CN114921503A

CN114921503A - Method for synthesizing polyhydroxyalkanoate and application thereof

Info

Publication number: CN114921503A
Application number: CN202210713557.4A
Authority: CN
Inventors: 刘研萍; 闫旭升; 景辉艳
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2022-06-22
Filing date: 2022-06-22
Publication date: 2022-08-19
Anticipated expiration: 2042-06-22
Also published as: CN114921503B

Abstract

The invention provides a method for synthesizing polyhydroxyalkanoate and application thereof, belonging to the technical field of environmental protection. The invention takes anaerobic hydrolysis acidification liquid of kitchen waste as a carbon source and rhodopseudomonas palustris as a functional microorganism to synthesize the product polyhydroxyalkanoate through constant-temperature culture. According to the invention, rhodopseudomonas palustris is used as a functional microorganism for the first time to synthesize the polyhydroxyalkanoate by utilizing the kitchen waste, so that the synthesis efficiency of the polyhydroxyalkanoate is effectively improved, and the yield of volatile fatty acid in anaerobic hydrolytic acidification of the kitchen waste is improved by means of ultrasonic-alkali combination and addition of exogenous substances, so that the synthesis efficiency of the polyhydroxyalkanoate is greatly improved.

Description

Method for synthesizing polyhydroxyalkanoate and application thereof

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to a method for synthesizing polyhydroxyalkanoate and application thereof.

Background

Polyhydroxyalkanoate (PHA) is a recognized green environment-friendly high polymer material, has the advantages of thermoplasticity, biodegradability, biosolubility, renewability and the like, can be used as a substitute of difficultly-degradable plastics, and is applied to the fields of biomedical equipment, electronics, buildings, automobiles, packaging and agriculture. Common PHA monomers are poly-3-hydroxybutyrate (PHB) and poly-hydroxyvalerate (PHV). In recent years, PHA is produced mainly by crops such as edible vegetable oil and grains, and directly competes with grain supply production. Therefore, extensive studies by scholars at home and abroad have been made by using other raw materials as carbon sources for producing PHA.

The kitchen waste is the most important one of food waste, comprises edible residues generated in families, schools, canteens, catering industries and the like, has complex components, and is a mixture of various substances such as oil, water, fruit peels, vegetables, rice flour, fish, meat, bones, waste tableware, plastics, paper towels and the like. The kitchen waste has high organic matter content, Volatile Fatty Acids (VFAs) generated by anaerobic hydrolysis and acidification can be used as a carbon source for synthesizing PHA by microorganisms, and the advantages are as follows: (1) the kitchen waste has huge yield and contains a large amount of organic matters; (2) anaerobic digestion is a well-known resource-based harmless treatment method; (3) VFAs are important intermediates generated in the acidification step of organic materials subjected to anaerobic digestion and have a wide range of industrial applications. However, in the current technology of synthesizing PHA by using kitchen waste as a carbon source and using microorganisms, the PHA synthesis rate is generally not high, so it is necessary to develop a method with high PHA synthesis rate to synthesize PHA, so as to realize resource treatment of waste and production of sustainable products.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for synthesizing polyhydroxyalkanoate, which can effectively improve the synthesis rate of polyhydroxyalkanoate and recycle kitchen waste.

In order to achieve the above purpose, the invention provides the following technical scheme:

the invention provides a method for synthesizing polyhydroxyalkanoate, which comprises the following steps: inoculating rhodopseudomonas palustris in anaerobic hydrolysis acidification liquid of the kitchen waste for culture, and extracting polyhydroxyalkanoate in the rhodopseudomonas palustris after the culture is finished.

Preferably, the preparation method of the anaerobic hydrolytic acidification liquid for kitchen waste comprises the following steps: and (3) carrying out anaerobic hydrolysis acidification after the kitchen waste is pretreated, centrifuging a hydrolysis acidification product, and reserving and taking supernatant.

Preferably, the pretreatment method comprises the following steps: and (3) crushing the kitchen waste and then carrying out ultrasonic-alkali combined pretreatment.

Preferably, the conditions of the ultrasonic-alkali combined pretreatment are as follows: ultrasonic treatment is carried out for 8-12 min, and the pH value is 8.5-9.5.

Preferably, the mass ratio of the kitchen waste to the inoculated sludge is 1.5-2.5: 1 mixing and then carrying out anaerobic hydrolysis acidification, wherein the anaerobic conditions are as follows: the pH value is 8.5-9.5, the anaerobic temperature is 33-36 ℃, and the time is 6-8 d.

Preferably, one or more of magnetite, anthraquinone-2-sulfonic acid and alkyl glycoside is added into the anaerobic hydrolysis acidification system.

Preferably, the anaerobic hydrolysis acidification liquid for kitchen waste is used for eliminating mixed bacteria, diluted to the concentration of 2000-2400 mg/L and inoculated with rhodopseudomonas palustris.

Preferably, the inoculation amount of the rhodopseudomonas palustris is 13-16%.

Preferably, the culture conditions are: the illumination intensity is 1800-2200 lux, the rotating speed is 160-200 rpm, the reaction temperature is 28-32 ℃, the initial pH value is 7.8-8.2, and the culture time is 28-32 d.

The invention also provides application of the method in kitchen waste treatment or polyhydroxyalkanoate industrial production.

Compared with the prior art, the invention has the following beneficial effects:

according to the method, the kitchen waste anaerobic hydrolysis acidification liquid is used as a carbon source, rhodopseudomonas palustris is used as a functional microorganism to synthesize the polyhydroxyalkanoate, so that the kitchen waste can be subjected to resource treatment, VFAs in the kitchen waste anaerobic hydrolysis acidification liquid are effectively utilized to synthesize PHA, and the method has high PHA synthesis efficiency.

According to the invention, by pretreating the kitchen waste, the yield of volatile fatty acid in the anaerobic hydrolysis acidification liquid of the kitchen waste can be increased, so that the synthesis efficiency of polyhydroxyalkanoate is improved.

According to the invention, exogenous substances are added into the anaerobic hydrolysis acidification system of the kitchen waste, so that the yield of volatile fatty acid in the anaerobic hydrolysis acidification liquid of the kitchen waste is further increased, and the synthesis efficiency of polyhydroxyalkanoate is improved.

