Method for obtaining acetoin

Abstract

The invention relates to a method for obtaining acetoin from a medium containing same, the method comprising a step of dehydration by pervaporation using a hydrophilic membrane. With this method, the acetoin can be satisfactorily isolated and purified, both in terms of quality and yield. Furthermore, with the method of the invention it is possible to dispense with the use of solvents and prevent impurities from being generated.

Description

[0001] PROCESS FOR OBTAINING ACETOIN

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a process for obtaining acetoin from a medium comprising it, the process comprising a step of dehydration by pervaporation using a hydrophilic membrane. This process makes it possible to isolate and purify acetoin satisfactorily, both from the point of view of quality and yield. In addition, it makes it possible to dispense with the use of solvents and to avoid the generation of impurities.

[0004] TECHNICAL BACKGROUND

[0005] Acetoin (3-hydroxybutanone) is a chiral organic molecule with the formula C4H8O2 belonging to the class of hydroxylated ketones and comprising two enantiomeric forms. Acetoin comprises two functional groups, a hydroxyl group and a carbonyl group, which make it particularly reactive and prone to decomposition, notably into acetaldehyde.

[0006] Acetoin is present in trace amounts in many foods, including grapes, raspberries, apples, bananas, corn, honey, and coffee. This molecule is also present in certain cheeses and meats. Finally, this molecule is also a synthetic intermediate in the sugar metabolism of certain microorganisms.

[0007] Acetoin, along with diacetyl (2,3-butanedione), is one of the molecules that gives butter its characteristic flavor. It can be used as a flavoring agent.

[0008] Acetoin is frequently used in the food industry, particularly in dairy products, beverages, bakery, pastries and cakes, to give a "buttery flavor" to products containing it. In this field, regulations require the use of acetoin with a high degree of purity, for example at least 95% (see EC Regulation No. 1334 / 2008).

[0009] Acetoin is also used in other fields, particularly in perfumery, pharmacy, and tobacco. Acetoin can be obtained from chemical synthesis processes or biological processes.

[0010] Chemical synthesis processes can use, for example, 2,3-butanedione and 2,3-butanediol as raw materials.

[0011] Biological processes can use wild microorganisms, selected microorganisms, or recombinant microorganisms. Recombinant microorganisms are known that do not naturally produce acetoin or produce it in too low a yield and / or as a synthetic intermediate. For example, recombinant microorganisms have been obtained from the following microorganisms: Bacillus subtilis, Bacillus pumilus, Bacillus methanolicus, Bacillus licheniformis, Corynebacterium glutamicum, Escherichia coli, Lactococcus lactis, Saccharomyces cerevisiae, and Serratia marcescens.

[0012] Regardless of the production method, the quantity and quality of the product obtained may not be sufficient, especially for use in the food and pharmaceutical industries. In addition, a medium may be obtained that includes impurities, including acetoin by-products, organic residues (biomass) if obtained using a biological process, and other molecules. It is therefore necessary to isolate and purify acetoin from the medium containing it.

[0013] A number of purification techniques are known, for example distillation, liquid-liquid extraction or salting-out extraction. The effectiveness of these techniques, particularly distillation, may be limited by the fact that acetoin forms an azeotropic mixture with water, with separation being hindered or limited as soon as the liquid and gas phases reach the same water / acetoin composition.

[0014] The use of solvents is not recommended, particularly when acetoin is intended for the food industry. Indeed, for regulatory reasons, only certain solvents can be used for a product containing acetoin to be labeled "natural". Among the available solvents, only ethyl acetate is both compliant with European regulations and particularly suitable for the purification of acetoin. However, the use of this solvent requires large quantities, which makes the process less economically viable on an industrial scale for efficient extraction. In addition, this solvent does not allow the use of the American NOP (for "national organic program") label. International application WO 2021 / 060334 A1 published on April 1, 2021 discloses a purification process using tangential filtration technology implemented by a nanofiltration step, followed by a reverse osmosis step.However, this process does not allow residual moisture contents below 50% to be efficiently achieved.

[0015] Thus, there is a real need to provide a process for obtaining acetoin that can be used directly in agri-food preparations. There is also a real need to provide a process for obtaining acetoin in a high yield and at an affordable cost. There is also a real need to provide a process implemented without using solvents, in particular ethyl acetate. There is also a real need to provide a process for obtaining acetoin that can be labeled "natural".

