Flavobacterium-containing complex microbial inoculant and application thereof

Abstract

The invention relates to the field of microbial engineering, and discloses a complex microbial inoculant containing flavobacterium and application of the complex microbial inoculant. The invention relates to a compound bacterial agent, which is characterized in that the compound bacterial agent contains Neomelatonea (Neomelatonea), vibrio azoarcus (Azoarcus), Aromatobacterium (Aromatobacterium), Flavobacterium (Flavobacterium) and Paracoccus (Paracoccus). The complex microbial inoculant has high utilization rate of organic acid (especially acetic acid and / or propionic acid), and can quickly adapt to PHA synthesis of mixed organic acid dominated by acetic acid and / or propionic acid, so that the raw material source of PHA is widened, and large-scale production of PHA is facilitated.

Description

Technical Field

[0001] The invention relates to the field of microbial engineering, in particular to a composite bacterial agent containing Flavobacterium and application thereof. Background Art

[0002] Petroleum-based traditional plastics have long been an indispensable material in the production and life of human beings around the world. From 1950 to 2015, a total of 8.3 billion virgin plastics have been produced worldwide. There is a lack of effective treatment methods for the large amount of plastic waste produced. From 1950 to 2015, about 4.6 billion tons of plastic waste were discarded or landfilled in natural systems. Due to the non-degradability of petroleum-based plastics, plastic waste in the natural environment seriously threatens the survival of wildlife and is enriched in the food chain in the form of "microplastics", which directly threatens human health. In order to reduce the plastic pollution caused by the use of petroleum-based plastics, the development of biodegradable "biodegradable plastics" is an important research direction. Among them, polyhydroxyalkanoic acid (PHA) is regarded as the most promising substitute for petroleum-based plastics due to its good biodegradability, biocompatibility and complete biosynthesis. At present, PHA is mainly synthesized by pure bacterial fermentation, but due to the need for refined substrates and strict sterilization environment, PHA still cannot be expanded for production and application. In order to reduce costs, various organic wastes (straw, kitchen waste, etc.) will be used as low-cost alternative substrates. In actual application, organic wastes are first converted into various short-chain organic acids (acetic acid, propionic acid, butyric acid, valeric acid and lactic acid, etc.) through anaerobic fermentation, and then supplied to various PHA-synthesizing microorganisms for PHA synthesis.

[0003] At present, the bacteria commonly used for PHA biosynthesis mainly come from Azoarcus, Paracoccus, Pseudofulvimonas, Amaricoccus, etc. In the actual anaerobic fermentation process, if the sugar content in the organic waste is high, the acid composition of the organic acid produced is often acetic acid and propionic acid as the main organic acid components. It is difficult for current PHA synthesizing microorganisms to efficiently utilize acetic acid and propionic acid while also utilizing other organic acids (n-butyric acid, n-valeric acid and lactic acid). Therefore, it is of great significance to develop a bacterial agent that can efficiently utilize organic acids (especially mixed organic acids dominated by acetic acid and propionic acid) for PHA synthesis. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that it is difficult to efficiently utilize organic acids in the prior art, and to provide a composite bacterial agent containing Flavobacterium and use thereof.

[0005] In order to achieve the above-mentioned object, the first aspect of the present invention provides a composite bacterial agent, which contains Neomegalonema, Azoarcus, Aromatoleum, Flavobacterium and Paracoccus.

[0006] The second aspect of the present invention provides a method for preparing polyhydroxyalkanoate, which comprises: inoculating the composite bacterial agent as described above into a fermentation medium for fermentation to obtain a fermentation product containing polyhydroxyalkanoate.

[0007] The third aspect of the present invention provides the use of bacteria or composite bacterial agents in synthesizing polyhydroxyalkanoates using organic acids.

[0008] Through the above technical scheme, the composite bacterial agent of the present invention has a high utilization rate of organic acids (especially acetic acid and / or propionic acid), and can quickly adapt to the synthesis of PHA with mixed organic acids dominated by acetic acid and / or propionic acid, thereby broadening the raw material source of PHA and being more conducive to the large-scale production of PHA. DETAILED DESCRIPTION

[0009] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0010] The composite bacterial agent provided by the present invention contains new big silk catfish, nitrogen fixing vibrio, dearomatous bacteria, Flavobacterium and Paracoccus. Among them, as long as the different microorganisms as described above are combined, the utilization rate of organic acids (especially acetic acid and / or propionic acid) can be effectively improved, and there is no special requirement for the ratio of each microorganism, but preferably, the cell dry weight ratio of new big silk catfish to Paracoccus in the composite bacterial agent is 11-25:1, more preferably 13-18:1.

