Method for processing lignocellulosic biomass

Abstract

The present invention relates to a method for treating lignocellulosic biomass, comprising the steps of: a) pretreating biomass (2) to obtain pretreated biomass (3); b) a first solid / liquid separation step of separating the solids / liquids of all or a portion (3a) of the pretreated biomass (3) into a first solid fraction (7) and a first liquid fraction (6) comprising a mixture of sugars; c) enzymatic hydrolysis of the first solid fraction (7) of the pretreated biomass to obtain a hydrolysate (15) in the form of one or more sugars (14); d) purifying the first liquid fraction (6) by contacting it with a microorganism that consumes only C6 sugars to obtain a purified liquid fraction (26) (24); and e) a second solid / liquid separation step (27) of separating the solids / liquids of the purified liquid fraction (26).

Description

[Technical Field]

[0001] The present invention relates to the treatment of sugar liquors, in particular "second generation (2G)" sugar liquors that can be obtained from lignocellulosic biomass.

[0002] These sugar liquors can be used to produce other products via chemical or biochemical routes (e.g., alcohols, such as ethanol or butanol, or other molecules, such as solvents, such as acetone, or intermediates used in the chemical industry, etc.), especially as replacements for petrochemical derivatives. [Background technology]

[0003] Lignocellulosic biomass represents one of the most abundant renewable resources on Earth. The substrates considered are extremely diverse; they relate to both woody substrates, such as different woods (hardwoods and softwoods), by-products resulting from agriculture (straw, corn cobs, etc.) or by-products resulting from other industries, such as the food processing industry, the paper industry, etc.

[0004] Various types of methods exist for converting lignocellulosic biomass into sugar liquor, depending on the type of biomass: In the case of sugar-producing plants (sugar beet, sugarcane) and starch-producing plants (corn and wheat), "first generation (1G)" sugar liquor is obtained, for example, by extraction operations.

[0005] In the case of biomass of the agricultural, forestry or paper-making residue type, "second generation (2G)" sugar liquors are obtained by biochemical conversion methods that generally include a pretreatment step and a step of enzymatic hydrolysis with an enzyme cocktail. The pretreatment generally includes a step of impregnation with an acidic, basic or oxidizing liquor, followed by digestion of the impregnated biomass, possibly accompanied by steam explosion.

[0006] The sugar liquors resulting from the hydrolysis can then be processed, for example by fermentation, to convert them into alcohols, the process also including separation and / or purification steps.

[0007] These sugar liquors can also originate from a mixture of sugar liquors originating from different types of biomass.

[0008] Lignocellulosic biomass is composed of three major polymers: cellulose (35%-50% by weight); hemicellulose (20%-30% by weight); and lignin (15%-25% by weight). Cellulose is a polysaccharide consisting essentially of hexoses, hemicellulose is usually a polysaccharide consisting essentially of pentoses, and lignin is a complex, high-molecular-weight polymer composed of aromatic alcohols connected via ether bonds. These different molecules are intricately intertwined and organized, responsible for the unique properties of plant walls.

[0009] Of the three base polymers that make up lignocellulosic biomass, cellulose and hemicellulose are the ones that allow for the production of 2G sugar liquor.

[0010] Typically, hemicellulose is decomposed mainly into sugars during pretreatment, and cellulose is converted into glucose by enzymatic hydrolysis. However, crude cellulose remains difficult for enzymes to access, hence the need for the aforementioned pretreatment. This pretreatment makes it possible to modify the physicochemical properties of lignocellulosic biomass, improving the accessibility of cellulose to enzymes and its reactivity to enzymatic hydrolysis.

[0011] There are many techniques relevant to the invention for carrying out this pretreatment, which will be grouped together hereinafter under the general term "cooking": acid cooking, alkaline cooking, autohydrolytic cooking, steam explosion, and the "organosolv pulping" method. This "organosolv pulping" method involves a pretreatment in the presence of one or more organic solvents and generally water. The solvent can be an alcohol (ethanol), an acid of the acetic or formic type, or alternatively acetone.

[0012] Various configurations have been reported, for example, in the literature (Non-Patent Document 1) and also in the literature (Non-Patent Document 2).

[0013] One of the most effective pretreatments is steam explosion, especially under acidic conditions, which allows for nearly complete hydrolysis of hemicellulose and a significant improvement in the accessibility and reactivity of cellulose to enzymes. This pretreatment can also be preceded by one or more other treatments.

[0014] Therefore, pretreatment can generally include three stages: preparation of a liquor, impregnation of biomass with this liquor, and pretreatment of the impregnated biomass, for example by cooking, possibly combined with steam explosion. Patent (US Pat. No. 5,499,299) discloses a method for impregnating biomass with an acidic liquor, followed by cooking and steam explosion of the impregnated biomass, adjusting the acidity of the acidic liquor, and recycling it. Patent (US Pat. No. 5,499,299) also describes a method for pretreating biomass by acid impregnation and then steam explosion, and furthermore, washing the means feeding the reactor and recycling the aqueous washing liquor to this method.

