A bioelectrochemical system and method for enhancing plastic degradation

Abstract

The present invention provides a bioelectrochemical system and method for enhancing plastic degradation. The method of the present invention utilizes a bioelectrochemical system to couple electroactive plastic degrading bacteria to enhance the degradation of plastics in the environment. The device is composed of an anode system and a cathode system. The electroactive plastic degrading bacteria and the plastic are both located in the anode system and the cathode system. The anode system is placed in a sedimentary layer in an actual environment, and the cathode system floats on the water surface. The two are connected by wires and resistors and fixed with a barrel. The electroactive plastic degrading bacteria can not only degrade plastics, but also provide electrons to the bioelectrochemical system, promote electron transfer in the bioelectrochemical system, and further accelerate the degradation of plastics. Under the dual strengthening effects of the bioelectrochemical system and the electroactive plastic degrading bacteria, the method realizes the enhanced degradation of plastics. The method has low cost and low energy consumption. It can also recycle electrical energy while accelerating the restoration of the water environment, and has good economic benefits and application prospects.

Description

Technical field:

[0001] The invention relates to the field of engineering technology, and in particular to a bioelectrochemical system and method for enhancing plastic degradation. Background technology:

[0002] Since the large-scale production of plastic products in the 1940s, plastic products have become an indispensable part of modern society. However, only about 10% of plastics can be recycled each year, and the rest are incinerated, buried, or even directly discarded into the ecological environment. They enter different environments such as seawater, lakes, soil, and sediments through various channels, seriously threatening the global ecological environment security and life health.

[0003] Plastics are chemically stable and difficult to remove from the natural environment. Traditional methods such as incineration and thermal degradation not only have harsh reaction conditions, high treatment costs, and are prone to secondary pollution, but microbial degradation methods have the advantages of mild reaction conditions, simple operation, and no secondary pollution, providing a new green and environmentally friendly way to solve the problem of plastic pollution.

[0004] Electroactive microorganisms can use their unique extracellular electron transfer function to couple the degradation and transformation of pollutants. The bioelectrochemical system, with electroactive microorganisms as the core driving force, has great potential to achieve the synergistic effect of pollutant degradation and electricity production simultaneously. For example, Xu Meiying and others invented a bioelectrochemical system for enhancing the degradation of polybrominated diphenyl ethers (patent number: ZL201010220381.6) and a bioelectrochemical system for enhancing the degradation of azo dyes (patent number: ZL 201010220362.3), which simultaneously achieved pollutant degradation and electricity production. Although it has been found that bioelectrochemical systems can enhance the degradation of a variety of pollutants, there are very few reports on bioelectrochemical systems enhancing plastic degradation. Recently, Xu Meiying and others screened a plastic-degrading bacterium Priestia aryabhattai Red22 (patent number: ZL202310784776.6) from discarded plastic bags, and found that the bacterium has strong electroactivity, can enhance plastic degradation in bioelectrochemical systems, and has broad application prospects in plastic pollution control. Summary of the invention:

[0005] In view of the increasingly severe situation of plastic pollution, the purpose of the present invention is to provide a bioelectrochemical system and method for enhancing plastic degradation, so as to provide cutting-edge scientific and technological support for solving the problem of plastic pollution.

[0006] The bioelectrochemical system for enhanced plastic degradation of the present invention comprises an anode system and a cathode system. The anode system comprises an anode electrode (1) and a plastic sheet (4) to be degraded on or around the anode electrode. The cathode system comprises a cathode electrode (2) and a plastic sheet (4) to be degraded on or around the cathode electrode. The anode electrode and / or the cathode electrode are also attached with an electroactive plastic degrading functional microbial community (3). The anode electrode and the cathode electrode are electrically connected via an electric wire (6).

[0007] Preferably, the anode electrode is composed of one or two of a carbon plate, a carbon felt, a carbon cloth, and a carbon brush.

[0008] Preferably, the cathode system is carbon felt or carbon cloth or a combination thereof.

[0009] Preferably, the plastic sheet is composed of one or more of polystyrene, polyethylene and polyvinyl chloride.

