Bacterial system for synthesizing PHA (polyhydroxyalkanoate) by efficiently utilizing mixed acid mainly comprising lactic acid and application of bacterial system

Abstract

The invention relates to the technical field of microbial fermentation, in particular to a bacterial system for PHA synthesis by efficiently utilizing mixed acid mainly comprising lactic acid and application of the bacterial system. The fermentation strain composition provided by the invention can efficiently utilize the mixed organic acid mainly containing lactic acid to synthesize PHA, has higher PHA yield and conversion rate, is suitable for fermentation production of PHA by taking the mixed organic acid mainly containing lactic acid generated by anaerobic fermentation of organic wastes as a substrate, and is beneficial to improvement of substrate utilization rate and PHA production efficiency; the production cost of the PHA is reduced, the fermentation process of the PHA is simplified, and the application prospect is relatively good.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial fermentation, and particularly relates to a bacterial strain for efficiently synthesizing PHA by using a mixed acid mainly composed of lactic acid and its application. Background Art

[0002] Petroleum-based traditional plastics have long been an indispensable material in human production and life. From 1950 to 2015, 8.3 billion tons of virgin plastics have been produced globally. However, for the large amount of plastic waste generated, there is a lack of effective treatment methods. It is estimated that from 1950 to 2015, about 4.6 billion tons of plastic waste were discarded or landfilled into natural systems. Due to the non-degradability of petroleum-based plastics, plastic waste in the natural environment seriously threatens the survival of wild animals and accumulates in the food chain in the form of "microplastics", thus directly threatening human health. In order to reduce plastic pollution caused by the use of petroleum-based plastics, the development of "biodegradable plastics" is an important research direction. Among them, polyhydroxyalkanoates (PHA) are regarded as the most promising substitutes for petroleum-based plastics due to their good biodegradability, biocompatibility and complete biosynthesis.

[0003] At present, PHA is mainly synthesized by pure bacteria fermentation. However, due to the need for refined substrates and a strictly sterilized environment in this fermentation method, PHA still cannot be produced and applied on a large scale. To reduce costs, various organic wastes (such as straw, food waste, etc.) will be used as low-cost alternative substrates. The organic wastes are first anaerobically fermented into various short-chain organic acids (acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, etc.) and then supplied to various PHA-synthesizing microorganisms for PHA synthesis.

[0004] At present, the bacteria commonly used for PHA biosynthesis mainly come from Azoarcus, Paracoccus, Pseudofulvimonas, Amaricoccus, etc. During the anaerobic fermentation of organic wastes, under certain conditions, the organic acids produced are mixed organic acids dominated by lactic acid. For such anaerobic fermentation products, it is difficult for a single strain to efficiently utilize lactic acid while also utilizing other organic acids (acetic acid, butyric acid, propionic acid, valeric acid). However, there has been no report on a PHA mixed fermentation strain that can efficiently utilize lactic acid and simultaneously utilize acetic acid, butyric acid, propionic acid, and valeric acid. Therefore, it is necessary to develop a mixed strain that can efficiently utilize mixed organic acids dominated by lactic acid for PHA synthesis. Summary of the Invention

[0005] The present invention provides a bacterial strain for efficiently synthesizing PHA by using a mixed acid mainly composed of lactic acid and its application.

[0006] For the development of mixed fermentation strains for PHA synthesis, the prior art mostly enriches PHA-producing mixed flora through activated sludge. However, the mixed flora obtained by enriching activated sludge contains various known and unknown microorganisms, and their activity is inhibited when using mixed organic acids (mixed acids) dominated by lactic acid, resulting in low PHA synthesis efficiency. The present invention aims to develop an artificial bacterial system with a clear and simple composition for PHA production. During the research and development process, it was unexpectedly found that a mixed strain obtained by combining five bacteria, namely Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC49933, and Azomonas agilis NBRC 102607, can efficiently utilize mixed organic acids dominated by lactic acid to synthesize PHA. The rate of lactic acid utilization by this mixed strain is significantly higher than that of other organic acids, and it can also utilize organic acids such as acetic acid, propionic acid, butyric acid, and valeric acid at the same time. It is particularly suitable for fermenting PHA using mixed organic acids dominated by lactic acid as the substrate.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] The present invention provides a fermentation strain composition, which comprises Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC49933, and Azomonas agilis NBRC 102607.