[0015] The sugar liquor thus obtained from lignocellulosic biomass, in particular after its pretreatment or, in the case of "2G" sugars, after enzymatic hydrolysis, is provided in the form of a mixture of sugars in an aqueous phase, in which "C5" sugars (i.e., sugars containing five carbons), such as xylose and arabinose, and "C6" sugars (i.e., sugars containing six carbons), such as glucose, mannose and galactose, are found.

[0016] In particular, in the case of 2G type sugar liquors resulting from the pretreatment of lignocellulosic biomass, a proportion of C5 sugars significantly higher than the proportion of C6 sugars is observed in the sugar liquor for most of the lignocellulosic biomass. The term "sugar liquor" is understood to mean that sugars are released by the pretreatment and that they can be dissolved by mixing the pretreated biomass with, for example, water.

[0017] In fact, an outlet specifically exists for C5 sugar liquor (eg, for converting xylose to xylitol).

[0018] To a lesser extent, the sugar liquor may also contain furfural or furfural derivatives, products of sugar degradation, carboxylic acids, furan compounds (which are fermentation inhibitors), which are detrimental if it is desired to continue the conversion of the sugar liquor to alcohol by fermentation using yeast or bacterial type microorganisms.

[0019] For example, a publication by Kuang Zhang et al. (Non-Patent Document 3) demonstrated the inhibitory properties of furfural on the bacterium Zymomonas mobilis A3 during fermentation at a content of 4 g / L.

[0020] Therefore, there is a need to separate or purify C5 sugars from other sugars, particularly C6 sugars, and in some cases from other undesired compounds to obtain a pure C5 sugar liquor, or at least a sugar liquor having an increased content of C5 sugars relative to the other sugars in the sugar liquor, and this applies very particularly to the production of sugars or alcohols from 2G lignocellulosic biomass.

[0021] A variety of purification / separation techniques have already been devised.

[0022] Thus, patent application EP 1 099 266 describes a biomass treatment that involves pretreatment followed by enzymatic hydrolysis to obtain a sugar liquor containing glucose, which is then clarified and then purified by filtration over activated carbon to remove suspended solids and capture certain soluble contaminants. This is a simple technique, but it does not allow for the separation of C5 sugars from C6 sugars.

[0023] A publication by Tielin Wang et al. (Non-Patent Document 4) proposes to increase the yield of sugar liquor fermentation by removing furfural and its derivatives from sugar liquor using nanofiltration and reverse osmosis membrane techniques, which is a complex and expensive technique that does not allow the separation of C5 sugars from both C6 sugars and furfural derivatives unless multiple membrane filtration operations are performed.

[0024] Patent application (Patent Document 4) proposes using barium or calcium hydroxide to cause precipitation of non-sugar compounds, resulting in a liquor containing only glucose, xylose and other sugar types. This technique therefore does not allow selective separation of sugars from sugar liquor, but simply allows the removal of minor compounds that are by-products of biomass pretreatment.

[0025] Patent (US Pat. No. 5,629,499) describes the separation of glucose from a mixture of C5 and C6 sugars by adsorption of glucose on a zeolitic adsorbent of the FAU type. This is an advantageous method, however, which does not allow optimal separation of glucose, and the selectivity it shows can be improved.

[0026] The patent (US Pat. No. 5,629,499) describes the separation of xylose from a mixture of C5 and C6 sugars, which is also carried out, in this xylose example, by adsorption on a zeolite adsorbent of the FAU type, with the same limitations regarding the selectivity of the separation carried out.

[0027] Indeed, in one case (glucose separation) or in another (xylose separation), it may be necessary to obtain very pure separated sugars depending on the application to which the target is put.

[0028] The object of the present invention is therefore to overcome the above-mentioned drawbacks and to improve the technology for the selective separation of different sugars, in particular sugars in a sugar liquor containing C5 and C6 sugars, by specifically targeting the obtaining of a liquor enriched in C5 sugars ("enriched" liquor is understood to mean that the C5 / C6 sugar ratio of the sugar liquor obtained according to the invention is greater than that of a sugar liquor obtained without the invention).

[0029] Another object of the present invention is to integrate this separation into a line for the production of sugars or alcohols from lignocellulosic biomass to improve operational or performance qualities, in particular to obtain a higher quality sugar liquor in the case of sugar production and / or a higher degree of conversion to alcohol in the case of alcohol production. [Prior art documents] [Patent documents]

[0030] [Patent Document 1] French Patent Application Publication No. 3075203 [Patent Document 2] French Patent Application Publication No. 3075201 (Patent Publication No. 2021-508355) [Patent Document 3] International Publication No. 2022 / 023686 [Patent Document 4] US Patent Application Publication No. 2013 / 0149761 [Patent Document 5] European Patent Application Publication No. 3990464 [Patent Document 6] European Patent Application Publication No. 3990668 [Non-patent literature]