[0010] Preferably, the electroactive plastic degrading functional microbial community is a microbial community containing the plastic degrading bacteria Priestia aryabhattai Red22, and the Priestia aryabhattai Red22 has a preservation number of GDMCC No:63428.

[0011] The present invention also provides a method for degrading plastics using a bioelectrochemical system, which is to utilize the bioelectrochemical system to couple electroactive plastic degrading bacteria to enhance the degradation of plastics in an environment. Specifically, electroactive plastic degrading bacteria are added to the degradation system of the bioelectrochemical system.

[0012] Preferably, the anode electrode and the cathode electrode are attached with a biofilm of an electroactive plastic-degrading functional microbial community by immersion or cyclic inoculation, and then the anode system is placed in an aquatic environment or sediment layer containing plastic sheets, and the cathode system floats on the water surface, and the anode electrode and the cathode electrode are connected and fixed by a support rod.

[0013] Preferably, there is also a barrel, and the bioelectrochemical system is fixed on the barrel.

[0014] Preferably, the water environment containing the plastic sheets is a river, a fish pond, a secondary sedimentation tank of a sewage or wastewater treatment system, an organic solid waste treatment system, etc.

[0015] Preferably, the anode electrode and the cathode electrode are immersed or circulated to form biofilms, so that the biofilms of the electroactive plastic-degrading functional microorganisms are attached, and the OD of the bacterial solution of Priestia aryabhattai Red22 used for immersion or circulated inoculation is600 The temperature is 0.8-1.8, and the film formation time by immersion or circulation inoculation is 48-72 hours.

[0016] The present invention provides a bioelectrochemical system and method for enhancing plastic degradation. The method of the present invention utilizes a bioelectrochemical device coupled with electroactive plastic-degrading bacteria to enhance the degradation of plastics in an environment. Electroactive plastic-degrading bacteria can not only degrade plastics, but also provide electrons to the bioelectrochemical device, promote electron transfer in the reaction system, and further accelerate the degradation of plastics. Under the dual strengthening effects of the bioelectrochemical system and the electroactive plastic-degrading bacteria, the device achieves enhanced degradation of plastics. In addition, the plastic pollution control method provided by the present invention has low cost and low energy consumption, and can also recycle electrical energy while accelerating the restoration of the water environment, and has good economic benefits and application prospects.

[0017] Priestia aryabhattai Red22, the bacteria has been deposited in Guangdong Microbiological Culture Collection Center (GDMCC) on May 8, 2023, address: Building 59, No. 100, Xianlie Middle Road, Yuexiu District, Guangzhou City, Guangdong Province, Postal Code: 510070, and the deposit number is GDMCC No: 63428. The strain is disclosed in the patent: Application No.: 202310784776.6, the invention name: A polystyrene plastic degrading bacteria and a method for degrading plastics using the same Chinese patent application. Description of the drawings:

[0018] Figure 1 Schematic diagram of the device of the present invention; reference numerals: 1. anode carbon plate, 2. cathode carbon felt, 3. electroactive plastic degrading bacteria, 4. plastic sheet, 5. resistor, 6. wire, 7. screw, 8. plastic rod, 9. acrylic barrel

[0019] Figure 2 The power density diagram of the device described in Example 1 of the present invention when it is operated for different days;

[0020] Figure 3 This is a graph showing the mass loss of a polystyrene plastic sheet after the device described in Example 1 of the present invention has been running for 100 days (wherein an open circuit means that the anode and cathode are not connected, and a closed circuit means that the anode and cathode are connected via a resistor and a wire);

[0021] Figure 4 This is a SEM comparison image of a polystyrene plastic sheet after the device described in Example 1 of the present invention has been running for 100 days (wherein an open circuit means that the anode and cathode are not connected, and a closed circuit means that the anode and cathode are connected via a resistor and a wire);

[0022] Figure 5This is a GPC relative molecular weight change chart of a polystyrene plastic sheet after the device described in Example 1 of the present invention has been running for 100 days (wherein an open circuit means that the anode and cathode are not connected, and a closed circuit means that the anode and cathode are connected via a resistor and a wire). Specific implementation method:

[0023] The present invention is further described below in conjunction with the examples. The examples are intended to illustrate the present invention, but are not intended to limit the present invention in any form.

