Method for regulating polyhydroxyalkanoate production by mixed bacterial population

Abstract

The application discloses a kind of mixed flora production polyhydroxyalkanoate's regulation method, comprising the following steps: obtaining the mixed flora with the ability of synthesizing polyhydroxyalkanoate;The mixed flora obtained is inoculated into reactor and is cultivated, and in the cultivation process, according to the aeration amount, the synthesis process of polyhydroxyalkanoate is regulated.Compared with conventional synthesis method, according to the aeration amount, the aeration operation window of PHA synthesis ability, biomass concentration and PHA total output is obtained in the application method, and then the aeration amount can be adjusted, the synthesis process of polyhydroxyalkanoate is regulated, the PHA accounts for cell dry weight ratio, biological concentration and PHA yield are improved, especially, by optimizing aeration amount, while reducing energy consumption, PHA yield can also be significantly improved, with the advantages of convenient operation, low energy consumption, easy to improve PHA yield, high use value, good application prospect.

Description

Technical Field

[0001] This invention belongs to the fields of environmental biotechnology and biodegradable plastic synthesis technology, and relates to a method for regulating the production of polyhydroxy fatty acid esters by mixed bacterial communities. Background Technology

[0002] Polyhydroxyalkanoates (PHAs) are intracellular carbon source storage substances synthesized by microorganisms under conditions of abundant carbon sources and nutrient imbalance. They possess excellent biodegradability and biocompatibility, and are considered ideal materials to replace traditional petroleum-based plastics. Currently, the production of PHAs using mixed microbial communities is the mainstream approach to reduce production costs and realize the resource utilization of organic wastewater.

[0003] Existing PHA production processes using mixed microbial communities typically involve two stages: an enrichment stage—cultivating a stable microbial community with high PHA synthesis capacity through an "abundance-starvation" cycle; and a synthesis stage—using a fed-batch feeding model to allow the microbial community to continuously accumulate PHA under an abundant state. However, this method still faces technical bottlenecks such as low total PHA yield and high production costs.

[0004] Total PHA production is jointly determined by the PHA synthesis capacity per unit cell (PHA as a percentage of cell dry weight) and the total amount of active microorganisms (biomass) in the reactor. Studies have shown an inherent conflict between the metabolic conditions required to maximize cell storage capacity and maximize biomass accumulation: a high dissolved oxygen environment promotes rapid microbial proliferation to achieve high biomass, but often diverts more carbon flux to respiration energy production and growth metabolism, weakening PHA synthesis efficiency; while a low dissolved oxygen environment can induce PHA accumulation, microbial growth is inhibited, making it difficult to increase total production. Therefore, decoupling and synergistically optimizing these two competing indicators is a key scientific problem for improving total PHA production.

[0005] Aeration rate is a core engineering parameter directly affecting dissolved oxygen levels and is also a major source of energy consumption in bioreactors. However, existing studies mostly employ constant aeration strategies and use only the ratio of dissolved oxygen (DO) to cell dry weight as an evaluation indicator, without systematically examining the impact of aeration rate on biomass accumulation and the synergistic contribution of both to total yield. Furthermore, some researchers have attempted to optimize DO synthesis by controlling dissolved oxygen (DO) or volumetric oxygen mass transfer coefficient (KLa), but the accuracy of real-time monitoring of DO is easily affected by interference in low-concentration areas, and KLa, being a derived parameter, exhibits lag, making it difficult to directly guide engineering scale-up. In addition, aeration energy consumption typically accounts for 40%–70% of reactor operating costs, and currently, there is a lack of systematic control methods aimed at reducing aeration energy consumption while ensuring high DO production.

[0006] It is evident that existing mixed microbial PHA production methods suffer from technical drawbacks such as limited total output and high energy consumption, and the following technical issues still need to be addressed: (1) Existing technologies have not systematically revealed the differential effects of aeration on PHA synthesis capacity and biomass accumulation, and lack aeration regulation strategies based on the goal of maximizing total yield.

[0007] (2) Existing aeration control relies on indirect indicators such as DO or KLa, which have problems such as monitoring lag, difficulty in calibration, and poor scaleability.

[0008] (3) The existing process does not optimize energy saving and consumption reduction in conjunction with capacity improvement, and the aeration energy consumption accounts for a high proportion of the operating cost.

