EP3172331A1 - Method for producing organic molecules from fermentable biomass - Google Patents

Abstract

The invention relates to a method for producing organic molecules from fermentable biomass, which includes a step of anaerobic fermentation (5) producing volatile fatty acids (6), said precursors being transformed into final organic molecules by non-fermentation means. The method also includes at least the following steps: a) extracting (9) at least one portion of the volatile fatty acids from the fermentation medium such that the production of fermentation metabolites by the microorganisms (M) is not affected and injecting a portion of the liquid phase (11) containing microorganisms from the extraction (9); b) synthesising (13) organic molecules from the fermentation metabolites or volatile fatty acids extracted in step a); and c) continuing steps a) to b) until obtaining a final amount and quality of organic molecules. The invention also relates to a facility for implementing the method.

Description

 PROCESS FOR PRODUCING ORGANIC MOLECULES FROM

 BIOMASS FERMENTESCIBLE

The present invention relates to a method for producing molecules from fermentable biomass. This production is made from biomass to the production of molecules of interest and directly usable, similar to a production of molecules in a biorefinery. Here, the process comprises, inter alia, an anaerobic fermentation step.

 By fermentable biomass, is meant here an organic substrate, preferably but not exclusively, non-food, obtained from waste, by-products and co-products formed from organic materials, that is to say biomass, resulting from human activities whether domestic, industrial, agricultural, forestry, aquaculture, agro-industrial or livestock. By way of non-limiting example, mention may be made, as organic substrate, of manure, the organic fraction of household refuse, slaughterhouse co-products, cellulosic or lignocellulosic residues from agro-industry such as those resulting from the transformation. sugar cane (bagasse), sunflower or soy.

 By anaerobic fermentation is meant a fermentation carried out under anaerobic conditions by microorganisms, eukaryotic or prokaryotic, such as bacteria, fungi, algae or yeasts.

 The term molecule means here, but not exclusively, so-called precursor molecules. These precursors subsequently allow the production of other molecules which have an energy and / or chemical interest higher than that of the precursors, it being understood that they are organic molecules. Examples of molecules having an energy and / or chemical interest are molecules having a carbon chain, such as acids, hydrocarbons, methane, esters, alcohols, amides or polymers.

Today, molecules with an energy and chemical interest are generally derived from fossil raw materials, such as hydrocarbons. Their Production from renewable raw materials, such as biomass, is therefore an economically and environmentally sound solution. Processes are thus known for producing a given type of molecule from an organic substrate. Examples include the production of ethanol, which is an important component of first-generation biofuels for vehicles, from biomass, mainly foodstuffs such as maize, wheat, sugar beet or sugar cane. Such methods not only produce a recoverable molecule monotype but a substantial portion of the substrate carbon is converted into a low-interest co-product, such as carbon dioxide. In addition, the recovery, by various means, molecules of interest leads to the production of a large amount of waste, which generates environmental problems. In addition, the microorganisms used in such processes are generally genetically modified microorganisms. To remedy this, we know processes aimed at producing, by fermentation of the biomass generally pretreated or food, so-called precursor molecules. These molecules are subsequently transformed, by known chemical routes, into different usable molecules. The transformation into final molecules takes place later and independently of the production phase of these so-called precursor molecules.

US-A-6,043,392 discloses such a process for producing ketones by heat treatment of volatile fatty acid salts obtained by anaerobic fermentation. Part of the volatile fatty acids are also converted into hydrocarbons, aldehydes, alcohols. In addition to a limited number of end products obtained by such a process, it turns out that it is carried out in two distinct stages, namely the fermentation and then the treatment of the AGV salts. In other words, the process is not continuous. It is known that the production of volatile fatty 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 discontinuous. For this, AGVs are extracted after a given fermentation time. We also know by US-A-4,358,537, a process, in situ, for producing carbohydrates from a peat plot. Here, AGVs are not a sought-after product as a precursor. Similarly, US-A-2013/309 740 describes an anaerobic fermentation whose object is the production of methane, the AGV is a waste to be eliminated. These processes therefore do not allow rapid and continuous production of so-called precursor molecules, the yield being not optimal.