[0031] [Non-Patent Document 1] M. Balat, “Production of Bioethanol from Lignocellulosic Materials via the Biochemical Pathway: A Review,” Energy Conversion and Management, 52 (2011), 858-875. [Non-patent document 2] N. Sarkar, S. Kumar Ghos, S. Bannerjee and K. Aikat, “Bioethanol Production from Agricultural Wastes: An Overview”, RenewableEnergy,37(2012), 19-27 [Non-patent document 3] Kuang Zhang et al., “Removal of the Fermentation Inhibitor, Furfural, Using Activated Carbon in Cellulosic-Ethanol Production,” Industrial&EngineeringChemistry Research, 2011, 50, 14055-14060 [Non-patent document 4] Tielin Wang et al., “Removal of Furfural and HMF from Monosaccharides by Nanofiltration and Reverse Osmosis Membranes”, Journal of the Energy Institute, 91(2018), 473-480) Summary of the Invention [Means for solving the problem]

[0032] (Summary of the Invention) The subject of the present invention is firstly a method for the treatment of lignocellulosic biomass, comprising the following steps: - a) a stage of biomass pretreatment, including cooking of the biomass, possibly with steam explosion, to obtain pretreated biomass; - b) a first stage of solid / liquid separation: separation of all or part (3a) of the pretreated biomass (3) obtained in stage a) into a first solid fraction (7) of pretreated biomass and a first liquid fraction (6) containing a mixture, particularly in the aqueous phase, of compounds containing C5 sugars having 5 carbons and C6 sugars having 6 carbons; the weight content of C5 sugars is higher than the weight content of C6 sugars, - c) a step of enzymatic hydrolysis (14) of the first solid fraction (7) of the pretreated biomass obtained in step b), to obtain a hydrolysate (15) in the form of one or more sugars, comprising C6 sugars having six carbons, - d) a step of purifying said first liquid portion by contacting said first liquid portion with a first microorganism, which consumes essentially only C6 sugars among the sugars of said portion, to obtain a purified liquid portion containing C5 sugars but depleted in C6 sugars. - e) a second stage of solid / liquid separation of the purified liquid fraction obtained in stage d) containing C5 sugars but depleted in C6 sugars; obtaining a second solid fraction containing the first microorganism and a second liquid fraction containing C5 sugars but depleted in C6 sugars.

[0033] The term "essentially only C6 sugars" is understood in the present text to mean the fact that the microorganism does not consume the other sugar or sugars present in the mixture, in particular the C5 sugars, or alternatively they are present in negligibly low / immeasurably low proportions.

[0034] For simplicity, in this text, sugars with 5 carbons will be referred to as C5 sugars and sugars with 6 carbons will be referred to as C6 sugars.

[0035] Preferably, the first liquid portion contains mainly, in particular completely, sugars resulting from the depolymerization of hemicellulose present in the lignocellulosic biomass, this first portion being a sugar liquor obtained without the addition of enzymes and obtained at the end of the pretreatment of the lignocellulosic biomass.

[0036] The present invention has therefore developed a novel technology for the separation of C5 and C6 sugars in a sugar liquor resulting from the pretreatment of lignocellulosic biomass: in the "purification" step d), the invention selects microorganisms that will selectively consume the sugars that are desired to be removed from the first liquid portion, the sugar liquor, in this example C6 sugars, to obtain a liquid portion said to be purified in C5 sugars, which can be upgraded as is, in particular in the chemical industry, or used in a line for the production of alcohol, in particular ethanol.

[0037] This is a separation by a biochemical route, rather than a physical or chemical one, and is highly advantageous: it is easier to perform and significantly more effective and selective than known filtration techniques.

[0038] In the sense of the present invention, the microorganisms can be a single type of microorganism or a combination of different microorganisms.

[0039] In the sense of the present invention, the term "a mixture of compounds containing C5 sugars having five carbons and C6 sugars having six carbons in an aqueous phase" can also be written under the term "sugar liquor" for the sake of brevity.

[0040] In the sense of the present invention, the term "sugars" is understood to mean sugars in their monomeric form (not in oligomeric / polymeric form).

[0041] In the sense of the present invention, a "liquor" is equivalent to a mixture of compounds in an aqueous phase: the liquor is aqueous; it is the same for the first and second liquid parts of the treatment method according to the invention described above.

[0042] Generally, in this text, all liquid portions are aqueous, unless expressly stated otherwise.

[0043] In this purification step d), the microorganisms will consume the C6 sugars of the first liquid portion at least for their own maintenance / metabolism or growth: the C6 sugars can therefore be eliminated in their entirety or substantially in their entirety by appropriately measuring the amount / activity of the microorganisms according to the amount / concentration of C6 sugars in the first liquid portion to be purified.