[0016] SUMMARY OF THE INVENTION

[0017] The invention relates firstly to a method for obtaining acetoin from a medium to be treated, the method comprising a step of dehydration by pervaporation using a hydrophilic membrane, to obtain a dehydrated medium comprising at least 70% acetoin, by total weight of the treated medium.

[0018] In embodiments, the hydrophilic membrane is selected from the group consisting of hydrophilic polymeric membranes, hydrophilic inorganic membranes, hydrophilic two-dimensional material-based membranes, hydrophilic mixed matrix membranes, or membranes derived therefrom.

[0019] In embodiments, the hydrophilic membrane is a hydrophilic silica-based membrane or a hydrophilic membrane derived therefrom.

[0020] In embodiments, the hydrophilic silica-based membrane is obtained from organoalkoxysilane precursors.

[0021] In embodiments, a subpressure of -700.10 5 mPa or more is applied at the permeation surface of the hydrophilic membrane.

[0022] In embodiments, the dehydration step is carried out in the absence of solvents and / or inorganic salts.

[0023] In embodiments, the method comprises a step of pre-treatment of the medium to be treated carried out, before the dehydration step, by a technique selected from the group consisting of centrifugation, frontal filtration, microfiltration and nanofiltration. In embodiments, the method comprises a step of post-treatment of the treated medium carried out, after the dehydration step, by distillation.

[0024] In embodiments, the medium comprising acetoin is obtained by a biological process carried out using recombinant microorganisms.

[0025] In embodiments, the recombinant microorganisms are yeasts belonging to the genus Saccharomyces.

[0026] The invention secondly relates to acetoin, obtained from the process described opposite.

[0027] Thirdly, the invention relates to the use of a hydrophilic membrane, as described opposite, to obtain acetoin. The present invention makes it possible to meet the needs expressed above. Surprisingly, the inventors have demonstrated that acetoin can be isolated and purified satisfactorily, both from the point of view of quality and yield, by selecting hydrophilic membranes. By using such membranes, only water and hydrophilic compounds migrate through the membrane into the permeate (filtrate), while the acetoin remains in the retentate (treated medium), which results in a progressive and satisfactory dehydration of the acetoin. This pervaporation dehydration technique also makes it possible to overcome the separation constraints associated with the formation of azeotropic mixtures.

[0028] The commonly used liquid-liquid extraction technique has the disadvantage of being implemented with solvents, for example ethyl acetate, used in large quantities. Furthermore, disadvantageously, the inventors have demonstrated that this technique leads to the formation of impurities, for example methylallyl acetate, a reaction product between acetoin and ethyl acetate. Finally, this technique does not make it possible to obtain acetoin that can be labeled "natural". The technique according to PCT application WO 2021 / 060334 A1 makes it possible to avoid the use of solvents, but is not economically viable, in that the yield of acetoin is too low, due to the formation of a water-acetoin azeotropic mixture and the elimination of a significant portion of the acetoin with water.

[0029] The use of the pervaporation dehydration technique according to the invention, using a hydrophilic membrane, makes it possible to avoid the use of solvent, to avoid the generation of impurities in the final product, to circumvent the separation difficulties linked to the formation of an azeotropic mixture and to obtain a satisfactory yield of acetoin.

[0030] Furthermore, and counter-intuitively, the inventors have also demonstrated that the use of a hydrophilic membrane makes it possible to obtain a process having improved performance compared to a process using an organophilic membrane, i.e. a higher yield and degree of dehydration, even though water is initially the majority in the medium.

[0031] BRIEF DESCRIPTION OF THE FIGURES

[0032] Figure 1 shows a graph of acetoin and water concentration (wt%) in the retentate versus time (min).

[0033] Figure 2 shows a graph of acetoin concentration in the retentate (mass %) and underpressure at the permeation surface (.10 5 mPa) as a function of time (min).

[0034] DETAILED DESCRIPTION

[0035] The invention is now described in more detail and in a non-limiting manner in the following description.

[0036] In the description, unless otherwise indicated, all percentages indicated are mass percentages.

[0037] In a first aspect, the present invention relates to a method for obtaining acetoin from a medium comprising it (medium to be treated), the method comprising a step of dehydration by pervaporation using a hydrophilic membrane.

[0038] Dehydration stage

[0039] The dehydration step consists of bringing the medium to be treated into contact with a first surface of the hydrophilic membrane and applying a pressure drop at the permeation surface (second surface) of the hydrophilic membrane.