[0011] Preferably, the ratio of dry cell weight of Azoarium to that of Paracoccus in the composite bacterial agent is 3-6:1, more preferably 4-5:1.

[0012] Preferably, the ratio of the dry cell weight of dearomatizing bacteria to that of Paracoccus in the composite bacterial agent is 1-3:1, more preferably 1.3-2:1.

[0013] Preferably, the ratio of the dry cell weight of Flavobacterium to that of Paracoccus in the composite bacterial agent is 0.6-3:1, more preferably 1-1.5:1.

[0014] In the present invention, the specific strain of the neomegalonema can be a common strain in the art. Preferably, the neomegalonema is filamentous neomegalonema (Neomegalonema perideroedes), more preferably filamentous neomegalonema DSM 15528 (abbreviated as NP, from the German Microbiological Collection Center (DSMZ)).

[0015] In the present invention, the specific strain of the nitrogen-fixing arc bacterium can be a common strain in the art. Preferably, the nitrogen-fixing arc bacterium is common nitrogen-fixing arc bacterium (Azoarcus communis), and more preferably, common nitrogen-fixing arc bacterium DSM 12120 (abbreviated as AC, from the German Microorganism Collection Center).

[0016] In the present invention, the specific strain may be a common strain in the art. Preferably, the dearomatizing bacterium is Aromatoleum Toluvorans, more preferably Aromatoleum Toluvorans DSM 15124 (AT for short, from the German Collection of Microorganisms).

[0017] In the present invention, the specific strain of can be a common strain in the art. Preferably, the Flavobacterium is Flavobacterium lacus, more preferably Flavobacterium lacus NBRC 109715 (FL for short, from the Bioresource Collection Center (NBRC) of the Biotechnology Institute, National Institute of Technology and Evaluation, Japan).

[0018] In the present invention, the specific strain of can be a common strain in the art. Preferably, the paracoccus is at least one of Paracoccus sanguinis, Paracoccus mangrovi and Paracoccus aurantiacus, more preferably Paracoccus sanguinis DSM 29303 (PS for short, from the German Collection of Microorganisms).

[0019] The composite bacterial agent of the present invention can efficiently utilize organic acid to synthesize PHA. Therefore, the method for preparing PHA provided by the present invention comprises: inoculating the composite bacterial agent as described above into a fermentation medium for fermentation to obtain a fermentation product containing PHA.

[0020] According to the present invention, the carbon source and inorganic salt in the fermentation medium can be substances commonly used in the art that can provide C and inorganic salt (trace elements), respectively.

[0021] According to a preferred embodiment of the present invention, the carbon source in the fermentation medium is an organic acid, which can be an organic acid commonly used in the art for fermentation to produce PHA, more preferably a monoacid with a carbon number of 1-5 (such as 1, 2, 3, 4, 5) (such as at least one (or all) of acetic acid, propionic acid, n-butyric acid, n-valeric acid and lactic acid), further preferably a monoacid with a carbon number of 2-4, and most preferably acetic acid and / or propionic acid. The organic acid can be provided by a mixed organic acid containing a plurality of organic acids (acetic acid, propionic acid, n-butyric acid, n-valeric acid and lactic acid), such as an anaerobic fermentation product of organic waste (various crop straws, kitchen waste and / or mixtures thereof), thereby further broadening the raw material source of PHA and reducing the synthesis cost of PHA. According to a preferred embodiment of the present invention, in the fermentation medium, the contents of acetic acid, propionic acid, n-butyric acid, n-valeric acid and lactic acid are each independently in the range of 0.2-2 g / L, preferably 0.7-1.2 g / L.

[0022] The anaerobic fermentation process of organic waste (various crop straws, food waste and / or mixtures thereof, etc.) can be carried out in a common manner in the art, and the anaerobic fermentation method can be medium temperature (37°C) / high temperature (55°C) continuous anaerobic fermentation.

[0023] According to a preferred embodiment of the present invention, the content of carbon source in the fermentation medium is 3-20 g / L.