[0044] The microorganism may also convert sugars into other upgradeable compounds, depending on the amount of C6 sugars present in the liquid portion, the operating conditions (e.g., pH, temperature, aeration, etc.) employed, and the amount and type of microorganism selected. (It should be noted, however, that while the microorganism may also consume very low amounts of C5 sugars, e.g., xylose, it is still essentially a consumer of C6 sugars.) Therefore, advantageously, the microorganism can convert at least a portion, in particular a majority, of the C6 sugars into alcohol, in particular ethanol. The conversion to alcohol is not necessarily complete, since the microorganism can use small amounts of sugar for non-alcohol by-products or their metabolism. The term "majority" is therefore understood herein to mean the fact that the microorganism can convert at least half of the C6 sugars (in particular more than half, for example at least two-thirds, in fact substantially all of the C6 sugars) into ethanol.

[0045] Ethanol is in fact a highly upgradeable product: it could be easily separated from the purified first liquid portion. For example, it could be separated from the aqueous mixture by distillation or entrainment by stripping. It could also be retained, in whole or in part, as a mixture with C5 sugars, particularly to take advantage of its antibacterial properties.

[0046] The microorganisms used in the purification step d) are present in the separated first liquid portion as a solid suspension, especially if they are yeasts. In most cases, measures are therefore taken to separate these solid microorganisms, so that the refined sugar liquor, devoid of solid suspension, can be upgraded. This separation, provided in the solid / liquid separation step e) of the method according to the invention, can be carried out using any device known to those skilled in the art, such as a filtration, centrifugation, sedimentation, sieving or cyclone device, or some combination of these devices.

[0047] It may be optional in the case that the purified liquid portion is used as such or after separation of the alcohol it contains, for example for the growth or fermentation of yeast-type microorganisms.

[0048] The present invention therefore "inserts" into methods for the treatment of biomass aimed at converting the biomass into sugars and then, optionally, into alcohols, providing, in a known manner, the stages of pretreatment of the biomass, then its enzymatic hydrolysis and then its optional fermentation, purification of the sugar liquor obtained at the end of the pretreatment, opening up a host of new possibilities for upgrading, product quality and yield of biomass conversion, as will be described in detail hereinafter.

[0049] Advantageously, only a first portion of the pretreated biomass obtained in step a) is conveyed to the first solid / liquid separation step b), and a second portion (or the remainder) of the pretreated biomass is conveyed directly to the enzymatic hydrolysis step c). The enzymatic hydrolysis can then be carried out simultaneously on two types of stream, one obtained directly from the pretreatment and the other having passed through the solid / liquid separation step, the relative proportion of the stream obtained from the impregnated biomass going to the solid / liquid separation and the stream obtained from the impregnated biomass going directly to the enzymatic hydrolysis being adjustable, for example, the relative proportion being between 90 / 10 and 10 / 90 by weight.

[0050] Enzymatic hydrolysis can therefore be carried out both together on: - the solid residue obtained from the solid / liquid separation b), since this residue still contains compounds that can be converted into sugars by enzymatic hydrolysis; and - pretreated biomass obtained directly from pretreatment; This allows for maintaining a high yield of enzymatic hydrolysis conversion relative to the initial amount of biomass despite withdrawing a portion of the pretreated biomass to recover soluble sugars therefrom.

[0051] The solid / liquid separation step b) can, according to a preferred embodiment, comprise a first step of contact between the pretreated lignocellulosic biomass and water, followed by a second step of filtration, optionally including a washing operation.

[0052] If the solid / liquid separation step b) comprises a step of contacting the pretreated biomass with a fluid followed by a washing step, this can be carried out in co-current or counter-current mode, in particular using part of the recovered liquid portion as washing and / or contacting fluid.

[0053] The solid / liquid separation step b) can, according to a preferred embodiment, be carried out by centrifugation or sedimentation on a filtration unit, in particular a belt filter or a filter press.

[0054] The method according to the invention can also comprise a step f) of fermentation of the hydrolysate in the form of one or more sugars obtained in step c) by a third microorganism to obtain a fermented biomass containing at least one alcohol, in particular ethanol. This is then a method for the production of alcohols of the ethanol type which can serve as biofuel.

[0055] Also in this case, according to a preferred embodiment, the enzymatic hydrolysis step b) and the fermentation step f) can be carried out simultaneously, which is then known as SSCF (Simultaneous Saccharification and Co-Fermentation).

[0056] Preferably, at least a portion of the second solid fraction containing the first microorganism obtained in step e) is recycled to purification step d), since the microorganism maintains a certain activity over a certain period of time, a certain concentration of sugars, in this example C6 sugars, which activity exceeds a single production if the purification is carried out, for example, not continuously but batchwise in a dedicated reactor: it is therefore possible to recover the microorganisms from the purified liquid fraction and reintroduce them into the reactor in which the purification is carried out, and n generations are subsequently carried out, optionally adding supplementary microorganisms as needed as their activity decreases.