[0009] Therefore, how to regulate the synthesis process of polyhydroxy fatty acid esters produced by mixed microbial communities and achieve higher yields of PHA with lower energy consumption is an urgent problem to be solved at this stage.

[0010] For the reasons stated above, this invention is proposed. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for regulating the production of polyhydroxy fatty acid esters by mixed bacterial communities that is easy to operate, has low energy consumption, and facilitates the increase of PHA production.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for regulating the production of polyhydroxy fatty acid esters by mixed bacterial communities includes the following steps: S1. Enrich a mixed microbial community with the ability to synthesize polyhydroxy fatty acid esters, and adjust the composition and biological concentration of the microbial community according to the aeration rate during the enrichment process. S2. The mixed microbial community obtained in step S1 is inoculated into the reactor for cultivation. During the cultivation process, the synthesis process of polyhydroxy fatty acid ester is adjusted according to the aeration rate.

[0013] In a further improvement to the above-described control method, in step S2, the aeration rate is adjusted within a range of 0.1 L / m³. 3 ·min~1.0 L / m 3 ·min.

[0014] A further improvement to the above-mentioned control method is that, in step S2, during the synthesis of polyhydroxyalkanoates, the aeration rate is adjusted to 0.4 L / m³. 3 ·min~0.6 L / m 3 •min, used to increase the proportion of PHA in cell dry weight.

[0015] A further improvement to the above-mentioned control method is that, in step S2, during the synthesis of polyhydroxyalkanoates, the aeration rate is adjusted to 0.8 L / m³. 3 ·min~1.0 L / m 3•min, used to increase biological concentration.

[0016] A further improvement to the above-mentioned control method is that, in step S2, during the synthesis of polyhydroxyalkanoates, the aeration rate is adjusted to 0.6 L / m³. 3 ·min~1.0 L / m 3 •min, used to increase PHA production.

[0017] In a further improvement to the above-mentioned control method, in step S2, when the reactor volume or configuration changes during the adjustment of the aeration rate, the equivalent aeration intensity or oxygen mass transfer coefficient corresponding to the aeration rate is maintained to achieve amplification.

[0018] The above-mentioned control method is further improved in step S2, which includes feedback control of the aeration volume based on the external circuit current signal during the adjustment process. The feedback control is as follows: a current change threshold is set, which is 10% to 30% of the average current value under normal operating conditions. When the current continuously decreases beyond the set current change threshold within a set time, the aeration volume is reduced. If the aeration volume exceeds the required adjustment range, the cultivation is stopped. When the current continuously rises beyond the set current change threshold within a set time, the aeration volume is increased. If the aeration volume exceeds the required adjustment range, the cultivation is stopped. The set time is 1 / 20 to 1 / 10 of one hydraulic retention time in the reactor.

[0019] In a further improvement to the above-mentioned control method, the external circuit current signal is detected by an external circuit monitoring system; the external circuit monitoring system includes a working electrode and a counter electrode disposed inside the reactor, as well as a potentiostat and a data recording device connected to the working electrode and the counter electrode; the constant voltage applied by the potentiostat is +0.6 V relative to the counter electrode.

[0020] The above-mentioned control method is further improved in step S1, which involves obtaining a mixed microbial community capable of synthesizing polyhydroxyalkanoates (PHA). This includes the following steps: using activated sludge as an inoculum, operating the system in a sequencing batch reactor (SBR) in an alternating "abundance-starvation" mode, adding enrichment substrates containing carbon, nitrogen, and phosphorus for cultivation, and continuing cultivation until the PHA synthesis capacity of the microbial community stabilizes, thus obtaining a mixed microbial community capable of synthesizing PHA; the cultivation process also includes aeration of the system; the aeration rate during the aeration process is controlled at 0.1 L / m³. 3 ·min~1.0 L / m 3 ·min.

[0021] In a further improvement to the above-mentioned control method, in step S1, the substrate for the enrichment stage is an anaerobic fermentation broth containing mixed fatty acids; the mixed fatty acids are acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid; the total COD concentration in the substrate for the enrichment stage is 2.0 g / L to 4.0 g / L, and the carbon-nitrogen mass ratio is 15 to 30:1.

[0022] In a further improvement to the above-mentioned control method, step S2 further includes the addition of carbon, nitrogen, and phosphorus source substrates during the cultivation process; the carbon, nitrogen, and phosphorus source substrates are anaerobic fermentation broth containing mixed fatty acids; the mixed fatty acids are acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid; the total COD concentration in the carbon, nitrogen, and phosphorus source substrates is 8.0 g / L to 15.0 g / L, and the carbon-nitrogen mass ratio is 15 to 30:1.

