Process and products for the production of long chain diacids

Abstract

The application provides a method for producing long-chain dibasic acid and a long-chain dibasic acid product. The method comprises: inoculating a seed solution of a fermentation strain into a fermentation tank, and the fermentation substrate comprises any one or several of fatty acids and derivatives thereof and alkanes. In the application, green raw materials such as fatty acids and derivatives thereof and plant-based alkanes are used as the substrate, and part or all of fossil energy such as petroleum alkanes is replaced, the product is green long-chain dibasic acid, and the bio-based content can be controlled. Moreover, the fermentation method of the application can still maintain a high yield and conversion rate.

Description

Technical Field

[0001] This invention belongs to the field of fermentation technology, specifically relating to a method for producing long-chain dicarboxylic acids and long-chain dicarboxylic acid products. Background Technology

[0002] Due to their unique molecular structure and reactivity, long-chain dicarboxylic acids have a wide range of applications in many fields. They can be used as raw materials to synthesize special nylon (polyamide), high-grade fragrances, high-grade hot melt adhesives, cold-resistant plasticizers, high-grade lubricants, high-grade rust inhibitors, high-grade paints and coatings, etc.

[0003] Long-chain dicarboxylic acids have important and wide-ranging industrial applications, but they do not exist independently in nature; their sources vary depending on the chain length. Synthetic methods include chemical synthesis and bio-fermentation. Chemical synthesis is characterized by complex processes, harsh conditions, numerous steps, low yield, low purity, high cost, and pollution. Bio-synthetic methods, on the other hand, typically use corresponding long-chain alkanes and their derivatives as substrates, utilizing Candida tropicalis fermentation to produce long-chain dicarboxylic acids. Compared to chemical synthesis, this method offers simpler production processes, milder conditions, more specific reactions, higher yields, lower energy consumption, and simpler extraction and purification processes.

[0004] my country has been engaged in the research of long-chain dicarboxylic acids for more than 40 years, mainly using petroleum-based alkanes as substrates. However, new plant-based resources such as fatty acids, fatty acid salts, and fatty acid esters can replace fossil raw materials such as petroleum-based alkanes, which is of great significance to the sustainable development of industrial processes. Summary of the Invention

[0005] This invention provides a method and product for producing long-chain dicarboxylic acids. This method can utilize environmentally friendly fermentation substrates such as fatty acids and their derivatives, including fatty acid salts and fatty acid esters, as well as plant-based alkanes, to partially or completely replace fossil fuels such as petroleum-based alkanes, while maintaining high yields and conversion rates.

[0006] To achieve the above objectives, a first aspect of the present invention is to provide a method for producing long-chain dicarboxylic acids, the method comprising: inoculating a seed culture of a fermentation strain into a fermenter, wherein the fermentation substrate comprises any one or more of fatty acids and their derivatives, and alkanes.

[0007] In one embodiment, the long-chain dicarboxylic acid has the chemical formula HOOC(CH2)nCOOH, where n≥8, and includes any one of sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

[0008] In one embodiment, the fatty acid derivative includes fatty acid esters and fatty acid salts.

[0009] In one embodiment, the fermentation substrate preferably includes at least one of fatty acids, fatty acid esters, and fatty acid salts.

[0010] In one embodiment, the fermentation substrate includes alkanes and at least one of fatty acids, fatty acid esters, and fatty acid salts.

[0011] In one embodiment, the alkane is a petroleum-based alkane and / or a bio-based alkane.

[0012] In one embodiment, the fatty acid is a straight-chain monocarboxylic acid with 10 or more carbon atoms, and more specifically, a straight-chain monocarboxylic acid with 10 to 18 carbon atoms, including any one of: decadecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, and octadecanoic acid.

[0013] In one embodiment, the fatty acid salt includes any one of the sodium, potassium, ammonium, and calcium salts of fatty acids. The fatty acids have the same limitations as described above. Fatty acids are mainly derived from the seeds of oil-rich tropical crops such as palm and coconut trees. This novel renewable resource can replace fossil fuels such as petroleum and alkanes, and is of great significance to the sustainable development of industrial processes.

