PHA extraction and purification method, PHA product and application

Abstract

The invention relates to the technical field of fermentation extraction, and particularly provides a PHA extraction and purification method, a PHA product and application, the PHA extraction and purification method comprises the following steps: (1) adding a surfactant I into a PHA fermentation broth, stirring while keeping the temperature, adding alkali until the feed liquid is alkaline, and carrying out mechanical wall breaking treatment to obtain a first feed liquid; (2) adding lysozyme into the first feed liquid, keeping the temperature, adding alkali until the feed liquid is alkaline, adding alkaline protease, keeping the temperature, and obtaining second feed liquid; and (3) adding a surfactant II into the second feed liquid, stirring and washing, wherein the surfactant II comprises SDS (sodium dodecyl sulfate), sodium lauryl sulfate and lauryl glucoside. The PHA product obtained by adopting the PHA extraction and purification method has excellent purity and whiteness, so that the PHA product has a wider application prospect, and the method is simple in process, convenient to operate and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of fermentation extraction, and in particular to a method for extracting and purifying PHA, and a PHA product and application. Background Art

[0002] PHA (i.e. polyhydroxyalkanoate) is an intracellular polyester synthesized by many bacteria such as halophiles and Roseburia. It exists in the body mainly as a storage substance for carbon source and energy. It has physical and chemical properties similar to synthetic plastics and many excellent properties that synthetic plastics do not have, such as biodegradability, biocompatibility, optical activity, piezoelectricity, gas barrier properties, etc. Polyhydroxyalkanoates have broad application prospects in food packaging and medical materials, but the quality of PHA produced on a large scale still needs to be improved if it is to meet the requirements of food packaging and medical grade materials.

[0003] Although there are many reports on the separation and purification of PHA, on the one hand, the process of separation and purification of PHA is complicated, the equipment investment is large, and the environmental pollution is serious. On the other hand, the purity of the obtained PHA is not good enough and the color is poor. The color difference is mainly caused by the low purity and the oxidation of impurities encapsulated or doped in PHA to cause Maillard browning reaction. For some high-end products, PHA with high purity and good color is required. Therefore, it is necessary to provide a process for the preparation of high-purity PHA. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the prior art to at least a certain extent. To this end, one object of the present invention is to provide a method for extracting and purifying PHA and a PHA product and application.

[0005] In a first aspect of the present invention, the present invention provides a method for extracting and purifying PHA, the method comprising: (1) Adding surfactant I to the PHA fermentation broth, stirring at a constant temperature, adding alkali until the broth becomes alkaline, and subjecting the broth to a mechanical cell wall breaking treatment to obtain a first broth; (2) adding lysozyme to the first liquid, maintaining the temperature, then adding alkali until the liquid becomes alkaline, and then adding alkaline protease and maintaining the temperature to obtain a second liquid; (3) Adding surfactant II to the second liquid for washing with stirring, wherein the surfactant II comprises SDS, sodium lauryl sulfate and lauryl glucoside.

[0006] First, surfactant I is added to the PHA fermentation broth, and then alkali is added to adjust the slurry to be alkaline. The synergistic effect of surfactant I and alkali can effectively improve the efficiency and degree of cell wall breaking, which is conducive to the thorough removal of impurities. The slurry is then mechanically broken to achieve more thorough cell wall breaking and improve the later impurity removal effect. Lysozyme is added to the first slurry to maintain heat preservation, and then alkali is added to adjust the slurry to be alkaline. Lysozyme is used to dissolve the cell wall. Most importantly, the slurry is treated with alkali twice before and after the addition of lysozyme, which can make the saponification degree deeper and thus make the removal of impurities more thorough. In an alkaline environment, alkaline protease is added to the slurry to achieve the decomposition of proteins, peptides, etc. Finally, surfactant II is added to the second slurry for stirring and washing, which achieves effective removal of impurities.