[0040] The underpressure applied at the permeation surface of the hydrophilic membrane is -700.10 5 mPa or more, preferably - 300.10 5 at -0.1 .10 5 mPa, very preferably -100.10 5 at -10 5 mPa . The underpressure is defined in relation to the pressure at the surface in contact with the medium to be dehydrated. The temperature applied at the feed level is 150°C or less, preferably 5 to 100°C, very preferably 30 to 90°C.

[0041] A permeate is therefore gradually formed, comprising water and hydrophilic compounds having migrated through the hydrophilic membrane (medium to be eliminated), while the residual medium, comprising acetoin, forms the retentate (treated medium).

[0042] Hydrophilic membrane

[0043] By "hydrophilic membrane" we mean a membrane which preferentially allows water and hydrophilic molecules to pass through the permeate.

[0044] The hydrophilic membrane may be selected from the group consisting of hydrophilic polymeric membranes, hydrophilic inorganic membranes, hydrophilic two-dimensional membranes, hydrophilic mixed-matrix membranes or hydrophilic membranes derived therefrom; preferably the hydrophilic membrane is an inorganic membrane or a hydrophilic membrane derived therefrom.The hydrophilic inorganic membrane may be selected from the group consisting of hydrophilic zeolite-based membranes, hydrophilic silica-based membranes, hydrophilic metal-organic framework (MOF) membranes, hydrophilic covalent organic framework (COF) membranes or hydrophilic membranes derived therefrom; preferably the hydrophilic inorganic membrane is a hydrophilic silica-based membrane or a hydrophilic membrane derived therefrom; very preferably the hydrophilic inorganic membrane is a hydrophilic silica-based hybrid membrane. Silica-based hybrid membranes are referred to interchangeably as organic-inorganic silica membranes, organosilica membranes, or organosilica hydrid membranes.

[0045] The hydrophilic silica-based hybrid membrane can be chosen from the group consisting of hydrophilic pendant-type organosilica membranes or hydrophilic bridged-type organosilica membranes; preferably hydrophilic bridged silica-based hybrid membranes. Silica-based hybrid membranes are known (see the review by X. Ren entitled “Organosilica-based membranes in gas and liquid-phase separation”, Membranes, 2019, 9, 107; the book entitled “Pervaporation, vapour permeation and membrane distillation - Principles and applications”, Ed. Woodhead Publishing Series in Energy, 2015, in particular chapter 5 entitled “Next-generation pervaporation membranes: recent trends, challenges and perspectives”, 107-141; article by G.Liu entitled “Pervaporation membrane materials: Recent trends and prospects”, Journal of Membrane Science, 2021, 636).

[0046] Bridged silica-based hybrid membranes can be obtained from organoalkoxysilane precursors (monomers), i.e. alkoxysilane precursors comprising organic groups.

[0047] The organoalkoxysilane precursor may be selected from organoalkoxysilane precursors comprising one, two, three or more silica atoms. The organoalkoxysilane precursor comprising a silica atom may be selected from the group consisting of methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), phenyltriethoxysilane (PhTES), hydroxymethyl(triethoxy)silane (HMTES), 3-aminopropyltriethoxysilane (APTES) and mixtures thereof.

[0048] The organoalkoxysilane precursor comprising two silica atoms may be selected from the group consisting of bis(triethoxysilyl)methane (BTESM), 1,2-bis(triethoxysilyl)ethane (BTESE), 1,3-bis(triethoxysilyl)propane (BTESP), 1,8-bis(triethoxysilyl)octane (BTESO), 1,2-bis(triethoxysilyl)ethylene (BTESEthy), 1,2-bis(triethoxysilyl)acetylene (BTESA), 1,4-bis(triethoxysilyl)diacetylene (BTESDA), bis(trimethoxysilyl)norbornane (BTMS-Nor), 1,2-bis(triethoxysilyl)benzene (BTESB), 2,5-bis[2-triethoxysilyl)ethyl]-1,4-dioxane (BTES-ED), bis[3-(triethoxysilyl)propyl]amine (BTESPA), 1,6-diacetoxy-3,4-bis(triethoxysilyl)hexa-2,4-diene (BTES-Ac), 4,6-bis(3-triethoxysilyl-1-propoxy)-1,3-pyrimidine (BTPP), bis(triethoxysilyldimethyl / dipropyl-N,N'-oxalylurea (BTESMOU / BTESMPU) and mixtures thereof;preferentially the organoalkoxysilane precursor comprising two silica atoms is chosen from the group consisting of BTESM, BTESE and their mixture; very preferentially the organoalkoxysilane precursor comprising two silica atoms is BTESE.;