[0014] In one embodiment, the fatty acid ester includes any one of decadecanoate, undecanoate, laurate, tridecanoate, myristate, pentadecanoate, palmitate, heptadecanoate, and octadecanoate. Examples include methyl laurate, ethyl laurate, butyl laurate, methyl myristate, ethyl myristate, butyl myristate, methyl palmitate, ethyl palmitate, and butyl palmitate. Because fatty acid esters are liquid at room temperature, they have good dispersion and characteristics similar to alkanes, and can replace currently used alkanes as substrates. Fatty acid esters are mainly derived from the seeds of oil-rich tropical crops such as palm and coconut trees. This new type of renewable resource can replace fossil fuels such as petroleum alkanes, which is of great significance for the sustainable development of industrial processes. The fatty acids have the same limitations as described above.

[0015] In one embodiment, the alkane includes straight-chain alkane with 10 or more carbon atoms, and more particularly, straight-chain alkane with 10 to 18 carbon atoms, including any one of: decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecanane, n-hexadecane, n-heptadecane, and n-octadecane.

[0016] In one embodiment, the fermentation substrate is fatty acid and alkane, and the mass ratio of fatty acid to alkane is (0.1-25):15, more specifically (1-20):15.

[0017] In one embodiment, the fermentation strain includes Candida viswanathii, Candida albicans, Candida tropicalis, Candida sake, or Yarrowia lipolytica.

[0018] In one embodiment, the seed culture is inoculated into the fermenter at an inoculum of 10% to 50%. Percentages represent volume percentages (v / v).

[0019] The fermenter contains a fermentation medium. The fermentation medium includes a nitrogen source, a carbon source, growth factors, inorganic salts, and may also contain additives such as antifoaming agents.

[0020] In one embodiment, the fermentation medium comprises the following components: corn steep liquor 0%–1.0%, glucose 2.0%–6.0%, yeast extract 0%–0.8%, potassium dihydrogen phosphate 0.4%–1.0%, magnesium sulfate 0.2%–0.6%, ammonium sulfate 0.1%–1%, and potassium nitrate 0.2%–0.8%.

[0021] In one embodiment, the seed culture of the fermentation strain is inoculated into a fermenter containing a fermentation medium.

[0022] In one embodiment, the optical density value (OD) of the seed culture of the fermentation strain at a 30-fold dilution is... 620 It ranges from 0.5 to 1.0.

[0023] In one embodiment, the method for preparing the seed culture includes the following steps: activating the fermentation strain in a shake flask, and determining the optical density (OD) value of the seed culture at a 30-fold dilution. 620 When the optical density (OD) of the shake flask seeds is between 0.5 and 1.0, the seeds are inoculated into a seed tank containing seed culture medium for seed culture until the optical density of the resulting seed solution is diluted 30 times. 620 It reaches 0.5 to 1.0.

[0024] The activation culture conditions include: a temperature of 27–35℃, a shaking speed of 150–250 rpm, and a time of 38–42 h.

[0025] The conditions for seed culture include: temperature of 27–35℃, air volume of 0.2–0.8 vvm, pressure of 0.05–0.20 MPa, and dissolved oxygen of 5–50%.

[0026] Seed culture medium includes nitrogen source, carbon source, inorganic salts, growth factors and antifoaming agent. Carbon sources in seed culture medium include glucose, maltose, sucrose, etc. Nitrogen sources include corn steep liquor, urea, yeast extract, potassium nitrate, ammonium sulfate, etc. Inorganic salts include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, potassium nitrate, sodium chloride, ferrous sulfate, magnesium sulfate, etc. Nutrients include vitamin B1, vitamin B2, vitamin B5, biotin, etc.

[0027] In one embodiment, the seed culture medium comprises the following components: corn steep liquor 0.2%–0.8%, sucrose 0.5%–3.5%, urea 0.2%–0.8%, yeast extract 0.1%–1%, potassium dihydrogen phosphate 0.2%–1.0%, and defoamer 0.02%–0.10%.