Drawings

FIG. 1: a gas chromatography standard curve of PHB and PHV;

FIG. 2: VFAs change rule under different ultrasonic-alkali pretreatment conditions;

FIG. 3: the influence of different ultrasonic-alkaline pretreatment conditions on acetic acid;

FIG. 4 is a schematic view of: the influence of different ultrasonic-alkali pretreatment conditions on butyric acid;

FIG. 5: SEM pictures of the kitchen waste under different ultrasonic-alkali pretreatment conditions;

FIG. 6: methanogenic bacteria morphology;

FIG. 7 is a schematic view of: different Fe ₃ O ₄ The production rule of VFAs under the condition of adding amount;

FIG. 8: different Fe ₃ O ₄ The distribution of VFAs components under the condition of adding amount;

FIG. 9: the production rule of VFAs under the condition of different AQS addition amounts;

FIG. 10: the distribution of VFAs components under different AQS addition amounts;

FIG. 11: the production rule of VFAs under the condition of different APG06 adding amounts;

FIG. 12: the distribution of VFAs components under different APG06 dosage conditions;

FIG. 13: the influence of the rhodopseudomonas palustris culture time on the PHA synthesis rate;

FIG. 14: the influence of the substrate concentration on the synthesis of PHA by rhodopseudomonas palustris;

FIG. 15: the effect of pH on PHA synthesis by P.palustris;

FIG. 16: the influence of the rhodopseudomonas palustris inoculation amount on PHA synthesis;

FIG. 17: the influence of the composition of VFAs on PHA synthesis by Rhodopseudomonas palustris.

Detailed Description

The invention provides a method for synthesizing polyhydroxyalkanoate, which comprises the following steps: inoculating rhodopseudomonas palustris in anaerobic hydrolysis acidification liquid of the kitchen waste for culture, and extracting polyhydroxyalkanoate in the rhodopseudomonas palustris after the culture is finished. According to the method, kitchen waste anaerobic hydrolysis acidification liquid is used as a carbon source, rhodopseudomonas palustris is used as a functional microorganism, VFAs in the kitchen waste anaerobic hydrolysis acidification liquid are synthesized into PHA through metabolic activity of the rhodopseudomonas palustris, and then polyhydroxyalkanoate in the rhodopseudomonas palustris is extracted to obtain a powdery PHA crude product.

The PHA crude product obtained by the invention contains PHB as the main component.

The kitchen waste is kitchen waste generated in daily life, and the specific source is not limited.

In the invention, the preparation method of the anaerobic hydrolytic acidification liquid for the kitchen waste comprises the following steps: and (3) carrying out anaerobic hydrolysis acidification after the kitchen waste is pretreated, centrifuging a hydrolysis acidification product, and reserving and taking supernatant.

The method comprises the steps of firstly crushing the kitchen waste by using a conventional crusher, and then carrying out ultrasonic-alkali combined pretreatment on the crushed kitchen waste.

According to the invention, alkaline substances are added into the smashed kitchen waste to adjust the pH value, and the alkaline substances are preferably one of calcium hydroxide, potassium hydroxide and sodium hydroxide. According to the invention, the pH value of the kitchen waste is adjusted to 8.5-9.5, preferably 8.8-9.2, and more preferably 9 by adding an alkaline substance.

The invention can lead the system to contain a large amount of OH by alkali treatment ^- The cells of the acidified substrate are damaged, the macromolecular organic matters are hydrolyzed and saponified, the methanogenesis process is inhibited, the hydrolysis rate is improved, and more VFAs are generated in the same time. In addition, the pH value range is selected to be 8.5-9.5, the influence of an extreme alkaline environment on the enzyme activity and the microbial growth and metabolism in a system is avoided, and the content of VFAs can be improved to the maximum extent.

The method comprises the step of carrying out ultrasonic treatment on the alkali-treated kitchen waste for 8-12 min. The ultrasonic treatment time is preferably 9-11 min, and more preferably 10 min. As an optional implementation mode, the kitchen waste is placed in a double-frequency air ultrasonic cleaner (KQ-300VDE) and is subjected to ultrasonic treatment for 8-12 min under the condition of 80 kHz.

According to the invention, through ultrasonic pretreatment, the structure of large-particle organic matters in the kitchen waste can be destroyed by ultrasonic waves, and the generation of VFAs is facilitated. Meanwhile, the ultrasonic treatment time is selected to be 8-12 min, so that the phenomenon that small particles in the system are reunited into large organic particles to be unfavorable for hydrolysis is avoided.

The kitchen waste subjected to ultrasonic-alkali combined pretreatment is placed in an anaerobic reactor for anaerobic hydrolytic acidification, and the mass ratio of the kitchen waste to inoculated sludge is (1.5-2.5): 1, preferably 2: 1. the anaerobic hydrolysis acidification conditions are as follows: the pH value is 8.5-9.5, and preferably the pH value is 9; the temperature is 33-36 ℃, and the preferable temperature is 35 ℃; the time is 6-8 d, and preferably 7 d.

According to the invention, the kitchen waste is pretreated by combining ultrasound and alkali, so that the dissolution of organic matters can be promoted, the hydrolysis rate of the kitchen waste is improved, the methane production process is inhibited, a large amount of VFAs are generated in the system after anaerobic hydrolysis acidification, and the synthetic potential of FHA can be effectively improved.

According to the invention, exogenous substances can be further added into the anaerobic hydrolysis acidification system to promote the generation of VFAs. Preferably, the exogenous material comprises one or more of magnetite, anthraquinone-2-sulfonic acid and alkyl glycoside.

Magnetite (Fe) according to the invention ₃ O ₄ ) The addition amount of (b) is preferably 9-11 g/L, and more preferably 10 g/L; the addition amount of the anthraquinone-2-sulfonic Acid (AQS) is preferably 110-130 mg/L, and more preferably 120 mg/L; the amount of the alkyl glycoside (APG06) added is preferably 9 to 10g/L, more preferably 9.45 to 9.6 g/L.

According to the invention, magnetite, anthraquinone-2-sulfonic acid or alkyl glycoside is added under an alkaline condition, so that the complex macromolecular organic matter can be promoted to be hydrolyzed into soluble micromolecular organic matter, thereby being beneficial to the conversion and utilization of hydrolytic acidification bacteria on the soluble organic matter, improving the activity of hydrolytic enzyme in an anaerobic hydrolytic acidification system, inducing the enrichment of different acid-producing bacteria groups in the system and further being beneficial to the generation of VFAs.