 However, in the context of an industrial process for the production of molecules by fermentation from biomass, it is important, in order to guarantee the productivity of the plant, to have a process whose yield and adaptability to the production of different molecules are not only as high as possible but above all regular, controlled while limiting the production of waste and effluents to be treated later. This is all the more important as the organic substrates used as fermentable biomass are mainly of agricultural, industrial, domestic and / or agro-food origin in order to guarantee large volumes. As a result, there is great variability, qualitative and quantitative, of the substrate, depending on various factors such as location or season.

 The invention aims more particularly at remedying these drawbacks by proposing a method making it possible to produce, in a regular and controlled manner, various so-called biobased molecules, that is to say molecules derived from biomass, in a biorefinery-type approach.

For this purpose, the subject of the invention is a process for producing organic molecules from fermentable biomass, comprising an anaerobic fermentation step, said fermentation producing so-called precursor fermentative metabolites, such as volatile fatty acids, these so-called precursor metabolites being transformed into final organic molecules by non-fermentative route, the process comprising at least one step of fermenting an organic substrate formed by fermentable biomass in a fermentation reactor to production as fermentative metabolites of fatty acids volatile compounds (AGV) having a carbon chain of 1 to 8 carbons, characterized in that it comprises at least the following stages: - a) extracting, between the beginning of production and the maximum production of said volatile fatty acids, at least a portion of the volatile fatty acids of the fermentation medium so that the production of fermentative metabolites by the microorganisms is not affected and introduce at least a portion of the liquid phase, containing microorganisms, resulting from the extraction in the fermentation reactor,

 b) synthesizing organic molecules from fermentative metabolites produced in the fermentation reactor or volatile fatty acids extracted in step a),

- c) continue steps a) to b) until obtaining, in quantity and quality, the final organic molecules.

Such a process makes it possible to produce so-called precursor fermentative metabolites, namely volatile fatty acids, continuously and preserving the population of microorganisms present in the bioreactor. In fact, the extraction step not only makes it possible to avoid the accumulation of volatile fatty acids in the medium, but also to preserve the microorganisms, the extraction being carried out under non-lethal conditions for all the microorganisms. In other words, the extraction is biocompatible, that is to say that it does not interfere with or degrade the biological medium in which it is carried out. In this way, it is overcome problems related to the accumulation of precursors in the fermentation reactor, for example acidification of the fermentation medium by accumulation of volatile fatty acids produced which are harmful to microorganisms. The activity of the microorganisms is maintained at a high level, close to the initial level, throughout the fermentation cycle, most of the microorganisms not being inhibited by this extraction step.

 According to advantageous but non-mandatory aspects of the invention, such a method may comprise one or more of the following features:

 before step a), a mixture of microorganisms from defined natural ecosystems is inoculated in the fermentation reactor.

Steps a) to c) are carried out continuously. - The residues from the process are suitable for use as an amendment, fertilizer or as a co-product such as methane.

 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,

 an extracting organ suitable for extracting the volatile fatty acids contained in the liquid phase produced during the fermentation and

 a synthesis organ, such as a chemical reactor or an electrolysis cell, capable of ensuring the synthesis of fermentative metabolites obtained during the fermentation into final organic molecules.

 According to advantageous but non-mandatory aspects, such an installation may include the following features:

 - It comprises at least one storage member of the substrate.

 The invention will be better understood and other advantages thereof will appear more clearly on reading the description of several embodiments of the invention, given by way of non-limiting example and with reference to the following drawings in which:

 FIG. 1 is a simplified diagram representative of the method that is the subject of the invention.

 The various steps of the method are now described with reference to several embodiments, it being understood that the steps known per se are not detailed. In particular, reference will be made later to the diagram of FIG. 1 as illustrating an advantageous embodiment of the invention. In particular, the process is described in the case of the steady state fermentation. Indeed, the steps relating to the start of the fermentation are known per se.

First of all, the substrate 1 used here is advantageously untreated, namely that it has undergone no physicochemical or enzymatic pretreatment. Alternatively, the substrate 1 may have undergone mechanical treatment, for example grinding 2, facilitating the action of microorganisms on the substrate. This is mainly constituted by biomass 3 resulting from human activities. By way of non-limiting example, mention may be made of agricultural or plant wastes (straw, bagasse, maize, grass, wood, mowing) paper waste (cardboard, paper), agro-food waste, slaughterhouse waste, the organic fraction of household waste, livestock manure (manure, slurry, droppings), algae, aquaculture waste, forestry waste or fermentable co-products from the cosmetics industry. In another embodiment, the substrate 1 has undergone a physicochemical or enzymatic pretreatment, although this mode is not a preferred embodiment.