[0009] In the above-mentioned bacterial strain composition, Amaricoccus kaplicensis ACM 5099 is a Gram-negative, aerobic coccus isolated from activated sludge and is currently mainly used as a polyphosphate-accumulating bacterium; Paracoccus sanguinis DSM29303 is a Gram-negative, non-motile, rod-shaped bacterium isolated from clinical samples; Aminobacter aganoensis ATCC 49933 is a Gram-negative, non-pore-forming, sub-large, flagellated rod-shaped bacterium; Azoarcus communis DSM12120 is a Gram-negative, chemoorganoheterotrophic bacterium isolated from the soil environment of plant roots and is mainly used as a nitrogen-fixing bacterium; Azomonas agilis NBRC102607 is an aerobic, mesophilic, Gram-negative bacterium and is mainly used as a nitrogen-fixing bacterium. None of the above-mentioned bacterial strains are known PHA-producing bacterial strains. However, the present invention unexpectedly discovers that when they are used in combination, they can efficiently utilize a mixed organic acid dominated by lactic acid to ferment and produce PHA.

[0010] Preferably, in the fermentation bacterial strain composition, the proportions of the cell dry weights of Amaricoccus kaplicensis ACM5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 40-50%, 25-35%, 15-20%, 3-7%, and 1-5% respectively.

[0011] More preferably, in the fermentation bacterial strain composition, the proportions of the cell dry weights of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 40-44%, 28-30%, 18-20%, 5-7%, and 3-5% respectively.

[0012] Inoculate and ferment within the above-mentioned range of cell dry weight ratio. Each of the above-mentioned strains can not only grow rapidly, but also cooperate more effectively to improve the efficiency of synthesizing PHA using organic acids such as lactic acid. In particular, it can ensure the efficient utilization of lactic acid to synthesize PHA, enabling the effective utilization of the mixed organic acid substrate dominated by lactic acid.

[0013] The above-mentioned fermentation strain composition is a fermentation strain composition for PHA synthesis, preferably a fermentation strain composition for synthesizing PHA using a mixed organic acid dominated by lactic acid.

[0014] In the present invention, the fermentation strain composition can be prepared into a liquid inoculant (such as a bacterial solution) or a solid inoculant (such as freeze-dried bacterial powder).

[0015] The present invention provides the application of the above-mentioned fermentation strain composition in PHA production.

[0016] In the above application, the fermentation strain composition serves as the fermentation strain for PHA production.

[0017] Preferably, the carbon source for PHA production contains organic acids.

[0018] Preferably, the organic acid is a mixed organic acid containing lactic acid.

[0019] Preferably, in the mixed organic acid, the content of lactic acid is higher than that of other organic acids.

[0020] More preferably, the mixed organic acid contains lactic acid and one or more selected from acetic acid, propionic acid, butyric acid, and valeric acid.

[0021] In some embodiments of the present invention, the mixed organic acid contains lactic acid, acetic acid, propionic acid, butyric acid, and valeric acid.

[0022] In the above application, the fermentation substrate for PHA production can be the anaerobic fermentation broth of organic waste (such as straw, food waste, etc.), which contains lactic acid, acetic acid, propionic acid, butyric acid, and valeric acid, and the content of lactic acid is higher than that of acetic acid, propionic acid, butyric acid, and valeric acid.

[0023] The present invention provides the application of the above-mentioned fermentation strain composition in preparing a fermentation strain for PHA production.

