Method and system for controlling purification process through color value monitoring and method for producing polyhydroxyalkanoate resin

Abstract

According to the present invention, a high-quality polyhydroxyalkanoate resin having excellent color quality can be reliably produced by monitoring the color value during the process of purifying a crude solution containing polyhydroxyalkanoate (PHA) and controlling the conditions of the purification step in real time on the basis thereof.

Description

Technical Field

[0001] The present disclosure relates to a method and system for controlling a purification process for preparing a polyhydroxyalkanoate resin by monitoring the color value during the purification process. In addition, the present disclosure relates to a method for preparing a polyhydroxyalkanoate resin having excellent color quality using the method and system. Background Art

[0002] Polyhydroxyalkanoates (PHAs) are biodegradable polymers composed of various hydroxycarboxylic acids produced by various microorganisms and used as intracellular storage materials. PHAs have similar physical properties to traditional petroleum-derived synthetic polymers such as polybutylene terephthalate (PBAT), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), and polybutylene succinate adipate (PBSA), and exhibit complete biodegradability and excellent biocompatibility.

[0003] Specifically, polyhydroxyalkanoate is a natural thermoplastic polyester polymer that accumulates in microbial cells. Since it is a biodegradable material, it can be composted and eventually decomposed into carbon dioxide, water, and organic waste without generating toxic waste. In particular, polyhydroxyalkanoate is biodegradable under any environmental conditions (such as soil and ocean) and has environmentally friendly characteristics.

[0004] In a general method for preparing polyhydroxyalkanoate resins, PHA particles formed and accumulated inside microbial cells are surrounded by proteins, phospholipids, polypeptides, etc. even after extraction. Therefore, additional purification processes such as decolorization and deproteinization are performed to remove these impurities.

[0005] [Prior art literature]

[0006] (Patent Document 1) Korean Patent Publication No. 2001-0009719 Summary of the invention

[0007] Technical issues

[0008] In the process of preparing polyhydroxyalkanoate resin, there are various types of impurities to be removed by decolorization and deproteinization, including components of cell origin. There is a problem that it is impossible to distinguish and qualitatively or quantitatively determine the impurities present in the solid PHA particles and the liquid in real time while the process is being carried out. In particular, since the impurities remaining in the PHA resin particles cause discoloration and deterioration of polymer properties during processing, these impurities must be strictly controlled during large-scale production. However, due to the above-mentioned problems, real-time management of the impurity removal process is very difficult.

[0009] As a result of studies conducted by the present inventors, it was possible to design a method for stably preparing a polyhydroxyalkanoate resin having excellent color quality by monitoring the color value of a process solution during purification and adjusting purification conditions such as decolorization based on the color value or predicting the color value of a final product.

[0010] An object of the present disclosure is to provide a method and system for controlling a purification process by monitoring a color value during the purification process, and a method for preparing a polyhydroxyalkanoate resin having excellent color quality using the method and system.

[0011] Technical Solution

[0012] According to one aspect of the present disclosure, there is provided a method for controlling a purification process, which includes measuring the color value of a process solution or its supernatant during a purification process for preparing a polyhydroxyalkanoate (PHA) resin, or measuring the color value of a purified solution and its supernatant after the purification process, and controlling the purification process based on the measured color value.

[0013] In one embodiment, the measurement of the color value includes measuring the a* value in the CIE LAB color space, and the purification process conditions may be adjusted based on changes in the a* value of the process solution or its supernatant.

[0014] In another embodiment, the change in a* value can be determined by comparing the a* value of the process solution or its supernatant with the a* value of the crude solution or its supernatant before the purification process, or by the change in the a* value of the process solution or its supernatant over time during the purification process.

[0015] In another embodiment, the measurement of the color value includes measuring an a* value in the CIE LAB color space, and the b* value of the polyhydroxyalkanoate resin in the CIE LAB color space can be predicted based on the a* value of the purified solution and its supernatant.

[0016] According to another aspect of the present disclosure, a system for controlling a purification process is provided, which includes a purification unit for performing a purification process for preparing a polyhydroxyalkanoate (PHA) resin; a monitoring unit for measuring a color value of a process solution or a supernatant thereof during the purification process, or measuring a color value of a purified solution and a supernatant thereof after the purification process; and a control unit for controlling the purification process based on the measured color value.

[0017] According to another aspect of the present disclosure, there is provided a method for preparing a polyhydroxyalkanoate (PHA) resin from a crude solution containing polyhydroxyalkanoate through a purification process, comprising at least one of the following steps: (a) measuring a color value of the process solution or a supernatant thereof during the purification process; and (b) measuring a color value of the purified solution and a supernatant thereof after the purification process.

[0018] In one embodiment, the measurement of the color value in step (a) comprises measuring the a* value of the process solution or its supernatant in the CIELAB color space, and the purification process conditions can be adjusted based on the change in the a* value of the process solution or its supernatant.

[0019] In another embodiment, the method further comprises measuring the a* value of the crude solution or its supernatant, and a change in the a* value of the process solution or its supernatant relative to the a* value of the crude solution or its supernatant can be determined.

[0020] In another embodiment, the purification process includes a decolorization process, wherein the decolorization process is performed by using a first oxidant, a second oxidant, or both in sequence, the first oxidant may include sodium chlorite (NaClO2), and the second oxidant may include hydrogen peroxide (H2O2).

[0021] In another embodiment, the decolorization process is performed by a second oxidant, and when the following relationship (1A) is satisfied, the amount of the oxidant added to the decolorization process can be increased.

[0022] a0 <a30(1A)

[0023] In equation (1A), a0 is the a* value of the raw solution, and a30 is the a* value of the process solution after the addition of the second oxidant.

[0024] In another embodiment, the decolorization process is performed by sequentially using the first oxidant and the second oxidant, and when the following relationship (1B) is satisfied, the amount of at least one of the first oxidant and the second oxidant added to the decolorization process may be increased.

[0025] a0'>a30'(1B)

[0026] In the relation (1B), a0' is the a* value of the supernatant of the crude solution, and a30' is the a* value of the supernatant of the process solution after the addition of the first oxidant.

[0027] In one embodiment, the measurement of the color value in step (b) comprises measuring the a* value of the purified solution and its supernatant, and the b* value of the polyhydroxyalkanoate resin in the CIE LAB color space can be predicted based on the a* value of the purified solution and its supernatant.

[0028] In another embodiment, the b* value of the polyhydroxyalkanoate resin can be predicted by the following relationship (2A).

[0029] b*=Y+(X1×a1)+(X2×a2)(2A)

[0030] In the relational formula (2A), a1 is the a* value of the purified solution, a2 is the a* value of the supernatant of the purified solution, Y is 10 to 21, X1 is -2.5 to 4.0, and X2 is -3.5 to 3.0. More specifically, Y is 14.68 to 16.68, X1 is -0.39 to 1.61, and X2 is -1.35 to 0.65.

[0031] In another embodiment, the b* value of the polyhydroxyalkanoate resin can be predicted by the following relationship (2B).

[0032] b*=Y'+(X1'×a1')+(X2'×a2')(2B)

[0033] In relational formula (2B), a1' is the a* value of the purified solution, a2' is the a* value of the supernatant of the purified solution, Y' is 4 to 15, X1' is -7 to -1, and X2' is -8 to -1. More specifically, Y' is 8.15 to 10.15, X1' is -5.15 to -3.15, and X2' is -5.04 to -3.04.

[0034] In another embodiment, if the predicted b* value of the polyhydroxyalkanoate resin is greater than the target b* value, an additional purification process may be performed.

[0035] In another embodiment, a crude solution containing polyhydroxyalkanoate can be prepared by a method comprising: subjecting a fermentation broth containing polyhydroxyalkanoate to solid-liquid separation to obtain biomass; mixing an additive containing a surfactant with the biomass to obtain a suspension; crushing the biomass in the suspension to obtain a slurry; and subjecting the slurry to solid-liquid separation.

[0036] Advantageous Effects of the Invention

[0037] According to the method and system of the present disclosure, the color value is monitored during the purification process, and the purification process conditions can be adjusted based on the color value to more effectively remove impurities, and the color value of the final product can be predicted and responded to in advance. Therefore, polyhydroxyalkanoate resins with excellent color quality can be stably prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A method for controlling the purification process by monitoring the color value is shown.

[0039] Figure 2a A method for preparing a PHA resin including a purification process (decolorization using only H2O2) according to one embodiment is shown.