 In a preferred but nonlimiting manner, the substrate 1 is used as supplied, provided that its fermentable power is preserved. This fermentable power is characterized by the methanogenic potential of biomass, commonly referred to as the BMP (Biochemical Methane Potential). Controlled dehydration, as described in patent application FR1302119 filed by the applicant allows to maintain over a period of several months this fermentable power.

 Some substrates also 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 as a precursor, in the production of the final organic molecules.

With certain types of substrate, it may be advantageous to incorporate nutrients and / or mineral compounds in order to increase bacterial growth and / or regulate the pH of the substrate and / or co-products promoting the production of AGVs or other molecules. By way of example, there may be mentioned the addition, in a small amount, of NaOH, KOH, Ca (OH) ₂ , K ₂ HPO ₃ , KH ₂ PO 3, glycerol or vitamin or trace element solutions. This addition is represented by the arrow A.

The substrate is introduced into a fermentation reactor 4, known per se and dimensioned for the desired production, whether the latter is on a laboratory scale to carry out tests or on an industrial scale in the case of a production. In other words, the fermentation reactor 4 or bioreactor has a volume ranging from a few liters to several hundred cubic meters, as needed.

 Microorganisms are advantageously but not mandatory, previously introduced into the fermentation reactor 4, at least during startup, in an amount sufficient to initiate the fermentation. It is conceivable that the quantity of microorganisms introduced depends, among others, on the substrate. These microorganisms are inoculated in the form of a consortium, illustrated by the arrow M. By the term consortium, is meant a mixture or mixture of microorganisms, eukaryotic or prokaryotic, whether bacteria, yeasts, fungi or algae. These microorganisms M come mainly from natural ecosystems suitable for carrying out a fermentation under anaerobic conditions. By way of non-limiting example, there may be mentioned as ecosystems the anaerobic zone of aquatic environments such as the anoxic zone of certain lakes, soils, marshes, sewage sludge, the rumen of ruminants or the intestine of termites. It should be borne in mind that the qualitative and quantitative distribution of the different types and species of microorganisms in the M consortium is not known precisely and above all can vary significantly. It turns out that this qualitative and quantitative diversity of microorganisms surprisingly provides a robustness and adaptability to the fermentation process to ensure optimal use of substrates, whatever the composition of the latter and this under conditions variable fermentation.

 Moreover, because the substrate 1 is used as it is, that is to say, it is not sterilized or, more generally, it is not cleared of microorganisms that it contains beforehand. its introduction into the bioreactor, it turns out that these microorganisms endemic to the substrate 1 are, de facto, incorporated in the consortium M or at least associated with the latter in the bioreactor 4.

There is also significant fluctuation not only between different consortia with the same source but also within the same consortium during fermentation. The work of the inventors (Pessiot et al., Fed-batch Anaerobic Valorization of Slaughterhouse By-products with Mesophilic Microbial Consortia Without Methane Production. Applied Biochemistry and Biotechnology, January 6, 2012) have shown that this fluctuation is due to successive waves of population of microorganisms but that these populations are, overall, similar in activity and types of microorganisms, over a given period. As a result, there is a relative constant in the products of the fermentation, at least qualitatively.

 The fermentation 5 to produce volatile fatty acids has, according to the process of the invention, interesting characteristics such as being carried out in a non-sterile condition. The consortium M of microorganisms makes it possible to optimally use the substrate 1, without adding products such as enzymes. Furthermore, the fermentation 5 takes place under anaerobic conditions, more specifically when the redox potential is less than -300mV, advantageously between -550mV and -400mV, when the pH is less than 8, preferably between 4 and 7. Thus, the fermentation 5 is advantageously limited to the production of fermentative metabolites called precursors, therefore volatile fatty acids or AGV. It is, in fact, to perform, in a fermentation reactor 4, a reaction similar to the phenomenon of acidosis that is encountered in ruminants while limiting as much as possible the production of methane, which is generally one of the end metabolites obtained at the end of such anaerobic fermentation.