[0028] In one embodiment, the fermentation substrate is added before, simultaneously with, or after the seed culture of the fermentation strain is introduced into the fermenter.

[0029] Fermentation substrates can be added or supplemented in a single addition, batch addition, or continuous addition manner.

[0030] In one embodiment, the seed culture of the fermentation strain is first inoculated into the fermenter. When the optical density value (OD) of the fermentation strain in the fermentation system... 620 When diluted 30 times to reach a concentration of 0.5–1.0, add the fermentation substrate to begin fermentation.

[0031] In one embodiment, during fermentation, the viscosity of the fermentation system is maintained at a suitable level by supplementing the fermentation substrate, thereby enabling the strain to maintain high activity and acid production capacity.

[0032] In one embodiment, within T hours after the start of fermentation, the viscosity η of the fermentation system and the fermentation time t are related by the following numerical relationship: η = a * e bt +c, where 135≤T≤165, 1.05≤a≤5.8, 0.02≤b≤0.045, 0≤c≤5.5, the viscosity η is in MPa·s, and the fermentation time t is in hours. e is a natural constant, an infinite non-repeating decimal with a value of approximately 2.718281828459045.

[0033] In one embodiment, 145≤T≤155.

[0034] In one embodiment, 1.2 ≤ a ≤ 4.5.

[0035] In one embodiment, 0.02 ≤ b ≤ 0.04.

[0036] In one embodiment, 0.2 ≤ c ≤ 3.

[0037] In one embodiment, fermentation substrate is added to the fermentation system within T hours after the start of fermentation.

[0038] In one embodiment, after fermentation for 135–165 hours, the addition of fermentation substrate is stopped.

[0039] In one embodiment, after fermentation for 145–155 hours, the addition of fermentation substrate is stopped.

[0040] After fermentation has proceeded for a certain period, the addition of fermentation substrate is stopped. Fermentation continues using the remaining substrate in the system until the substrate is completely consumed or no longer long-chain dicarboxylic acids are produced. The total fermentation time is calculated.

[0041] In one embodiment, the temperature is controlled at 27–33°C during fermentation.

[0042] In one embodiment, during fermentation, the air volume is controlled at 0.2 to 0.8 vvm, and / or the pressure is controlled at 0.05 to 0.20 MPa, and / or the pH value is controlled at 4.5 to 6.5, more preferably 6.0 to 6.5, and / or the dissolved oxygen value is controlled at 5% to 50%, more preferably 25% to 50%.

[0043] The fermentation broth produced by fermentation can be used directly as a product, or long-chain dicarboxylic acids can be extracted from the fermentation broth as a final product.

[0044] In one embodiment, the method includes: purifying the fermentation broth, wherein the purification process includes: acidifying the fermentation broth, separating the solids, dissolving the solids in an organic solvent, crystallizing and separating the solids, washing and drying the separated solids to obtain a long-chain dicarboxylic acid product.

[0045] In some embodiments, the pH of the acidification is 2 to 5, preferably 3.5 to 4.5. The long-chain dicarboxylic acid is crystallized through acidification.

[0046] In one embodiment, the separation method described above includes at least one of filtration or centrifugation.

[0047] In one embodiment, the mass ratio of solids to organic solvent is 1:(3-6).

[0048] In one embodiment, the organic solvent includes one or more of acids, alcohols, esters, and ketones; wherein the alcohol includes one or more of methanol, ethanol, n-butanol, and isopropanol, the acid includes acetic acid, the ketone includes acetone, and the ester includes at least one of ethyl acetate and butyl acetate.

[0049] In one embodiment, the solution is decolorized after dissolving in an organic solvent and before crystallization. The decolorization method preferably uses activated carbon, with the amount of activated carbon added not exceeding 4% of the clarified liquid. The decolorization temperature is 90–110°C, and the decolorization time is 30–190 min.

[0050] In one embodiment, the crystallization is cooling crystallization, and the endpoint temperature of the cooling crystallization is 20-40°C.

[0051] A second aspect of the present invention is to provide a long-chain dicarboxylic acid product with a purity of 98% or higher, and more preferably 99% or higher.