[0040] Figure 2b A method for preparing a PHA resin including a purification process (decolorization using NaClO 2 and H 2 O 2 ) according to another embodiment is shown.

[0041] Figure 3a Shown are the results of monitoring the change in color value over time during the purification process in the method for preparing a PHA resin according to one embodiment.

[0042] Figure 3b Shown are the results of monitoring the change in color value over time during the purification process in the method for preparing a PHA resin according to another embodiment.

[0043] Figure 4a The correlation between the predicted b* value and the actually measured b* value of a PHA resin in the method for preparing a PHA resin according to one embodiment is shown.

[0044] Figure 4b The correlation between the predicted b* value and the actually measured b* value of a PHA resin in a method of preparing a PHA resin according to another embodiment is shown.

[0045] Figure 5 The concept of predicting the color value of the final PHA resin assumed in the present disclosure is schematically illustrated.

[0046] Figure 6 The concepts of L*, a*, and b* of the CIE (International Commission on Illumination) LAB color space are shown. DETAILED DESCRIPTION

[0047] Best Mode for Carrying Out the Invention

[0048] The present disclosure will be described in more detail below with reference to various embodiments.

[0049] In the present specification, the terms relating to each component are used to distinguish them from each other, and are not intended to limit the scope of the present disclosure. In addition, in the present specification, a singular expression is interpreted as also covering the plural, unless otherwise indicated in the context.

[0050] In this specification, the term "comprising" is intended to specify specific features, regions, steps, processes, elements and / or components. It does not exclude the existence or addition of any other features, regions, steps, processes, elements and / or components, unless there is a specific description to the contrary.

[0051] In this specification, the terms first, second, etc. are used to describe various components. However, the components should not be limited by these terms. These terms are used to distinguish one element from another element.

[0052] Control the purification process and preparation of PHA resin by monitoring color values

[0053] One aspect of the present disclosure provides a method for controlling a purification process of a polyhydroxyalkanoate (PHA) resin by monitoring a color value. The method for controlling a purification process includes measuring the color value of a process solution or its supernatant during a purification process for preparing a polyhydroxyalkanoate (PHA) resin, or measuring the color value of a purified solution and its supernatant after a purification process, and controlling the purification process based on the measured color value.

[0054] The process solution can be obtained during the purification process (e.g., decolorization process or deproteinization process) of the crude PHA solution, and the purified solution can be obtained after the purification process is completed. The crude solution, the process solution, and the purified solution can each contain PHA, impurities, a solvent, etc., and can have a form such as a solution, a suspension, a dispersion, a slurry, etc. In addition, the color value can be measured by separating the supernatant from the crude solution, the process solution, or the purified solution. The supernatant refers to the upper layer liquid, excluding the insoluble solids precipitated to the bottom by centrifugation, precipitation, etc.

[0055] As described above, the present disclosure includes monitoring color values ​​during the process, and the method has the advantage that no separate pretreatment of the sample to be analyzed is required, and rapid analysis and immediate confirmation of the results are possible. The color values ​​monitored in the present disclosure include a* and b* in the CIE LAB color space, which can be measured using a spectrophotometer. Figure 6 The concepts of L*, a*, and b* of the CIE LAB color space are shown (source: https: / / terms.naver.com / entry.naver?docId=1118148&cid=40942&categoryId=33048). Figure 6 , the a* value indicates whether the color is closer to red or green. If it is negative, it is closer to green. If it is positive, it is closer to red. The b* value indicates whether the color is closer to blue or yellow. If it is negative, it is closer to blue. If it is positive, it is closer to yellow.

[0056] In the method of preparing polyhydroxyalkanoate resin, there are various types of impurities to be removed by the purification process, including cell-derived components. There is a problem that it is impossible to distinguish and qualitatively or quantitatively determine the impurities present in the solid PHA particles and the liquid in real time during the purification process. In particular, since the impurities remaining in the PHA resin particles cause discoloration and deterioration of polymer properties during processing, these impurities must be strictly controlled during large-scale production. However, due to the above-mentioned problems, real-time management of the impurity removal process is very difficult.

[0057] The present inventors have noticed that since the b* value of the final PHA resin increases with the increase in the amount of impurities, the b* value reflects the impurity content in the final PHA resin to a certain extent. Therefore, the present inventors analyzed the data obtained by monitoring the color values ​​in several purification processes to find that the a* value measured during the purification process has the most significant relationship with the b* value of the final PHA resin (see Table 1).

[0058] As a result, the measurement of color values ​​in the present disclosure may include measuring a* values ​​in the CIE LAB color space.

[0059] Figure 1 A method for controlling the purification process by monitoring the color value is shown. Figure 1 The method includes monitoring an a* value of a process solution or a supernatant thereof in a CIE LAB color space during a purification process (S100) and / or monitoring an a* value of a purified solution and a supernatant thereof after the purification process (S200).

[0060] According to one embodiment, purification process conditions may be adjusted based on changes in the a* value of the process solution or its supernatant.

[0061] For example, the change in a* value can be determined by comparing the a* value of the process solution or its supernatant with the a* value of the crude solution or its supernatant before the purification process, or by the change in the a* value of the process solution or its supernatant over time during the purification process.

[0062] As a specific example, the change in the a* value of the process solution or its supernatant is monitored at the beginning of the purification process to distinguish between normal and abnormal conditions based on its increase or decrease. If it is abnormal, the amount of oxidant added to the decolorization process can be increased. To this end, the method also includes measuring the a* value of the crude solution or its supernatant, and the change in the a* value of the process solution or its supernatant relative to the a* value of the crude solution or its supernatant can be determined.

[0063] As another specific example, while the purification process is being carried out, the change of the a* value of the process solution or its supernatant is continuously monitored to distinguish normal and abnormal states based on its increase or decrease. If it is abnormal, the amount of the oxidant added to the decolorization process can be increased. For this purpose, after the purification process begins, the a* value of the process solution or its supernatant is repeatedly measured at regular time intervals, such as 10 minute intervals, 20 minute intervals, or 30 minute intervals. These a* values ​​can be compared to determine whether it is reduced or increased.

[0064] According to another embodiment, the b* value of the polyhydroxyalkanoate resin in the CIE LAB color space can be predicted based on the a* values ​​of the purified solution and its supernatant.

[0065] Another aspect of the present disclosure provides a system for controlling a purification process of a polyhydroxyalkanoate (PHA) resin by monitoring a color value. The system for controlling a purification process includes a purification unit for performing a purification process for preparing a polyhydroxyalkanoate (PHA) resin; a monitoring unit for measuring the color value of a process solution or its supernatant during the purification process, or measuring the color value of a purified solution and its supernatant after the purification process; and a control unit for controlling the purification process based on the measured color value.

[0066] The purification unit can include, for example, a decolorization unit and a deproteinization unit. The crude PHA solution is fed to the decolorization unit and decolorized, and then the process solution is passed through the deproteinization unit to provide a purified solution in which deproteinization has been completed. In addition, an acid or alkaline component for pH regulation and one or more types of oxidants for decolorization can be added to the decolorization unit. Decolorization can be performed at least once. An acid or alkaline component for pH regulation and one or more types of proteases for deproteinization can be added to the deproteinization unit. Therefore, the decolorization unit and the deproteinization unit are each equipped with a reactor, and the reactor can be equipped with an inlet for supplying raw materials and samples, an outlet for discharging process solutions or purified solutions, and a temperature controller. A connecting unit, such as a pipeline, can be provided for connecting the inlet and outlet between the reactors.

[0067] The monitoring unit may include, for example, a spectrophotometer capable of measuring the color value of the sample. In addition, the monitoring unit may include an extractor for extracting a portion of the crude solution, the process solution, or the purified solution sample from each reactor equipped in the purification unit. It may also include a centrifuge for separating the supernatant from the process solution or the purified solution sample.

[0068] The control unit may be equipped with an analyzer that receives information about the color values ​​measured by the monitoring unit and analyzes it (compares, interprets, determines, predicts, etc.). In order to transmit such color value information, the control unit and the monitoring unit may be electrically connected. In addition, the control unit may also be equipped with a processor that adjusts the purification process conditions or transmits feedback about whether to perform an additional purification process based on the results of the analyzer analysis. The control unit is also electrically connected to the purification unit so that the flow of the purification process can be controlled based on the feedback transmitted from the processor.