[0024] Example 1

[0025] 1. Assembly and preparation of a bio-electrochemical system enhanced plastic in-situ degradation device:

[0026] (1) Ecotoxicological verification of Priesteria afroyi Red22: The device in the present invention is operated in an actual environment, so the bacterial agent used in the device must not be toxic to the ecology in the actual environment. Therefore, the present invention must first conduct an ecotoxicological test on the bacterial agent added to the actual environment. The electroactive plastic degrading bacteria Priesteria afroyi Red22 were tested for acute toxicity to zebrafish embryos, Lunaea horneda, and zebrafish, as well as activity inhibition to Daphnia magna. The specific operation is as follows: Under specified conditions, zebrafish embryos, Lunaea horneda, zebrafish, and Daphnia magna were exposed to aqueous solutions containing different concentrations of the test substance. The test cycle was 96 hours. The mortality rate or the number of organisms that lost their ability to move was recorded at 24 hours, 48 ​​hours, 72 hours, and 96 hours, and the test substance concentration LC at which 50% of the test organisms died was determined. 50 and 50% activity inhibition loading rate EC 50 The specific test results are shown in Table 1. The half-lethal concentration and active inhibition rate of Priesteria axyri Red22 against zebrafish embryos, Algae, zebrafish and Daphnia magna were all greater than 10 6 cfu / mL, which proves that the electroactive plastic-degrading bacteria Priesteria africana Red22 has no obvious toxic effect on algae, fish and their embryos in the actual environment, is environmentally friendly, and can be added to the actual ecological environment.

[0027] Table 1 shows the ecotoxicological test results of Priesteria axyri Red22 described in Example 1 of the present invention

[0028]

[0029] (2) Preparation of polystyrene plastic sheets: In order to facilitate the characterization of plastics and the accuracy of recycling and weighing, this experiment uses polystyrene plastic sheets for degradation experiments. Add polystyrene powder to xylene (3g / mL), stir mechanically and leave it overnight to dissolve, then absorb 5 ml of transparent liquid and spread it on a 90mm glass culture dish to solidify for 36 hours, then cut the film-formed polystyrene film into small pieces of 10*10mm, clean them with 75% ethanol and sterile water respectively, and dry them naturally, then string the plastic sheets together with a rope and tie them to the anode and cathode of the device.

[0030] (3) Activation and fermentation culture of electroactive plastic-degrading bacteria: Inoculate Priesteria aeruginosa Red22 on LB agar plates and culture at 30°C for 24 hours until the colonies mature. Pick a single colony of the activated Priesteria aeruginosa Red22 and inoculate it into 100 mL of LB liquid culture medium for constant temperature shaking culture. Culture it at 30°C and 180 rpm for 16 hours to obtain seed liquid. Inoculate the seed culture liquid into 5 L of LB liquid culture medium at a volume ratio of 2% inoculation rate for fermentation culture. After constant temperature shaking culture at 30°C and 180 rpm for 48 hours, continue to add 2 L of LB culture medium for standby use, so that the final OD of the fermentation liquid is 600 Around 0.8.

[0031] (4) Assembly of the anode system: The anode electrode is composed of a 20*15*1 cm carbon plate and a 15*10*0.5 cm carbon felt. Then, a string of 9 plastic sheets is tied to the surface of the anode carbon felt. Then, a "V"-shaped acrylic plate is fixed to the side of the anode with plastic. Finally, the assembled anode is immersed in the fermentation broth of the above-mentioned electroactive plastic-degrading bacteria Priesteria aegypti Red22 for 48 hours.

[0032] (5) Assembly of cathode system: The cathode electrode is a 20*15*0.5 cm carbon felt. A string of 9 plastic sheets is then tied to the surface of the cathode carbon felt. The carbon felt is then tied to a 20*15*2 cm foam board with titanium wire. Finally, the assembled cathode is immersed in the fermentation broth of the electroactive plastic-degrading bacteria Apricotella Red22 for 48 hours.

[0033] The carbon felt in the anode system and the carbon felt in the cathode system are connected through wires and external resistors (100-2000Ω) on the wires. The connection between the cathode and cathode and the wires is sealed with epoxy resin, and the exposed part of the wire is also covered and sealed with epoxy resin.