[0024] The fermentation strain composition provided by the present invention can be used alone as the fermentation strain for PHA production or in combination with other PHA fermentation strains.

[0025] The present invention provides a method for fermentatively producing PHA, which includes the step of culturing the above-mentioned fermentation strain composition to obtain a culture containing PHA.

[0026] Preferably, the cultivation includes fermentation cultivation, and the carbon source for the fermentation cultivation contains organic acids.

[0027] Preferably, the organic acid is a mixed organic acid containing lactic acid, and in the mixed organic acid, the content of lactic acid is higher than that of other organic acids.

[0028] More preferably, the mixed organic acid contains lactic acid and one or more selected from acetic acid, propionic acid, butyric acid, and valeric acid.

[0029] In some embodiments of the present invention, the mixed organic acid contains lactic acid, acetic acid, propionic acid, butyric acid, and valeric acid.

[0030] In the above method, the fermentation substrate for PHA production can be the anaerobic fermentation broth of organic waste (such as straw, food waste, etc.), which contains lactic acid, acetic acid, propionic acid, butyric acid, and valeric acid, and the content of lactic acid is higher than that of acetic acid, propionic acid, butyric acid, and valeric acid.

[0031] Preferably, the temperature of the fermentation cultivation is 25 - 28 °C, the pH is 6.8 - 7.2, and the dissolved oxygen is 3 - 8 mg / L.

[0032] More preferably, the temperature of the fermentation cultivation is 25 - 27 °C, the pH is 6.9 - 7.1, and the dissolved oxygen is 4 - 7 mg / L.

[0033] Preferably, the inoculum amount for the fermentation cultivation is 4000 - 6000 mg of cell dry weight / L.

[0034] The above cultivation may further include a step of activating the fermentation strain. Preferably, Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are separately activated and cultured, and after collecting the bacterial cells, they are mixed and inoculated into the fermentation medium in proportion.

[0035] In some embodiments of the present invention, in addition to the mixed organic acid, the fermentation medium further contains inorganic salts, or further contains inorganic salts, EDTA, and thiourea. Preferably, the fermentation medium contains the mixed organic acid and MgSO4, EDTA, CaCl2, K2HPO4, KH2PO4, thiourea, FeCl3, H3BO3, CuSO4, KI, MnCl2, Ma2MoO, ZnSO4, and CoCl2.

[0036] In some embodiments of the present invention, the fermentation medium comprises: acetic acid 200 - 300 mg / L, propionic acid 200 - 300 mg / L, butyric acid 200 - 300 mg / L, valeric acid 200 - 300 mg / L, lactic acid 3000 - 5000 mg / L, and MgSO4·7H2O 0.5 - 0.8 g / L, EDTA 0.1 - 0.15 g / L, CaCl2·2H2O 0.05 - 0.15 g / L, K2HPO4 0.04 - 0.08 g / L, KH2PO4 0.03 - 0.05 g / L, thiourea 5 - 15 mg / L, FeCl3·6H2O 1 - 2 mg / L, H3BO3 0.1 - 0.2 mg / L, CuSO4·5H2O 0.02 - 0.04 mg / L, KI 0.02 - 0.04 mg / L, MnCl2·4H2O 0.1 - 0.2 mg / L, Ma2MoO·2H2O 0.05 - 0.07 mg / L, ZnSO4·7H2O 0.1 - 0.2 mg / L, CoCl2·6H2O 0.1 - 0.2 mg / L.

[0037] The beneficial effects of the present invention at least include: The fermentation strain composition provided by the present invention can efficiently utilize mixed organic acids mainly composed of lactic acid to synthesize PHA, and has a high PHA yield and conversion rate. This fermentation strain composition is suitable for fermenting and producing PHA using mixed organic acids mainly composed of lactic acid generated by anaerobic fermentation of organic waste as a substrate, which is conducive to improving the substrate utilization rate and PHA production efficiency, provides an effective method for reducing the production cost of PHA and simplifying its fermentation process, and has good application prospects. Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0039] The medium formulations used in the following examples are as follows:

[0040] Medium1 (1L): Tryptone 10 g, yeast extract 5 g, sodium chloride 10 g, pH 7.4.