[0049] The organoalkoxysilane precursor may be chosen from the group consisting of TTESPT, TESE-POSS, MTMS, MTES, PhTES, HMTES, APTES, BTESM, BTESE, BTESP, BTESO, BTESEthy, BTESA, BTESDA, BTMS-Nor, BTESB, BTES-ED, BTESPA, BTES-Ac, BTPP, BTESMOU / BTESMPU, TTESPT, TESE-POSS and mixtures thereof; preferably the organoalkoxysilane precursor is chosen from the group consisting of BTESM, BTESE and mixtures thereof; very preferably the organoalkoxysilane precursor is BTESE.

[0050] The organic group can be used to functionalize alkoxysilane precursors.

[0051] The organic group used to form organic bridges between the organoalkoxysilane precursors may be selected from the group consisting of methane (Ch ), ethane (CH3-CH3), propane (CH3-CH2-CH3), hexane (CH3-(CH2)4-CH3), octane (CH3-(CH2)6-CH3), phenyl, ethylene (CH2= CH2), acetylene (CHCH), diethylenedioxane, norbornane, triazine, pyrimidine and mixtures thereof. For example, organic bridges such as -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -(CH2)6-, -(CH2)8, phenyl, -CH=CH-, an acetylene bridge, a diethylenedioxane bridge, a norbornane bridge, a triazine bridge, a pyrimidine bridge and their mixtures are obtained.

[0052] Silica-based hybrid membranes can be further treated, for example with metals.

[0053] Hydrophilic membranes are commercially available, for example under the name Hybsi® from Hybsi® (Pervatech®).

[0054] Environment to be treated

[0055] The medium to be treated corresponds to the starting product (non-pretreated medium) or alternatively to the intermediate product (pretreated medium) which has previously undergone a pretreatment step. The terms "medium", "composition", "solution" and "substrate" can be used interchangeably to designate the medium to be treated (and the treated medium where applicable).

[0056] The medium to be treated may comprise from 2 to 50%, preferably from 6 to 30%, of acetoin, by total weight of the medium. For example, the medium to be treated may comprise from 1 to 5%, or from 5 to 10%, or from 10 to 15%, or from 15 to 20%, or from 20 to 25%, or from 25 to 30%, or from 30 to 35%, or from 35 to 40%, or from 40 to 45%, or from 45 to 50%, of acetoin, by total weight of the medium.

[0057] Acetoin may be present in the form of its (3R)-3-hydroxybutanone enantiomer (natural enantiomer), its (3S)-3-hydroxybutanone enantiomer or the mixture of these two enantiomers (including their racemic mixture). The medium to be treated is an aqueous medium. The medium to be treated may comprise at least 15%, preferably at least 45%, very preferably at least 65%, of water, by total weight of the medium.

[0058] The medium to be treated can be obtained from a chemical synthesis process or from a biological process.

[0059] Treated environment

[0060] After implementing the dehydration step, a treated medium (corresponding to the retentate) is obtained.

[0061] The treated medium may comprise at least 70% (from 70 to 99%), preferably at least 80% (from 80 to 99%), very preferably at least 90% (from 90 to 99%), of acetoin, by total weight of the medium. For example, the dehydrated medium may comprise from 70 to 75%, or from 75 to 80%, or from 80 to 85%, or from 85 to 90%, or from 90 to 95%, or from 95 to 99%, of acetoin, by total weight of the medium.

[0062] As a corollary, the treated medium may comprise 30% or less (from 1 to 30%), preferably 20% or less (from 1 to 20%), very preferably 10% or less (from 1 to 20%), of water and additional compounds (impurities), by total weight of the medium.

[0063] Filtration agents (absence)

[0064] The dehydration step is carried out in the absence of solvents, for example ethyl acetate, methyl tert-butyl ether, butyl acetate, dimethyl carbonate, diethyl ether, diethyl carbonate, ethanol, methanol, acetone, isopropanol, acetonitrile, dichloromethane and / or chloroform. In particular, the dehydration step is carried out in the absence of ethyl acetate.