[0069] According to the method and system of the present disclosure, the results of monitoring the color value during the process are applied to the purification process in real time, thereby removing impurities more effectively. Since the color value of the final PHA resin can be predicted and responded to in advance, PHA resin with excellent color quality can be stably prepared.

[0070] Another aspect of the present disclosure provides a method for preparing a polyhydroxyalkanoate resin by monitoring a color value. A method for preparing a polyhydroxyalkanoate (PHA) resin from a crude solution containing polyhydroxyalkanoate by a purification process, comprising at least one of the following steps: (a) measuring the color value of the process solution or its supernatant during the purification process; and (b) measuring the color value of the purified solution and its supernatant after the purification process.

[0071] In the method of the present disclosure, the purification process may include, for example, a decolorization process and a deproteinization process.

[0072] Hereinafter, each process and step of the preparation method according to the present disclosure will be described in detail.

[0073] Polyhydroxyalkanoate

[0074] Polyhydroxyalkanoates (PHA) can be classified into crystalline, semi-crystalline or amorphous polyhydroxyalkanoates according to their molecular structure.

[0075] According to one embodiment, the polyhydroxyalkanoate may include an amorphous polyhydroxyalkanoate. In the case of an amorphous polyhydroxyalkanoate, due to its unique flexibility and viscosity, repeated solid-liquid separation and washing in a water-based purification process is difficult, and the impurity content in the purified final PHA is still high, making its commercialization difficult. However, according to the present disclosure, since two types of oxidants are sequentially used for decolorization during the purification process of the amorphous PHA, the color of the final product can be significantly improved.

[0076] According to another embodiment, the polyhydroxyalkanoate may include a semi-crystalline polyhydroxyalkanoate. According to another embodiment, the polyhydroxyalkanoate may include a crystalline polyhydroxyalkanoate. According to another embodiment, the polyhydroxyalkanoate may include two or more of an amorphous polyhydroxyalkanoate, a semi-crystalline polyhydroxyalkanoate, and a crystalline polyhydroxyalkanoate.

[0077] The polyhydroxyalkanoate may comprise at least one repeating unit selected from the group consisting of 2-hydroxybutyrate (2-HB), 3-hydroxybutyrate (3-HB), 3-hydroxypropionate (3-HP), 3-hydroxyvalerate (3-HV), 3-hydroxyhexanoate (3-HH), 3-hydroxyheptanoate (3-HHep), 3-hydroxyoctanoate (3-HO), 3-hydroxynonanoate (3-HN), 3-hydroxydecanoate (3-HD), 3-hydroxydodecanoate (3-HDd), 4-hydroxybutyrate (4-HB), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV) and 6-hydroxyhexanoate (6-HH).

[0078] In addition, the polyhydroxyalkanoate may contain isomers. For example, the polyhydroxyalkanoate may contain structural isomers, enantiomers or geometric isomers. Specifically, the polyhydroxyalkanoate may contain structural isomers.

[0079] The polyhydroxyalkanoate may be a homopolymer or a copolymer. According to one embodiment, the polyhydroxyalkanoate may comprise a copolymer, in particular, a copolymer comprising two or more different repeating units randomly distributed in the polymer chain.

[0080] As an example, the polyhydroxyalkanoate may include 4-hydroxybutyrate (4-HB) repeating units. For example, the content of 4-hydroxybutyrate (4-HB) repeating units in the polyhydroxyalkanoate may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, or 60% by weight or more, and 100% by weight or less, 99% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less, based on the total weight of the polyhydroxyalkanoate. Specifically, the polyhydroxyalkanoate may include 25% by weight or more of 4-hydroxybutyrate (4-HB) repeating units.

[0081] Specifically, the polyhydroxyalkanoate may be a copolymer comprising a 4-HB repeating unit. Examples of repeating units that may be included in the polyhydroxyalkanoate together with 4-HB may include at least one selected from the group consisting of lactic acid, glycolic acid, 2-hydroxybutyrate (2-HB), 3-hydroxybutyrate (3-HB), 3-hydroxypropionate (3-HP), 3-hydroxyvalerate (3-HV), 3-hydroxyhexanoate (3-HH), 3-hydroxyheptanoate (3-HHep), 3-hydroxyoctanoate (3-HO), 3-hydroxynonanoate (3-HN), 3-hydroxydecanoate (3-HD), 3-hydroxydodecanoate (3-HDd), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV) and 6-hydroxyhexanoate (6-HH).

[0082] More specifically, in addition to the 4-HB repeating unit, the polyhydroxyalkanoate may include one or more repeating units selected from the group consisting of 3-HB, 3-HP, 3-HH, 3-HV, 4-HV, 5-HV and 6-HH. For example, the polyhydroxyalkanoate may include a copolymer containing a 4-HB repeating unit and a 3-HB repeating unit. Specifically, it may include poly-3-hydroxybutyrate-co-4-hydroxybutyrate (P3HB-co-4HB).

[0083] The PHA may comprise one or more types of PHA. For example, it may comprise a first PHA, a second PHA, or a mixture thereof. For example, the first PHA may be an amorphous PHA, and the second PHA may be a semi-crystalline PHA. The first PHA may comprise, for example, 15% to 60% by weight, 15% to 55% by weight, 20% to 55% by weight, 25% to 55% by weight, 30% to 55% by weight, 35% to 55% by weight, 20% to 50% by weight, 25% to 50% by weight, 30% to 50% by weight, 35% to 50% by weight, or 20% to 40% by weight of 4-HB repeating units. The second PHA may include, for example, 0.1 wt % to 30 wt %, 0.5 wt % to 30 wt %, 1 wt % to 30 wt %, 3 wt % to 30 wt %, 1 wt % to 28 wt %, 1 wt % to 25 wt %, 1 wt % to 24 wt %, 1 wt % to 20 wt %, 1 wt % to 15 wt %, 2 wt % to 25 wt %, 3 wt % to 25 wt %, 3 wt % to 24 wt %, 5 wt % to 24 wt %, 5 wt % to 20 wt %, greater than 5 wt % to less than 20 wt %, 7 wt % to 20 wt %, 10 wt % to 20 wt %, 15 wt % to 25 wt %, or 15 wt % to 24 wt % of 4-HB repeating units. In addition, the PHA may be a mixture of the first PHA and the second PHA in a weight ratio of 20:80 to 80:20 or 30:70 to 70:30.

[0084] Crude polyhydroxyalkanoate solution

[0085] Crude polyhydroxyalkanoate solutions can be prepared by a fermentation process.

[0086] The method of producing polyhydroxyalkanoate (PHA) by fermentation can be performed by a known method. For example, polyhydroxyalkanoate can be produced by fermentation using a wild-type or transgenic microorganism cultured on a specific substrate, and is not particularly limited.

[0087] During fermentation, the polyhydroxyalkanoates thus produced accumulate within the microbial cells; therefore, a process for isolating and purifying them is absolutely necessary.

[0088] For example, biomass containing polyhydroxyalkanoate is separated from a fermentation broth, a surfactant is added thereto, and microbial cells are disrupted to separate only polyhydroxyalkanoate.

[0089] As an example, a crude solution containing polyhydroxyalkanoate can be prepared by a method including: subjecting a fermentation broth containing polyhydroxyalkanoate (PHA) to solid-liquid separation to obtain biomass; mixing an additive containing a surfactant with the biomass to obtain a suspension; crushing the biomass in the suspension to obtain a slurry; and subjecting the slurry to solid-liquid separation.

[0090] First, a fermentation broth formed by a microorganism is subjected to solid-liquid separation using a mechanical separation method (such as centrifugation or membrane separation) or other known methods to separate a biomass containing cells in which polyhydroxyalkanoate (PHA) is accumulated.

[0091] The biomass thus separated can be mixed with a solvent to adjust the solid concentration. In addition, the biomass can be mixed with a surfactant. For example, an anionic surfactant or a nonionic surfactant can be used as a surfactant. Specifically, sodium laureth sulfate, sodium lauryl sulfate, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate can be used. As a result, a suspension comprising biomass, a surfactant, etc. can be obtained.

[0092] After this, the biomass in the suspension is broken, and the breaking can be carried out by mechanical breaking (physical breaking) or chemical breaking (non-mechanical breaking). For example, the breaking can be carried out by ultrasonic breaking, high pressure breaking or milling breaking. Ultrasonic breaking can be carried out for example at 20Hz or higher energy levels for 10 minutes to 60 minutes. In addition, high pressure breaking can be carried out for example at 10 bar or higher pressure for 1 minute to 60 minutes. In addition, milling breaking can be carried out for 1 minute to 60 minutes by colloid mill, bead mill or ball mill.