[0052] The bio-based content of long-chain dicarboxylic acid products can be adjusted according to different fermentation substrates, ranging from 1% to 100%, further from 5% to 100%, further from 5% to 99%, further from 5% to 80%, further from 5% to 50%, for example 95%, 80%, 70%, 50%, 45%, 35%, 30%, 25%, 15%, and 10%.

[0053] This invention uses green raw materials such as fatty acids, fatty acid salts, fatty acid esters, and plant-based alkanes as substrates to partially or completely replace fossil energy sources such as petroleum alkanes, while the target product, long-chain dicarboxylic acid, can still maintain a high yield and conversion rate. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In the following examples, the content of dodecanoic acid in the fermentation broth was determined by gas chromatography. Purity testing of long-chain dicarboxylic acids: gas chromatography. Bio-based content testing: ASTM D6866 method (American Society for Testing and Materials).

[0056] In this invention, the percentages used to characterize the content of components in the culture medium are all in accordance with the general conventions in the field of fermentation. The percentage represents the mass-volume ratio (w / v), that is, % represents g / 100mL.

[0057] The strain used in the examples, Candida viswanathii CAES2113, has been disclosed in patent CN111748480A and deposited on February 24, 2020, at the China Center for Type Culture Collection (address: Wuhan University, Wuhan, China), with accession number CCTCC M 2020048 and classified as Candidaviswanathii.

[0058] In Examples 1-3, n-dodecane was derived from petroleum, i.e., a petroleum-based alkane, with a purity of 99.92%. In Example 4, n-dodecane was obtained through processing vegetable oil, and is a bio-based alkane with a purity of 99.91%.

[0059] The viscosity η of the fermentation system was monitored using an online viscometer, and the substrate addition was controlled to ensure that the relationship between the viscosity η and the fermentation time t satisfied η = a*e bt +c.

[0060] Example 1

[0061] (1) First, adjust the pH of the 10 Baume wort to about 5.4. Then, take 100 mL and place it in an Erlenmeyer flask. Sterilize at 121℃ for 20 min. Then, inoculate one 2 mL tube of Candida viride (strain CAES2113) seed that has been stored in a -80℃ freezer. Activate and culture on a rotary shaker at 29℃ and 220 rpm for 40 h. The cell OD 620 The activation culture ends when the value reaches 0.7 (30-fold dilution).

[0062] (2) Inoculate the shake flask seeds obtained in step (1) into a seed tank containing seed culture medium and culture them. The inoculation amount is 1.6% (v / v), and the temperature, airflow and pressure are controlled at 29°C, 0.33 vvm and 0.11 MPa during the culture process. The dissolved oxygen is maintained at 15% until the OD of the obtained seed solution is 30 times diluted. 620 The value reached 0.8.

[0063] The seed culture medium consists of: 0.5% corn steep liquor (total nitrogen content 2.5%), 2.3% sucrose, 0.3% urea, 0.5% yeast extract, 0.6% potassium dihydrogen phosphate, and 0.05% defoamer.

[0064] (3) The seed liquid obtained in step (2) above was introduced into a fermenter containing fermentation medium and fermented. The inoculation amount was 15% (v / v), the fermentation temperature was 29℃, the pH value was 6.4, the air volume was 0.31vvm, the pressure during fermentation was 0.12MPa, and the dissolved oxygen during fermentation was 42%.

[0065] The fermentation medium in the fermenter consists of: 0.9% corn steep liquor, 3.3% glucose, 0.4% yeast extract, 0.5% potassium dihydrogen phosphate, 0.2% magnesium sulfate, 0.4% ammonium sulfate, and 0.4% potassium nitrate.

[0066] After the seed culture is introduced into the fermenter, when the cell OD... 620 When the viscosity reached 0.80 (30-fold dilution), substrate was added to the fermenter for fermentation. From the start of fermentation to 150 hours, the relationship between the viscosity η (MPa·s) and the fermentation time t (h) of the fermentation system satisfied the following: η = 2.95 * e 0.026t +1.2. After 150 hours of fermentation, the feeding of substrate was stopped. The fermentation substrate was lauric acid and n-dodecane in a mass ratio of 12:18.