[0057] Advantageously, the second liquid portion obtained in step e) containing C5 sugars but depleted in C6 sugars contains alcohol, in particular ethanol, obtained by total or partial conversion of the C6 sugars under the action of the first microorganism, as seen above. According to the invention, it is then possible in step g) to separate said second liquid portion, in particular by evaporation or stripping, into a third liquid portion rich in sugars and a fourth liquid portion rich in alcohol, since this separation between one or more sugars and alcohols can offer various advantages depending on the product or products desired to be upgraded.

[0058] Therefore, if it is desired to upgrade a very pure liquid fraction of C5 sugars, it may be necessary to remove the alcohol it contains from it in order to obtain a given degree of purity. It is also possible to remove only a portion from it, and the residual content of alcohol in the sugar solution will ensure its antibacterial effect.

[0059] Furthermore, ethanol is itself an upgradeable product in one of two ways: either directly as an upgradeable product or by reincorporating it into the process of the invention if the conversion of biomass to alcohol (ethanol) is targeted: so it can be added to the ethanol obtained in the process by, for example, enzymatic hydrolysis / fermentation followed by distillation (to dehydrate it); the two ethanol streams can be mixed either upstream or downstream of a distillation column type dehydration device in the on-board installation, thus increasing the biomass to ethanol conversion yield of the process.

[0060] Advantageously, it is also possible to send all or part of the fourth liquid portion containing alcohol obtained in step g) to fermentation step f) or to mix all or part of said fourth liquid portion with the fermented biomass containing at least one alcohol obtained at the end of fermentation step f), as described in detail above.

[0061] The method according to the invention can also include a step h) of enzyme production from a second microorganism, in particular a fungus, using the enzyme to ensure the enzymatic hydrolysis in step c). In this case, the second liquid fraction containing C5 sugars but depleted of C6 sugars obtained in step e) or the sugar-rich third liquid fraction obtained in step g) can be sent in whole or in part to step h) as a substrate for the growth of a second microorganism and / or the production of an enzyme by the second microorganism. This is the scenario when the method incorporates in situ production of enzymes to carry out the enzymatic hydrolysis of the pretreated biomass (another alternative is to bring enzymes produced at a different site onto the production site). In this case, the liquid fraction containing C5 sugars (in whole or in part) obtained according to the invention as a result of the introduction of a purification step is particularly suitable for the growth of fungi and the production of enzymes.

[0062] It should be noted that it is equally or alternatively possible to send all or part of the hydrolysate obtained at the end of the enzymatic hydrolysis and containing sugars, in particular glucose, to stage h) of the production of the enzyme as substrate for the growth of a second microorganism or the production of an enzyme by a second microorganism.

[0063] The method according to the invention can also include a step i) of propagation of a third fermentation microorganism, in particular a yeast, to ensure the fermentation of step f) if step f) is provided. This is the scenario when the microorganism is propagated in situ on the site of biomass treatment. In this case, it is also possible to send all or part of the second liquid portion containing C5 sugars but depleted of C6 sugars obtained in step e) or the sugar-rich third liquid portion obtained in step g) to step i) as a substrate for the propagation of the third microorganism. Here again, these portions (all or part) are particularly suitable for aiding in the propagation of yeast-type microorganisms used for the fermentation of the hydrolyzed biomass, also called hydrolysate.

[0064] According to the method of the invention, it is also possible to send all or part of the second liquid portion obtained in step e) containing C5 sugars but depleted in C6 sugars or the third liquid portion rich in sugars obtained in step g) to a fermentation step f). In this case, if the production of alcohol is targeted, the C5 sugars contained in this / these portions continue their conversion into alcohol by the hydrolysate obtained from the biomass.

[0065] It can thus be seen that one or both liquid portions containing C5 sugars resulting from the purification provided by the present invention (or at least a portion of one or the other of these portions) can be used according to at least three different modes, each of which can be operated alternately or simultaneously with the other two. The choice will depend, in particular, on whether the microorganisms for fermentation and enzyme production are generated in situ, whether the targeted end product is a liquor solution of C5 sugars or alcohol (ethanol), or indeed both, and even on the type of biomass, since the relative content of C6 sugars in the first liquid portion before purification can vary depending on the biomass chosen.

[0066] The first liquid fraction obtained in step b) may also contain furfural. This is particularly true when the liquid fraction to be purified is obtained from biomass pretreated under acidic conditions. The first microorganism may also advantageously consume furfural, in particular by converting it at least in part into alcohol, in particular furfuryl alcohol. Again, this consumption is highly advantageous insofar as furfural is known to be an inhibitor of fermentation reactions (using yeast): the productivity and yield of possible biochemical conversions expected for the purified liquor are thereby improved. It has also been observed that furfural may also be an inhibitor of the growth of enzyme-producing microorganisms, in particular the fungus Trichoderma reesei.

[0067] The first liquid portion obtained in step b) may also contain 5-(hydroxymethyl)furfural (5-HMF). This is particularly true when the liquid portion to be purified is obtained from biomass pretreated under acidic conditions. The first microorganism may also advantageously consume 5-(hydroxymethyl)furfural, in particular by converting 5-(hydroxymethyl)furfural, at least in part, to 5-(hydroxymethyl)furfuryl alcohol.