The anaerobic hydrolysis acidification product is subjected to centrifugal treatment, bottom sludge is removed, and a supernatant is left, wherein the supernatant is the anaerobic hydrolysis acidification liquid for the kitchen waste. As an optional implementation mode, the anaerobic hydrolysis acidification product is centrifuged for 8-10 min at 7500-8500 rpm, bottom sludge is removed, and supernatant is left.

According to the method, foreign bacteria in the anaerobic hydrolysis acidification liquid of the kitchen waste are eliminated, and then the kitchen waste is diluted to the concentration of 2000-2400 mg/L and used for inoculating rhodopseudomonas palustris. The method for eliminating the mixed bacteria is preferably membrane filtration by adopting a bacterial filter membrane (0.22 mu m) or high-pressure steam sterilization; the diluting is preferably performed by adding water, and the concentration of the diluted anaerobic hydrolysis acidification liquid for the kitchen waste is 2000-2400 mg/L, preferably 2200-2300 mg/L, and more preferably 2202-2220 mg/L. The invention avoids the influence of other strains on the rhodopseudomonas palustris by eliminating the mixed bacteria; the proper concentration and abundant nutrient substances in the hydrolytic acidification solution are ensured through dilution, the cell growth and proliferation of strains and the synthesis of PHA are mainly carried out, and the main physiological activities are mainly the synthesis of PHA, so that the synthesis rate of PHA is improved.

The inoculation amount of the rhodopseudomonas palustris is 13-16%, and the preferable inoculation amount is 14-15%. As an alternative embodiment, the invention carries out the enlarged culture of rhodopseudomonas palustris before inoculation. The invention does not limit the condition of the enlarged culture of the rhodopseudomonas palustris.

The culture conditions for synthesizing PHA by rhodopseudomonas palustris are as follows: the illumination intensity is 1800-2200 lux, and the preferred illumination intensity is 2000 lux; the rotation speed is 160-200 rpm, preferably 170-180 rpm; the reaction temperature is 28-32 ℃, and the preferable temperature is 29-30 ℃; the initial pH value is 7.8-8.2, and the optimal pH value is 8; the time is 28 to 32d, preferably 29 to 30 d.

The extraction method of PHA of the present invention is preferably SDS-sodium hypochlorite method. As an alternative embodiment, the cultured rhodopseudomonas palustris is taken, freeze-dried thalli of the rhodopseudomonas palustris are added into an SDS solution and stirred, deionized water is used for washing, supernatant liquid is poured, precipitate is washed by water, 30% sodium hypochlorite solution is added at room temperature and stirred for reaction for 3min, the precipitate is immediately washed by the deionized water, the precipitate is washed by water again, the precipitate is dried, a dried sample is placed into a condensing reflux device, chloroform is added, water bath heating is carried out, and then the dried sample is placed into an oven for drying to obtain a powdery PHA crude product, wherein the main component of the PHA crude product is PHB.

The invention also provides the application of the method in the treatment of kitchen waste or the industrial production of polyhydroxyalkanoate, thereby ensuring the resource treatment of the kitchen waste and reducing the production cost of PHA.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

In a specific embodiment, the kitchen waste is taken from a canteen of Beijing chemical university, impurities such as bones, eggshells, fishbones and the like in the kitchen waste are manually picked out, crushed and stored in a refrigerator at the temperature of-20 ℃. The rhodopseudomonas palustris is purchased from China center for culture collection and management of industrial microorganisms and is numbered as CICC 23812. The anaerobic inoculation sludge is taken from the discharge of an anaerobic digestion tank of a certain municipal sewage treatment plant in Beijing, the inoculation sludge is kept stand in a shade place for a period of time, then supernatant is removed, and the inoculated sludge is stored in a refrigerator at 4 ℃. The ultrasonic equipment used was a dual-frequency digital air ultrasonic cleaner (KQ-300 VDE). The rhodopseudomonas palustris culture medium is a tryptone soybean agar culture medium.

In specific embodiments, the VFAs are determined by: centrifuging appropriate amount of anaerobic hydrolysis acidification liquid at 10000rpm for 10min, dripping phosphoric acid into supernatant, centrifuging at 10000rpm for 10min, filtering the supernatant with filter membrane, dripping phosphoric acid, and measuring with gas chromatograph FID detector. The chromatography was performed using a GC1120, FID detector from Shunhua Neuguenza, Shanghai, Inc.

The determination method of Polyhydroxyalkanoates (PHAs) comprises the following steps: solid phase extraction-gas chromatography. The chromatography was performed by using GC1120, FID detector from Shunhun Shuangzhen Co.

The drawing of the PHB and PHV quality standard curve is as follows:

(1) the pure PHB standards were accurately weighed with weighing paper at 0.7mg, 2.4mg, 2.9mg, 4.3mg, 4.8mg, 6mg, 8.1mg, 10.1 mg. Copolymer standards 0.8mg, 1.7mg, 3.5mg, 4.5mg, 6mg, 10.7mg, 21.2mg, 32.3 mg. The PHV content is 0.07mg, 0.15mg, 0.31mg, 0.41mg, 0.54mg, 0.96mg, 1.90mg, 2.91 mg.

(2) Pouring the sample into a digestion tube, adding trichloromethane and a benzoic acid-methanol solution in sequence, uniformly mixing, and digesting in a digestion instrument for 6 hours.

(3) After digestion, 1mL of deionized water is added, shaking and mixing are carried out, standing is carried out in a refrigerator, 1mL of lower-layer organic solvent is absorbed into a sample injection bottle by a needle tube, and detection is carried out by a gas chromatograph. PHB peak-off time: 2-2.9 min, PHV peak-off time: 3.5-4 min. The standard curve is shown in FIG. 1.

PHB, PHV standards were purchased from Sigma, USA, wherein the PHV content in the copolymer was 9 wt%, wherein the standard curve of PHB, PHV is the relationship between PHB, PHV and peak area ratio.

The acidified solution obtained in example was freeze-dried, weighed and the weight of the dried sample (about 50mg) was recorded, added to a digestion tube, and then 2mL of chloroform and 2mL of benzoic acid-methanol were added thereto, mixed well and placed in a digestion apparatus (105 ℃ C.) to be digested for 6 hours. After cooling, 1mL of ultrapure water was added, mixed by shaking, placed in a refrigerator and allowed to stand for stratification, and the supernatant was collected, passed through a membrane (0.22 μm), and examined by gas chromatography.