The fermentation carried out according to the invention with the consortium M makes it possible, unlike fermentations with defined strains, to degrade not only the sugars (pentoses, hexoses or others) present in the substrate 1 but also the major part of the substrate 1 components such as proteins, nucleic acids, lipids, carboxylic acids. Thus, the yield of such fermentation is particularly high, waste production being low. The fermentation of complex molecules such as proteins is particularly interesting because it allows, inter alia, the production of isobutyric acid, 2-methyl butyric acid and isovaleric acid. These branched volatile fatty acids are precursors with high potential for the production of branched molecules such as branched hydrocarbons which have advantages as a fuel. In other words, the fermentation 5 produces, among the various compounds generated, precursors for a synthesis of bio-fuels and biomolecules of interest for chemistry.

 More precisely, this fermentation leads, in a first step, to the formation of volatile fatty acids having from one to eight carbons, mainly from two to four carbons such as acetic acid, propionic acid and butyric acid. . Volatile fatty acids with a longer chain, thus greater than four carbons, such as valeric and caproic, heptanoic or octanoic acids, are also obtained. By continuing the fermentation and / or increasing the quantity of microorganisms in the bioreactor 4, if necessary with selected microorganisms, it is possible to promote the production of long-chain carbon-based AGV, thus greater than four carbons. In other words, the metabolites produced in quantity during the fermentation are volatile fatty acids, predominantly of two to six carbons.

 It should be noted that it is also possible to add in the fermentation reactor 4 carboxylic acids with long carbon chains (C8 to C22) which will be fermented or transformed, during the subsequent chemical conversion steps, into hydrocarbons such as octane and kerosene. These carboxylic acids can be added, according to the arrow C, in their raw form or by means of substrates containing them as certain vegetable products which contain oils. By way of non-restrictive examples, mention may be made of sunflower, soybean, coconut, oil palm, peanut or Jatropha oils. These carboxylic acids or these oils are advantageously incorporated in the substrate 1.

 The fermentation can be carried out batchwise or batchwise, continuously batchwise or fed-batch or continuously in one or more fermentation reactors arranged in series.

Fermentation is performed using conventional fermentation techniques to generate anaerobic conditions. For this the use of a carbon dioxide atmosphere is preferred, although other gases such as nitrogen or argon may be considered to achieve anaerobic conditions. The temperature in the fermentation reactor (s) 4 is between 20 and 60 ° C, preferably between 35 and 42 ° C. The pH is less than 8, preferably between 4 and 7. The redox potential is less than -300mV, advantageously between -550mV and -400mV. The means for managing and maintaining the temperature and the pH are known per se. The fermentation is maintained for a time sufficient to produce volatile fatty acids in the liquid phase, illustrated by reference 6. The fermentation time varies, among others, depending on the substrate 1, the microorganisms M present, the initial concentration of AGV and fermentation conditions. Typically, the fermentation period is between 1 and 7 days, preferably between 2 and 4 days. The concentration of AGV 6 obtained in the fermentation medium at the end of this period is variable, but is generally of the order of 10 to 20 g / L, depending on the volatile fatty acids, it being understood that under certain conditions it can to be greater than 35 g / L for example close to 50 g / l. At the end of the fermentation step, the fermentation medium is at an acidic pH, which is generally between 4 and 6. It is conceivable that fermentation produces other compounds, in particular gases 7, such as dioxide. carbon, hydrogen or methane which, advantageously, are recovered and used in known manner, according to reference 8.

Carbon dioxide is, for example, reintroduced into the fermentation reactor 4 to participate in the maintenance of anaerobic conditions. Alternatively, it is used as a carbon source for the production of photosynthetic biomass. Other metabolites are produced, for example lactic acid, esters, alcohols. These funds can either be reintroduced into the bioreactor 4, to continue the fermentation 5, or be used for other applications, as is or after transformation.

The next step is extraction 9 of the volatile fatty acids 6 thus formed. These, by reactions known per se, will produce, in a next step 10, so-called biosourced molecules, according to the defined needs. Alternatively, as indicated above, they form a substrate for a so-called secondary fermentation for produce volatile fatty acids with longer carbon chain. This fermentation can be conducted in the same reactor, in the continuity of the first fermentation, or, alternatively, in another reactor. By way of example, mention may be made of the secondary fermentation, by certain microorganisms such as Megasphaera edelsnii or Clostridium kluyveri, of acetic and butyric acids into caproic and caprylic acids. Such fermentation thus makes it possible to increase the amounts of certain AGV initially present in a limited amount.

 In any case, the volatile fatty acids 6 produced in the liquid phase by the anaerobic fermentation and which are, at least in part, extracted are under conditions such that the extraction 9 does not affect, or at least marginal, the production of volatile fatty acids by the microorganisms present in the fermentation medium. When volatile fatty acids are extracted from the fermentation medium, de facto acidification of the medium is reduced by these acids.