[0065] The dehydration step is carried out in the absence of inorganic salts, for example ammonium sulfate, magnesium sulfate, sodium sulfate, copper sulfate, calcium chloride, potassium hydrogen phosphate (dipotassium phosphate), potassium pyrophosphate, sodium carbonate and / or potassium carbonate.

[0066] Pre-processing step

[0067] The method may comprise a step of pretreating the medium to be treated, carried out before the dehydration step. In this embodiment, the medium to be treated is pretreated and the pretreated medium, thus obtained, is subsequently dehydrated.

[0068] A pretreatment step may be implemented in order to remove suspended solids from the medium to be treated. In particular, a pretreatment step may be implemented when the acetoin is produced by a biological process and the medium to be treated therefore comprises biomass. When the medium comprising the acetoin is obtained from a biological process, it may comprise biomass. By "biomass" is meant organic matter of bacterial or fungal, plant or animal origin, preferably organic matter of bacterial or fungal origin. When the medium is obtained from a biological process using bacteria or fungi including yeasts, the biomass may comprise whole microorganisms (living or dead), residues of these microorganisms (residues of nuclei, organelles, cytoplasm, membrane, etc.) and molecules produced by them (proteins, carbohydrates, lipids, etc.).The medium to be treated (not pretreated) may comprise from 1 to 20%, preferably from 1 to 10%, of dry biomass, by total weight of the medium. The pretreatment step may make it possible to eliminate at least 80%, preferably at least 90%, of the dry biomass contained in the medium to be dehydrated.

[0069] The pretreatment step can be chosen by the techniques consisting of centrifugation, frontal filtration, microfiltration, ultrafiltration, nanofiltration or any other conventional clarification technique.

[0070] Post-processing step

[0071] The method may comprise a post-treatment step of the treated medium (retentate), carried out after the dehydration step.

[0072] A post-treatment step can be implemented to increase the purity of the acetoin.

[0073] The post-treatment step can be implemented by distillation.

[0074] The process according to the invention is particularly advantageous in that it makes it possible to overcome the difficulties encountered during the implementation of direct distillation, due to the formation of an azeotropic water-acetoin mixture.

[0075] Chemical synthesis process of acetoin

[0076] The medium comprising acetoin can be obtained by a chemical synthesis process. Biological process for obtaining acetoin

[0077] The medium comprising acetoin can be obtained by a biological process. The biological process can be carried out using microorganisms, including wild microorganisms, selected microorganisms or recombinant microorganisms.

[0078] Wild microorganisms are microorganisms that naturally produce acetoin at usable concentrations. Selected (non-genetically modified) microorganisms are microorganisms with improved performance in terms of acetoin production.

[0079] Recombinant (genetically modified) microorganisms - not naturally producing acetoin or producing it in too low a yield and / or as a synthesis intermediate - may be chosen from the group consisting of Bacillus subtilis, Bacillus pumilus, Bacillus methanolicus, Bacillus licheniformis, Corynebacterium glutamicum, Escherichia coli, Lactococcus lactis, Serratia marcescens and yeasts of the genus Saccharomyces; preferably a microorganism being a yeast of the genus Saccharomyces; very preferably Saccharomyces cerevisiae.

[0080] Acetoin thus obtained

[0081] The process according to the invention makes it possible to obtain a product comprising at least 70% acetoin, by total weight of the treated medium.

[0082] EXAMPLES

[0083] Example according to the invention: Process for obtaining acetoin using a hydrophilic membrane

[0084] Materials

[0085] Medium to be purified: Aqueous solution comprising 10% acetoin, by total weight of the aqueous solution

[0086] Hydrophilic membrane: Hybsi® AR membrane marketed by Hybsi® Dehydration device: PTU-044 device

[0087] Parameters of the pervaporation dehydration step

[0088] Medium temperature: 100°C Medium feed linear velocity (velocity): 1-2 m / s Permeate underpressure (vacuum pressure): -20.10 5 mPa

[0089] Distillation post-treatment step parameters

[0090] Distillation method: batch

[0091] Column characteristic: 20 floors

[0092] Applied vacuum: 150 mbar

[0093] Steam temperature: Between 44 and 86°C

[0094] Reflux rate: between 1 and 5

[0095] Water content measurement

[0096] The water content in the retentate and filtrate is measured by the Karl Fischer filtration method (KF titration).