[0067] Example 2

[0068] Step (1): Same as in Example 1.

[0069] Step (2): Same as in Example 1.

[0070] Step (3): When the bacterial cell OD 620 When the viscosity reached 0.75 (30-fold dilution), substrate was added to the fermenter for fermentation. From the start of fermentation to 152 hours, the relationship between the viscosity η (MPa·s) and the fermentation time t (h) satisfied the following: η = 3.05 * e 0.015t +0.91. After 152 hours of fermentation, the feeding of substrate was stopped. The fermentation substrate was lauric acid and n-dodecane in a mass ratio of 10:20. The rest was the same as in Example 1.

[0071] Example 3

[0072] Step (1): Same as in Example 1.

[0073] Step (2): Same as in Example 1.

[0074] Step (3): When the bacterial cell OD 620 When the viscosity reached 0.84 (30-fold dilution), substrate was added to the fermenter for fermentation. From the start of fermentation to 154 hours, the relationship between the viscosity η (MPa·s) and the fermentation time t (h) satisfied the following: η = 4.02 * e 0.032t +0.02. After 154 hours of fermentation, the feeding of substrate was stopped. The fermentation substrate was lauric acid and n-dodecane in a mass ratio of 8:22. The rest was the same as in Example 1.

[0075] Example 4

[0076] Step (1): Same as in Example 1.

[0077] Step (2): Same as in Example 1.

[0078] Step (3): After the seed culture is introduced into the fermenter, when the cell OD... 620 When the viscosity reached 0.82 (30-fold dilution), substrate was added to the fermenter for fermentation. From the start of fermentation to 155 hours, the relationship between the viscosity η (MPa·s) and fermentation time t (h) of the fermentation system satisfied the following: η = 2.98 * e 0.022t +0.7. After fermentation for 155 hours, the substrate addition was stopped. The rest was the same as in Example 1.

[0079] Comparative Example 1

[0080] Step (1): Same as in Example 1.

[0081] Step (2): Same as in Example 1.

[0082] Step (3): After the seed culture is introduced into the fermenter, when the cell OD... 620 When the viscosity reaches 0.80 (30-fold dilution), substrate is added to the fermenter for fermentation. From the start of fermentation to 150 hours, the relationship between the viscosity η (MPa·s) and fermentation time t (h) satisfies: η = 2.88 * e 0.075t +0.9. After 150 hours of fermentation, the feeding of substrate was stopped. The fermentation substrate was lauric acid and n-dodecane in a mass ratio of 15:15. The rest was the same as in Example 1.

[0083] The acid production, conversion rate, and total fermentation time after fermentation are shown in Table 1.

[0084] Table 1

[0085] Example 1 178.8 97.2 162 Example 2 180.5 97.8 160 Example 3 184.7 98.5 158 Example 4 173.6 96.4 163 Comparative Example 1 172.6 93.2 173

[0086] The fermentation broths obtained in the above examples and comparative examples were separated and purified as follows:

[0087] Sulfuric acid was added to the fermentation broth to adjust the pH to 3.7 for acidification and crystallization. The solid was separated to obtain the crude product of dodecanoic acid.

[0088] The crude dodecanoic acid product was placed in a decolorization tank, and acetic acid was added. The mass ratio of crude dodecanoic acid to acetic acid was controlled at 1:4. Activated carbon was added at a concentration of 1.6% (v / v) of the decolorization system. The mixture was heated to 95°C and decolorized for 50 minutes. The resulting liquid was filtered through a plate and frame filter press. The clarified liquid was cooled to 30°C, and crystals were precipitated. The crystals were then separated by centrifugation. The resulting solid was washed and dried to obtain the dodecanoic acid product. The purity and bio-based content of the dodecanoic acid product are shown in Table 2.