 Advantageously, insofar as the extraction method chosen is not lethal for all the microorganisms, it turns out that the residual liquid phase 1 1, after extraction 9, also contains a certain amount of microorganisms. alive, so potentially active. As in this liquid phase 1 1 there is a concentration of volatile fatty acids 6 lower than that of the fermentation medium, it is therefore possible to reinject it into the fermentation reactor 4. Thus, not only are the volatile fatty acids present in the medium being fermented 5, the pH of the medium is raised, but the medium is also resuspended with microorganisms, ensuring the fermentation 5, by extraction 9 of the acidic compounds 6.

 Such a solution makes it possible to optimize the fermentation yield and to carry out a continuous fermentation, by lowering the reaction times and limiting the production of waste so as to tend towards zero waste.

The extraction 9 is advantageously carried out in the liquid phase. It is conducted continuously or sequentially, for example with extraction every 12 hours. In all cases, the extraction of a part of the volatile fatty acids is carried out between the beginning of production and the maximum production of metabolites. Advantageously, the extraction is carried out near the threshold of inhibition of microorganisms by volatile fatty acids. This threshold depends on, among other things, the substrate and the fermentation conditions. Likewise, the introduction of the liquid phase resulting from the extraction is carried out within a period which makes it possible to maintain a high level of production of the volatile fatty acids, that is to say close to the level at which the extraction has been made. .

 Once extracted 9, the volatile fatty acids 6 are purified 12 and / or transformed, according to the step referenced 10, into other products, such as alkanes, alkenes, amides, amines, esters, polymers and the like. by techniques known per se such as distillation, electrosynthesis, esterification, amidation or polymerization.

 Concomitantly, as an advantageous variant, a part of the volatile fatty acids 6 produced during the fermentation is not extracted but undergoes an electrosynthesis or electrolytic synthesis step. Thus hydrocarbons are produced, primarily from volatile fatty acids long carbon chain to acetate.

 Electrosynthesis step 13 converts volatile fatty acids produced in large amounts of gaseous and liquid compounds via the known reactions of Kolbe and / or Hofer-Moest electrochemical decarboxylation. These two reactions occur simultaneously during the electrolysis synthesis but an adjustment is possible to favor one or the other of these reactions by modifying easily controllable parameters as described below. Various metabolites can be produced by playing on these parameters, which allows a flexible production of different molecules, both qualitatively and quantitatively.

Electrosynthesis 13 makes it possible to convert the volatile fatty acids directly into the fermentation medium. As a result, electrosynthesis is also a means of extracting volatile fatty acids from the fermentation medium. When other organic molecules such as carboxylic acids or alcohols are added to the volatile fatty acids, the range of hydrocarbons and products that can be formed increases.

 Surprisingly, the Applicant has found that the electrosynthesis step can be carried out in the fermentation medium, under mild reaction conditions, at ambient temperature and pressure, at 3V or more than 3V and at 1 mA / cm 2 or more. of 1 mA / cm 2 of current density at the anode, using, for example, platinum or carbon electrodes, for example graphite.

 As regards the electrosynthesis conditions, the pH of the aqueous phase containing the volatile fatty acids is between 2 and 1 1, preferably between 5.5 and 8. Under acidic or neutral pH conditions, the Kolbe reaction providing alkanes is favored, while under alkaline pH conditions it is the oxidative deprotonation of the Hofer-Moest reaction providing alkenes that is favored.

 In this electrosynthesis step 13, the AGVs, thus carboxylic acids, with short and medium carbon chains must be in the form of carboxylates to be used. This is why a low pH will tend not only to reduce the concentration of volatile fatty acids in the form of anions but also the solubility of carboxylic acids or AGV medium carbon chain. The pH can be adjusted, inter alia, with sodium hydroxide to maintain high carboxylate concentrations to be subjected to electrolysis. In general, there is no need to use organic solvents, the fermentation media being good electrolytes for the electrosynthesis step 13.

Organic solvents are necessary almost exclusively for the reagents poorly soluble in water, such as carboxylic acids or AGV with long carbon chains. In the latter case, methanol, ethanol and isopropanol may be solvents of choice. Alternatively, because of their low solubility in aqueous solution, these carboxylic acids or AGV with long carbon chains can be easily separated and concentrated in order to undergo the electrolysis step in a second step and lead to high yields of electrolytic products. Insofar as it is possible, as a non-compulsory variant, to use a divided electrolysis cell, the products formed respectively at the anode and at the cathode can be easily separated.