[0024] According to a preferred embodiment of the present invention, the fermentation medium may also contain organic amines to inhibit denitrification, but the total content of nitrogen in the fermentation medium is less than 20 mg / L. The content of the organic amines may be 50-170 mg / L, and the organic amines may be selected from ethylenediaminetetraacetic acid and / or thiourea. More preferably, each liter of the fermentation medium contains 0.05-0.15 g of ethylenediaminetetraacetic acid. More preferably, each liter of the fermentation medium contains 5-15 mg of thiourea. Further preferably, the fermentation medium also contains ethylenediaminetetraacetic acid and thiourea. According to a preferred embodiment of the present invention, the fermentation medium does not contain common nitrogen sources used for bacterial culture (such as corn steep liquor, peptone, yeast powder, urea, ammonium sulfate, ammonia, nitrates, etc.).

[0025] According to the present invention, the inorganic salt in the fermentation medium can mainly provide trace elements, and can be various water-soluble inorganic salts commonly used in the art. In a preferred embodiment of the present invention, the inorganic salt in the fermentation medium includes at least one of magnesium salts, calcium salts, potassium salts, iron salts, copper salts, manganese salts, sodium salts, zinc salts, and cobalt salts, and more preferably includes at least one of magnesium sulfate, calcium chloride, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, thiourea, ferric chloride, copper sulfate, potassium iodide, manganese chloride, sodium molybdate, zinc sulfate, and cobalt chloride.

[0026] According to a preferred embodiment of the present invention, the content of inorganic salts in the fermentation medium is 0.1-2 g / L.

[0027] More preferably, the fermentation medium contains 0.3-0.5 g of magnesium sulfate per liter.

[0028] More preferably, the fermentation medium contains 0.04-0.1 g of calcium chloride per liter.

[0029] More preferably, each liter of the fermentation medium contains 0.02-0.1 g of dipotassium hydrogen phosphate.

[0030] More preferably, the fermentation medium contains 0.01-0.08 g of potassium dihydrogen phosphate per liter.

[0031] More preferably, the fermentation medium contains 0.5-2 mg of ferric chloride per liter.

[0032] More preferably, the fermentation medium contains 0.01-0.05 mg copper sulfate per liter.

[0033] More preferably, each liter of the fermentation medium contains 0.01-0.05 mg potassium iodide.

[0034] More preferably, the fermentation medium contains 0.05-0.1 mg manganese chloride per liter.

[0035] More preferably, each liter of the fermentation medium contains 0.03-0.1 mg of sodium molybdate.

[0036] More preferably, the fermentation medium contains 0.05-0.3 mg zinc sulfate per liter.

[0037] More preferably, the fermentation medium contains 0.05-0.2 mg of cobalt chloride per liter.

[0038] According to a preferred embodiment of the present invention, the fermentation medium further contains boric acid, and more preferably, each liter of the fermentation medium contains 0.05-0.2 mg of boric acid.

[0039] According to a particularly preferred embodiment of the present invention, each liter of fermentation medium contains 3-20 g of organic acid, 0.3-0.5 g of magnesium sulfate, 0.05-0.15 g of ethylenediaminetetraacetic acid, 0.04-0.1 g of calcium chloride, 0.02-0.1 g of dipotassium hydrogen phosphate, 0.01-0.08 g of potassium dihydrogen phosphate, 5-15 mg of thiourea, 0.5-2 mg of ferric chloride, 0.05-0.2 mg of boric acid, 0.01-0.05 mg of copper sulfate, 0.01-0.05 mg of potassium iodide, 0.05-0.1 mg of manganese chloride; 0.03-0.1 mg of sodium molybdate, 0.05-0.3 mg of zinc sulfate, and 0.05-0.2 mg of cobalt chloride.

[0040] According to the present invention, the initial pH value of the fermentation medium may be 6-8, preferably 7±0.1.

[0041] According to the present invention, the fermentation can be carried out under conditions that are conducive to the synthesis of PHA by the microorganisms in the composite bacterial agent. Preferably, the fermentation conditions include: a temperature of 20-35°C and a time of 2-10 hours. The fermentation is preferably carried out under aerobic conditions, preferably, the oxygen content is ≥4 mg / L, more preferably 6-8 mg / L.

[0042] According to the present invention, the inoculation amount of the composite bacterial agent can be 4000-10000 mg of dry cell weight per liter of fermentation medium.

[0043] According to the present invention, before fermentation, the method may further include: the steps of activating and amplifying the composite bacterial agent (pre-culture), wherein the activation can restore the dormant microorganisms to a normal living state, usually on a solid culture medium. The amplification can increase the total amount and concentration of the microorganisms so as to meet the fermentation requirements, usually in a liquid culture medium. The activation and amplification can be performed in a manner commonly used in the art, for example, LB culture medium can be used.