[0068] Here again, inasmuch as 5-HMF is also known to be an inhibitor for fermentation reactions, this consumption is highly advantageous: the yield of possible biochemical conversions expected for the purified liquor is therefore improved.

[0069] The first liquid portion to be purified, containing C5 sugars having five carbons and C6 sugars having six carbons, may also contain other compounds of the decomposition of the C5 or C6 sugars, including furan compounds, organic acids, and high molecular weight compounds, especially if these compounds are obtained from pretreatment of lignocellulosic biomass at high temperatures or with solvents.

[0070] What is advantageous and surprising about the method according to the invention is that the biochemical purification according to the invention of this first liquid portion remains effective even if the liquid portion contains compounds of this type, whereas there may be concern that they may potentially act as one or more inhibitors for the conversion of C6 sugars during the purification according to the invention.

[0071] The first liquid portion to be purified may also contain organic salts.

[0072] The first liquid portion to be purified may also contain sugars in oligomeric form.

[0073] Preferably, the first and third microorganisms are selected from yeasts, bacteria, and fungi, in particular yeasts of the genus Saccharomyces, in particular the species Saccharomyces cerevisiae, or bacteria of the genus Corynebacterium, in particular the species Corynebacterium, Zymomonas mobilis. The choice of Saccharomyces cerevisiae is particularly advantageous because wild strains naturally consume C6 sugars but not C5 sugars, and research is being conducted to genetically modify it so that it can accurately consume both types of sugar. Therefore, the present invention recommends, in particular for the first microorganism, returning to a non-modified / natural version of this yeast in order to accurately exploit its selectivity for sugars that has previously been considered a disadvantage.

[0074] Preferably, the second microorganism is selected from fungi, in particular filamentous fungi, preferably of the genus Trichoderma, in particular Trichoderma reesei.

[0075] According to a preferred embodiment of the present invention, the pretreatment of biomass according to step a) comprises the following substeps: a1) a sub-step of impregnation of the biomass with a liquor, in particular an acidic liquor, to obtain an impregnated biomass (alternatively, the liquor can be basic or acidic or just water), a2) a sub-step of cooking the impregnated biomass, possibly with steam explosion; obtaining a pretreated biomass.

[0076] The process according to the invention can also comprise a step j) of separation, in particular by distillation, of the fermented biomass obtained in step f) in the form of alcohol, optionally preceded or followed by a step k) of solid / liquid separation of the fermented biomass.

[0077] Step j) makes it possible in particular to dehydrate the alcohol, a preferred embodiment of which makes it possible to use a beer column to carry out the distillation, with the desired ethanol being obtained at the top and the vinasse being recovered at the bottom.

[0078] Optional step k) is preferably carried out before separation step j) to avoid any risk of traces of solid residues in the distillation column when step j) is carried out by distillation.

[0079] Preferably, the temperature at which the microbial purification d) of the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons is carried out is between 20° C. and 60° C., in particular between 25° C. and 40° C., in particular between 30° C. and 35° C. The treatment temperature will be adapted depending on the microorganism selected, each microorganism having a temperature range in which it is most active.

[0080] Advantageously, the duration of the microbial purification d) of the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons is between 5 minutes and 15 hours, in particular between 10 minutes and 8 hours.

[0081] Advantageously, the microbial purification d) of the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons can be carried out in batch mode, in fed-batch mode of said liquid portion or continuously.

[0082] The selected microorganism that will selectively consume C6 sugars according to the present invention, i.e., the first microorganism, can be added at once directly with the first liquid portion or by continuous feeding, with or without being independent from the feeding of the first liquid portion.

[0083] The duration of the purification step d) will depend on the type and amount of microorganisms used, on the amount of C6 sugars in the liquid portion to be purified, on the amount of compounds known to be inhibitors of microorganisms against the yeast Saccharomyces cerevisiae (furan compounds, e.g., furfural or 5-(hydroxymethyl)furfural, carboxylic acids, e.g., acetic acid or formic acid, or phenolic compounds), and on the final content of C6 sugars tolerated in the purified liquor, expressed in other terms as the desired degree of purity in C5 sugars.

[0084] Advantageously, the microbial purification d) of the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons can be carried out at a pH of 2 to 10, in particular 4 to 6, in particular 4.5 to 5.5.

[0085] Advantageously, the microbial purification d) of the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons can be carried out under aerobic or anaerobic conditions, depending on the microorganism chosen and the desired products from the consumption of the sugars (alcohol, microbial growth, etc.).

[0086] Advantageously, the concentration of microorganisms in the first liquid portion containing C5 sugars having 5 carbons and C6 sugars having 6 carbons is 1 to 200 g / kg C6 sugar, in particular 10 to 30 g / kg C6 sugar, per kg weight of C6 sugar.