[0007] Specifically, surfactant II is added to the system after alkaline protease is added. On the one hand, it can promote the effective flocculation of PHA particles, avoid the problem of small particle size caused by non-flocculation, effectively solve the problem of plate-frame filtration material leakage, and improve the product yield; on the other hand, it can prevent the irregular aggregation of flocculated particles that may occur after the addition of alkaline protease, avoid the problem that impurities are wrapped in flocculated particles and cannot be completely removed, thereby significantly improving the impurity removal effect. In particular, compared with traditional surfactants, the use of surfactant II containing SDS, sodium lauryl sulfate and lauryl glucoside can effectively solve the problems of high impurity content and poor color of PHA purified products. At the same time, the extraction and purification process uses conventional alkaline reagents and enzyme reagents, and does not have particularly high requirements for equipment. The temperature of the process is also low, and the process is simple, thereby reducing production costs. The purity of PHA obtained by the extraction and purification process of the present invention can reach more than 99%, the whiteness can reach more than 75%, and the melt index is less than 1g / 10min.

[0008] It should be noted that the PHA of the present invention includes but is not limited to polyhydroxybutyrate (PHB), 3-hydroxybutyric acid and 3-hydroxyvaleric acid copolymer (PHBV) and 3-hydroxybutyric acid and 3-hydroxybutyric acid copolymer (P34HB). At the same time, the PHA fermentation broth used in the present invention is obtained by conventional PHA fermentation strains under conventional fermentation conditions, and this application does not make any special restrictions. For example, the fermentation strain of PHA is a halophilic bacteria.

[0009] According to the above-mentioned method for extracting and purifying PHA of the present invention, the above-mentioned PHA fermentation broth is prepared by performing solid-liquid separation on the initial fermentation broth, washing with water, separating again, and then re-dissolving in equal volumes.

[0010] Preferably, the conductivity of the PHA fermentation broth is not higher than 7 ms / cm, for example, the conductivity is 7 ms / cm, 6 ms / cm, 5 ms / cm, etc. By controlling the conductivity of the PHA fermentation broth to be not higher than 7 ms / cm before adding the surfactant I, the impurity content of the fermentation broth can be reduced and the purity of the final product can be improved.

[0011] In some embodiments of the present invention, the surfactant I comprises SDS, lauryl glucoside and sodium laureth-6 carboxylate. Preferably, the mass ratio of the SDS, the lauryl glucoside and the sodium laureth-6 carboxylate is 1: (2~2.8): (1.8~2.3), for example, the mass ratio is 1:2:2, 1:2.5:2, 1:2.8:2, 1:2.5:1.8, 1:2.5:2.3, etc., or the range between any two of the above values. By adopting the surfactant I of the above components and controlling the mass proportion of each component within the above range, the wall breaking effect under alkaline conditions can be better achieved, and the later impurity removal effect can be improved.

[0012] Preferably, the amount of surfactant I added is 0.01% to 0.1% of the mass of the PHA fermentation broth, for example, the amount of surfactant I added is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc., or the range between any two of the above values. By controlling the amount of surfactant I added within the above range, the cell wall can be broken more thoroughly, the impurity removal effect can be better, and the obtained product purity can be higher.

[0013] In some embodiments of the present invention, the surfactant I is added to the PHA fermentation broth and stirred for 0.8-1.5 hours, and the temperature of the PHA fermentation broth during stirring is 43° C.-47° C. By controlling the stirring time and temperature after the addition of the surfactant I, the surfactant I can better act on the fermentation broth, thereby improving the impurity removal rate in the later stage.

[0014] According to the above-mentioned PHA extraction and purification method of the present invention, in step (1), the pH value of the feed solution after adding alkali is 10-11.5, and the pH value is maintained for 0.5h-2h. By controlling the pH value of the feed solution within the above range and maintaining it within the above time, it can better cooperate with the surfactant I to improve the cell wall breaking effect.

[0015] In some embodiments of the present invention, the alkali added refers to an alkali solution, and the alkali solution includes a sodium hydroxide solution or a potassium hydroxide solution, preferably a sodium hydroxide solution with a concentration of about 20 wt%.

[0016] According to the above-mentioned method for extracting and purifying PHA of the present invention, in step (1), the mechanical cell wall breaking device includes a homogenizing and emulsifying pump, a homogenizer or a cell disruptor, preferably a homogenizing and emulsifying pump.