[0041] Medium2 (1L): MgSO4·7H2O, 0.67 g; EDTA, 0.11 g; CaCl2·2H2O, 0.08 g; K2HPO4, 0.048 g; KH2PO4, 0.038 g; thiourea (10 mg); Medium3, 1 mL.

[0042] Medium 3 (1 L): FeCl3·6H2O, 1.5 g; H3BO3, 0.15 g; CuSO4·5H2O, 0.03; KI, 0.03 g; MnCl2·4H2O, 0.12 g; Ma2MoO·2H2O, 0.06 g; ZnSO4·7H2O, 0.12 g; CoCl2·6H2O, 0.15 g.

[0043] Example 1 Strain Activation and Pre - culture

[0044] After aerobic activation of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 on the solid medium of Medium 1 at 37°C for 24 h respectively, they were then inoculated into the liquid medium of Medium 1 respectively and pre - cultured under aerobic conditions at 26°C for 24 h. The pre - cultured bacterial liquid was centrifuged at 8000×g for 2 min to collect the bacterial cells for the preparation of the fermentation strain composition.

[0045] Example 2 Detection of Fermentation Strain Composition and Its Organic Acid Utilization Efficiency

[0046] This embodiment provides a fermentation strain composition, which comprises Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607. Among them, the proportions of the dry cell weights of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 44.0%, 30.0%, 18.0%, 5.0%, and 3.0% respectively in sequence.

[0047] The above fermentation strain composition can be obtained by mixing the bacterial cells pre-cultured from each strain in Example 1 according to a proportion.

[0048] To prove that the above fermentation strain composition can specifically utilize lactic acid and can also utilize acetic acid, propionic acid, butyric acid, and valeric acid, the above fermentation strain composition is used for aerobic fermentation in a 400 mL fermenter with a mixed organic acid (acetic acid, propionic acid, butyric acid, valeric acid, and lactic acid) as the carbon source. The fermentation medium is: adding the corresponding organic acid to Medium2 and adjusting the pH to 7.0 ± 0.1. The proportions of different organic acids in the mixed organic acid are shown in Table 1. The inoculation amount of the fermentation strain composition is 5000 mg dry cell weight / L. The fermentation temperature is 26 °C, the pH is 7, and the dissolved oxygen is 5 - 7 mg / L.

[0049] Table 1 Composition of the mixed organic acid

[0050]

[0051] The fermentation adopts 3 h batch fermentation, and samples are taken during the fermentation process to measure the organic acid concentration and the proportion of PHA in the cells.

[0052] The results are shown in Table 2.

[0053] Table 2 Experimental results of batch fermentation of the mixed organic acid

[0054]

[0055] The results showed that, whether in the startup stage of 0.5 h before fermentation or in the overall fermentation process of 3 h, the consumption rate of lactic acid was significantly faster than that of other organic acids. After 3 h of fermentation, the PHA content in the cells increased from 6.2% of the cell dry weight to 37% of the cell dry weight, and the contribution rate of lactic acid to the PHA increment was up to 56% at most. The above results indicate that this fermentation strain composition can preferentially utilize lactic acid in the mixed organic acids for PHA synthesis and can also utilize other organic acids.

[0056] Example 3 Fermentation Strain Composition and Detection of Its Utilization Efficiency of Organic Acids

[0057] This example provides a fermentation strain composition, which comprises Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607. Among them, the proportions of the cell dry weights of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 40%, 28%, 20%, 7%, and 5% respectively in turn.

[0058] The above fermentation strain composition can be obtained by mixing the thalli pre-cultured from each strain in Example 1 according to the proportion.

