Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P7/00—Preparation of oxygen-containing organic compounds
  • C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
  • C12P7/42—Hydroxy-carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/48—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/006—Refining fats or fatty oils by extraction
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/12—Refining fats or fatty oils by distillation
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M47/00—Means for after-treatment of the produced biomass or of the fermentation or metabolic products, e.g. storage of biomass
  • C12M47/10—Separation or concentration of fermentation products

Definitions

• the present invention relates to a process for extracting carboxylic acids produced by anaerobic fermentation from fermentable biomass.
• the process is particularly intended for the extraction of carboxylic acids in the liquid phase.
• fermentable biomass is meant here an organic substrate, preferably non-food, obtained from waste, byproducts and coproducts formed of organic materials, that is to say biomass from human activities, whether they are domestic, industrial, agricultural, forestry, aquaculture, agro-industrial or livestock.
• organic substrate of manures, the organic fraction of household refuse, slaughterhouse co-products, cellulosic or lignocellulosic residues originating from agro-industry, such as those resulting from the transformation of the sugar cane (bagasse), sunflower or soy.
• anaerobic fermentation is meant a fermentation carried out under anaerobic conditions by microorganisms, eukaryotic or prokaryotic, such as bacteria, fungi, algae or yeasts.
• the carboxylic acids are fermentative metabolites known as precursors, it being understood that other fermentative metabolites are also known as precursors.
• precursors By way of non-limiting example, mention may be made of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid and phenyl acetic acid.
• acetic acid propionic acid
• butyric acid valeric acid
• caproic acid heptanoic acid
• octanoic acid nonanoic acid
• phenyl acetic acid subsequently allow the production of molecules that have a greater energetic and / or chemical interest, it being understood that they are organic molecules.
• molecules having an energy and / or chemical interest are molecules having a carbon chain, such as acids, hydrocarbons, methane, esters, alcohols, amides and polymers.
• carboxylic acids it being understood that the invention applies to the extraction of fermentative metabolites in general.
• the carboxylic acids, and especially the volatile fatty acids or VFAs can be converted, for example, into ketones, alkanes, alcohols, alkenes. It is conceivable that such fermentation also produces other metabolites than carboxylic acids, in more or less significant amount.
• esters, gases, lactic acid, alcohols, hydrogen and carbon dioxide may be mentioned. It is also known that the production of carboxylic acids carried out by anaerobic fermentation induces an acidification of the medium detrimental to microorganisms.
• the acidification of the medium induces an inhibition of the microorganisms, therefore a slowing down or a stop of the fermentation, it is necessary to work in batch.
• the carboxylic acids are extracted in a separate step, after a given fermentation time. Such an extraction therefore does not allow rapid and continuous production of so-called precursor molecules, the yield being not optimal.
• such an extraction process, in batch is consumer of strains of microorganisms and generates waste little or not recoverable. It is interesting to extract, in an optimal way, the carboxylic acids produced by anaerobic fermentation without inhibiting the microorganisms.
• WO-A-201 1/063391 discloses a process for extracting a given metabolite, in this case butanol, with an extraction solvent comprising a carboxylic acid.
• the solvent is a commercially available solvent.
• Also known from FR-A-2 591 505 is a water treatment method making it possible to extract organic compounds, including amines, amino acids and phenols, using as solvent an organic solvent, in this case a solvent.
• carboxylic acid liquid and immiscible with water in order to obtain an organic phase and an aqueous phase. It turns out that these processes are not suitable for the extraction of metabolites, such as carboxylic acids, produced continuously by fermentation.
• the invention aims more particularly at remedying these drawbacks by proposing an extraction process making it possible to produce continuously, biocompatible, regular, controlled and with a minimum of non-recoverable waste and without inhibiting microorganisms, various fermentative metabolites, so-called precursors, obtained by anaerobic fermentation.