[0017] In some embodiments of the present invention, the homogenizing and emulsifying pump is circulated for 5 to 10 times, preferably 8 to 10 times. By repeatedly passing through the homogenizing and emulsifying pump, it not only achieves the combined cell wall breaking effect of alkali treatment and enzymatic hydrolysis, but also plays the role of pure mechanical cell wall breaking such as high-energy-consuming homogenizer or cell disruptor to a certain extent, thereby reducing energy consumption and improving cell wall breaking effect.

[0018] According to the above-mentioned method for extracting and purifying PHA of the present invention, in step (2), the amount of lysozyme added is 0.01% to 0.1% of the mass of the first feed liquid. Controlling the amount of lysozyme added within the above range can effectively dissolve the cell wall and improve the removal rate of impurities. Further, the lysozyme can be diluted 10 times and then added to the first feed liquid.

[0019] It should be noted that the present invention does not particularly limit the specific type of lysozyme, as long as it can dissolve the cell wall. For example, lysozyme includes but is not limited to one or more of endolysin, autolysin and β-N-acetylglucosaminidase.

[0020] In some embodiments of the present invention, the temperature after adding lysozyme is maintained at 48°C to 53°C for 20min to 30min. By controlling the temperature and time within the above range, the dissolution rate and degree of cell wall can be improved.

[0021] In some embodiments of the present invention, in step (2), the pH value of the feed solution after adding the alkali is 9.5-12, and is maintained at the pH value for 0.5h-2h. Controlling the pH value of the system within the above range and maintaining it within the above time can make the saponification effect of the system better, not only improving the effect of the alkaline protease, but also improving the impurity removal rate in the later stage.

[0022] According to the above-mentioned method for extracting and purifying PHA of the present invention, in step (2), the amount of alkaline protease added is 0.01% to 0.1% of the mass of the alkaline liquid, preferably 0.06-0.1%. Controlling the amount of alkaline protease added within the above range can increase the decomposition rate of system proteins, polypeptides, etc. and improve the removal effect of impurities. Furthermore, the alkaline protease can be diluted 10 times and then added to the alkaline liquid.

[0023] It should be noted that the present invention does not particularly limit the type of alkaline protease, as long as it can decompose protein. For example, alkaline protease includes but is not limited to one or more of papain and chymosin.

[0024] In some embodiments of the present invention, in step (2), alkaline protease is added to the alkaline liquid and then maintained at a temperature of 48°C to 53°C for 20 min to 30 min. After the alkaline protease is added to the liquid, the temperature of the liquid is within the above range and the maintenance time is within the above range, which can improve the decomposition rate of proteins, polypeptides, etc. and improve the efficiency of impurity removal in the later stage.

[0025] According to the above-mentioned method for extracting and purifying PHA of the present invention, in step (3), the amount of surfactant II added is 0.01% to 0.1% of the mass of the second liquid, for example, the amount of surfactant II added is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc., of the mass of the second liquid, or a range between any two of the above values. By controlling the amount of surfactant II added within the above range, not only can the PHA particles be better promoted to flocculate more regularly and the amount of impurities coated on the PHA particles be reduced, but also the removal effect of impurities can be better improved.

[0026] Preferably, the mass ratio of the SDS, the sodium lauryl sulfate and the lauryl glucoside is 1:(1.8-2.3):(0.5-1), for example, the mass ratio is 1:1.8:0.5, 1:2:0.5, 1:2.3:0.5, 1:1.8:1, 1:2:1, 1:2.3:1, etc., or the range between any two of the above values. Controlling the mass ratio of each component within the above range can improve the removal effect of impurities and improve the purity and whiteness of the product.

[0027] In some embodiments of the present invention, before adding surfactant II to the system, the system is centrifuged, washed with water, and redissolved with an equal volume, and then surfactant II is added and stirred for washing.

[0028] In some embodiments of the present invention, bleaching agent is added to the slurry at the same time as surfactant II is added, which can remove residual pigments in the slurry on the one hand, and assist in reducing the residual surfactant II on the other hand.