[0097] Measurement of acetoin content

[0098] Acetoin content is measured by HPLC and / or gas chromatography.

[0099] Dehydration process

[0100] The objective of this process is to obtain the permeation of water from the medium to be treated through the hydrophilic membrane towards the permeate and as a corollary the dehydration of the acetoin (retentate).

[0101] As illustrated in Figure 1, which represents a graph of acetoin and water concentration (wt%) in the retentate versus time (min), the water concentration (white squares) decreases and conversely the acetoin concentration (black circles) increases in the retentate over time. After 485 min of treatment, the water concentration decreases to about 1.1%, by total weight of the retentate, while the acetoin concentration increases to about 77%, the difference corresponding to organic residues other than acetoin.

[0102] The implementation of a post-treatment step by distillation makes it possible to obtain acetoin with a purity of 98% with a yield of 80%.

[0103] Comparative example: Process for obtaining acetoin using an organophilic membrane

[0104] Materials Medium to be purified: Aqueous solution comprising 10% acetoin, by total weight of the aqueous solution

[0105] Organophilic membrane: PDMS-FS membrane marketed by Pervatech®

[0106] Extraction Device: PTU-044 Device

[0107] Settings

[0108] Environment temperature: 55°C

[0109] Medium feed rate: 200 L / h

[0110] Permeate vacuum pressure: 20.10 5 mPa at 4.10 5 mPa

[0111] Liquid-liquid extraction process

[0112] The objective of this process is to obtain the permeation of acetoin from the medium comprising it through the organophilic membrane towards the filtration agent.

[0113] As illustrated in Figure 2, which represents a graph concerning the concentration of acetoin in the retentate (left ordinate, mass %) and the underpressure at the permeation surface (right ordinate, X.10 5 mPa) as a function of time (min), the filtration is not sufficiently selective, in that the migration of acetoin (black circles) through the membrane is also accompanied by a migration of water, despite the organophilic property of the membrane used and despite the application of increasing underpressures (white circles). This insufficient selectivity therefore does not allow acetoin dehydration to be obtained at a useful level.

[0114] Conclusion

[0115] The tests carried out demonstrate that efficient purification of acetoin is possible by selecting a hydrophilic membrane. Conversely and counterintuitively, tests carried out with an organophilic membrane did not give conclusive results, in the absence of sufficient membrane selectivity.

Claims

DEMANDS 1. Process for obtaining acetoin from a medium to be treated comprising acetoin, the process comprising a dehydration step by pervaporation using a hydrophilic membrane to obtain a treated medium comprising at least 70% acetoin, by total weight of the treated medium.

2. A process for obtaining acetoin, according to claim 1, wherein the hydrophilic membrane is selected from the group consisting of hydrophilic polymeric membranes, hydrophilic inorganic membranes, membranes based on two-dimensional hydrophilic materials, hydrophilic mixed-matrix membranes or hydrophilic membranes derived therefrom.

3. A process for obtaining acetoin, according to any one of the preceding claims, wherein the hydrophilic membrane is a hydrophilic silica-based membrane or a hydrophilic membrane derived therefrom.

4. A process for obtaining acetoin, according to claim 3, wherein the hydrophilic silica-based membrane is obtained from organoalkoxysilane precursors.

5. A process for obtaining acetoin, according to any one of the preceding claims, wherein a subpressure of -700.10 5 mPa or more is applied at the permeation surface of the hydrophilic membrane.

6. A process for obtaining acetoin, according to any one of the preceding claims, wherein the dehydration step is carried out in the absence of solvents and / or inorganic salts.

7. A process for obtaining acetoin, according to any one of the preceding claims, comprising a pretreatment step of the medium to be treated, carried out before the dehydration step, by a technique selected from the group consisting of centrifugation, frontal filtration, microfiltration and nanofiltration.

8. A process for obtaining acetoin, according to any one of the preceding claims, comprising a post-treatment step of the treated medium carried out, after the dehydration step, by distillation.

9. A process for obtaining acetoin, according to any one of the preceding claims, wherein the medium comprising the acetoin is obtained by a biological process implemented using recombinant microorganisms.

10. A process for obtaining acetoin, according to the preceding claim 9, wherein the recombinant microorganisms are yeasts belonging to the genus Saccharomyces.

11. Acetoin, obtained from the process, according to any one of the preceding claims.

12. Use of a hydrophilic membrane, according to any one of claims 1 to 10, to obtain acetoin.

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