[0093] As a result of the disruption, a slurry containing fine particles of polyhydroxyalkanoate and cell-derived impurities (such as cell walls) can be obtained. The slurry is subjected to solid-liquid separation using a mechanical separation method (such as centrifugation or membrane separation) or other known methods to obtain a crude polyhydroxyalkanoate solution.

[0094] Since the crude solution of polyhydroxyalkanoate contains trace amounts of cell-derived impurities (proteins, lipids, etc.), further purification is required.

[0095] For example, the protein content in the crude solution can be 3.5 wt % or less, 3 wt % or less, 2.7 wt % or less, or 2.5 wt % or less, and can be 0.1 wt % or more, 1 wt % or more, or 1.5 wt % or more, based on the total solids weight in the crude solution.

[0096] In addition, the lipid content in the crude solution can be 1.5 wt % or less, 1.3 wt % or less, 1 wt % or less, or 0.7 wt % or less, and can be 0.1 wt % or more, 0.2 wt % or more, or 0.3 wt % or more, based on the total solid weight in the crude solution.

[0097] In addition, the solid content in the crude solution can be 1 wt % or more, 3 wt % or more, 5 wt % or more, 7 wt % or more, or 10 wt % or more, and can be 80 wt % or less, 50 wt % or less, 30 wt % or less, 20 wt % or less, or 15 wt % or less, based on the total weight of the crude solution.

[0098] Furthermore, a supernatant can be separated from the crude solution thus prepared by centrifugation, sedimentation, etc., to be used for measuring a color value, which will be explained in detail in the following section on monitoring color values.

[0099] Purification process

[0100] The purification process for preparing PHA resin from the crude solution may include a decolorization process.

[0101] The decolorization process can be carried out by adding one or more types of oxidants to the crude solution. Specifically, the decolorization process is carried out by using a first oxidant, a second oxidant, or both in sequence, wherein the first oxidant can include sodium chlorite (NaClO2) and the second oxidant can include hydrogen peroxide (H2O2).

[0102] According to one embodiment, the decolorization process may be performed by a second oxidizing agent.

[0103] The amount of hydrogen peroxide used in the decolorization process can be 0.01 wt % or more, 0.02 wt % or more, 0.03 wt % or more, 0.04 wt % or more, 0.05 wt % or more, 0.06 wt % or more, 0.1 wt % or more, 0.2 wt % or more, 0.3 wt % or more, 0.4 wt % or more, or 0.5 wt % or more, and 2.0 wt % or less, 1.7 wt % or less, 1.5 wt % or less, 1.3 wt % or less, 1.2 wt % or less, 1.1 wt % or less, 1 wt % or less, 0.9 wt % or less, 0.8 wt % or less, 0.7 wt % or less, or 0.6 wt % or less, based on the total weight of the crude solution.

[0104] The decolorization process can be carried out under alkaline pH conditions. For example, the pH range in the decolorization can be 7 or more, 7.5 or more, 8 or more, or 8.5 or more, and can be 13 or less, 12 or less, 11 or less, 10.5 or less, 10 or less, 9.5 or less, or 9 or less. As a specific example, the decolorization can be carried out at a pH of 7 to 13 or a pH of 8 to 13. As a more specific example, the decolorization can be carried out at a pH of 8 to 11 or a pH of 8 to 10.

[0105] The alkaline component can be used to adjust the alkaline pH. Examples of alkaline components used for pH adjustment during decolorization include sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium carbonate, but are not limited thereto. Because the crude solution contains an appropriate amount of such alkaline components, it can be adjusted to the desired alkaline pH.

[0106] In addition, the temperature of the decolorization process can be 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, or 60°C or higher, and 90°C or lower, 80°C or lower, 75°C or lower, 70°C or lower, or 65°C or lower. As a specific example, decolorization can be carried out at a temperature of 40°C to 90°C or 50°C to 70°C.

[0107] In addition, the required time for the decolorization process can be 10 minutes or more, 30 minutes or more, or 50 minutes or more, and 3 hours or less, 2 hours or less, or 1 hour and 30 minutes or less. As a specific example, it can be 30 minutes to 1 hour and 30 minutes.

[0108] According to another embodiment, the decolorization process can be performed by sequentially using a first oxidant and a second oxidant. Specifically, the decolorization process can sequentially include a first decolorization process using a first oxidant and a second decolorization process using a second oxidant.

[0109] The first decolorization process can be performed by a first oxidant including sodium chlorite (NaClO2). When sodium chlorite is used as an oxidant for decolorization, the color improvement effect is significant and there is almost no decrease in molecular weight, unlike other chlorine-based oxidants (such as NaClO). This is because cell-derived impurities (proteins, lipids, etc.) in the crude solution are decomposed by reacting with sodium chlorite, while PHA is hardly decomposed.

[0110] The amount of sodium chlorite used in the decolorization process can be 0.01 weight % or more, 0.02 weight % or more, 0.03 weight % or more, 0.04 weight % or more, 0.05 weight % or more, 0.06 weight % or more, 0.1 weight % or more, 0.2 weight % or more, 0.3 weight % or more, 0.4 weight % or more, or 0.5 weight % or more, and 1.3 weight % or less, 1.2 weight % or less, 1.1 weight % or less, 1 weight % or less, 0.9 weight % or less, 0.8 weight % or less, 0.7 weight % or less, or 0.6 weight % or less, based on the gross weight of the crude solution. As a specific example, in the first decolorization, the amount of sodium chlorite can be 0.01 to 1 weight % or 0.05 to 1 weight %, based on the gross weight of the crude solution. When the amount of sodium chlorite is within the above-mentioned preferred range, the decolorization effect can be fully achieved while minimizing the reduction of molecular weight.

[0111] The first decolorization can be carried out under acidic pH conditions. For example, the pH range in the first decolorization can be 7 or less, 6.5 or less, 6 or less, 5.5 or less, 5 or less, 4.5 or less, or 4 or less, and 1 or more, 1.5 or more, 2 or more, 2.5 or more, 3 or more, or 3.5 or more. As a specific example, the first decolorization can be carried out at a pH of 1 to 7 or a pH of 2 to 7. As a more specific example, the first decolorization can be carried out at a pH of 3 to 6 or a pH of 3 to 5.

[0112] The acid component can be used to adjust the acidic pH. Examples of acid components used for pH adjustment in the first decolorization include phosphoric acid, sulfuric acid, hydrochloric acid and nitric acid, but are not limited thereto. Because the crude solution contains an appropriate amount of such acid components, it can be adjusted to the desired acidic pH.

[0113] In addition, the temperature of the first bleaching may be 40° C. or higher, 45° C. or higher, 50° C. or higher, 55° C. or higher, or 60° C. or higher, and 90° C. or lower, 80° C. or lower, 75° C. or lower, 70° C. or lower, or 65° C. or lower. As a specific example, the first bleaching may be performed at a temperature of 40° C. to 90° C. or 50° C. to 70° C.

[0114] In addition, the required time for the first decolorization can be 10 minutes or more, 30 minutes or more, or 50 minutes or more, and 3 hours or less, 2 hours or less, or 1 hour and 30 minutes or less. As a specific example, it can be 30 minutes to 1 hour and 30 minutes.

[0115] The second decolorization can be performed using a second oxidant containing hydrogen peroxide (H2O2). The pH conditions of the second decolorization and examples of the alkaline components added thereto, the amount of the oxidant added, and the temperature and time conditions can be the same as those exemplified in the decolorization process using hydrogen peroxide described above.

[0116] When sodium chlorite is used as an oxidant in the first decolorization step and hydrogen peroxide is used as an oxidant in the second decolorization step, the impurity (protein and lipid) content after the second decolorization can be significantly reduced, and the rate of impurity re-adsorption during solid (PHA) recovery can be reduced. Therefore, the amount of enzyme used for protein decomposition can be reduced in the subsequent deproteinization step, thereby reducing production costs. In addition, since it is used sequentially with sodium chlorite (the first oxidant), the amount of hydrogen peroxide used in the second decolorization can be less.