• the subject of the invention is a process for extracting carboxylic acids having from one to nine carbons produced by microorganisms in an anaerobic fermentation fermentation reactor from fermentable biomass, said extraction being of type liquid-liquid, characterized in that it comprises at least the following steps:
• step c) collecting and storing or using the fermentative metabolites obtained in step c).
• Such a method makes it possible to continuously extract fermentative metabolites, while preserving the production capacity of the microorganisms present in the bioreactor.
• endogenous is to be understood to mean a compound-or a mixture of compounds-which are produced, but not exclusively, by anaerobic fermentation.
• the endogenous solvent can be produced by other routes that result in a similar product, if not identical to that produced during the anaerobic fermentation, regardless of the quantities produced.
• the extraction step not only makes it possible to continuously collect the molecules produced in the fermentation reactor, but also to preserve the microorganisms responsible for this production, the extraction being carried out, thanks to the endogenous solvent, under non-lethal conditions for the production. all the microorganisms, i.e., under biocompatible extraction conditions.
• all the microorganisms i.e., under biocompatible extraction conditions.
• the problems associated with the accumulation of precursors in the fermentation reactor are overcome, for example the acidification of the fermentation medium by the accumulation of the carboxylic acids produced which are harmful for the microorganisms.
• the activity of the microorganisms is maintained at a high level, close to the initial level, throughout the fermentation cycle.
• such a method may comprise one or more of the following features:
• the endogenous extraction solvent is a carboxylic acid having at least four carbons.
• step c) and before step d the carboxylic acids are separated by distillation, during a further step e), from the water of the organic phase obtained in step c).
• the extraction solvent is a carboxylic acid having from four to nine carbons.
• the extraction solvent is a carboxylic acid having seven or eight carbons.
• the extraction solvent is selected from heptanoic acid, octanoic acid or nonanoic acid.
• steps c) and d) allow a first separation between the organic and aqueous phases.
• the fermentation medium When the fermentation medium is brought into contact with the extraction solvent outside the reactor, the fermentation medium is taken continuously.
• the fermentation medium When contacting the fermentation medium with the extraction solvent outside the reactor, the fermentation medium is sampled sequentially.
• the invention also relates to an installation for implementing a method according to one of the preceding characteristics, characterized in that it comprises at least: a fermentation reactor,
• such an installation may comprise one or more of the following characteristics:
• the installation further comprises at least two distillation members and at least one settling member.
• FIG. 1 is a simplified diagram representative of an embodiment of the method of the invention comprising two distillations and a settling member.
• FIG. 1 illustrates a process comprising two distillations, that is to say an embodiment which represents an economically interesting solution for installations of common dimensions.
• An installation with a single distillation station is technically possible and even advantageous, but to be economically interesting, requires a larger installation, such as an installation the size of those encountered in an industrial refinery.
• carboxylic acids will be described later, by way of example, it being understood that other fermentative metabolites may be extracted by the endogenous carboxylic acids.
• the substrate S used for the anaerobic fermentation is advantageously untreated, namely that it has undergone no physicochemical or enzymatic pretreatment.
• This substrate S is mainly composed of fermentable biomass.
• waste agricultural or vegetable straw, bagasse, maize, grass, wood, mowing
• paper waste cardboard, paper
• agro-food waste cardboard, paper
• organic fraction of household waste livestock manure ( manure, manure, droppings), algae, aquaculture waste, forestry waste or fermentable co-products from the cosmetics industry.
• Some substrates contain organic molecules, such as organic acids, which will not influence, or marginally, the fermentation process. On the other hand, these molecules can be found in the fermentation medium and participate, for example, in the production of the defined final organic molecules.
• Substrate S is introduced into a fermentation reactor 1, known per se and dimensioned for the desired production, whether the latter is at the laboratory scale to carry out tests or on an industrial scale in the case of production.
• the fermentation reactor 1 or bioreactor has a volume ranging from a few liters to several hundred cubic meters, as needed.
• Microorganisms are advantageously introduced initially into the fermentation reactor 1, in an amount sufficient to start the fermentation.
• the microorganisms are advantageously inoculated in the form of a consortium, illustrated by the arrow M.