In the specific examples, the index determination reference standard GB 11914-89, and the Chemical Oxygen Demand (COD) is determined by the potassium dichromate method. Ammonia nitrogen was measured using the Nash reagent method. The pH was measured using a pH meter (Mettler-FE 28). The biogas production was measured by a drainage method. The composition of the gas sample was measured with a gas chromatograph (GC1120/TCD, Shunhua constant).

Example 1

This example provides a method for synthesizing polyhydroxyalkanoate:

(1) taking the stored kitchen waste, gradually adding Ca (OH) ₂ The pH was adjusted to 9, and then sonicated at 80kHz for 10 min.

(2) Anaerobic hydrolysis acidification is carried out on the treated kitchen waste: the effective volume of the experimental reactor is 0.4L, the load of the fed kitchen waste is set to be 30gVS/L, the load of the inoculation mud is 15gVS/L, the temperature is 35 ℃, the pH value is 9, and the reaction time is 7 d. Centrifuging the anaerobic hydrolysis acidification liquid for 10min (8000r/min), removing bottom sludge, collecting supernatant, and temporarily storing in a 4 deg.C refrigerator.

(3) And (3) performing amplification culture on rhodopseudomonas palustris: in an aerobic environment, adding the rhodopseudomonas palustris liquid into a 150mL conical flask, adjusting the pH value to 7.3, setting the temperature to be 30 ℃, and culturing for 5d under the condition of rotating speed of 180 rpm.

(4) Carrying out membrane (0.22 mu m) treatment on the supernatant of the anaerobic hydrolysis acidification liquid of the kitchen waste, diluting to 2202mg/L, adding the supernatant and the cultured rhodopseudomonas palustris liquid into a 150mL culture bottle, placing the culture bottle in a constant-temperature oscillation box to synthesize PHA, and setting the experimental conditions as follows: the inoculation amount of the bacterial liquid is 15 percent, the illumination intensity is 2000lux, the rotating speed is 180rpm, the reaction temperature is 30 ℃, the initial pH value is 8, and the operation is carried out for 30 days under the condition.

(5) The cultured Rhodopseudomonas palustris was freeze-dried, weighed, and the weight of the dried sample (about 50mg) was recorded, added to a digestion tube, followed by addition of 2mL of chloroform and 2mL of benzoic acid-methanol, mixing well, and digestion in a digestion apparatus (105 ℃ C.) for 6 hours. After cooling, 1mL of ultrapure water was added, mixed by shaking, placed in a refrigerator and allowed to stand for stratification, and the supernatant was collected, passed through a membrane (0.22 μm), and examined by gas chromatography. The PHA synthesis rate was 42.33%.

(6) Extracting PHA by an SDS-sodium hypochlorite method: taking cultured rhodopseudomonas palustris, freeze-drying 2g of thalli of the rhodopseudomonas palustris, adding an SDS solution (50 ℃, stirring for 10min), washing with deionized water (4000rpm, centrifuging for 15min), pouring supernatant, washing precipitates with water (4000rpm, centrifuging for 15min), adding a 30% sodium hypochlorite solution at room temperature, stirring for reacting for 3min, immediately washing the precipitates with the deionized water (4000rpm, centrifuging for 20min), washing the precipitates with water (4000rpm, centrifuging for 20min), drying the precipitates (drying in an oven at 60-70 ℃), putting dried samples into a condensing reflux device, adding trichloromethane, heating in a water bath at 60 ℃, and then putting the dried samples into the oven at 60-70 ℃ for drying to obtain a PHA crude product. The PHA content was 53.98%.

Example 2

This example differs from example 1 in that: reacting Ca (OH) ₂ Instead of KOH, the PHA synthesis rate was 40.89%.

Example 3

The present example differs from example 1 in that: reacting Ca (OH) ₂ The PHA synthesis rate was 41.56% by replacing it with NaOH.

Example 4

This example differs from example 1 in that: in the step (1), the pH value is adjusted to 8.8, and the PHA synthesis rate is 41.13%.

Example 5

This example differs from example 1 in that: in the step (1), the ultrasonic time is 9min, and the PHA synthesis rate is 40.98%.

Example 6

This example differs from example 1 in that: in the step (2), the load of the fed kitchen waste is 27gVS/L, the load of the inoculation mud is 15gVS/L, the temperature is 34 ℃, the pH value is 9.2, the time is 8d, and the PHA synthesis rate is 37.46%.

Example 7

The present example differs from example 1 in that: 10g/L Fe is added into the anaerobic hydrolysis acidification system in the step (2) ₃ O ₄ The PHA synthesis rate was 46.33%.

Example 8

This example differs from example 1 in that: 120mg/L of AQS in the anaerobic hydrolysis acidification system in the step (2) has the PHA synthesis rate of 45.68 percent.

Example 9

This example differs from example 1 in that: 9.45g/L of APG06 in the anaerobic hydrolysis acidification system in the step (2) has the PHA synthesis rate of 44.16 percent.

Example 10

This example differs from example 1 in that: and (4) sterilizing the supernatant of the anaerobic hydrolyzed acidification liquid of the kitchen garbage at 121 ℃ for 15min by high-pressure steam, wherein the PHA synthesis rate is 41.23%.

Example 11

This example differs from example 1 in that: in the step (4), the anaerobic hydrolysis acidification liquid of the kitchen garbage is diluted to 2250mg/L, and the PHA synthesis rate is 42.05%.

Example 12

This example differs from example 1 in that: the inoculation amount of the rhodopseudomonas palustris in the step (4) is 14 percent, and the PHA synthesis rate is 41.61 percent.

Example 13

This example differs from example 1 in that: in the step (4), the illumination intensity is 2100lux, the rotating speed is 190rpm, the reaction temperature is 29 ℃, the initial pH value is 7.9, the operation is carried out for 30 days, and the PHA synthesis rate is 38.76 percent.

Comparative example 1

This comparative example differs from example 1 in that: the step (1) is omitted, the crushed kitchen waste is directly subjected to anaerobic hydrolysis acidification, the content of VFAs in the kitchen waste anaerobic hydrolysis acidification liquid is 2800mg/L, and the PHA synthesis rate is 28.56%. Through detection, compared with the comparative example 1, the yield of VFAs in the anaerobic hydrolysis acidification liquid of the kitchen waste in the example 1(7838mg/L) can be improved by 1.8 times.

