular enzyme activity after centrifugation at 10,000xg for 10 min at 4℃. Figure 6 As can be seen from Table 1, the esterase and protease activities in the medium containing TPU film were higher than those of the bacterial agent alone, and the activity of esterase was the highest.

Claims

1. A consortium of degradable polyurethanes, characterized in that, The bacterial flora consists of Ornithinibacter raoultii Raoultella ornithinolytica , Klebsiella pneumoniae Klebsiella pneumoniae , Kordia rugato-radix Kosakonia radicincitans and Acidovorax xylosoxidans Achromobacter xylosoxidans .

2. Use of the bacterial consortium of claim 1 for degrading waterborne polyurethanes.

3. Use of the bacterial consortium of claim 1 for degrading thermoplastic polyurethane elastomers.

4. A method of degrading an aqueous polyurethane, characterized by, The method is degrading using the bacterial consortium of claim 1.

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