• consortium is meant a mixture or mixture of microorganisms, eukaryotic and prokaryotic, whether bacteria, yeasts, fungi or algae.
• These microorganisms come mainly from natural ecosystems, advantageously but not exclusively from anaerobic ecosystems such as, by way of non-limiting example, the anaerobic zone of aquatic environments such as the anoxic zone of certain lakes, soils, marshes, sludge purification, the rumen of ruminants or the intestine of termites.
• the substrate S is used as such, that is to say that it is not sterilized or, more generally, that it is not rid of the microorganisms that it contains beforehand. its introduction into the bioreactor 1, it turns out that the microorganisms endemic to the substrate S are, de facto, incorporated in the consortium M or at least associated with the latter in the bioreactor 1.
• the consortium M of microorganisms associated with the microorganisms possibly present in the substrate 1, allows the fermentation of the substrate S, without adding products such as enzymes. Moreover, the fermentation takes place under anaerobic conditions, more specifically when the redox potential is less than -200mV, advantageously between -550mV and -200mV and when the pH is less than 8, preferably between 4 and 7.
• the fermentation is advantageously limited to the production of so-called precursor fermentative metabolites, namely carboxylic acids. A reaction similar to the acidosis phenomenon encountered in ruminants is thus induced while having a production of methane close to zero. Methane is usually one of the final fermentative metabolites obtained during anaerobic fermentation by microorganisms from natural ecosystems.
• Fermentation leads, initially, to the formation of carboxylic acids having from one to nine carbons, mainly from two to four carbons such as acetic acid, propionic acid and butyric acid.
• Longer chain carboxylic acids thus greater than four carbons, such as valeric and caproic, heptanoic, octanoic or nonanoic acids are also obtained.
• the metabolites produced in quantity during the fermentation are essentially carboxylic acids of two to six carbons. Thereafter, the extraction will essentially concern the extraction of these carboxylic acids, it being understood that the process may be implemented for other carboxylic acids or other fermentative metabolites produced during other types of fermentation.
• the fermentation can be carried out, preferably, in continuous mode, in batch or batch mode, or in continuous-batch or fed-batch mode in one or more fermentation reactors 1 arranged in series.
• the fermentation medium comprises a solid phase containing, at least initially, the solid fraction of the substrate S as well as the solid fraction of the M consortium of microorganisms.
• the liquid phase of the fermentation medium contains the molecules produced during fermentation, or fermentative metabolites, as well as the liquid fraction of the substrate S, at least during the beginning of fermentation.
• the fermentation time varies, among other things, depending on the substrate S, the microorganisms M present and the fermentation conditions.
• the fermentation period is between 1 and 7 days, preferably between 2 and 4 days.
• the concentration of metabolites obtained in the fermentation medium at the end of this period is variable, but, for carboxylic acids, is generally of the order of 10 to 20 g / L, depending on the carboxylic acids, it being understood that in certain conditions it may be greater than 35 g / l, for example close to 50 g / l.
• the fermentation medium is at an acidic pH, which is generally between 4 and 6, because of the presence of the carboxylic acids in the fermentation medium.
• this quantity of predefined carboxylic acids corresponds to a slowing down of the growth of the microorganisms, and therefore lies in the vicinity of a threshold of inhibition of the microorganisms, which is linked to an acidification of the fermentation medium.
• carboxylic acids The extraction is of liquid-liquid type.
• the extraction solvent is an endogenous solvent, that is to say a solvent chosen from at least one of the compounds produced during the fermentation. It is conceivable that the solvent may be a mixture of several compounds produced during the fermentation.
• the endogenous solvent is selected from carboxylic acids that are part of the fermentative metabolites.
• carboxylic acids it is possible, inter alia, to extract not only carboxylic acids but also other metabolites such as alcohols, amines, amino acids, and aromatic compounds such as phenyl acids.
• carboxylic acids it is possible, inter alia, to extract not only carboxylic acids but also other metabolites such as alcohols, amines, amino acids, and aromatic compounds such as phenyl acids.