[0034] (6) Assemble and operate the bioelectrochemical system in the actual environment: Move the anode system and cathode system prepared above to the river site, and select a river with a lower water level for on-site assembly of the device. First, fix the anode system and the support system with screws, then insert the anode system into the sediment layer of the river, adjust the length of the wire according to the water level, then float the cathode system on the water surface (with the foam facing upwards), and finally insert the supporting acrylic barrel into the sediment layer to protect the entire bioelectrochemical system. The specific device diagram is shown in the figure. Figure 1 As shown. The assembled system consists of an anode system, a cathode system, a connection system and a support system. The anode system includes an anode electrode (1) and a plastic sheet to be degraded (4) on the surface of the anode electrode, the cathode system includes a cathode electrode (2) and a plastic sheet to be degraded (4) on the surface of the cathode electrode, the connection system includes a resistor (5) and a wire (6), and the anode electrode or the cathode electrode is also attached with an electroactive plastic degrading functional microbial community (3), the support system includes a screw (7), a support rod (8) and a barrel (9), the two ends of the screw are connected to fix the adjacent anode electrodes, the support rod connects and fixes the anode electrode and the cathode electrode, and the entire anode system and cathode system are placed in a barrel. In this embodiment, two bioelectrochemical systems are placed in a barrel, one is an open circuit control group (the anode and the cathode are not connected), and the other is a closed circuit experimental group (the anode and the cathode are connected through a resistor and a wire). In addition, a set of anode systems and cathode systems without electroactive plastic degrading functional microbial communities are inserted into an open water body without a barrel for comparison.

[0035] 2. A bio-electrochemical system to enhance the effect of plastic in-situ degradation device on plastic degradation:

[0036] (1) Power generation capacity of the device: Generally, the stronger the power generation capacity of a bioelectrochemical device, the stronger its pollutant degradation capacity. Power density is one of the important parameters of the device's power output. The power density curve can determine the power generation performance of the system and also reflect the size of the system's electron transfer capacity. The measurement method is to adjust the size of the external resistor to change the current in the SMFC circuit, and obtain a relationship diagram between voltage and current, and further obtain a power density curve. Figure 2 The power density diagram of the bio-electrochemical system enhanced plastic in-situ degradation device at different operating times can be seen from the figure. No matter what stage the device is in, the power density of the device with electroactive plastic degrading bacteria Priesteria axyri Red22 is greater than that of the device without Priesteria axyri Red22. Moreover, the power density of the device with Priesteria axyri Red22 added to the anode is still at a high level after 90 days of operation, and the maximum power can reach 33.06mW·m -2However, the power density of the device without Priesteria afroicola Red22 had decreased on the 75th day. This shows that the addition of Priesteria afroicola Red22 to the device can significantly promote the electron transfer ability of SMFC and significantly extend the effective operation time of the bioelectrochemical system, thereby improving the degradation ability of plastics.

[0037] (2) Plastic sheet mass loss test: After the device has been running for 100 days, all the polystyrene plastic sheets in the anode and cathode are taken out, and then ultrasonically cleaned with 2% SDS and 75% anhydrous ethanol respectively to remove the biofilm on the surface of the polystyrene plastic sheets, and then vacuum dried. The dried polystyrene plastic sheets are weighed and their weight loss rate is calculated. Plastic sheet weight loss rate (%) = (initial mass of plastic sheet - mass after degradation) ÷ initial mass × 100%. Figure 3 It can be seen from the weight loss rate data that after 100 days of operation, the weight loss rate of plastics in all closed-circuit devices was higher than that in open-circuit devices. The weight loss rate of plastic sheets with Priesteria Affymetrix Red22 added to the anode alone reached 7.1%, and the weight loss rate of plastic sheets with Priesteria Affymetrix Red22 added to the cathode alone reached 6.9%. The weight loss rate of plastic sheets in open water was only 3.2%. This shows that the bioelectrochemical device with Priesteria Affymetrix Red22 can promote the degradation of polystyrene plastic sheets.