 Alternatively, all the compounds obtained by electrosynthesis can be recovered in a single container and separated or transformed thereafter.

 Once collected, the gaseous products 15 formed at the end of the electrosynthesis 13 such as hydrogen, carbon dioxide, alkanes, alkenes can be, by way of non-limiting example, compressed and separated by gas liquefaction. as previously indicated under reference 8.

 In another embodiment, it is possible to envisage the use of semi-porous membranes in double electrochemical cells to separate the two electrodes. Also, the electrodes can be placed very close to each other to avoid arcing.

 On the other hand, the products 14 obtained at the end of this electrochemical conversion step are, among others, mixtures of hydrocarbons, hydrogen and carbon dioxide which contain no contaminant relative to, among others, , natural gas from the oil industry.

 Alternatively, in order to increase the yields of the synthesis by electrolysis, additional techniques are used such as, for example, ultrasound, magnetic fields, alternating current.

At the end of the electrosynthesis 13, the non-transformed AGV residues 16 partially leave in step 6 to be extracted (step 9) and / or undergo a new electrosynthesis (step 13). Part of the residues 16 is recycled to step 17, namely gasified, incinerated or converted. Fermentative metabolites, such as volatile fatty acids and residual substrates resulting from the different fermentation, extracting, or electrosynthesis stages, are methanized (step 17) to produce fertilizers and amendments, grouped under reference 18 and biogas. This methanation step 17 is, according to an industrial ecology approach, also applied to a fraction of unfermented residues or substrates. Thus, we produce energy and heat, typically by cogeneration. This production of energy and heat is, at least in part, used to cover the energy requirements of the process.

 Thus, the process of the invention makes it possible to produce, advantageously continuously, and with a high yield of the carbon-based molecules with a minimum loss of initial organic carbon.

 The following examples illustrate the implementation of the method that is the subject of the invention with different substrates and fermentation conditions.

 Example 1: Discontinuous fermentation of slaughterhouse by-products in a non-sterile bioreactor mode

A 5L volume fermenter or bioreactor of useful volume containing an anaerobic culture medium (0.5 g / LK ₂ HPO 4, 0.5 g / L KH ₂ PO 4, 1.0 g / L MgSO 4, 0.1 g / L LCaCI2, 1 ml Hemin and 5 ml vitamin) at a concentration of 100 g / L of a mixture of non-sterilized slaughterhouse waste (blood, viscera, stercorals, meat waste, in ratio 1/1/1 / 2) was inoculated at a temperature of 38 ° C with shaking with a consortium of natural microorganisms from anaerobic ecosystems such as the anoxic zone of hyper-oligotrophic lake, such as Lake Pavin. During 1042 hours of fermentation, nine operations of fed-batch and 6 additions of meat substrates (886 g of total solids) non-sterile were performed. During this fermentation, monitoring of the metabolites in the liquid phase and in the gas phase were carried out. The fermentation products of the liquid phase were monitored and analyzed. At the end of fermentation, the fermentation medium contained 16 g / L of total volatile fatty acids. The yield obtained is 0.38 g of total AGVs / g of dry matter added to the reactor. This example is to be considered as a reference test, no extraction and / or electrosynthesis chemical synthesis, unlike the process of the invention, having been performed.

 Example 2: Semi-continuous fermentation of organic fractions of household waste bioreactor non-sterile mode.

Example 1 is repeated with the same culture medium but using a substrate composed of the fermentable fraction of the household waste at a concentration of 50 g / L dry matter instead of slaughterhouse waste. In addition, and in accordance with the process of the invention, extractions are carried out on the medium during fermentation. Here the fermentation takes place over 2000 hours and several in situ extraction sequences are carried out in the bioreactor. The extraction is of the liquid-liquid type, it being understood that the volatile fatty acids are always produced in the liquid phase and that the solvent used for this example is pentane. These operations made it possible on the one hand to reduce the final concentration of total fatty acids with, for example, an extraction in which the concentration in the reactor increased from 26.8 g / l to 20.1 g / l of total AGVs. (23% decrease), which makes it possible to reduce the acidity of the medium and thus to preserve an optimal activity of the consortium M of microorganisms. The extraction also makes it possible to recover volatile fatty acids that have been used for various chemical syntheses, such as the production of esters and amides.