Comparative example 2

This comparative example differs from example 1 in that: replacing rhodopseudomonas palustris with rhodobacter sphaeroides.

Comparative example 3

The comparative example differs from example 1 in that: the rhodopseudomonas palustris is replaced by rhodobacter capsulatus.

As a result, the PHA synthesis rates of comparative examples 2 and 3 were examined to be about 35.65% and 34.14%, respectively. The results show that the synthesis rate of PHA in example 1 is remarkably improved compared with comparative examples 2-3.

Test example 1

The ultrasonic-alkali combined pretreatment conditions were verified, 3 replicates per set of experiments were performed:

the ultrasound time was set to 5min, 10min, 20min, 30min in order, and the initial pH was set to 7.5 (initial pH), 8, 9, 10, 11, 12, respectively, in order. The rest of the experimental conditions were the same as in example 1. And after the anaerobic hydrolysis acidification is finished, detecting the anaerobic hydrolysis acidification liquid obtained by each group.

(1) The content of VFAs in each group of anaerobic hydrolytic acidification liquid is detected, and the result is shown in a table 1 and a figure 2.

TABLE 1 VFAs content (mg/L) in anaerobic hydrolyzed acidic solution

As can be seen from Table 1 and FIG. 2, when the ultrasonic time is 10min, the initial pH adjustment promotes the system to generate a large amount of VFAs, and the concentration of the VFAs is 4024-7838 mg/L. When the initial pH is 9.0, the maximum concentration of VFAs is 7838mg/L, which is 94.8 percent higher than that of the unadjusted group, and the hydrolysis acidification promotion effect is most obvious by adjusting the initial pH. As the pH value is increased, the acid production effect of the system is reduced compared with the pH value 9.0 group. At pH 11 and pH 12 as the starting conditions, VFAs production was low and almost no methane was produced, since the extreme alkaline environment affected the activity of the enzyme, thereby inhibiting microbial growth metabolism. The method shows that the kitchen waste is pretreated by combining the ultrasonic treatment and the alkali treatment to promote the generation of VFAs. And when the ultrasonic pretreatment time is 10min and the initial pH is 9, the acid production effect is optimal.

(2) The content of acetic acid and butyric acid in each group is detected, and the result is shown in figures 3-4.

As can be seen from FIG. 3, the concentration of acetic acid was significantly higher in the case of 10min sonication time than in the other groups. The methanogenic bacteria are more active when the initial pH is 7.5, so that the acetic acid produced is consumed by the methanogenic bacteria and is not high, the highest concentration of acetic acid occurring at 36h being 1523.43 mg/L. At an initial pH of 9, the acetic acid concentration was higher at 2855.98mg/L, with VFAs decreasing with increasing sonication time. The activity of methanogenic microorganisms is inhibited by adjusting the initial pH, and most of acetic acid is not utilized, so that acetic acid is accumulated in a large amount in the system. When the pH is 11.0 and 12.0, the accumulation of acetic acid is small because the pH is high, the activity of hydrolytic acidification bacteria is inhibited, and the organic substances in the system cannot be decomposed well.

As can be seen from FIG. 4, butyric acid production was increased in the initial pH-adjusted group compared to the non-adjusted pH group, indicating that butyric acid production was promoted by the initial pH adjustment. The dissolution of soluble organic matters in the system can be increased by adjusting the pH, and the content of undissociated VFAs is reduced, thereby promoting the generation of butyric acid. When the sonication time was 10min, the butyric acid concentration was increased to 2486.46mg/L by adjusting the pH. At pH 11.0 and 12.0, butyrate content was significantly lower than other groups because higher pH inhibited the activity of the relevant enzymes, resulting in decreased butyrate production.

Fig. 3-4 show that when the pH value is higher, the pH value has a great promotion effect on anaerobic hydrolysis acidification acid production, and the process of methanogens is inhibited, so that the methanogens cannot timely decompose volatile fatty acids such as acetic acid, butyric acid and propionic acid. In the anaerobic hydrolysis acidification process of the kitchen waste, the VFAs mainly comprises acetic acid and butyric acid, the content of the butyric acid and the acetic acid exceeds 60.00 percent, and the VFAs is acidified in a butyric acid type and can be used for subsequent accumulation of a large amount of available VFAs. When the ultrasonic pretreatment time is 10min and the initial pH is 9.0, the content of butyric acid and acetic acid is high, and the subsequent PHA yield can be effectively improved.

(3) The gas production rate and the methane production change in each hydrolysis acidification stage are detected, and the results are shown in table 2.

Table 2 gas production and methane production changes in each kitchen waste hydrolysis and acidification stage

As can be seen from Table 2, the methane production was relatively high at initial pH 7.5 and 8.0, indicating that the lower pH also favoured the survival of the methanogenic bacteria, so that the VFAs produced by anaerobic hydrolytic acidification were not accumulated and consumed by the methanogenic bacteria. When the initial pH is 9.0 and 10.0, the methane production is relatively less, which indicates that the addition of the alkali liquor influences the growth and metabolism of methanogens in the system and cannot timely degrade VFAs in the system, thereby causing the accumulation of a large amount of VFAs. After the initial pH is adjusted, the pH change in the system is in a proper range for hydrolyzing and acidifying bacteria, and simultaneously, the activity of methanogens can be inhibited, so that a large amount of VFAs are generated in the system. When the initial pH is 11.0 and 12.0, almost no methane is generated within 64h, the amount of the subsequently generated methane is small, the pH in the reaction system is 8.6-10.0, the activity of hydrolytic acidification bacteria is inhibited, and anaerobic digestion is not facilitated under an extremely alkaline condition.

(4) And (3) carrying out scanning electron microscope observation on the kitchen waste subjected to alkali pretreatment, ultrasonic pretreatment and ultrasonic alkali combined pretreatment. The results are shown in FIG. 5.