• solvent losses are inevitable. They occur during storage, during distillation or even during fermentation if the solvent is likely to be consumed by the microorganisms. Solvent addition is therefore necessary, which generates additional costs and constraints in terms of transport and environment.
• such an endogenous solvent avoids any risk of an unwanted and / or uncontrolled reaction between the solvent and not only the volatile fatty acids produced during the fermentation but, more generally, with the products resulting from the fermentation.
• the carboxylic acids, produced during the fermentation and used as a solvent, which may be present in the fermentation medium are, for example but not exclusively, acids having from four to nine carbons.
• the carboxylic acid will be chosen so that its number of carbons is greater than or equal to the number of carbons of the metabolite to be extracted.
• Non-limiting examples of such acids produced during the fermentation are given in Table 1 below.
• Heptanol acid ' as C7H1402 Density in g / cm3: Boiling point at pressure
• the Applicant has found, from tests carried out, that the carboxylic acids having six to nine carbons and, advantageously, seven or eight carbons, were particularly advantageous endogenous solvents.
• the Applicant has retained as endogenous solvent caproic, heptanoic and octanoic acids. Alternatively, it is possible to use the isomers of these acids.
• the molecules, and hence the fermentative metabolites are preferably extracted individually, or at least extracted by molecular families, from the liquid phase of the fermentation medium, which allows, among other things, better yields and facilitates the production of specific compounds from of these extracted molecules.
• the metabolites which are at least partly extracted are under conditions such that the extraction does not destroy or inhibit the microorganisms M, or at least in such proportions that it does not change. appreciably the continuation of the fermentation by the microorganisms M present in the fermentation medium. In other words, the solvent is not lethal for all the microorganisms.
• the extraction does not interfere with or degrade the fermentation medium or the fermentative capacities of the microorganisms M it contains. The extraction is therefore performed under conditions such that it is biocompatible.
• the residual liquid phase after extraction, may contain living microorganisms M, therefore potentially active.
• the pH of the liquid phase is less acidic. It is therefore possible to reinject it into the fermentation reactor 1.
• the medium is also resuspended with fermentation-producing microorganisms M, without significantly lowering the pH of the fermentation medium .
• the extraction is carried out continuously or sequentially, for example with extraction every 12 hours. In other words, it is possible to continue the fermentation while extracting the metabolites produced, either as they are produced or regularly.
• the metabolites are purified and / or converted into other products, such as alkanes, alkenes, amides, amines, esters, polymers by known chemical techniques such as, for example, the distillation, synthesis, electrosynthesis, amidation or polymerization.
• fermenting mash is fed with an extraction column 2 at the top of the column, according to arrow 3.
• the endogenous solvent therefore an acid or a mixture of carboxylic acids is injected beforehand.
• the endogenous solvent is, advantageously, a carboxylic acid with seven or eight carbons.
• the amount produced by the fermentation is not, in general, sufficient to ensure the extraction of the majority of the other carboxylic acids produced. It is therefore necessary to introduce such carboxylic acids from a source other than the current fermentation. It may be, for example, carboxylic acids extracted previously and stored for this purpose or even acids, advantageously biobased, from a commercial source.
• Circulating against the current or stirring allows a contact between the carboxylic acids and the solvent.
• the carboxylic acids or at least a part of them, are transferred into the solvent.
• the fermenting must, de facto depleted in carboxylic acids, is collected at the bottom of the extraction column 2 and, preferably, reintroduced into the fermenter 1, according to the arrow 4.
• the solvent is also one of the carboxylic acids present in the fermentation must, no harmful contamination to the continuation of the fermentation by the solvent following the reintroduction of the must is possible.
• the solvent, with the carboxylic acids it contains, is collected at the top of the extraction column 2 and, according to the arrow 5, transfer to a first distillation column 6.
• the solvent and the extracted carboxylic acids form at least one organic phase miscible, at least partially, with water. It will be recalled here that the example described and illustrated corresponds to an embodiment with more than one, namely two, distillation columns. Such an embodiment is the one that will be encountered for so-called average size installations.