[0059] To prove that the above fermentation strain composition can specifically utilize lactic acid and can also utilize acetic acid, propionic acid, butyric acid, and valeric acid, aerobic fermentation was carried out in a 400 mL fermenter using the above fermentation strain composition with mixed organic acids (acetic acid, propionic acid, butyric acid, valeric acid, and lactic acid) as the carbon source. The fermentation medium was: adding the corresponding organic acids to Medium2 and adjusting the pH to 7.0 ± 0.1. The proportions of different organic acids in the mixed organic acids are shown in Table 1. The inoculum amount of the fermentation strain composition was 5000 mg cell dry weight / L. The fermentation temperature was 26 °C, the pH was 7, and the dissolved oxygen was 5 - 7 mg / L.

[0060] The fermentation was carried out in 3-hour batch fermentation. During the fermentation process, samples were taken to measure the concentration of organic acids and the proportion of PHA in the cells.

[0061] The results are shown in Table 3.

[0062] Table 3 Results of batch fermentation of mixed organic acids

[0063]

[0064] Example 4 Fermentation strain composition for synthesizing PHA using mixed organic acids

[0065] This example provides a method for synthesizing PHA using the fermentation strain composition of Example 2 with a mixed organic acid dominated by lactic acid, as follows:

[0066] Fermentation medium: Appropriate organic acids were added to Medium2 and the pH was adjusted to 7.0 ± 0.1. The composition of the mixed organic acids (final concentration in the fermentation medium) is shown in Table 4.

[0067] Table 4 Composition of mixed organic acids dominated by lactic acid

[0068]

[0069] Inoculation amount of the fermentation strain composition: 5000 mg cell dry weight / L.

[0070] Fermentation conditions: 400 mL aerobic fermentation tank, fermentation temperature 26 °C, pH 7, dissolved oxygen 5 - 7 mg / L.

[0071] Repeated batch fermentation, 1 hour for each batch, repeated 5 times.

[0072] The results showed that after 5 batches of fermentation, the PHA content in the cells increased from 7.49% of the cell dry weight to 59.45% of the cell dry weight. Among them, poly-3-hydroxybutyrate (PHB) accounted for 52.18% of the cell dry weight, and poly-3-hydroxyvalerate (PHV) accounted for 7.27% of the cell dry weight. By calculating the ratio of the mass of carbon in the PHA increment to the mass of carbon in the consumed organic acids, this fermentation strain composition could convert 65.3% of the carbon in the organic acids into PHA and store it in the cells. Therefore, this fermentation strain composition could efficiently utilize the mixed organic acids dominated by lactic acid for PHA synthesis.

[0073] Example 5 Fermentation strain composition for synthesizing PHA using mixed organic acids

[0074] This example provides a method for synthesizing PHA using the fermentation strain composition of Example 3 with a mixed organic acid dominated by lactic acid, as follows:

[0075] Fermentation medium: Add the corresponding organic acids to Medium2 and adjust the pH to 7.0 ± 0.1. The composition of the mixed organic acids (final concentration in the fermentation medium) is shown in Table 5.

[0076] Table 5 Composition of Mixed Organic Acids with Lactic Acid as the Main Component

[0077]

[0078] Inoculum amount of the fermentation strain composition: 5000 mg cell dry weight / L.

[0079] Fermentation conditions: 400 mL aerobic fermentation tank, fermentation temperature 26 °C, pH 7, dissolved oxygen 5 - 7 mg / L.

[0080] Repeat batch fermentation, 1 hour for each batch, repeat 5 times.

[0081] The results showed that after 5 batches of fermentation, the PHA content in the cells increased from 6.87% of the cell dry weight to 60.89% of the cell dry weight. Among them, poly-3-hydroxybutyrate (PHB) accounted for 53.46% of the cell dry weight, and poly-3-hydroxyvalerate (PHV) accounted for 7.43% of the cell dry weight. By calculating the ratio of the mass of carbon in the increased PHA to the mass of carbon in the consumed organic acids, this fermentation strain composition could convert 66.34% of the carbon in the organic acids into PHA and store it in the cells. Therefore, this fermentation strain composition could efficiently utilize mixed organic acids with lactic acid as the main component for PHA synthesis.