[0023] The above-mentioned regulation method is further improved in step S2, where the carbon source substrate is added during the cultivation process as follows: when the pH value of the reaction system rises to 9.5±0.5 and remains unchanged for 5 min, a carbon source substrate concentrated 2 to 4 times is added to maintain the microorganisms in a state of abundant metabolism.

[0024] Compared with the prior art, the advantages of the present invention are as follows: (1) To address the technical shortcomings of existing synthesis methods, such as limited total yield and high energy consumption, this invention creatively proposes a method for regulating the production of polyhydroxyalkanoates (PHA) by mixed microbial communities. Based on a systematic aeration gradient experiment, it reveals for the first time the nonlinear and differential regulatory law of aeration on the PHA synthesis capacity and biomass accumulation of mixed microbial communities. During cultivation, the synthesis process of PHA is regulated according to the aeration rate. Based on the aeration rate, an aeration operation window for PHA synthesis capacity, biomass concentration, and total PHA yield is obtained. Furthermore, by adjusting the aeration rate, the PHA percentage in cell dry weight, biomass concentration, and PHA yield can be increased. This invention's regulation method can control the synthesis process of PHA by adjusting the aeration rate, significantly increasing PHA yield while reducing energy consumption. It has advantages such as convenient operation, low energy consumption, and ease of increasing PHA yield, making it highly valuable and promising for application.

[0025] (2) In the process of adjusting the aeration volume, the aeration volume is also adjusted by feedback control based on the external circuit current signal. By constructing a bioelectrochemical system coupled with external circuit monitoring, the activity of the microbial electron transport chain is tracked in real time, providing online physiological indication signals for aeration control, thereby establishing a new high-yield and energy-saving PHA process that can be quantified and scaled up. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] Figure 1 The graph shows the effects of different aeration rates on the percentage of PHA in cell dry weight, biomass weight, and total PHA production under different aeration conditions in Example 1 of this invention.

[0028] Figure 2 This is a graph showing the change in current formed by electrons leaking into the circuit system under different aeration conditions in Embodiment 1 of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0030] In the following embodiments of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0031] Example 1 A method for regulating polyhydroxyalkanoate (PHA) production by mixed microbial communities, specifically involving the coupling regulation of aeration volume and external circuit during the mixed microbial community enrichment and domestication stage and PHA synthesis, includes the following steps: (1) Take the residual activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant, pass it through a 40-mesh sieve to remove large particulate impurities, let it settle for 24 h, discard the supernatant, and obtain concentrated sludge. The concentration of total suspended solids (TSS) in the concentrated sludge was measured to be 31.2 g / L and the concentration of volatile suspended solids (VSS) was 15.4 g / L.

[0032] (2) Using activated sludge as the inoculum, the sequencing batch reactor was operated in an alternating "abundance-starvation" mode, and enrichment substrates containing carbon, nitrogen, and phosphorus were added for cultivation. The operation continued until the ability of the bacterial community to synthesize polyhydroxy fatty acids (PHFAs) stabilized, resulting in a mixed bacterial community capable of synthesizing PHFAs. Specifically: A sequencing batch reactor (SBR) with an effective volume of 2 L was used. The reactor bottom was equipped with microporous aeration sand heads and a mechanical agitator. 500 mL of the aforementioned concentrated sludge was added to the reactor, and the volume was brought up to 2 L with enrichment stage substrate. The reactor was operated in a constant temperature chamber at 25°C, with a stirring speed of 300 r / min, a hydraulic retention time of 24 h, and a sludge retention time of 10 d. The operating cycle was 24 h, including: instantaneous influent (5 min), aeration reaction (23 h 20 min), settling (30 min), and effluent (5 min). After settling, the supernatant was discharged, with a discharge volume of approximately 80% of the reactor's effective volume (i.e., 1.6 L). Simultaneously, 1 / 10 of the activated sludge was discarded to maintain the sludge retention time.