• the distillation is carried out at temperatures allowing to recover, selectively, the carboxylic acids whose boiling point is lower than that of the solvent.
• the solvent which is collected at the bottom of column 6, is heavier than the extracted carboxylic acids.
• the solvent is redirected, according to the arrow 9, to the extraction column 2.
• the solvent is reused, minimizing losses and limiting the need for external supply of endogenous solvent.
• the aqueous phase is collected and returned, according to the arrow 10, in the extraction column 2.
• the carboxylic acids constituting the organic phase recovered at the bottom of the decanter 8 are therefore a mixture of different carboxylic acids and, optionally, water in proportions requiring, in some cases, a complementary treatment.
• a complementary distillation For this, the carboxylic acids are directed, according to the arrow 1 1 to a second distillation column 12.
• a solution essentially comprising only an organic phase is introduced into the distillation column 12 .
• the carboxylic acids are collected at the bottom of the column 12, the boiling points being greater than that of the water and, according to the arrow 13, directed towards a member 14 for collection and storage .
• at least a portion of the carboxylic acids collected, purified or mixed is directly directed to an organ for synthesizing final molecules.
• the water collected at the end of the second distillation is, preferably, according to the arrow 15, directed towards the extraction column 2.
• These different distillations can be conducted in a single distillation unit, provided that the latter is of a sufficient size and design. In practice, it is generally distillation columns as encountered in industrial refinery type facilities.
• the heat thus recovered is used to preheat the solvent leaving the top of the extraction column, before its introduction into the distillation column 6. In this way, it is possible to reduce the energy consumption necessary for the first distillation , that significantly. It is conceivable that either at least two heat exchangers are provided for these different thermal flows, ie only one. In other embodiments, the number and / or dimensions of the different members are different from those described. In particular, several parallel installations can be provided.
• the carboxylic acids produced during a fermentation which is carried out on a substrate comprising the fermentable fraction of household waste at a concentration of 50 g / l of dry matter (DM). 50 ml of the fermentation medium, and thus the liquid phase, are recovered. The pH of this sample is 4.3. These 50 ml are then subjected to extraction with heptanoic acid in a volume ratio of 1/1. The extraction yield obtained is 37%.
• DM dry matter
• Comparative fermentation tests have also been conducted by the Applicant, according to various embodiments, to evaluate the effect of the presence of extraction solvents in the fermentation medium on the fermentation yield.
• Test 2 Comparison of fermentations in the presence or absence of heptanoic acid.
• the yields obtained for the production of volatile fatty acids is 0.33 g of AGV / g of dry matter in the case of the experiment with the addition of heptanoic acid and 0.39 g of AGV / g of dry matter for the control fermentation. It is therefore found that the presence of solvent induces a slightly negative effect, of the order of 15% on the production of volatile fatty acids, while keeping yields higher than 30%, which is in itself a value that is widely acceptable as than performance.
• heptanoic acid in the bioreactor produces the same metabolic behavior as an excessive accumulation of volatile fatty acids in the fermentation medium.
• a carboxylic acid as solvent having a lower solubility than that of heptanoic acid in the culture medium, it would achieve yields equivalent to those obtained with the control culture.
• Test 3 Fermentation comparison in the presence or absence of octanoic acid.
• Test 2 is reproduced, with the same culture conditions but from 50 g / L of dry matter of restoration waste and this time comparing the yields obtained during a fermentation with an initial addition of 0.7 g / L of octanoic acid against a control fermentation experiment which does not contain any.
• Such an installation also advantageously comprises at least one storage member for the products resulting from the extraction.
• Management and control means such as temperature sensors, pH and / or redox probes, are provided.
• the monitoring of the activity of the microorganisms is carried out by methods known per se, for example by the analytical monitoring of the production of gaseous and liquid metabolites, flow cytometry counts, molecular biology techniques such as the molecular fingerprints or biochips.

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