[0044] According to the method of the present invention, organic acids are used to synthesize PHA, and the utilization rate of organic acids is high, especially acetic acid and / or propionic acid. When fermentation is carried out with a mixed organic acid containing acetic acid and propionic acid, the consumption rates of acetic acid and propionic acid are both greater than 180 mg / L / h.

[0045] The inventors of the present invention have discovered for the first time that the new large silk catfish, dearomatized bacteria and Flavobacterium (or the composite bacterial agent) can metabolize organic acids as carbon sources to produce PHA. Therefore, the present invention also provides the use of bacteria or composite bacterial agents in synthesizing PHA using organic acids, characterized in that the bacteria are selected from at least one of the new large silk catfish, dearomatized bacteria and Flavobacterium as described above, and the composite bacterial agent is the composite bacterial agent as described above. The specific types of the organic acids are as described above and will not be repeated here.

[0046] The present invention will be described in detail below through examples. In the following embodiments, the method for determining the cell dry weight is a drying weighing method (10 ml of fermentation broth is centrifuged at 10,000 rpm, the supernatant is removed, and the biomass is then placed at 105° C. for drying for 12 h); the method for detecting the organic acid content in the fermentation broth is a high performance liquid chromatography detection method; the method for detecting the proportion of PHA in the cell is a gas chromatography-mass spectrometry detection method (based on trihydroxybutyric acid monomer and trihydroxyvaleric acid monomer): the fermentation broth is taken, centrifuged at 10,000 rpm, the supernatant is removed, the biomass is frozen at -80° C., and then freeze-dried to remove moisture; the dried biomass is placed in a glass digestion tube, 2 ml of acidified methanol (5% sulfuric acid) and 2 ml of chloroform are added; hydrolyzed at 105° C. for 6 hours; 1 mL of water is then added to the hydrolyzate, fully shaken, and after standing and stratification, 1 μL of the lower chloroform phase is taken; it is placed on a GCMS for detection; the standard curve is constructed using trihydroxybutyric acid monomer and trihydroxyvaleric acid monomer standards purchased from Sigma by the above method.

[0047]

[0048]

[0049] Example 1

[0050] (1) Culture medium

[0051] Culture medium 1 (1 L): 10 g tryptone, 5 g yeast extract, 10 g sodium chloride, pH = 7.4.

[0052] Medium 2 (1 L): MgSO 4 7H 2 O, 0.67g; EDTA, 0.11g; CaCl 2 ·2H 2 O, 0.08g; K 2 HPO 4 , 0.048g; KH 2 PO 4 , 0.038g; thiourea, 10mg; culture medium 3, 1mL.

[0053] Medium 3 (1 L): FeCl 3 6H 2 O, 1.5 g; H 3 BO 3 , 0.15g; CuSO 4 ·5H 2 O, 0.03 g; KI, 0.03 g; MnCl 2 ·4H 2 O, 0.12g; Na 2 MoO 4·2H 2 O, 0.06g; ZnSO 4 7H 2 O, 0.12 g; CoCl 2 6H 2 O, 0.15g.

[0054] (2) Strain activation and pre-culture

[0055] NP, AC, AT, FL and PS strains were inoculated on the solid medium of medium 1 (agar addition amount was 18 g / L) and activated at 37°C for 24 hours, and then inoculated into medium 1 (liquid medium) for 24 hours of pre-culture at 26°C. The pre-cultured bacterial solution was centrifuged at 8000g for 2 minutes, the bacteria were collected, and the composite bacterial agent was prepared according to the following cell dry weight ratio: NP (64%), AC (20%), AT (7%), FL (5%), PS (4%).

[0056] Example 2

[0057] This example is used to illustrate the method of using artificial bacteria to synthesize PHA using mixed organic acids. The specific operation is as follows:

[0058] In order to illustrate that the composite bacterial agent of the present invention can specifically and efficiently utilize acetic acid and propionic acid, the bacterial agent is used in the presence of mixed organic acids (acetic acid, propionic acid, n-butyric acid, n-valeric acid and lactic acid) in a 400mL fermenter (inoculation amount is 5000mg cell dry weight / L) for aerobic fermentation. The fermentation adopts 3h batch fermentation, the fermentation temperature is 26°C, and the oxygen content in the system is controlled to 6-8mg / L; the corresponding organic acid is added to the culture medium 2 and the pH is adjusted to 7±0.1 with sodium hydroxide as the fermentation medium, and the concentration of different organic acids in the fermentation medium is shown in Table 1; during the fermentation process, the organic acid content in the fermentation broth and the proportion of PHA in the cells are sampled and measured, and the results are shown in Table 2.