[0082] Comparative Example 1

[0083] This comparative example provides a fermentation strain composition, which comprises Amaricoccus kaplicensis ACM 5099, Paracoccus aurantiacus CGMCC 1.13898, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Prosthecobacter vanneervenii ATCC 700199. Among them, the dry cell weight percentages of Amaricoccus kaplicensis ACM 5099, Paracoccus aurantiacus CGMCC 1.13898, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Prosthecobacter vanneervenii ATCC 700199 are 44.0%, 30.0%, 18.0%, 5.0%, and 3.0% respectively.

[0084] The above fermentation strain composition can be obtained by mixing the bacteria obtained through preculture in proportion, and the preculture method refers to Example 1.

[0085] Using the above fermentation strain composition, the method of Example 4 is adopted to synthesize PHA using a mixed organic acid dominated by lactic acid. The results show that after 5 batches of fermentation, the PHA content in the cells increases from 6.98% of the dry cell weight to 30.76% of the dry cell weight. Among them, poly-3-hydroxybutyrate (PHB) accounts for 24.53% of the dry cell weight, and poly-3-hydroxyvalerate (PHV) accounts for 6.23% of the dry cell weight. By calculating the ratio of the mass of carbon in the PHA increment to the mass of carbon in the consumed organic acid, this fermentation strain composition can convert 40.78% of the carbon in the organic acid into PHA and store it in the cells. It can be seen that the efficiency of this fermentation strain composition in synthesizing PHA using a mixed organic acid dominated by lactic acid is significantly lower than that of the fermentation strain composition in the example.

[0086] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A fermentation strain composition, characterized in that, The fermentation bacterial strain composition comprises Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607.

2. The fermentation strain composition according to claim 1, characterized in that, In the fermentation bacterial strain composition, the dry cell weight percentages of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 40-50%, 25-35%, 15-20%, 3-7%, and 1-5% respectively.

3. The fermentation strain composition according to claim 2, characterized in that, In the fermentation bacterial strain composition, the dry cell weight percentages of Amaricoccus kaplicensis ACM 5099, Paracoccus sanguinis DSM 29303, Azoarcus communis DSM 12120, Aminobacter aganoensis ATCC 49933, and Azomonas agilis NBRC 102607 are 40-44%, 28-30%, 18-20%, 5-7%, and 3-5% respectively.

4. Use of the fermentation strain composition according to any one of claims 1 to 3 in PHA production.

5. The use according to claim 4, characterized in that, The carbon source for the PHA production comprises organic acids; Preferably, the organic acid is a mixed organic acid containing lactic acid; More preferably, in the mixed organic acid, the content of lactic acid is higher than that of other organic acids.

6. The use according to claim 5, characterized in that, The mixed organic acid comprises lactic acid and one or more selected from acetic acid, propionic acid, butyric acid, and valeric acid.

7. Use of the fermentation strain composition according to any one of claims 1 to 3 in preparing a fermentation strain for PHA production.

8. A method for fermentatively producing PHA, characterized in that, The method includes the step of culturing the fermentation bacterial strain composition according to any one of claims 1 to 3 to obtain a culture containing PHA.

9. The method according to claim 8, characterized in that, The culturing includes fermentation culture, and the carbon source for the fermentation culture comprises organic acids; Preferably, the organic acid is a mixed organic acid containing lactic acid, and in the mixed organic acid, the content of lactic acid is higher than that of other organic acids; More preferably, the mixed organic acid comprises lactic acid and one or more selected from acetic acid, propionic acid, butyric acid, and valeric acid.

10. The method according to claim 9, characterized in that, The temperature of the fermentation culture is 25-28 °C, the pH is 6.8-7.2, and the dissolved oxygen is 3-8 mg / L.

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