[0117] The deproteinization process can be carried out after the decolorization process. The deproteinization process can be carried out by protease. Examples of proteases include alkaline proteases, pepsin, trypsin, papain, chymotrypsin, aminopeptidase and carboxypeptidase, and one, two or more thereof can be used. Deproteinization can be carried out under alkaline pH conditions. For example, the pH range in the deproteinization can be 7 or more, 7.5 or more, 8 or more, or 8.5 or more, and can be 12 or less, 11 or less, 10.5 or less, 10 or less, 9.5 or less, or 9 or less. In addition, the temperature of the deproteinization process can be 40°C or more, 45°C or more, 50°C or more, 55°C or more, or 60°C or more, and 90°C or less, 80°C or less, 75°C or less, 70°C or less, or 65°C or less.

[0118] Furthermore, a supernatant may be separated from a process solution during a purification process, or a supernatant may be separated from a purified solution after a purification process, for measuring a color value, which will be explained in detail in the following monitoring of color values.

[0119] Controlling purification process conditions by monitoring color values

[0120] According to one embodiment, the method of the present disclosure includes measuring and analyzing the color value of the process solution or its supernatant during the purification process to control the purification process conditions.

[0121] For example, the measurement of the color value includes measuring the a* value of the process solution or its supernatant in the CIE LAB color space, and the purification process conditions may be adjusted based on changes in the a* value of the process solution or its supernatant.

[0122] For example, the change in a* value can be determined by comparing the a* value of the process solution or its supernatant with the a* value of the crude solution or its supernatant before the purification process, or by the change in the a* value of the process solution or its supernatant over time during the purification process.

[0123] As a specific example, the change in the a* value of the process solution or its supernatant is monitored at the beginning of the purification process to distinguish between normal and abnormal conditions based on its increase or decrease. If it is abnormal, the amount of oxidant added to the decolorization process can be increased. To this end, the method also includes measuring the a* value of the crude solution or its supernatant, and the change in the a* value of the process solution or its supernatant relative to the a* value of the crude solution or its supernatant can be determined.

[0124] As another specific example, while the purification process is being carried out, the change of the a* value of the process solution or its supernatant is continuously monitored to distinguish normal and abnormal states based on its increase or decrease. If it is abnormal, the amount of the oxidant added to the decolorization process can be increased. For this purpose, after the purification process begins, the a* value of the process solution or its supernatant is repeatedly measured at regular time intervals, such as 10 minute intervals, 20 minute intervals, or 30 minute intervals. These a* values ​​can be compared to determine whether it is reduced or increased.

[0125] According to another embodiment, the method of the present disclosure includes measuring the color value of the purified solution and its supernatant after the purification process, based on which the color value of the final PHA is predicted. If the predicted color value does not meet the target color value, an additional purification process can be performed.

[0126] Specifically, the a* value of the purified solution and its supernatant is monitored after the deproteinization process, thereby predicting the b* value of the final PHA resin to determine suitability. If it is determined to be unsuitable, an additional decolorization process can be performed.

[0127] Figure 2a A method for preparing a PHA resin including a decolorization process (using only hydrogen peroxide) according to one embodiment is shown.

[0128] Figure 2b A method for preparing a PHA resin including a decolorization process (using sodium chlorite, etc.) according to another embodiment is shown.

[0129] refer to Figure 2a and Figure 2b , the purification process for preparing PHA resin can be divided into the following cases: (A) the purification process proceeds abnormally, (B) the purification process proceeds normally, but the color value of the final product is predicted to be inappropriate, and (C) the purification process proceeds normally, and the color value of the final product is predicted to be appropriate.

[0130] In cases (A) and (B), PHA resins with low color quality are obtained; therefore, it is necessary to make appropriate responses by monitoring the color value.

[0131] Case (A) The purification process is abnormal

[0132] If the impurity content in the initial crude PHA solution is high, the oxidant added during the decolorization process cannot remove the impurities attached to the PHA particles; instead, it will first react with the impurities dissolved in the crude solution, resulting in insufficient oxidant; therefore, the decolorization process cannot proceed normally. Therefore, the change in color value (change in a* of the process solution) at the initial stage is different between the normal and abnormal progress of the decolorization process.

[0133] According to one embodiment, reference Figure 2a If the a* value of the process solution increases relative to the a* value of the crude solution during the decolorization process using the second oxidant (H2O2), it can be considered abnormal. Therefore, the amount of the added oxidant can be increased. Specifically, the amount of the oxidant added to the decolorization process can be increased when the following relationship (1A) is satisfied.

[0134] a0 <a30(1A)

[0135] In equation (1A), a0 is the a* value of the raw solution, and a30 is the a* value of the process solution after the addition of the second oxidant.

[0136] The time of measuring the a* value of the process solution after adding the second oxidant can be, for example, 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes or 60 minutes after adding the second oxidant. Specifically, it can be about 30 minutes after adding the second oxidant.

[0137] According to another embodiment, reference Figure 2b , if during the decolorization process using the first oxidant (NaClO2), the a* value of the supernatant of the process solution decreases relative to the a* value of the crude solution, it can be considered abnormal. Therefore, the amount of the added oxidant can be increased. Specifically, when the following relationship (1B) is satisfied, the amount of at least one of the first oxidant and the second oxidant added to the decolorization process can be increased, and more specifically, the amount of the second oxidant added can be increased.

[0138] a0'>a30'(1B)

[0139] In the relation (1B), a0' is the a* value of the supernatant of the crude solution, and a30' is the a* value of the supernatant of the process solution after the addition of the first oxidant.

[0140] The time of measuring the a* value of the supernatant of the process solution after adding the first oxidant can be, for example, 1 minute, 5 minutes, 10 minutes, 20 minutes, 30 minutes or 60 minutes after adding the first oxidant. Specifically, it can be about 30 minutes after adding the first oxidant.

[0141] As described above, in the decolorization process using sodium chlorite, only the color value of the supernatant of the process solution is monitored, and the supernatant can be obtained by treating the process solution by centrifugation or the like.

[0142] In particular, in the decolorization process using hydrogen peroxide and the decolorization process using sodium chlorite, the determination of normal and abnormal states based on the change of the a* value of the process solution (or its supernatant) is different. Figure 3a If the a* value of the process solution increases 30 minutes after the addition of hydrogen peroxide, it can be determined to be abnormal, and the reference Figure 3b , if the a* value of the supernatant decreases 30 minutes after the addition of sodium chlorite, it can be determined to be abnormal.

[0143] Case (B) The color value of the final product is predicted to be inappropriate

[0144] Meanwhile, even if the purification process of the polyhydroxyalkanoate resin proceeds normally, there may be cases where the desired final properties (color value) cannot be achieved due to reasons such as the subsequent rapid decrease in the activity of the oxidizing agent.

[0145] In this case, the color value of the purified solution after the purification process (eg, decolorization and deproteinization process) is measured, whereby the color value of the final PHA resin can be predicted to take appropriate measures in advance.

[0146] Therefore, the method of the present disclosure may include monitoring the color value of the purified solution after the purification process to predict the color value of the polyhydroxyalkanoate resin.

[0147] After the purification process, impurities attached to the surface of PHA particles fall off and exist in the solvent in a dissolved state.

[0148] When this is taken into account, Figure 5 As shown, it can be assumed that the color of the PHA resin mixed alone in the purified solution can be predicted by excluding the color of the supernatant in which the impurities are dissolved from the color of the purified solution (PHA and impurities mixed in the solvent).

[0149] Therefore, the measurement of the color value of the purified solution includes measuring the a* value of the purified solution and its supernatant in the CIE LAB color space, and the b* value of the polyhydroxyalkanoate resin in the CIE LAB color space can be predicted based on the a* value of the purified solution and its supernatant.

[0150] Specifically, the present inventors have measured the a* value of the purified solution obtained by the purification process, the a* value of the supernatant thereof, and the b* value of the final PHA resin in multiple processes, and thus a correlation can be obtained by statistical analysis based on these data. The statistical analysis method can be, for example, regression analysis, specifically, linear regression analysis or nonlinear regression analysis, more specifically, multiple linear regression analysis, but is not limited thereto.

[0151] For example, the b* value of the polyhydroxyalkanoate resin can be predicted by the following relationship (2A).

[0152] b*=Y+(X1×a1)+(X2×a2)(2A)

[0153] In relation (2A), a1 is the a* value of the purified solution, and a2 is the a* value of the supernatant of the purified solution.