As can be seen from fig. 5, the surface structure of the kitchen waste is seriously damaged when the micro surface of the kitchen waste is pretreated compared with the micro surface of the kitchen waste which is not pretreated. The ultrasonic pretreatment destroys the porous medium structure of the organic matters of the kitchen waste through the high oscillation of the ultrasonic waves and the cavitation effect generated by the ultrasonic waves, and the alkali treatment destroys the organic matters of the kitchen waste through OH ^- Cells of the acidified substrate are damaged, and the saponified protein and the polysaccharide are hydrolyzed at the same time, so that the combined action of the protein and the polysaccharide can better promote the hydrolysis of organic matters in the kitchen waste, and the accumulation of VFAs is facilitated.

(5) The methanogens were observed using an ultraviolet fluorescence microscope and the results are shown in FIG. 6. As is clear from FIG. 6, the group with an initial pH of 7.5 showed a higher number of methanogens at 4d, while the test group showed a lower number of methanogens with an increase in initial pH. When the initial pH was 11.0 and 12.0, methanogens were hardly observed and the flocculation property of sludge was poor. The results show that the consumption of VFAs can be reduced by properly adjusting pH to increase the production of VFAs, but that the growth metabolism of the microorganism is not favored by excessively high pH.

Test example 2

For foreign matter Fe ₃ O ₄ The addition was verified, 3 replicates per set of experiments were performed:

provided with Fe ₃ O ₄ The adding amount is 0, 1, 2.5, 5, 10 and 15g/L in sequence, and the rest experimental conditions are the same as those of the embodiment 7; and after the anaerobic hydrolysis acidification is finished, detecting the anaerobic hydrolysis acidification liquid obtained by each group.

(1) Detection of different Fe ₃ O ₄ Effect of dosage on VFAs yield and composition.

Fe ₃ O ₄ The effect of dosing on VFAs yield is shown in FIG. 7. As can be seen from FIG. 7, Fe is initially present ₃ O ₄ When the addition amount of (2.5 g/L) is low, the acceleration effect on acid production is not obvious, the generation amounts of VFAs are 8950.92mg/L and 9860.13mg/L respectively, and Fe is not added ₃ O ₄ The yield of VFAs in the control group (7238mg/L) was 1.24 and 1.36 times higher. When Fe ₃ O ₄ When the addition amount is 5g/L, the yield of VFAs is obviously increased, and the yield of VFAs is 16650.12mg/L at the moment, the Fe is not added ₃ O ₄ 2.30 times the yield of VFAs in the blank group. The maximum VFAs yield was 22813.56mg/L at an initial feed rate of 10g/L, with no Fe added ₃ O ₄ 3.15 times the yield of VFAs from the blank group. However, at an initial 15g/L loading, the VFAs produced 13427.00mg/L, which is 1.85 times greater than the control. Is due to the fact that when Fe is present ₃ O ₄ The excessive addition amount inhibits the activity of hydrolytic acidification flora and influences the normal growth and metabolism of the hydrolytic acidification flora, thereby reducing the acid production capability of a system and the yield of VFAs (vacuum fatty acids) and being still higher than that of the bacteria without Fe ₃ O ₄ The control group of (1).

Adding Fe ₃ O ₄ The time distribution of the VFAs components is shown in FIG. 8, and FIG. 8 shows the composition of the VFAs components at the time of acidification at 4 d. As can be seen from FIG. 8, the most abundant VFAs produced by each group were acetic acid and butyric acid by acidification at 4 d. Whereas propionic, isobutyric and pentanoic acids are produced less throughout the hydrolytic acidification process. When Fe ₃ O ₄ When the adding amount is 10g/L, the concentration of acetic acid reaches 9004.86mg/L, and the concentration of butyric acid reaches 8777.07 mg/L. Wherein the acetic acid content is increased by 2.04 times, the butyric acid content is increased by 2.52 times, and the sum of the two accounts for 80.53 percent of VFAs, which is typical butyric acid acidification. Mixing Fe ₃ O ₄ Put into an anaerobic hydrolytic acidification system and can be used as an electron acceptor to simultaneously generate Fe ²⁺ And the yield of acetic acid and butyric acid is improved by enhancing the hydrolytic acidification process, and the yield of VFAs can be improved.

(2) Detection of Fe ₃ O ₄ (10g/L) effect of addition on the activity of enzymes involved in the conversion of acetic acid and butyric acid during anaerobic hydrolytic acidification, the results are shown in Table 3. The blank was only subjected to ultrasonic-alkaline pretreatment.

TABLE 3Fe ₃ O ₄ Enzyme activity related to acidification stage after adding

As can be seen from Table 3, FW + IS (treated with only ultrasonic-alkaline pretreatment) experimental groups were associated with acetic acid and butyric acidThe enzyme activity IS obviously lower than FW + IS + Fe ₃ O ₄ And (6) grouping. The growth rate of acetate kinase in FW + IS group was 15.38% and the growth rate of butyrate was 42.31%. When Fe ₃ O ₄ When the adding amount is 10g/L, the growth rate of the acetate kinase can reach 90.77%, and the growth rate of the butyrate kinase can reach 291.27%.

Test example 3

The addition amount of the foreign substance AQS is verified, and 3 parallels are carried out in each group of experiments:

setting the addition amounts of AQS to be 0, 40, 80, 120, 160 and 200mg/L in sequence, and keeping the other experimental conditions the same as that of example 8; and after the anaerobic hydrolysis acidification is finished, detecting the anaerobic hydrolysis acidification liquid obtained by each group.

(1) The effect of different AQS dosing on VFAs yield and composition was examined.

The effect of AQS dosing on VFAs production is shown in FIG. 9. As can be seen from fig. 9, the production of VFAs produced during anaerobic hydrolytic acidification also showed a tendency to increase and decrease with the increase of the initial AQS dosage. The VFAs yield is 7738mg/L when the AQS dosage is 0mg/L, and the maximum VFAs yield can reach 8721.00mg/L and 10382.65mg/L when the initial AQS dosage is 40mg/L and 80 mg/L. The maximum VFAs was 18130.21mg/L at AQS dosage of 120 mg/L. The maximum VFAs yields were 16247.10mg/L and 11797.30mg/L when AQS was dosed at 160mg/L and 200mg/L, respectively. After the AQS is added, the yield of the VFAs is 1.13-2.34 times higher than that of a control group.