[0038] (3) Changes in the surface morphology of the degraded plastic sheet: After the degraded polystyrene plastic sheet was cleaned and dried, its surface morphology was observed using a scanning electron microscope (SEM). Figure 4 As shown in the figure, after 100 days of degradation, some obvious irregular grooves or pits appeared on the surface of the polystyrene plastic sheet in the bioelectrochemical device with Priesteria aeruginosa Red22, while the surface of the polystyrene plastic sheet in the open water was relatively smooth, indicating that the device had a significant degradation effect on the polystyrene plastic sheet.

[0039] (4) Changes in molecular weight of polystyrene before and after degradation: Gel permeation chromatography (GPC) was used to measure the changes in molecular weight of polystyrene plastic sheets before and after degradation after the device was operated for 100 days. The results are as follows: Figure 5 As shown in the figure, the mass average molecular weight (Mw) and number average molecular weight (Mn) of the polystyrene plastic sheet in the bioelectrochemical device with Priesteria aeruginosa Red22 added after 100 days of degradation are lower than those before degradation, while the molecular weight distribution index (PDI=Mw / Mn) after degradation is higher than that before degradation. The higher the PDI value, the wider the molecular weight distribution of the polymer and the higher the degree of depolymerization. Therefore, the bioelectrochemical device with Priesteria aeruginosa Red22 further added has a higher degradation ability for polystyrene and can degrade the long chains of polystyrene into products with shorter carbon chains.

[0040] Comparative Example 1

[0041] This comparative example provides a conventional bioelectrochemical method for degrading plastics. The difference between this method and Example 1 is that the electroactive plastic-degrading bacteria Apricotella Red22 are not added to the anode system and the cathode system in the device.

[0042] The comparative method was used to degrade plastics. The results showed that the weight loss rate of polystyrene plastic sheets was only 4.6% ( Figure 3 ), and the maximum power of the device after 90 days of operation is only 11.88mW·m -2 ( Figure 2 ).

Claims

1. A method for degrading plastics using a bioelectrochemical system for enhanced plastic degradation, characterized in that: The anode electrode and the cathode electrode are immersed or circulated to form biofilms with electroactive plastic-degrading functional microbial communities, and then the anode system is placed in a water environment or sediment layer containing plastic sheets, and the cathode system floats on the water surface, and the anode electrode and the cathode electrode are connected and fixed by a support rod; The bioelectrochemical system for enhancing plastic degradation comprises an anode system and a cathode system. The anode system comprises an anode electrode (1) and a plastic sheet to be degraded (4) on or around the anode electrode. The cathode system comprises a cathode electrode (2) and a plastic sheet to be degraded (4) on or around the cathode electrode. The anode electrode and the cathode electrode are also attached with an electroactive plastic degrading functional microbial community (3). The anode electrode and the cathode electrode are electrically connected via an electric wire (6). The electroactive plastic degrading functional microbial community comprises plastic degrading bacteria Priesteria aegypti ( Priestia aryabhattai ) Red22 microbiota, the A. aegypti ( Priestia aryabhattai ) Red22, its deposit number is GDMCC No: 63428.

2. The method according to claim 1, characterized in that The anode electrode is composed of one or two of a carbon plate, carbon felt, carbon cloth and a carbon brush.

3. The method according to claim 1, characterized in that The cathode system is composed of carbon felt or carbon cloth or both.

4. The method according to claim 1, characterized in that The plastic sheet is composed of one or more of polystyrene, polyethylene and polyvinyl chloride.

5. The method according to claim 1, 2, 3 or 4, characterized in that: A round barrel is also provided, on which the bioelectrochemical system is fixed.

6. The method according to claim 1, 2, 3 or 4, characterized in that: The water environment containing plastic sheets is a river, a fish pond, a sewage or a secondary sedimentation tank of a wastewater treatment system.

7. The method according to claim 1, 2, 3 or 4, characterized in that: The anode electrode and the cathode electrode are immersed or circulated to form biofilms, so that the biofilms of the electroactive plastic-degrading functional microbial community are attached. The apricot bacteria ( Priestia aryabhattai ) Red22 bacterial solution OD 600 The temperature is 0.8-1.8, and the film formation time by immersion or circulation inoculation is 48-72 hours.

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