These in situ extraction operations made it possible to show the biocompatibility of the process, in other words the sequential recovery of metabolites of energy and chemical interest, such as volatile fatty acids, from biomass via a process combining fermentation and fermentation steps. extraction. This biocompatibility is characterized by the number of microorganisms per ml present in the bioreactor determined by the flow cytometry analysis technique. These results are, for example, between samples taken before and after in situ extraction, from 2.3 × 10 ⁸ to 8.0 × 10 ⁷ microorganisms / ml, in a series of measurements and from 2.9 to 2.3 × 10 ⁸ microorganisms / ml. for another series of measures. This shows that there is a decrease in the population of microorganisms present in the bioreactor, following the extraction of volatile fatty acids, but that this reduction does not involve massive destruction of microorganisms. The population of microorganisms is sufficient, quantitatively and qualitatively, for the microorganisms to be active and for there to be no, or very little, loss of the fermentative activity of the consortium of microorganisms.

In another embodiment, the extraction can be carried out without irreversible constraints directly in the fermentation reactor 4. It is possible to carry out a continuous fermentation with the extraction of the metabolites. fermentation inhibitors, that is, by extracting the volatile fatty acids responsible for the acidosis of the medium as they are produced. Alternatively, these extraction operations may be performed in a second compartment, the latter compartment being able to be located in the bioreactor 4.

 The following tests illustrate the step of electrosynthesis from volatile fatty acids as precursors, it being understood that it is necessary to use these volatile fatty acids as carboxylate during these chemical reactions.

Example A

A solution of 1M sodium acetate was subjected to an electrolysis reaction using graphite electrodes with a current density of 100 mA / cm ² .

 After 180 minutes of reaction, 63% of the initial acetate concentration was consumed. The metabolites obtained in the gas phase are hydrogen (350 ml or 15 mmol), carbon dioxide (330 ml or 13.8 mmolC), methane (7 ml or 0.3 mmolC) and ethane ( 30 ml or 2.51 mmolC). The metabolites obtained in the liquid phase are methyl acetate (66 mg or 0.9 mmol) and methanol (87 mg or 2.7 mmol). The Cmol (Cmol.Product / Cmol.Substrate) balance of this reaction is 0.9 ± 0.1. The yields of hydrogen, carbon dioxide, ethane, methane, methyl acetate and methanol are respectively 473 ml / g of acetate, 446 ml / g of acetate, 41 ml / g of acetate, 10 ml / g acetate, 90 mg / g acetate and 1 18 mg / g acetate. Example B:

 Example A is repeated but with 1M sodium propionate as the substrate. After 180 minutes, 56% of the initial propionate concentration was consumed. Hydrogen, methane, carbon dioxide, ethene and butane are obtained in the gas phase and ethanol and ethyl propionate are obtained in the liquid phase.

 Amidation reactions were also conducted:

Example C Amidation-acetate

The amidation reaction is carried out in a reflux assembly from a mixture of a biosourced acetic acid solution and an ammonia solution under conditions stoichiometric. The reaction mixture is heated at 80 ° C for 4 hours and then the excess reagents are distilled off. The product of the reaction is recrystallized in order to obtain the biosourced acetamide. The yield of the amidation reaction under these conditions is 63%.

Example D Amidation-butyrate

 Example C is repeated, but with a biosourced butyric acid solution and at a temperature of 90 ° C. After 5 hours and after crystallization of the biobased butyramide, the yield of the amidation reaction was 69%.

Example E Amidation-AGV Blend

Example C is repeated with a mixture of biosourced volatile fatty acids (acetic acid, propionic acid, butyric acid, isobutyric acid, isovaleric acid, valeric acid, isocaproic acid, caproic acid, heptanoic acid, octanoic acid, etc.) derived from the extraction phase as described in the previous examples at a temperature of 85 ° C. After 6 hours, after removal of excess reagents by distillation and after recrystallization of the biosourced amides, the yield of the amidation reaction is 74%. The biosourced amides obtained are the amides corresponding to the biosourced carboxylic acids present in the mixture (acetamide, propanamide, isobutyramide, butyramide, isovaleramide, valeramide, isohexanamide, hexanamide, heptanamide and octanamide, etc.).