The distribution of VFAs components when AQS is added is shown in FIG. 10, and FIG. 10 shows the composition of VFAs components at the 4 d. As can be seen from fig. 10, as the amount of AQS added increases, the contents of butyric acid and acetic acid in the system gradually increase, and the contents of propionic acid and valeric acid decrease. The maximum time appears when the AQS dosage is 120mg/L, the acetic acid concentration reaches 7526.42mg/L, and the butyric acid concentration reaches 6897.65 mg/L. Wherein the acetic acid content is increased by 1.54 times, the butyric acid content is increased by 1.77 times, and the sum of the two accounts for more than 70 percent of the total VFAs. The AQS is put into an anaerobic hydrolysis acidification system to reduce the oxidation-reduction potential, so that the environment is favorable for the generation of butyric acid and acetic acid. The AQS can accelerate electron transfer, reduce activation energy of reaction, promote degradation of organic matters and increase the content of VFAs in a system.

(2) The influence of the addition of AQS (120mg/L) on the activity of enzymes related to the conversion of acetic acid and butyric acid during anaerobic hydrolytic acidification was examined, and the results are shown in Table 4. The blank was subjected to ultrasonic-alkaline pretreatment only.

TABLE 4AQS post-addition acidification phase-related enzyme Activity

As can be seen from Table 4, after the addition of AQS, the increase rate of the activity of acetate kinase is 63.07%, and the increase rate of the activity of butyrate kinase is 230.00%, which is 1.63-3.30 times higher than the activity of the group without the addition of AQS. Experimental results show that the addition of the AQS can promote anaerobic hydrolysis acidification of the kitchen waste.

Test example 4

The amount of the exogenous substance APG06 added was verified, and 3 replicates were performed for each set of experiments:

setting the dosage of APG06 as 0, 3.15, 6.3, 9.45, 12.6 and 15.75g/L in sequence, and the rest experimental conditions are the same as those of example 9; and after the anaerobic hydrolysis acidification is finished, detecting each group of anaerobic hydrolysis acidification liquid.

(1) The effect of different amounts of APG06 dosed on VFAs yield and composition was examined.

The effect of APG06 dosing on VFAs production is shown in FIG. 11. As can be seen from FIG. 11, the production of VFAs produced during anaerobic hydrolytic acidification increased and then decreased as the initial amount of APG06 was increased. The maximum VFAs production occurred at 4d, 8250.92mg/L and 9260.13mg/L, respectively, when the initial APG06 dosage was 3.15g/L and 6.31 g/L. When the addition amount reaches 9.45g/L, the increase of the yield of the VFAs is obvious, and the yield of the VFAs is 16650.13mg/L, which is 2.3 times higher than that of a control group. When the dosages were 12.6g/L and 15.77g/L, the maximum yield of VFAs appeared at 4d, which reached 11452.58mg/L and 8814.01mg/L, respectively.

The distribution of the VFAs components when APG06 was added is shown in FIG. 12, and FIG. 12 shows the composition of the VFAs components at the 4 d. As can be seen from FIG. 12, the VFAs components in the acidified system were mainly acetic acid and butyric acid. The propionic acid content increased with the increase in the amount of APG06, but the increase was small and no propionic acid type fermentation was formed. When the dosage of the APG06 is 9.45g/L, the contents of acetic acid, propionic acid and butyric acid are respectively 37.07 percent, 14.94 percent and 36.58 percent. This increased propionic acid content by 1.56 times and acetic acid and butyric acid content by 99.73% and 1.34 times, respectively, compared to the contemporary control group. When the dosage of APG06 was further increased to 12.60g/L and 15.75g/L, the percentages of acetic acid, propionic acid, butyric acid increased to 41.92%, 16.61%, 37.16% and 37.16%, 23.56%, 33.85%. APG06 as surfactant reduces interfacial tension, increases solubility of organic matter and improves anaerobic hydrolysis acid production effect.

(2) The effect of APG06(9.45g/L) addition on the activity of enzymes involved in the conversion of acetic acid and butyric acid during anaerobic hydrolytic acidification was examined and the results are shown in Table 5. The blank was only subjected to ultrasonic-alkaline pretreatment.

TABLE 5 enzyme Activity in acidification stage after APG06 addition

As can be seen from Table 5, after APG06 is added into the acidification acid production system, the activity of acetate kinase and butyrate kinase is improved to 0.96U/g VSS and 50.42U/g VSS, which are improved by 47.69% and 140.55% compared with the control group. Probably due to the addition of APG06, butyrate kinase and acetate kinase originally embedded in the solid particles are released to the acidizing fluid, thereby promoting the hydrolytic acidification process.

Test example 5

The culture conditions of rhodopseudomonas palustris were verified, and 3 replicates were performed for each set of experiments:

(1) the culture time was set to 15, 20, 25, 30, 35 days in this order. The experimental conditions are as follows: 10g/L Fe is added into an anaerobic hydrolytic acidification system for producing VFAs ₃ O ₄ The conditions were the same as in example 1 except that the amount of inoculated strain was 10% and the pH was 7.3 when PHA was synthesized. After the completion of the culture, the PHA synthesis ratio of each group was measuredThe results of the measurements are shown in FIG. 13.

As is clear from FIG. 13, under the above-mentioned experimental conditions, the highest PHA synthesis rate was 34.60% when the culture time was 30 days. The PHA synthesis rate showed a downward trend with time. In the photoaerobic system for synthesizing PHA, rhodopseudomonas palustris mainly utilizes VFAs to generate PHA, polysaccharide can be taken into cells to participate in the synthesis of PHA, and protein is involved in the composition of cell frameworks, the synthesis of enzymes and the like. As the reaction time increased, most of the VFAs in the system were consumed, while P.palustris degraded the intracellular PHA stored to meet its metabolic demand for growth, indicating that the culture time was optimal at 30 d.

(2) The anaerobic hydrolysis acidified solution obtained in example 1 was diluted 5 times, 10 times (2202.21mg/L), 20 times, 40 times, and 60 times in this order. The experimental conditions are as follows: 10g/L Fe is added into an anaerobic hydrolytic acidification system for producing VFAs ₃ O ₄ The conditions were the same as in example 1 except that the amount of inoculated strain was 10% and the pH was 7.3 when PHA was synthesized. After completion of the culture, the PHA synthesis ratio of each group was measured, and the results are shown in FIG. 14.