[0033] Enrichment stage substrate formulation (per liter): anaerobic fermentation broth containing mixed fatty acids (acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid), with a total COD concentration of 2.562 g. The substrate pH was adjusted to 6.8–7.2, and the carbon, nitrogen, and phosphorus mass ratio in the reactor was controlled at 100:5:1. After more than 150 continuous cycles, a stable enriched PHA-synthesizing mixed microbial community was obtained, which is a mixed microbial community capable of synthesizing polyhydroxyalkanoates. Under standard testing conditions, the proportion of PHA in the cell dry weight of this microbial community remained stable at 40%–45%.

[0034] (3) Take 200 mL of the stable mixed bacterial culture (PHA synthetic mixed bacterial community) from step (2) and inoculate it into a fed-batch reactor (FBR) with an effective volume of 0.4 L. At the same time, add 200 mL of the carbon, nitrogen, and phosphorus source substrates used in step (1). The FBR reactor is equipped with a mass flow controller (accuracy ±0.01 L / min), an online pH meter, a dissolved oxygen electrode, and an external circuit monitoring system. The aeration rate is controlled at 0.8 L / m³ by the mass flow controller. 3 •min, to carry out synthesis culture, during which the growth of mixed bacterial community is promoted and a large amount of PHA is synthesized by the mixed bacterial community. During the synthesis culture, the pH is measured in real time. When the pH rises to 9.5±0.5 and remains unchanged for 5min, it is used as a sign that the substrate consumption is complete. At this time, PHA synthesis substrate (a 4-fold concentrated enrichment stage substrate) is added.

[0035] In this step, the carbon, nitrogen, and phosphorus source substrate is an anaerobic fermentation broth containing mixed fatty acids, namely acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid. The total COD concentration in this carbon, nitrogen, and phosphorus source substrate is 10.248 g / L, and the mass ratio of carbon, nitrogen, and phosphorus is 100:5:1.

[0036] In this step, the external circuit monitoring system includes a working electrode and a counter electrode disposed inside the reactor, as well as a potentiostat and a data recording device connected to the working electrode and the counter electrode. The working electrode is a carbon felt (3 cm × 3 cm), and the counter electrode is a graphite rod. A constant voltage of +0.6 V relative to the counter electrode is applied to the working electrode by the potentiostat, and the external circuit current signal is continuously recorded at a sampling frequency of 1 Hz.

[0037] During the adjustment of aeration rate, an external circuit monitoring system is used to detect the external circuit current signal, and the aeration rate is adjusted based on the external circuit current signal. The feedback adjustment involves setting a current change threshold, which is 20% of the average current value under normal operating conditions. When the current fluctuates and decreases below the set current change threshold within a set time, the aeration rate is reduced. If the aeration rate exceeds the required adjustment range (e.g., below 0.6 L / m³), the aeration rate is further reduced. 3 If the current fluctuates and rises above the set current change threshold within a set time (·min), then stop the incubation. If the current fluctuates and rises above the set current change threshold within a set time, increase the aeration rate. If the aeration rate exceeds the required adjustment range (e.g., higher than 1.0 L / m³), then stop the incubation. 3 (min). The set time is 1 / 10 of one hydraulic residence time in the reactor.

[0038] In the synthesis of polyhydroxyalkanoates, the aeration rate was adjusted to 0.4 L / m³. 3 ·min~0.6 L / m 3 •min, used to increase the proportion of PHA in cell dry weight.

[0039] In the synthesis of polyhydroxyalkanoates, the aeration rate was adjusted to 0.8 L / m³. 3 ·min~1.0 L / m 3 •min, used to increase biological concentration (biomass weight).

[0040] In the synthesis of polyhydroxyalkanoates, the aeration rate was adjusted to 0.6 L / m³. 3 ·min~1.0 L / m 3 •min, used to increase PHA production.

[0041] (4) Take the mixed sample obtained in step (3), freeze-dry it and then use gas chromatography (Agilent GC7890, acidified methanol methyl esterification) to determine the content and composition of PHA; at the same time, determine the cell dry weight, subtract the weight of PHA to obtain the biomass dry weight, and calculate the total PHA yield (PHA to cell dry weight ratio × biomass concentration × reactor volume).

[0042] In this embodiment, in step (3), the effects of different aeration rates on the proportion of PHA to cell dry weight, biomass weight, and total PHA production were also investigated. Specifically, the effects of an aeration rate of 0.1 L / m³ were investigated. 3 ·min、0.25 L / m 3 ·min、0.4 L / m 3 ·min、0.6 L / m 3 ·min、0.8 L / m 3 ·min、1.0 L / m 3 The effects of aeration rate of 0.1 L / m³ on the percentage of PHA in cell dry weight, biomass weight, and total PHA production were investigated. 3 ·min、0.25 L / m 3 ·min、0.4L / m 3 ·min、0.6 L / m 3 ·min、0.8 L / m 3 ·min、1.0 L / m 3 At min, the groups are, in order, the blank group, control group 1, control group 2, control group 3, control group 4, and control group 5.