[0059] Table 1 Composition of mixed organic acids

[0060] Organic Acid Molar concentration (mmol / L) Mole (mmoL) Mass concentration (mg / L) Acetic acid 12 4.8 720 Propionic acid 12 4.8 888 Butyric acid 12 4.8 1056 Valeric acid 12 4.8 1224 lactic acid 12 4.8 1080

[0061] Table 2 Mixed organic acid batch fermentation experimental results

[0062]

[0063]

[0064] The above experimental results show that the consumption rates of acetic acid and propionic acid are relatively fast, whether in the start-up phase of 0.5h before fermentation or in the overall 3h. After 3h of fermentation, the PHA weight content in the cells increased from 9.17% of the cell dry weight to 50.51% of the cell dry weight, and the contribution rates of acetic acid and propionic acid to the PHA increment were relatively high, 24% and 31% respectively. Therefore, the bacterial agent can preferentially utilize acetic acid and propionic acid in the mixed organic acid for PHA synthesis.

[0065] Example 3

[0066] This example is used to illustrate the method of using artificial bacteria to synthesize PHA using mixed organic acids mainly composed of acetic acid and propionic acid. The specific operation is as follows:

[0067] In order to detect the maximum accumulation capacity of PHA of the composite bacterial agent of the present invention using a mixed organic acid mainly composed of acetic acid and propionic acid, repeated batch fermentation was carried out in a 400 mL aerobic fermenter using mixed organic acids (inoculation amount was 5000 mg cell dry weight / L), the fermentation temperature was 26 ° C, the oxygen content in the system was controlled to 6-8 mg / L, each batch was 1 hour, and repeated 5 times, the specific operation was as follows:

[0068] First batch: After inoculating the fermenter with the bacterial agent and adding the culture medium, ferment for one hour, let it stand for 30 minutes, let the bacteria sink, and remove 200 mL of the supernatant.

[0069] Second batch: Add 200 mL of new culture medium to the fermenter, ferment for one hour, let stand for 30 minutes, allow the bacteria to sink, and remove 200 mL of supernatant.

[0070] Third batch: Repeat the second batch operation.

[0071] Fourth batch: Repeat the second batch operation.

[0072] The fifth batch: add 200 mL of new culture medium to the fermenter, ferment for one hour, collect the bacteria, and complete the fermentation.

[0073] Among them, the corresponding organic acid was added to the culture medium 2 and the pH was adjusted to 7±0.1 with sodium hydroxide as the fermentation medium. The specific composition of the organic acid in the fermentation medium is shown in Table 3. During the fermentation process, samples were taken to determine the organic acid content in the fermentation broth and the proportion of PHA in the cells.

[0074] Table 3 Composition of mixed organic acids mainly composed of acetic acid and propionic acid

[0075] Organic Acid Mass concentration mg / L Acetic acid 2000 Propionic acid 2000 Butyric acid 350 Valeric acid 350 lactic acid 350

[0076] The experimental results show that after 5 batches of fermentation, the weight content of PHA in the cells increased from 6.75% of the cell dry weight to 62.41% of the cell dry weight, of which polytrihydroxybutyric acid PHB (calculated as trihydroxybutyric acid monomer) accounted for 27.7% of the cell dry weight, and polytrihydroxyvaleric acid PHV (calculated as trihydroxyvaleric acid monomer) accounted for 34.71% of the cell dry weight. By calculating the mass ratio of carbon in the PHA increment to the mass ratio of carbon in the consumed organic acid, the bacterial agent can convert 76.556% of the carbon in the organic acid in the fermentation system into PHA and store it in the cells. Therefore, the artificial bacterial agent can efficiently utilize mixed organic acids mainly composed of acetic acid and propionic acid for PHA synthesis.

[0077] The inventors of the present invention also found that after the fermentation, the proportion of each strain in the system was equivalent to that at the time of inoculation, indicating that each strain worked synergistically to improve the utilization rate of organic acids (especially acetic acid and / or propionic acid). Moreover, the new large silk catfish was the dominant bacteria before and after fermentation, indicating that the strain played a significant role in the synthesis of PHA using organic acids, suggesting that the strain may also be able to better utilize organic acids (especially acetic acid and / or propionic acid) to synthesize PHA when used alone.