[0089] Table 2

[0090] Example 1 99.83 34.25 Example 2 99.80 28.37 Example 3 99.85 22.55 Example 4 99.72 99.57 Comparative Example 1 98.95 30.75

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing long-chain dicarboxylic acids, characterized in that, The method includes: inoculating a fermentation tank with the seed culture of the fermentation strain, wherein the fermentation substrate is a combination of lauric acid and petroleum-based n-dodecane, or a combination of lauric acid and bio-based n-dodecane; Within T hours after the start of fermentation, the fermentation substrate is added to the fermentation system, and the amount of substrate added is controlled so that the viscosity η of the fermentation system and the fermentation time t satisfy the following relationship: η = a × e bt +c, where 135≤t≤165, 2.95≤a≤4.02, 0.015≤b≤0.032, 0.02≤c≤1.2, the viscosity η is in MPa·s, and the fermentation time t is in h; The fermentation strain is Candida virescens or Candida tropicalis.

2. The method according to claim 1, characterized in that, The chemical formula of long-chain dicarboxylic acids is HOOC(CH2)nCOOH, where n≥8, including any one of the following: sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid.

3. The method according to claim 1, characterized in that, 145≤t≤155。 4. The method according to claim 1, characterized in that, The optical density value (OD) of the seed solution when diluted 30 times 620 The value is 0.5 to 1.0; and / or, The seed culture was inoculated into the fermenter at an inoculation rate of 10% to 50%.

5. The method according to claim 1, characterized in that, During fermentation, the air volume is 0.2–0.8 vvm, and / or the pressure is 0.05–0.20 MPa, and / or the pH value is 4.5–6.5, and / or the dissolved oxygen is 5%–50%.

6. The method according to claim 1, characterized in that, When the optical density value (OD) of the fermentation strain in the fermentation system 620 When diluted 30 times to reach a concentration of 0.5–1.0, add the fermentation substrate to begin fermentation.

7. The method according to claim 1 or 2, characterized in that, The fermentation substrate is a combination of lauric acid and petroleum-based n-dodecane, with a mass ratio of lauric acid to petroleum-based n-dodecane of (0.1–25):15; or The fermentation substrate is a combination of lauric acid and bio-based n-dodecane, with a mass ratio of lauric acid to bio-based n-dodecane of (0.1–25):

15.

8. The method according to claim 7, characterized in that, The mass ratio of lauric acid to petroleum-based n-dodecane is (1–20):15; or The mass ratio of lauric acid to bio-based n-dodecane is (1-20):

15.

9. The method according to claim 1, characterized in that, The fermentation medium includes the following components: corn steep liquor 0%–1.0%, glucose 2.0%–6.0%, yeast extract 0–0.8%, potassium dihydrogen phosphate 0.4%–1.0%, magnesium sulfate 0.1%–0.6%, ammonium sulfate 0.1%–1%, and potassium nitrate 0.2%–0.8%.

10. The method according to any one of claims 1-9, characterized in that, The fermentation broth is purified by: acidifying the fermentation broth, separating the solids, dissolving the solids in an organic solvent, crystallizing and separating the solids, washing and drying the separated solids to obtain a long-chain dicarboxylic acid product.

11. A long-chain dicarboxylic acid product, characterized in that, The long-chain dicarboxylic acid product is prepared by the method according to any one of claims 1-10, wherein the purity of the long-chain dicarboxylic acid product is 98% or higher; and / or, The bio-based content ranges from 1% to 100%.

12. The long-chain dicarboxylic acid product according to claim 11, characterized in that, The purity of the long-chain dicarboxylic acid product is above 99%.

13. The long-chain dicarboxylic acid product according to claim 11, characterized in that, The bio-based content of the long-chain dicarboxylic acid product ranges from 5% to 100%.

14. The long-chain dicarboxylic acid product according to claim 11, characterized in that, The bio-based content of the long-chain dicarboxylic acid product ranges from 5% to 99%.

15. The long-chain dicarboxylic acid product according to claim 11, characterized in that, The bio-based content of the long-chain dicarboxylic acid products is 95%, 80%, 70%, 50%, 45%, 35%, 30%, 25%, 15%, or 10%.