[0043] In this embodiment, the aeration rate used in step (2) is the same as that in step (3). That is, when the aeration rate in step (3) is 0.1 L / m³, the aeration rate is the same. 3 ·min、0.25 L / m 3 ·min、0.4 L / m 3 ·min、0.6 L / m 3 ·min、0.8 L / m 3 ·min、1.0 L / m 3 At min, the corresponding aeration rate in step (2) is also 0.1 L / m. 3 ·min、0.25 L / m 3 ·min、0.4 L / m 3 ·min、0.6 L / m 3 ·min、0.8 L / m 3 ·min、1.0 L / m 3 ·min.

[0044] Figure 1 The graph shows the effects of different aeration rates on the percentage of PHA in cell dry weight, biomass weight, and total PHA production under different aeration conditions in Example 1 of this invention.

[0045] Depend on Figure 1 It can be seen that, compared to the blank group (0.1 L / m) 3(·min), at an aeration rate of 0.25 L / m 3 ·min、0.4 L / m 3 ·min、0.6 L / m 3 ·min、0.8 L / m 3 ·min、1.0 L / m 3 Under the given aeration conditions, both the amount of PHA synthesized and the biological quality were improved to some extent. Specifically, the ratio of PHA to cell dry weight initially increased and then decreased with increasing aeration rate, reaching a maximum of 0.4 L / m³. 3 The optimal value is found at min, with a growth rate that is lower than that of the control group (0.1 L / m). 3 The biomass synthesis and total PHA synthesis are 1.44 times that of (·min), and the biomass synthesis and total PHA synthesis are at 0.8 L / m 3 It reached its peak at ·min, and its biomass growth rate was 0.1 L / m 3 The growth rate was 2.00 times that of the control group (0.1 L / m) and the growth rate was 2.00 times that of the control group (0.1 L / m). 3 (3.02 times that of ·min). It can be seen that during the synthesis stage of polyhydroxyalkanoates, at 0.4–0.6 L / m... 3 At a constant aeration rate of 0.8–1.0 L / m³, it can effectively promote the average PHA synthesis capacity of microorganisms. 3 At a concentration of 0.6–1.0 L / min, the biomass concentration can be effectively increased. In particular, the method of this invention combines the average synthetic capacity of microorganisms with the biomass concentration, achieving a concentration of 0.6–1.0 L / min. 3 • Under min, a higher amount of PHA accumulation can be obtained in a short period of time.

[0046] This embodiment also monitored the current generated by the amount of electrons overflowing from the reaction system to the external circuit during PHA synthesis, such as... Figure 2 As shown.

[0047] Figure 2 This is a graph showing the change in current formed by electrons leaking into the circuit system under different aeration conditions in Embodiment 1 of the present invention.

[0048] Depend on Figure 2 It can be seen that the aeration rate (0.4 L / m³) is... 3 ·min and 0.6 L / m 3The current is minimized at the minimum (·min), which is similar to the trend of PHA's proportion in cell dry weight: the better the PHA synthesis capacity, the fewer electrons flow into the circuit. When PHA synthesis, as an energy and electron storage substance, is hindered, a circuit is needed to release the overflow of electrons. This is because unsuitable aeration conditions limit PHA synthesis, leading to excessive electron accumulation and, more seriously, congestion of the electron transport chain, thus making the system more reliant on the external circuit's release pathway. Therefore, an external circuit can prevent the accumulation of electrons and reducing forces that affect intracellular electron transport, and, combined with aeration regulation, can ensure stable system operation and high PHA production.

[0049] As can be seen from the above results, compared with conventional synthesis methods, the method of the present invention can regulate the synthesis process of polyhydroxy fatty acid esters by adjusting the aeration rate, which can significantly increase the yield of PHA while reducing energy consumption. It has the advantages of convenient operation, low energy consumption, and easy to increase the yield of PHA, and has high application value and good application prospects.