[0029] It should be noted that bleaching agents are conventional reagents in the art, and those skilled in the art can select them according to actual conditions. For example, bleaching agents include but are not limited to hydrogen peroxide, sodium hypochlorite, sodium sulfite, thiourea dioxide, chlorine dioxide, etc. At the same time, those skilled in the art can select the specific amount of bleaching agent added according to actual conditions, for example, 0.01-0.04% of the mass of the feed liquid is added with hydrogen peroxide, and 0.005-0.02% of the mass of the feed liquid is added after 5-10 minutes.

[0030] In some embodiments of the present invention, the liquid obtained after stirring and washing the surfactant II is subjected to plate-frame filtration and then dried. The plate-frame used includes a high-pressure diaphragm filter press, which can be purchased from brands such as Jingjin filter press and Bellite filter press. The moisture content of the filter cake after pressing can be controlled within 35%. Drying can be carried out by using a rotary flash evaporator to dry the moisture content within 0.5%, which can be purchased from brands such as Changzhou Tianchang Dryer or Changzhou One-Step Desiccant.

[0031] In a second aspect of the present invention, the present invention provides a PHA product, which is obtained by using the above extraction and purification method.

[0032] In some embodiments of the present invention, the PHA product includes but is not limited to PHA powder or PHA granules.

[0033] In the third aspect of the present invention, the present invention proposes the application of the above-mentioned PHA product in the field of food packaging or medical materials.

[0034] The present invention has at least the following technical effects: (1) The present invention significantly reduces the residual impurities in the product through the combined action of two-step compounding surfactant + two-step alkali treatment + two-step enzymatic hydrolysis, and controls the order of adding each component, so as to achieve a whiteness of the product molten pellets of more than 75%, a melt index of less than 1g / 10min, and a purity of more than 99%.

[0035] (2) Controlling the order of adding surfactant II and alkaline protease can, on the one hand, promote the flocculation of PHA particles and avoid the problem of small particle size caused by non-flocculation, effectively solve the problem of material leakage in plate and frame filtration, and improve the product yield. On the other hand, it can prevent the irregular aggregation of flocculated particles that may occur after the addition of alkaline protease, avoid the problem that impurities are wrapped in flocculated particles and cannot be completely removed, thereby significantly improving the impurity removal effect.

[0036] (3) Using surfactant I to assist in cell wall breaking is more effective for removing impurities in the later stage, and using surfactant II to assist in washing can remove impurities more effectively and thoroughly. Compared with traditional surfactants, the use of surfactant II including SDS, sodium lauryl sulfate and lauryl glucoside can effectively improve the purity and color of PHA products.

[0037] (4) The alkali treatment is performed twice before and after the addition of lysozyme, which can deepen the degree of saponification and remove impurities more thoroughly.

[0038] (5) The extraction and purification process uses conventional alkaline reagents and enzyme reagents, and does not have particularly high requirements for equipment. The process temperature is also low and the process is simple, thereby reducing production costs. DETAILED DESCRIPTION

[0039] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0040] Example 1 The extraction and purification process of PHA in this embodiment is as follows: S1: Use halophilic bacteria (deposit registration number: CGMCC No. 4353) to produce fermentation liquid containing PHB, the fermentation cycle is 20-40h, and the OD 600 350-550, the repeating units of PHB copolymers are all 3HB.

[0041] S2: First, the fermentation liquid prepared in the above step S1 is separated into solid and liquid once, then washed and separated once with tap water, and redissolved in equal volumes to ensure that the final conductivity of the fermentation liquid obtained after redissolution is less than 7ms / cm, and the temperature is raised to 45°C, and 0.1% of the mass of the redissolved fermentation liquid surfactant I is added, and stirred for 1 hour. Surfactant I is a composition of SDS, lauryl glucoside and sodium laureth-6 carboxylate in a mass ratio of 1:2.5:2.

[0042] S3: Add sodium hydroxide to the fermentation liquid in step S2 above, and keep the pH of the system at 11.2 for 1 hour.

[0043] S4: The system in step S3 is passed through a homogenizing emulsification pump (DHX3) 10 times. During the whole process, two liquid storage tanks need to be switched back and forth. The emulsification pump wall breaking process needs to be heated and maintained at 45°C in the storage tank.