[0154] In the relational formula (2A), Y may be 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, or 15.5 or more, and may be 21 or less, 20 or less, 19 or less, 18 or less, 17 or less, 16.5 or less, or 16 or less. In the relational formula (2A), X1 may be -2.5 or more, -2.0 or more, -1.5 or more, -1 or more, -0.5 or more, 0 or more, 0.3 or more, or 0.5 or more, and may be 4.0 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, 1.5 or less, 1 or less, or 0.7 or less. In the relational formula (2A), X2 may be -3.5 or more, -3.0 or more, -2.5 or more, -2 or more, -1.5 or more, -1 or more, or -0.5 or more, and may be 3.0 or less, 2.5 or less, 2 or less, 1.5 or less, 1 or less, 0.5 or less, or 0 or less. As a specific example, in the relational formula (2A), Y may be 10 to 21 or 14.68 to 16.68, X1 may be -2.5 to 4.0 or -0.39 to 1.61, and X2 may be -3.5 to 3.0 or -1.35 to 0.65. As a more specific example, in the relational formula (2A), Y may be about 15.68, X1 may be about 0.61, and X2 may be about -0.35.

[0155] As another example, the b* value of a polyhydroxyalkanoate resin can be predicted by the following relationship (2B). b*=Y'+(X1'×a1')+(X2'×a2') (2B)

[0156] In relation (2B), a1' is the a* value of the purified solution, and a2' is the a* value of the supernatant of the purified solution.

[0157] In the relational formula (2B), Y' may be 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 8.5 or more, or 9 or more, and may be 15 or less, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, or 9.5 or less. In the relational formula (2B), X1' may be -7.0 or more, -6.5 or more, -6 or more, -5.5 or more, -5 or more, or -4.5 or more, and may be -1.0 or less, -1.5 or less, -2.0 or less, -2.5 or less, -3.0 or less, -3.5 or less, or -4.0 or less. In the relational formula (2B), X2' may be -8 or more, -7 or more, -6 or more, -5.5 or more, -5 or more, -4.5 or more, or -4.3 or more, and may be -1 or less, -1.5 or less, -2 or less, -2.5 or less, -3 or less, -3.5 or less, or -4 or less. As a specific example, in the relational formula (2B), Y' may be 4 to 15 or 8.15 to 10.15, X1' may be -7 to -1 or -5.15 to -3.15, and X2' may be -8 to -1 or -5.04 to -3.04. As a more specific example, in the relational formula (2B), Y' may be about 9.15, X1' may be about -4.15, and X2' may be about -4.04.

[0158] refer to Figure 4a and Figure 4b , the measured b* values ​​and predicted b* values ​​of PHA resins show a high correlation.

[0159] Since the b* value of the PHA resin is predicted after the purification process as described above, if the target b* range is not met, a further purification process may be performed before recovering the solid (PHA). The target b* value may be, for example, less than 15, specifically, 14 or less, 13 or less, 12 or less, 11 or less, or 10 or less.

[0160] Specifically, if the predicted b* value is greater than the target b* value of the preparation method, a purification process may be further performed, more specifically, a decolorization process may be further performed. Further decolorization may be performed once or multiple times, and the specific conditions of the decolorization process may be as exemplified above.

[0161] After purification, the solid is recovered, washed with water and dehydrated to obtain the purified final polyhydroxyalkanoate resin.

[0162] Polyhydroxyalkanoate resin

[0163] The polyhydroxyalkanoate resin prepared according to the method of the present disclosure may have improved color. For example, the polyhydroxyalkanoate resin may have a b* value of 20 or less in the CIE LAB color coordinates. Specifically, the b* value of the polyhydroxyalkanoate resin in the CIE LAB color coordinates may be 14 or less, 13.5 or less, 13 or less, and may be 0 or more, 1 or more, 5 or more, or 10 or more.

[0164] The glass transition temperature (Tg) of the polyhydroxyalkanoate resin may be, for example, -45°C to -10°C, -35°C to -10°C, -35°C to -15°C, -35°C to -20°C, or -30°C to -20°C.

[0165] In addition, the melting temperature (Tm) of the polyhydroxyalkanoate resin may not be measurable, or may be, for example, 100 to 170°C, 100 to 160°C, 110 to 160°C, or 120 to 150°C.

[0166] The polyhydroxyalkanoate resin of the present disclosure may include amorphous polyhydroxyalkanoate, semi-crystalline polyhydroxyalkanoate, and mixtures thereof. For example, the crystallization temperature (Tc) of the polyhydroxyalkanoate resin may not be measured, or the crystallization temperature (Tc) may be measured to be 60°C to 120°C, specifically, 60°C to 110°C, 70°C to 120°C, or 75°C to 115°C.

[0167] The repeating units constituting the polyhydroxyalkanoate resin may include at least one selected from the group consisting of 2-hydroxybutyrate (2-HB), 3-hydroxybutyrate (3-HB), 3-hydroxypropionate (3-HP), 3-hydroxyvalerate (3-HV), 3-hydroxyhexanoate (3-HH), 3-hydroxyheptanoate (3-HHep), 3-hydroxyoctanoate (3-HO), 3-hydroxynonanoate (3-HN), 3-hydroxydecanoate (3-HD), 3-hydroxydodecanoate (3-HDd), 4-hydroxybutyrate (4-HB), 4-hydroxyvalerate (4-HV), 5-hydroxyvalerate (5-HV) and 6-hydroxyhexanoate (6-HH).

[0168] According to one embodiment, the polyhydroxyalkanoate resin may include 4-hydroxybutyrate (4-HB) repeating units. Specifically, it may include a copolymer containing 4-HB repeating units. For example, the content of 4-hydroxybutyrate (4-HB) repeating units in the polyhydroxyalkanoate resin may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, or 60% by weight or more, and 100% by weight or less, 99% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less, based on the total weight of the polyhydroxyalkanoate resin. As a specific example, the polyhydroxyalkanoate resin may include 25% by weight or more of 4-hydroxybutyrate (4-HB) repeating units.

[0169] In addition, the weight average molecular weight (Mw) of the polyhydroxyalkanoate resin may be, for example, 50,000 or more, 100,000 or more, 200,000 or more, 300,000 or more, 400,000 or more, or 500,000 or more, and may be 1,200,000 or less, 900,000 or less, 800,000 or less, 700,000 or less, or 600,000 or less.

[0170] In addition, the polyhydroxyalkanoate resin may have a purity of 95% or more, 97% or more, 98% or more, 98.5% or more, 98.55% or more, or 98.6% or more.

[0171] Mode for the Invention

[0172] The present disclosure will be described in more detail below with reference to embodiments. However, these embodiments are provided for illustrative purposes only, and the present disclosure is not limited thereto.

[0173] Preparation Example 1: Preparation of PHA fermentation broth

[0174] PHA fermentation broth is prepared using genetically engineered Escherichia coli (E. coli) strains. First, the PHA-producing strain is seed cultured to ensure a certain amount, and then the main fermentation is carried out. For the fermentation of the PHA-producing strain, glucose or raw sugar is used as a carbon source, and various mineral components are added as nutrients. Sodium hydroxide solution or ammonia gas is used to adjust the fermentation pH. The fermentation process using the PHA-producing strain is carried out at 30 to 40°C and a pH of 6 to 9.

[0175] Preparation Example 2: Preparation of crude PHA solution

[0176] The PHA fermentation broth was subjected to solid-liquid separation using a mechanical separator to separate the culture medium impurities and the biomass containing PHA. The separated biomass was adjusted to a total solid content of 10 to 15% by weight. A surfactant (sodium laureth sulfate, 30%, Miwon Corporation) was added in an amount of 0.13% by weight, based on the total weight of the reaction solution. After sufficient stirring, physical cell disruption was performed using a high-pressure homogenizer (Bertoli) (400 to 800 bar, 1 pass). The crude PHA solution thus obtained was subjected to a second solid-liquid separation to separate the solids containing PHA and the cell-derived impurities to obtain a crude PHA solution (a solution containing unpurified PHA).

[0177] Preparation Example 3A: Decolorization Process - Using Hydrogen Peroxide Alone

[0178] A 20% aqueous sodium hydroxide (NaOH) solution was added to the crude PHA solution to adjust the pH to 9 to 9.5. A 30% aqueous hydrogen peroxide (H2O2) solution was added in an amount of 0.44 to 0.77 wt % based on the total weight of the reaction solution. The decolorization reaction was performed at a temperature of 60° C. in a shaking incubator (IS-971R, JEIO TECH) for 2 hours.