 These amidation reactions which make it possible to produce bio-sourced amides from biosourced volatile fatty acids can also be carried out with substituted amines in order to obtain secondary and tertiary amides.

Esterification reactions were also conducted.

Example F: Esterification of a mixture of AGV

To carry out this esterification, an equimolar mixture of biosourced volatile fatty acids obtained after fermentation and extraction (acetic acid, propionic acid, butyric acid, isobutyric acid, isovaleric acid, valeric acid, isocaproic acid, caproic acid, heptanoic acid, octanoic acid, phenyl acetic acid, phenyl propionic acid) (2 mL) ) and ethanol (1. 51 mL) is refluxed for 1 h15. Sulfuric acid (54 μί) is initially added to the reaction medium as a catalyst. At the end of the reaction, we find by phase chromatography gaseous ethyl esters corresponding to the acids present in the initial mixture that is to say in the example: ethyl acetate, ethyl propionate, ethyl isobutyrate, ethyl butyrate , ethyl isopentanoate, ethyl pentanoate, ethyl isohexanoate, ethyl hexanoate, ethyl heptanoate, ethyl octanoate, phenylacetate, ethyl and ethyl phenylpropionate. A conversion yield of 69% of the carboxylic acids to esters is obtained.

 It is thus shown that fermentative metabolites such as AGV, namely according to Examples A to F and in a non-limiting manner, acetic, propionic, butyric, isobutyric, isovaleric, valeric, isocaproic, caproic, heptanoic, octanoic, phenyl acetic, phenylpropionic acid are easily used as precursors of final molecules of economic and energetic interest, it being understood that these metabolites are produced by fermentation.

 There is thus an overall process whose different steps can be performed in offset. By this term are meant steps that can be repeated at different times and / or in different places. In other words, the process has great adaptability and flexibility of production.

 The implementation of such a process involves not only the presence in the installation of at least one fermentation reactor but also at least one extraction member, adapted to implement the extraction step 9 and at the same time. least one synthesis member, adapted to implement the electrosynthesis step 13 or, alternatively, another chemical step. These organs are known per se, their numbers and dimensions being adapted to the type of production.

 Such an installation advantageously comprises storage members of the substrate 1 and / or products from the extraction and / or electrosynthesis and other chemical synthesis stages. Management and control means, such as temperature sensors, pH probes, are provided.

Claims

1. - Process for producing organic molecules from fermentable biomass, comprising an anaerobic fermentation step (5), said fermentation producing so-called precursor fermentative metabolites, such as volatile fatty acids (6), these so-called precursor metabolites being converted into organic molecules non-fermentative processes, the process comprising at least one step of fermenting an organic substrate (1) formed of fermentable biomass (3) in a fermentation reactor (4) to production as metabolites fermenting agents of volatile fatty acids (VFA) having a carbon chain of 1 to 8 carbons, characterized in that it comprises at least the following stages:

 - a) extracting (9), between the start of production and the maximum production of said volatile fatty acids (6), at least a portion of the volatile fatty acids of the fermentation medium so that the production of fermentative metabolites by the microorganisms ( M) is not affected and introducing at least part of the liquid phase (1 1), containing microorganisms (M), resulting from the extraction (9) into the fermentation reactor (4),

b) synthesizing (13) organic molecules from fermentative metabolites produced in the fermentation reactor (4) or volatile fatty acids extracted in step a),

 - c) continue steps a) to b) until obtaining, in quantity and quality, the final organic molecules.

 2. - Process according to claim 1, characterized in that before step a), is inoculated in the fermentation reactor (4) a mixture (M) of microorganisms from defined natural ecosystems.

3. - Method according to one of the preceding claims, characterized in that steps a) to c) are carried out continuously.

4. -Procédé according to one of the preceding claims, characterized in that the residues (16, 20) from the process are suitable for use as an amendment, fertilizer (18) or as a co-product (19) such as methane.

 5. - Installation for implementing a method according to one of the preceding claims, characterized in that it comprises at least:

 a fermentation reactor (4),

 an extracting organ capable of ensuring the extraction (9) of the volatile fatty acids contained in the liquid phase produced during the fermentation and

 a synthesis organ, such as a chemical reactor or an electrolysis cell, capable of ensuring the synthesis of fermentative metabolites obtained during the fermentation into final organic molecules.

 6. - Installation according to claim 5, characterized in that it comprises at least one storage member of the substrate (1).