As is clear from FIG. 14, when the substrate concentration was 2202.21mg/L (dilution factor was 10), the PHA synthesis effect was the best, and the synthesis rate was 34.80%. The method is characterized in that when the concentration of the substrate in the acidizing fluid is proper and the nutrient substances are abundant, the cell growth, the proliferation and the PHA synthesis of strains are mainly carried out, and the PHA synthesis is mainly used as the main physiological activities, so that the PHA synthesis rate is higher; the low concentration of nutrients in the acidized fluid is deficient, and rhodopseudomonas palustris mainly uses nutrients taken in the environment and intracellular polymers (such as PHA) for maintaining the carbon source and energy of the vital activities of the rhodopseudomonas palustris and the growth and the propagation of cells, so that the PHA synthesis rate is low. And when the concentration of the substrate is lower, the substrate uptake of rhodopseudomonas palustris can be influenced, so that PHA bacteria grow too slowly, and the PHA synthesis efficiency is low. A substrate concentration that is too high may adversely affect P.palustris because excessive VFA will penetrate the cells and cause a decrease in intracellular pH, thereby affecting the microbial PHA synthesis. The concentration of the anaerobic hydrolysis acidification liquid is shown to be optimally diluted to 2202.21 mg/L.

(3) The initial pH value of the culture is determinedThe secondary settings are 6.5, 7, 7.5, 8, 8.5. The experimental conditions are as follows: 10g/L Fe is added into an anaerobic hydrolytic acidification system for producing VFAs ₃ O ₄ The amount of the inoculated strain was 10% when PHA was synthesized, and the other experimental conditions were the same as in example 1. After completion of the culture, the PHA synthesis ratio of each group was measured, and the results are shown in FIG. 15.

As can be seen from FIG. 15, when the pH was 6.5, the normal activity of Rhodopseudomonas palustris was affected, probably because the cell permeability and the enzyme activity of Rhodopseudomonas palustris were inhibited due to the excessively low pH in the reaction system. When the pH is raised to 7.0 and 8.0, the PHA synthesis rate is higher, and can reach 40.12 percent at most, which is obviously higher than other pH conditions. Under the condition of low pH value, the acetic acid is not easy to be absorbed and utilized by rhodopseudomonas palustris, and undissociated acetic acid can quickly diffuse into the bacteria body to reduce the pH value of the bacteria body, thereby being not beneficial to the synthesis of PHA; when PHA accumulation occurs at higher pH, cells are driven to sustain life activities instead of PHA accumulation due to higher demand for energy. It was shown that the initial pH of the culture was 8 at the optimum.

(4) The inoculation amounts of rhodopseudomonas palustris are set to be 5%, 10%, 15%, 20% and 25% in sequence. The rest of the experimental conditions were the same as in example 1. After completion of the culture, the PHA synthesis ratio of each group was measured, and the results are shown in FIG. 16.

As can be seen from FIG. 16, when the inoculation amount was 5%, the PHA synthesis rate was only 27.80% lower, VFAs were degraded relatively slowly, and COD and ammonia nitrogen removal rates were lower. The inoculation amount is 15%, and the PHA synthesis rate can reach 46.33%. When the amount of the inoculum reaches 25%, the PHA yield can be further improved by further increasing the amount of the inoculum, but the degree is very limited. The inoculation amount of rhodopseudomonas palustris is shown to be the best 15%.

Test example 6

Exploring the effect of rhodopseudomonas palustris PHA synthesis under substrate conditions of different VFAs components, each set of experiments was performed in 3 replicates: the composition of VFAs in anaerobic hydrolyzed acidified solution of kitchen garbage and the ratio of PHB to PHV in PHA product in example 1 were examined, and the results are shown in FIG. 17.

As can be seen from fig. 17, rhodopseudomonas palustris preferentially utilizes acetic acid, butyric acid, and then propionic acid, valeric acid. Acetic acid, butyric acid are used up by the microorganisms within 25 days, while propionic acid is consumed after 30 days. Differences in the VFAs component of the substrates used to synthesize PHA result in differences in the PHB and PHV monomer content. The anaerobic hydrolysis acidification liquid of the kitchen waste mainly contains VFAs with even carbon numbers such as butyric acid, acetic acid and the like, and the PHV content synthesized by rhodopseudomonas palustris is lower than PHB. The relative contents of PHV and PHB are changed along with the progress of fermentation, and when the reaction is run for 30 days, the relative contents of PHB and PHV are 96.90 percent and 3.10 percent respectively.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims

1. A method for synthesizing polyhydroxyalkanoate, comprising the steps of: inoculating rhodopseudomonas palustris in anaerobic hydrolysis acidification liquid of the kitchen waste for culture, and extracting polyhydroxyalkanoate in the rhodopseudomonas palustris after the culture is finished.

2. The method of claim 1, wherein the preparation method of the anaerobic hydrolytic acidification liquid for kitchen waste comprises the following steps: and (3) carrying out anaerobic hydrolysis acidification after the kitchen waste is pretreated, centrifuging a hydrolysis acidification product, and reserving and taking supernatant.

3. The method of claim 2, wherein the pre-processing method comprises: crushing the kitchen waste and then carrying out ultrasonic-alkali combined pretreatment.

4. The method according to claim 3, wherein the conditions of the combined ultrasound-base pretreatment are: performing ultrasonic treatment for 8-12 min, wherein the pH value is 8.5-9.5.

5. The method according to claim 2, characterized in that the mass ratio of the kitchen waste to the inoculated sludge is 1.5-2.5: 1 mixing and then carrying out anaerobic hydrolysis acidification, wherein the anaerobic conditions are as follows: the pH value is 8.5-9.5, the anaerobic temperature is 33-36 ℃, and the time is 6-8 d.

6. The method of claim 2, wherein one or more of magnetite, anthraquinone-2-sulfonic acid, and alkyl glycosides are added to the anaerobic hydrolytic acidification system.

7. The method according to claim 1, wherein the anaerobic hydrolytic acidification liquid of the kitchen waste is used for eliminating mixed bacteria, diluted to the concentration of 2000-2400 mg/L, and inoculated with rhodopseudomonas palustris.

8. The method according to claim 1, wherein the inoculum size of the Rhodopseudomonas palustris is 13-16%.

9. The method of claim 1, wherein the culture conditions are: the illumination intensity is 1800-2200 lux, the rotating speed is 160-200 rpm, the reaction temperature is 28-32 ℃, the initial pH value is 7.8-8.2, and the culture time is 28-32 d.

10. The use of the method according to any one of claims 1 to 9 in kitchen waste treatment or in the industrial production of polyhydroxyalkanoates.