[0078] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A composite bacterial agent containing Flavobacterium, It is characterized in that The composite bacterial agent contains Neomegalonema, Azoarcus, Aromatoleum, Flavobacterium and Paracoccus.

2. The composite bacterial agent according to claim 1, in, The cell dry weight ratio of Neoglobus sphaeroides, Azovibrio, Dearomatizing Bacteria, Flavobacterium and Paracoccus in the composite bacterial agent is 11-25:3-6:1-3:0.6-3:

1.

3. The composite bacterial agent according to claim 1, in, The cell dry weight ratio of Neoglobus sphaeroides, Azovibrio, Dearomatizing Bacteria, Flavobacterium and Paracoccus in the composite bacterial agent is 13-18:4-5:1.3-2:1-1.5:

1.

4. The composite bacterial agent according to claim 1, in, The new giant filamentous catfish bacteria is filamentous new giant filamentous catfish bacteria (Neomegalonema perideroedes); And / or, the Azoarcus is Azoarcus communis; And / or, the dearomatizing bacteria is Aromatoleum Toluvorans; And / or, the Flavobacterium is Flavobacterium lacus; And / or, the Paracoccus is at least one of Paracoccus sanguinis, Paracoccus mangrovi and Paracoccus aurantiacus.

5. The composite bacterial agent according to claim 1, in, The new giant catfish fungus is the filamentous new giant catfish fungus DSM15528; and / or, the Azoarium is Azoarium vulgaris DSM 12120; and / or, the dearomatizing bacteria is Toluvan dearomatizing bacteria DSM 15124; and / or, the Flavobacterium is Flavobacterium lacustris NBRC 109715; And / or, the Paracoccus is Paracoccus sanguineus DSM 29303.

6. A method for preparing polyhydroxyalkanoate, It is characterized in that The method comprises: inoculating the composite bacterial agent described in any one of claims 1 to 5 into a fermentation medium for fermentation to obtain a fermentation product containing polyhydroxyalkanoate.

7. The method according to claim 6, in, The carbon source in the fermentation medium is an organic acid, preferably a monobasic acid having 1 to 6 carbon atoms, more preferably acetic acid and / or propionic acid; And / or, the content of carbon source in the fermentation medium is 3-20 g / L.

8. The method according to claim 6, in, The fermentation medium further contains an organic amine, preferably, the organic amine is a diamine having a carbon number ≤ 15, more preferably, the organic amine is thiourea and / or ethylenediaminetetraacetic acid; And / or, the content of organic amines in the fermentation medium is 50-170 mg / L.

9. The method according to claim 6, in, The inorganic salt in the fermentation medium includes at least one of magnesium salt, calcium salt, potassium salt, iron salt, copper salt, manganese salt, sodium salt, zinc salt and cobalt salt; And / or, the inorganic salt content in the fermentation medium is 0.1-2 g / L.

10. The method according to claim 6, in, Each liter of fermentation medium contains 3-20 g of organic acid, 0.3-0.5 g of magnesium sulfate, 0.05-0.15 g of ethylenediaminetetraacetic acid, 0.04-0.1 g of calcium chloride, 0.02-0.1 g of dipotassium hydrogen phosphate, 0.01-0.08 g of potassium dihydrogen phosphate, 5-15 mg of thiourea, 0.5-2 mg of ferric chloride, 0.05-0.2 mg of boric acid, 0.01-0.05 mg of copper sulfate, 0.01-0.05 mg of potassium iodide, 0.05-0.1 mg of manganese chloride, 0.03-0.1 mg of sodium molybdate, 0.05-0.3 mg of zinc sulfate, and 0.05-0.2 mg of cobalt chloride; and / or, the initial pH value of the fermentation medium is 6-8; And / or, the fermentation conditions include: temperature of 20-35°C, fermentation time of 2-10h, oxygen content ≥4mg / L.

11. Use of bacteria or composite bacterial agents in the synthesis of polyhydroxyalkanoates using organic acids, It is characterized in that The bacteria is selected from at least one of the new giant catfish, dearomatized bacteria and Flavobacterium in the composite bacterial agent described in any one of claims 1-5, and the composite bacterial agent is the composite bacterial agent described in any one of claims 1-5.

12. The use according to claim 11, in, The bacteria or composite bacterial agent metabolizes the organic acid as a carbon source to produce polyhydroxyalkanoate; And / or, the organic acid is selected from monobasic acids having 1 to 5 carbon atoms, preferably acetic acid and / or propionic acid.

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