[0050] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating the production of polyhydroxyalkanoates by mixed bacterial communities, characterized in that, Includes the following steps: S1. Obtain a mixed microbial community with the ability to synthesize polyhydroxy fatty acid esters; S2. The mixed microbial community obtained in step S1 is inoculated into the reactor for cultivation. During the cultivation process, the synthesis process of polyhydroxy fatty acid ester is adjusted according to the aeration rate.

2. The control method according to claim 1, characterized in that, In step S2, the aeration rate is adjusted within a range of 0.1 L / m³. 3 ·min~1.0 L / m 3 ·min.

3. The control method according to claim 2, characterized in that, In step S2, during the synthesis of polyhydroxyalkanoate based on the aeration rate, the aeration rate is adjusted to 0.4 L / m³. 3 ·min~0.6 L / m 3 •min, used to increase the proportion of PHA in cell dry weight; And / or, in step S2, during the synthesis of polyhydroxyalkanoate based on the aeration rate, the aeration rate is adjusted to 0.8 L / m³. 3 ·min~1.0 L / m 3 •min, used to increase biological concentration; And / or, in step S2, during the synthesis of polyhydroxyalkanoate based on the aeration rate, the aeration rate is adjusted to 0.6 L / m³. 3 ·min~1.0 L / m 3 •min, used to increase PHA production.

4. The control method according to claim 3, characterized in that, In step S2, during the process of adjusting the aeration rate, when the reactor volume or configuration changes, the equivalent aeration intensity or oxygen mass transfer coefficient corresponding to the aeration rate is maintained to achieve a scale-up.

5. The control method according to claim 4, characterized in that, In step S2, the process of adjusting the aeration rate also includes feedback control of the aeration rate based on the external circuit current signal. The feedback control is as follows: a current change threshold is set, which is 10% to 30% of the average current value under normal operating conditions. When the current continuously decreases beyond the set current change threshold within a set time, the aeration rate is reduced. If the aeration rate exceeds the required adjustment range, the cultivation is stopped. When the current continuously rises beyond the set current change threshold within a set time, the aeration rate is increased. If the aeration rate exceeds the required adjustment range, the cultivation is stopped. The set time is 1 / 20 to 1 / 10 of one hydraulic retention time in the reactor.

6. The control method according to claim 5, characterized in that, The external circuit current signal is detected by an external circuit monitoring system; the external circuit monitoring system includes a working electrode and a counter electrode disposed inside the reactor, as well as a potentiostat and a data recording device connected to the working electrode and the counter electrode; the constant voltage applied by the potentiostat is +0.6 V relative to the counter electrode.

7. The control method according to any one of claims 1 to 6, characterized in that, Step S1 involves obtaining a mixed microbial community capable of synthesizing polyhydroxyalkanoates (PHA), comprising the following steps: using activated sludge as an inoculum, operating in a sequencing batch reactor (SBR) in an alternating "abundance-starvation" mode, adding enrichment-stage substrates containing carbon, nitrogen, and phosphorus for cultivation, and continuing cultivation until the PHA synthesis capacity of the microbial community stabilizes, thus obtaining a mixed microbial community capable of synthesizing PHA; the cultivation process also includes aeration of the system; the aeration rate during the aeration process is controlled at 0.1 L / m³. 3 ·min~1.0 L / m 3 ·min.

8. The control method according to claim 7, characterized in that, The substrate for the enrichment stage is an anaerobic fermentation broth containing mixed fatty acids; the mixed fatty acids are acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid; the total COD concentration in the substrate for the enrichment stage is 2.0 g / L to 4.0 g / L, and the carbon-nitrogen mass ratio is 15 to 30:

1.

9. The control method according to any one of claims 1 to 6, characterized in that, In step S2, the cultivation process also includes adding carbon, nitrogen, and phosphorus source substrates; the carbon, nitrogen, and phosphorus source substrates are anaerobic fermentation broth containing mixed fatty acids; the mixed fatty acids are acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid; the total COD concentration in the carbon, nitrogen, and phosphorus source substrates is 8.0 g / L to 15.0 g / L, and the carbon-nitrogen mass ratio is 15 to 30:

1.

10. The control method according to any one of claims 1 to 6, characterized in that, In step S2, the method for regulating the addition of carbon source substrate during the cultivation process is as follows: when the pH value of the reaction system rises to 9.5±0.5 and remains unchanged for 5 min, a carbon source substrate concentrated 2 to 4 times is added to maintain the microorganisms in a state of abundant metabolism.

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