[0087] The biomass from which the first liquid fraction containing C5 sugars having five carbons and C6 sugars having six carbons is obtained is of lignocellulosic type and originates in particular from forestry and / or agricultural and / or papermaking residues, and / or sugar-producing plants and / or starch-producing plants and / or fermentable household waste fractions (FHWF).

[0088] The pretreatment of the biomass from which the first liquid portion is obtained can be a pretreatment of the biomass that in particular involves hydrolysis (without enzymes) or impregnation of the biomass with an acidic, basic or oxidizing liquor, followed by cooking of the impregnated biomass, in particular cooking by steam explosion.

[0089] The first liquid portion comprising C5 sugars having 5 carbons and C6 sugars having 6 carbons is preferably obtained according to the present invention after solid / liquid separation step b), preferably using biomass pretreated by steam explosion, optionally reslurried with a solvent (especially water) and optionally washed with a solvent (especially water).

[0090] Another subject of the present invention is the purified first liquid portion obtained in step d) or the second liquid portion obtained in step e) according to the method of the invention (i.e. the "purified liquor" according to the invention before or after separation from the microorganisms by solid / liquid separation): the present invention therefore has as subject matter a liquid containing a mixture of compounds in aqueous solution, which comprises C5 sugars and conversion products of C6 sugars, and possibly other minor compounds present in the liquor to be purified.

[0091] For example, these conversion products of C6 sugars and other minor compounds are alcohols, such as ethanol, 5-(hydroxymethyl)furfuryl alcohol and furfuryl alcohol, particularly in the following concentrations: C5 sugars: 10-100 g / kg of solution, in particular 20-60 g / kg of solution, Ethanol: 1-12 g / kg of solution, in particular 2-7 g / kg of solution, per kg of solution; 5-(hydroxymethyl)furfuryl alcohol: from 0.1 to 9 g / kg of solution, in particular from 0.2 to 4 g / kg of solution, - Furfuryl alcohol: 0.05-9 g / kg of solution, in particular 0.1-3.8 g / kg, in particular 0.1-1.8 g / kg of solution by weight (kg) of solution.

[0092] The purified first liquid portion obtained in step d) or the second liquid portion obtained in step e) according to the method of the invention can therefore contain alcohols, in particular alcohols obtained from the conversion of C6 sugars under the action of microorganisms, such as ethanol, butanol or isopropanol, and alcohols obtained in particular from the conversion of two inhibitors (furfural and 5-HMF), also under the action of microorganisms.

[0093] The conversion product of C6 sugars can also be the microorganism itself, particularly yeast, when the treatment according to the present invention is carried out under aerobic conditions, since C6 sugars are consumed by the microorganism for its own growth or maintenance.

[0094] Advantageously, the purified liquid portion obtained in step d) or the second liquid portion obtained in step e) according to the method of the present invention contains less than 0.5 g / kg of C6 sugars, preferably no C6 sugars, less than 0.1 g / kg of furfural, in particular no furfural, less than 0.1 g / kg of 5-(hydroxymethyl)furfural, in particular no 5-(hydroxymethyl)furfural.

[0095] According to the invention, it is thus possible to go as far as completely removing all C6 sugars from the original sugar liquor (by consumption or conversion), and the same applies to the two furan derivatives: subject to the constraints of the degree of purity of the purified liquor in C5 sugars, the C6 sugars can thus be removed or kept at a very low content, e.g. at an acceptable content level.

[0096] Advantageously, the purified liquid portion obtained in step d) or the second liquid portion obtained in step e) according to the method of the invention contains the following compounds: - glucose: 0-0.3 g / kg solution per kg weight of solution, - Xylose: 9-91 g / kg solution per kg of solution weight, - arabinose: 1-9 g / kg solution per kg of solution weight, - galactose: 0-0.1 g / kg solution per kg weight of solution, - mannose: 0-0.1 g / kg solution per kg of solution weight, - 5-(hydroxymethyl)furfuryl alcohol: 0.1 to 9 g / kg of solution per kg of solution, - furfuryl alcohol: 0.05 to 3.8 g / kg solution per kg of solution weight, - Ethanol: 0-7g / kg.

[0097] The first purified liquid portion obtained in step d) or the second liquid portion obtained in step e) of the method of the invention may also contain carboxylic acids, such as acetic acid, formic acid or levulinic acid. Advantageously, the first purified liquid portion obtained in step d) or the second liquid portion obtained in step e) of the method of the invention (the "purified liquor" before or after separation from the microorganism by solid / liquid separation) contains less than 8 g / kg of acetic acid, preferably less than 5 g / kg of acetic acid. The purified liquor according to the invention may also contain sugars in oligomeric form, such as arabinoxylan-type compounds, pentose or hexose oligomers. Advantageously, the purified liquor according to the invention contains between 0% and 100% oligomeric sugars relative to the monomeric sugars, preferably between 0.1% and 50%, in particular between 0.1% and 20%, of the monomeric sugars.