[0179] Preparation Example 3B: Decolorization process - using sodium chlorite and hydrogen peroxide in sequence

[0180] (1) The first decolorization process

[0181] 0.22 to 0.55 wt % (based on the total weight of the crude PHA solution) of a 23% aqueous sodium chlorite (NaClO2) solution, the pH of which had been adjusted to 6.0 with a 10% aqueous phosphoric acid (H3PO4) solution, was added. The final pH of the reaction solution was fixed at 4.0 using a 10% aqueous phosphoric acid solution. The reaction was carried out at a temperature of 60°C in a shaking incubator (IS-971R, JEIO TECH) for 1 hour.

[0182] (2) Second decolorization process

[0183] A 20% sodium hydroxide (NaOH) aqueous solution was added to the first decolorized slurry to adjust the pH to 9 to 9.5. A 30% hydrogen peroxide aqueous solution was added at 0.22 to 0.55 wt % (based on the total weight of the reaction solution). The decolorization reaction was carried out at a temperature of 60° C. in a shaking incubator (IS-971R, JEIO TECH) for 1 hour.

[0184] Preparation Example 4: Deproteinization process

[0185] A 20% sodium hydroxide aqueous solution was added to the reaction solution obtained by the decolorization process to adjust the pH to 9.5. A protease (Alcalase TM ), based on the total weight of the reaction solution. The deproteinization reaction was carried out at a temperature of 60° C. in a shaking incubator (IS-971R, JEIO TECH) for 2 hours. After deproteinization, the recovered solid (PHA) was washed with water and then dried to obtain the purified final polyhydroxyalkanoate resin.

[0186] Test Example 1: Derivation of factors reflecting impurity behavior between processes (multiple linear regression analysis)

[0187] For the purified solution obtained by the purification process (decolorization and deproteinization) under various conditions, three color values ​​(L*, a* and b*) in the CIELAB color space were measured. The b* value of the PHA resin finally obtained from the purified solution was measured. The measurement was performed using a spectrophotometer (CM-5, Konica Minolta). Since the b* value of the final PHA resin increases with the increase in the amount of impurities, the b* value reflects the impurity content in the final PHA resin to a certain extent.

[0188] It was analyzed which of the three color values ​​of the purified solution, alone or in combination of two of them, had a significant correlation with the color value of the final product (i.e., the effect of impurity removal). The three color values ​​(L*, a*, and b*) of the purified solution obtained from 67 different purification processes were measured. Multiple linear regression analysis was performed on the b* value of the PHA resin finally obtained from each process (n=67). The results are shown in Table 1 below.

[0189] [Table 1]

[0190]

[0191] As can be seen from the above table, when considering the p value, an indicator for determining the reliability of correlation in the multiple linear regression analysis, the a* value in the color value of the purified solution after the purification process has the most significant relationship with the b* value of the final PHA resin.

[0192] Example 1A: Monitoring Color Value (Using Hydrogen Peroxide Alone)

[0193] The color value was monitored during the purification process (including the decolorization process using only hydrogen peroxide). Specifically, when the preparation of PHA fermentation broth (Preparation Example 1), the preparation of crude PHA solution (Preparation Example 2), and the decolorization process using only hydrogen peroxide (Preparation Example 3A) were performed, the color value of the process solution was monitored. The color value was monitored by extracting 12 ml of each process solution, charging it into a 20-mm quartz cell, and measuring the a* value of the sample transmission color.

[0194] First, the a* value of the crude PHA solution obtained in Preparation Example 2 (PHA solution recovered from the PHA fermentation broth by cell disruption and washing and before pH adjustment and decolorization) was obtained. Thereafter, while the decolorization process of Preparation Example 3A and the deproteinization process of Preparation Example 4 were performed, the process solution was sampled at intervals of 30 minutes to obtain the a* value.

[0195] The a* value of the process solution measured 30 minutes after the start of the decolorization process using hydrogen peroxide (addition of hydrogen peroxide) was classified as normal progress if it decreased relative to the a* value of the crude PHA solution before the decolorization process, and was classified as abnormal progress if it increased.

[0196] The results are shown in Table 2 and Figure 3a shown.

[0197] [Table 2]

[0198]

[0199] From Table 2 and Figure 3a It can be seen that the a* value of the initial crude PHA solution was measured to be 0 to 7. In the normal progress of the decolorization process, the a* value of the process solution decreased by 40 to 80% relative to the initial value after 30 minutes, while in the abnormal progress, the a* value of the process solution increased by 2.0 to 4.5 times relative to the initial value after 30 minutes.

[0200] Example 1B: Monitoring Color Value (Using Sodium Chlorite and Hydrogen Peroxide)

[0201] The color value was monitored during the purification process (including the decolorization process using sodium chlorite and hydrogen peroxide). Specifically, when the preparation of the PHA fermentation broth (Preparation Example 1), the preparation of the crude PHA solution (Preparation Example 2), and the decolorization process using sodium chlorite and hydrogen peroxide in sequence (Preparation Example 3B) were performed, the process solution was centrifuged to obtain its supernatant, and its color value was monitored.

[0202] The color value was monitored by extracting 15 ml of each process solution, centrifuging the process solution at 3,800 rpm for 20 minutes in a centrifuge (Combi-514R, Hanil), charging 12 ml of the thus separated supernatant into a 20-mm quartz cell, and measuring the a* value of the sample transmission color.

[0203] First, the a* value of the supernatant of the crude PHA solution obtained in Preparation Example 2 (PHA solution recovered from the PHA fermentation broth by cell disruption and washing and before pH adjustment and decolorization) was obtained. Thereafter, while the first decolorization process and the second decolorization process of Preparation Example 3B and the deproteinization process of Preparation Example 4 were performed, the process solution was sampled at intervals of 30 minutes, and the a* value of the supernatant thereof was measured.

[0204] The a* value of the supernatant of the process solution measured 30 minutes after the start of the first decolorization process using sodium chlorite (sodium chlorite addition) was classified as normal progress if it increased relative to the a* value of the supernatant of the crude PHA solution before the decolorization process, and was classified as abnormal progress if it decreased.

[0205] The results are shown in Table 3 and Figure 3b shown.

[0206] [Table 3]

[0207]

[0208] From Table 3 and Figure 3b It can be seen that the a* value of the supernatant of the initial crude PHA solution was measured to be -2 to 0. In the normal progress of the decolorization process, the a* value of the supernatant of the process solution increased by 50 to 75% relative to the initial value after 30 minutes, while in the abnormal progress, the a* value of the supernatant of the process solution decreased by 3.5 times relative to the initial value after 30 minutes.

[0209] Example 2A: Prediction of b* Values ​​of PHA Resins (Using Hydrogen Peroxide Alone)

[0210] The color value (a* value) after purification (including the decolorization process using hydrogen peroxide alone) was measured to predict the color value (b* value) of the final polyhydroxyalkanoate resin. Specifically, the preparation of PHA fermentation broth (Preparation Example 1), the preparation of crude PHA solution (Preparation Example 2), the decolorization process using hydrogen peroxide alone (Preparation Example 3A) and the deproteinization process (Preparation Example 4) were performed to obtain a purified solution. The color value thereof was measured, and the final color value was predicted based on this. The color value of the PHA resin finally obtained by recovering the solid was measured and compared with the predicted value.

[0211] First, the purified solution was extracted after the deproteinization process and the a* value was measured. The purified solution was centrifuged to obtain a supernatant and the a* value was measured. Thereafter, the b* value of the polyhydroxyalkanoate resin finally obtained by recovering the solid was measured. The color value was measured for 21 samples. The results are shown in the following table.

[0212] Using the measured color value data, the following relationship was obtained through multiple linear regression analysis.

[0213] b* of the final PHA resin = 15.68 + (0.61 × a1) + (-0.35 × a2)

[0214] Here, a1 is the a* value of the purified solution in the CIE LAB color space, and a2 is the a* value of the supernatant of the purified solution.

[0215] Additionally, the a* values ​​of the purified solution and supernatant were substituted into the above relationship to calculate the predicted b* values ​​for the final PHA resin, which are also shown in the table below.

[0216] [Table 4]

[0217]

[0218]

[0219] Based on the above results, the correlation between the measured b* value and the predicted b* value of the PHA resin is shown in Figure 4a and confirmed the coefficient of determination (R 2 ) as high as 0.8466.