[0044] S5: Add 0.1% lysozyme by mass of the feed liquid to the feed liquid obtained in the above step S4 (lysozyme can be diluted 10 times in advance before adding), maintain the system temperature at 50°C for 20 minutes.

[0045] S6: Repeat the alkali addition operation of step S3 with the liquid obtained in step S5.

[0046] S7: Add 0.1% alkaline protease by mass of the feed liquid to the feed liquid obtained in the above step S6, maintain the temperature at 50° C. for 20 min.

[0047] S8: Separate the slurry obtained in the above step S7 once with a disc centrifuge (DP500 Guangzhong), then dilute it with an equal volume of tap water and separate it again, then dilute it with an equal volume, heat it to 50°C, add 0.1% surfactant II by weight of the slurry, add 0.01-0.04wt% hydrogen peroxide by weight of the slurry, and after 5-10 minutes, add 0.01% sodium metabisulfite by weight of the slurry, where surfactant II is a composition of SDS, sodium lauryl sulfate and lauryl glucoside in a mass ratio of 1:2:1.

[0048] S9: The feed liquid obtained in the above step S8 was stirred for more than 30 minutes, washed three times with a disc centrifuge, and then filtered with a membrane filter press (Jingjin Model 100), and the moisture content of the filter cake was 33%.

[0049] S10: The material obtained in the above step S9 is dried by a rotary flash dryer (Changzhou one-step), with an inlet air temperature of 180°C, an outlet air temperature of 60°C, and a moisture content of 0.41%.

[0050] Example 2 The difference between the extraction and purification process of PHA in this embodiment and the extraction and purification process of PHA in Example 1 is as follows: In step S2 of Example 2, 0.04% by mass of surfactant I was added to the fermentation liquid.

[0051] Example 3 The difference between the extraction and purification process of PHA in this embodiment and the extraction and purification process of PHA in Example 1 is as follows: In step S8 of Example 3, 0.04% by mass of surfactant II is added based on the mass of the feed liquid.

[0052] Example 4 The difference between the extraction and purification process of PHA in this embodiment and the extraction and purification process of PHA in Example 1 is as follows: In step S2 of Example 4, the surfactant I is a composition of SDS, lauryl glucoside and sodium laureth-6 carboxylate in a mass ratio of 1:2:2.

[0053] Example 5 The difference between the extraction and purification process of PHA in this embodiment and the extraction and purification process of PHA in Example 1 is as follows: In step S8 of Example 5, surfactant II is a composition of SDS, sodium lauryl sulfate and lauryl glucoside in a mass ratio of 1:2.3:1.

[0054] Comparative Example 1 The difference between the extraction and purification process of PHA in this comparative example and the extraction and purification process of PHA in Example 1 is: In step S8 of comparative example 1, 0.1% of the mass of the feed liquid of surfactant I is added, and surfactant I is a composition of SDS, lauryl glucoside and sodium laureth-6 carboxylate in a mass ratio of 1:2.5:2.

[0055] Comparative Example 2 The difference between the extraction and purification process of PHA in this comparative example and the extraction and purification process of PHA in Example 1 is: In step S2 of comparative example 2, 0.1% of the mass of the re-dissolved fermentation broth was added as surfactant II, wherein surfactant II was a composition of SDS, sodium lauryl sulfate and lauryl glucoside in a mass ratio of 1:2:1.

[0056] Comparative Example 3 The difference between the extraction and purification process of PHA in this comparative example and the extraction and purification process of PHA in Example 1 is: In step S8 of comparative example 3, 0.005% of the mass of the feed liquid of surfactant II was added.

[0057] Comparative Example 4 The difference between the extraction and purification process of PHA in this comparative example and the extraction and purification process of PHA in Example 1 is: The process of step S7 of comparative example 4 adopts the process of step S8 of embodiment 1, and the process of step S8 of comparative example 4 adopts the process of step S7 of embodiment 1, that is, the order of S7 and S8 of embodiment 1 is interchanged.