[0220] Example 2B: Prediction of b* Values ​​of PHA Resins (Using Sodium Chlorite and Hydrogen Peroxide)

[0221] The color value (a* value) after purification (including the decolorization process using sodium chlorite and hydrogen peroxide in sequence) is measured to predict the color value (b* value) of the final polyhydroxyalkanoate resin. Specifically, the preparation of PHA fermentation broth (Preparation Example 1), the preparation of crude PHA solution (Preparation Example 2), the decolorization process using sodium chlorite and hydrogen peroxide in sequence (Preparation Example 3B) and the deproteinization process (Preparation Example 4) are carried out to obtain a purified solution. The color value thereof is measured, and the final color value is predicted based on this. The color value of the polyhydroxyalkanoate resin finally obtained by recovering the solid is measured and compared with the predicted value.

[0222] First, the purified solution was extracted after the deproteinization process, and the a* value was measured. The purified solution was centrifuged to obtain a supernatant, and the a* value was measured. In addition, thereafter, the b* value of the polyhydroxyalkanoate resin finally obtained by recovering the solid was measured. The color value was measured for 9 samples. The results are shown in the following table.

[0223] Using the measured color value data, the following relationship was obtained through multiple linear regression analysis.

[0224] The final PHA resin b* = 9.15 + (-4.15 × a1') + (-4.04 × a2')

[0225] Here, a1' is the a* value of the purified solution in the CIE LAB color space, and a2' is the a* value of the supernatant of the purified solution.

[0226] In addition, the a* values ​​of the purified solution and its supernatant were substituted into the above relationship to calculate the predicted b* value of the final PHA resin, which is also shown in the table below.

[0227] [Table 5]

[0228]

[0229] Based on the above results, the correlation between the measured b* value and the predicted b* value of the PHA resin is shown in Figure 4b and confirmed the coefficient of determination (R 2 ) as high as 0.8257.

[0230] Example 3: Controlling the purification process by monitoring the color value

[0231] When the decolorization process was abnormally performed in Example 2A, the decolorization process was performed by increasing the amount of hydrogen peroxide added (1.5 times, 2.0 times). Thereafter, the b* value of the PHA resin finally obtained through the deproteinization process and the recovery of the solid was measured.

[0232] In addition, when the decolorization process was abnormally performed in Example 2A, the decolorization process was further performed after deproteinization. Thereafter, the b* value of the PHA resin finally obtained by recovering the solid was measured.

[0233] In addition, when the decolorization process was abnormally performed in Example 2B, the decolorization process was performed by increasing the addition amount of sodium chlorite (0.5%). Thereafter, the b* value of the PHA resin finally obtained through the deproteinization process and the recovery of the solid was measured.

[0234] Furthermore, when the decolorization process was abnormally performed in Example 2B, the decolorization process was performed by increasing the addition amount of hydrogen peroxide (1.5%). Thereafter, the b* value of the PHA resin finally obtained through the deproteinization process and the recovery of the solid was measured.

[0235] Comparative Example

[0236] The purification process was carried out in the same procedure as in Example 3, except that the process conditions thereof were not adjusted even when the decolorization process abnormally proceeded. Thereafter, the predicted b* value was calculated based on the relational expression obtained in Example 2A or 2B.

[0237] The b* values ​​obtained in the comparative example and in Example 3 are compared in Table 6 below.

[0238] [Table 6]

[0239]

[0240] As can be seen from Table 6 above, when the bleaching process is abnormally performed, if the amount of the oxidant is increased or additional bleaching is performed, the b* value of the final PHA resin will decrease. In particular, increasing the amount of the oxidant is more effective in reducing the b* value than performing additional bleaching.

Claims

1. A method for controlling a purification process, comprising measuring the color value of a process solution or its supernatant during a purification process for preparing a polyhydroxyalkanoate (PHA) resin, or measuring the color value of a purified solution and its supernatant after the purification process; and controlling the purification process based on the measured color value.

2. The method of controlling a purification process according to claim 1, wherein the measurement of the color value comprises measuring an a* value in a CIE LAB color space, and adjusting purification process conditions based on a change in the a* value of the process solution or its supernatant.

3. The method for controlling a purification process according to claim 2, wherein the change in a* value is determined by comparing the a* value of the process solution or its supernatant with the a* value of a crude solution or its supernatant before the purification process, or by the change in the a* value of the process solution or its supernatant over time during the purification process.

4. The method for controlling a purification process according to claim 1, wherein the measurement of the color value comprises measuring an a* value in a CIE LAB color space, and predicting a b* value of the polyhydroxyalkanoate resin in the CIE LAB color space based on the a* value of the purified solution and the supernatant thereof.

5. A system for controlling a purification process, comprising a purification unit for performing a purification process for preparing a polyhydroxyalkanoate (PHA) resin; a monitoring unit for measuring the color value of the process solution or its supernatant during the purification process, or measuring the color value of the purified solution and its supernatant after the purification process, and A control unit is provided for controlling the purification process based on the measured color value.

6. A method for preparing a polyhydroxyalkanoate resin from a crude solution containing polyhydroxyalkanoate (PHA) through a purification process, comprising at least one of the following steps: (a) measuring the color value of the process solution or its supernatant during the purification process; and (b) measuring the color value of the purified solution and its supernatant after the purification process.

7. The method for preparing a polyhydroxyalkanoate resin according to claim 6, wherein the measurement of the color value in step (a) comprises measuring an a* value of the process solution or its supernatant in a CIE LAB color space, and adjusting purification process conditions based on changes in the a* value of the process solution or its supernatant.

8. The method for preparing a polyhydroxyalkanoate resin according to claim 7, wherein the method further comprises measuring the a* value of the crude solution or its supernatant, and determining the change in the a* value of the process solution or its supernatant relative to the a* value of the crude solution or its supernatant.

9. The method for preparing a polyhydroxyalkanoate resin according to claim 8, wherein the purification process includes a decolorization process, and the decolorization process is performed by using a first oxidant, a second oxidant, or both in sequence, the first oxidant comprising sodium chlorite (NaClO2), and the second oxidant comprising hydrogen peroxide (H2O2).

10. The method for preparing a polyhydroxyalkanoate resin according to claim 9, wherein the decolorization process is performed by the second oxidant, and When the following relationship (1A) is satisfied, the amount of oxidant added to the decolorization process is increased: a0 <a30(1A) In equation (1A), a0 is the a* value of the raw solution, and a30 is the a* value of the process solution after adding the second oxidant.

11. The method for preparing a polyhydroxyalkanoate resin according to claim 9, wherein the decolorization process is performed by the first oxidant and the second oxidant in sequence, and When the following relation (1B) is satisfied, the amount of at least one of the first oxidant and the second oxidant added to the decolorization process is increased: a0'>a30'(1B) In the relation (1B), a0' is the a* value of the supernatant of the crude solution, and a30' is the a* value of the supernatant of the process solution after the addition of the first oxidizing agent.

12. The method for preparing a polyhydroxyalkanoate resin according to claim 6, wherein the measurement of the color value in step (b) comprises measuring the a* value of the purified solution and the supernatant thereof, and predicting the b* value of the polyhydroxyalkanoate resin in the CIE LAB color space based on the a* value of the purified solution and the supernatant thereof.

13. The method for preparing a polyhydroxyalkanoate resin according to claim 12, wherein the b* value of the polyhydroxyalkanoate resin is predicted by the following relationship (2A): b*=Y+(X1×a1)+(X2×a2)(2A) In the relational formula (2A), a1 is the a* value of the purified solution, a2 is the a* value of the supernatant of the purified solution, Y is 10 to 21, X1 is -2.5 to 4.0, and X2 is -3.5 to 3.

0.

14. The method for preparing a polyhydroxyalkanoate resin according to claim 12, wherein the b* value of the polyhydroxyalkanoate resin is predicted by the following relationship (2B): b*=Y'+(X1'×a1')+(X2'×a2')(2B) In relational formula (2B), a1' is the a* value of the purified solution, a2' is the a* value of the supernatant of the purified solution, Y' is 4 to 15, X1' is -7 to -1, and X2' is -8 to -1. 15 . The method for preparing a polyhydroxyalkanoate resin according to claim 12 , wherein if the predicted b* value of the polyhydroxyalkanoate resin is greater than the target b* value, an additional purification process is performed.

16. The method for preparing a polyhydroxyalkanoate resin according to claim 6, wherein the crude solution containing polyhydroxyalkanoate is prepared by a method comprising: performing solid-liquid separation on a fermentation broth containing polyhydroxyalkanoate to obtain a biomass; mixing an additive comprising a surfactant with the biomass to obtain a suspension; disrupting the biomass in the suspension to obtain a slurry; and The slurry is subjected to solid-liquid separation.

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