[0058] Comparative Example 5 The difference between the extraction and purification process of PHA in this comparative example and the extraction and purification process of PHA in Example 1 is: In step S8 of Comparative Example 5, the surfactant used is SDS.

[0059] In order to verify the quality of PHA obtained by the extraction and purification process of the present invention, the melt index, whiteness and purity of PHA obtained in the examples and comparative examples were measured, as follows: (1) Melt index detection Test equipment: melt flow rate tester, measured according to the national standard GB / T3682.1 method, load 2.16kg, die diameter 2.095±0.005mm, melt flow rate unit g / 10min. Test temperature 190℃, shear once every 10s, a total of 6 shears. Then weigh the 6 shears to calculate the specific melt index. Calculation formula: PHA melt index (g / 10min) = 6 shears and weight / 6 / 10*600.

[0060] (2) Whiteness detection The color was measured using a CR-910 desktop spectrophotometer (Beijing Kemeirunda Instrument Co., Ltd.) after calibration with the L / A / B standard color plate.

[0061] (3) Purity testing.

[0062] Refer to the purity detection method in the specific implementation manner in CN115894981A.

[0063] The melt index, whiteness and purity test results of the PHA obtained in the examples and comparative examples are shown in Table 1.

[0064] Table 1

[0065] As can be seen from Table 1, the PHA prepared by the extraction and purification process of the present invention has good purity and high whiteness. The change of the addition order of surfactant I and surfactant II, the change of the addition order of alkaline protease and surfactant II, and the use of only surfactant I or surfactant II have a certain effect on the purity and whiteness of PHA. It can be seen that the combination of surfactant I and surfactant II of the present application and the control of the addition order can improve the purity and whiteness of PHA, ensuring that the purity of PHA is above 99% and the whiteness is above 77%.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting and purifying PHA, characterized in that: include: (1) Adding surfactant I to the PHA fermentation broth, stirring at a constant temperature, adding alkali until the broth becomes alkaline, and subjecting the broth to a mechanical cell wall breaking treatment to obtain a first broth; (2) adding lysozyme to the first liquid, maintaining the temperature, then adding alkali until the liquid becomes alkaline, and then adding alkaline protease and maintaining the temperature to obtain a second liquid; (3) Adding surfactant II to the second liquid for washing with stirring, wherein the surfactant II comprises SDS, sodium lauryl sulfate and lauryl glucoside.

2. The method according to claim 1, characterized in that: The surfactant I comprises SDS, lauryl glucoside and sodium laureth-6 carboxylate, and preferably the mass ratio of the SDS, the lauryl glucoside and the sodium laureth-6 carboxylate is 1:(2-2.8):(1.8-2.3).

3. The method according to claim 1 or 2, characterized in that: The added amount of the surfactant I is 0.01% to 0.1% of the mass of the PHA fermentation broth.

4. The method according to any one of claims 1 to 3, characterized in that: In step (1), the conductivity of the PHA fermentation broth is not higher than 7 ms / cm.

5. The method according to any one of claims 1 to 4, characterized in that: In step (1), the time of heat preservation and stirring is 0.8-1.5 hours, and the temperature is 43°C-47°C; And / or, the pH value of the feed solution after adding alkali is 10-11.5, and is maintained at the pH value for 0.5h-2h.

6. The method according to any one of claims 1 to 5, characterized in that: In step (2), the amount of lysozyme added is 0.01% to 0.1% of the mass of the first liquid; And / or, the pH value of the feed solution after adding alkali is 9.5-12, and is maintained at the pH value for 0.5h-2h.

7. The method according to any one of claims 1 to 6, characterized in that: The amount of alkaline protease added is 0.01% to 0.1% of the mass of the alkaline liquid.

8. The method according to any one of claims 1 to 7, characterized in that: The added amount of the surfactant II is 0.01% to 0.1% of the mass of the second liquid; And / or, the mass ratio of the SDS, the sodium lauryl sulfate and the lauryl glucoside is 1:(1.8-2.3):(0.5-1).

9. A PHA product, characterized in that: The product is obtained by the extraction and purification method according to any one of claims 1 to 8.

10. Use of the PHA product according to claim 9 in the field of food packaging or medical materials.

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