[0098] Another subject of the present invention is the use of the above-mentioned purified liquor, thus having a very high content of C5 sugars (relative to its content of C6 sugars), for converting C5 sugars by a chemical route, in particular for converting xylose into xylitol, or for acting as a carbon-based substrate by a biochemical route, in particular for the propagation of yeasts or the induction of fungi for the production of enzymes.

[0099] Xylose is considered a platform molecule, with many possible upgrading pathways (xylitol, monoethylene glycol, propanol, butanol, lactic acid, succinic acid, etc.).

[0100] Another subject of the present invention is any on-board installation for the treatment of lignocellulosic biomass using the biomass treatment method described above.

[0101] Another subject of the present invention is a loading facility for the treatment of lignocellulosic biomass, said loading facility comprising: - a) a unit for the pretreatment of biomass, including a device for digesting biomass, possibly with steam explosion, to obtain pretreated biomass; - b) a first unit for solid / liquid separation (4); which particularly comprises a filtration device; separation of all or part (3a) of the pretreated biomass (3) obtained in unit a) into a pretreated biomass first solid fraction (7) and a first liquid fraction (6); the first liquid fraction (6) comprises, particularly in an aqueous phase, a mixture of compounds comprising C5 sugars having 5 carbons and C6 sugars having 6 carbons, the weight content of C5 sugars being higher than the weight content of C6 sugars; c) a unit for enzymatic hydrolysis (14) of the first solid fraction (7) of the pretreated biomass obtained in step b), obtaining a hydrolysate (15) containing C6 sugars having six carbons in the form of one or more sugars; - d) a unit for purifying said first liquid portion, which is contacted with a first microorganism that consumes essentially only C6 sugars among the sugars of said portion, to obtain a purified liquid portion containing C5 sugars but depleted in C6 sugars, - e) a second unit for solid / liquid separation, which in particular comprises at least one filtration or centrifugation device; separation of the purified liquid fraction obtained in unit d) containing C5 sugars but depleted in C6 sugars; obtaining a second solid fraction containing the first microorganism and a second liquid fraction containing C5 sugars but depleted in C6 sugars.

[0102] Advantageously, according to an alternative embodiment, only a first portion (3a) of the pretreated biomass (3) obtained in the pretreatment unit a) is conveyed to a first unit b) for solid / liquid separation, and a second portion of the pretreated biomass (preferably the entire remainder of the pretreated biomass stream) is conveyed directly to the enzymatic hydrolysis unit c).

[0103] The solid / liquid separation unit b) may, according to a preferred embodiment, comprise a first device for contacting the pretreated lignocellulosic biomass with water, then a second filtration device, and optionally a washing device (either the same device with the two functions can be used or two separate devices can be used).

[0104] Advantageously, in this on-board installation, the second liquid portion obtained in unit e) containing C5 sugars but depleted of C6 sugars contains alcohol, in particular ethanol, obtained by total or partial conversion of the C6 sugars under the action of the first microorganism, said on-board installation comprising a unit g) for separation of said second liquid portion into a third liquid portion rich in sugars and a fourth liquid portion rich in alcohol, said separation unit g) comprising at least one evaporation or stripping device.

[0105] The invention will now be explained in more detail with the aid of non-limiting examples and the following figures. DETAILED DESCRIPTION OF THE INVENTION

[0106] (List of drawings) FIG. 1 is a highly schematic representation of a reactor for carrying out the purification step d) of the treatment method according to the invention, showing the compounds of interest entering and leaving the reactor.

[0107] FIG. 2 is a graph representing on the horizontal axis the duration (in hours) of the purification step d) of the method according to the invention and on the vertical axis the change in concentration (in g / kg reaction medium) of the compounds of the sugar mixture treated according to the invention.

[0108] The abbreviations in Figure 2 have the following meanings: glu: glucose xyl: xylose ara: arabinose gal: galactose man: mannose

[0109] FIG. 3 is a highly schematic representation of a reactor for carrying out the purification step d) of the treatment method according to the invention, showing the compounds of interest entering and leaving the reactor under aerobic conditions so as to allow the growth of microorganisms (yeasts).

[0110] FIG. 4 represents, in block diagram form, a method for the treatment of lignocellulosic biomass with a view to converting the lignocellulosic biomass to alcohol (ethanol) without employing purification according to the present invention.

[0111] FIG. 5 represents, in block diagram form, a method for the treatment of lignocellulosic biomass with a view to converting the lignocellulosic biomass to alcohol (ethanol), modifying the method of FIG. 4 to employ purification according to the present invention.

[0112] FIG. 6 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass into one or more sugars, without employing purification according to the present invention.

[0113] FIG. 7 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass into one or more sugars, modifying the method of FIG. 6 to employ purification in accordance with the present invention.

[0114] FIG. 8 represents, in block diagram form, a method for the treatment of lignocellulosic biomass in terms of partially converting the lignocellulosic biomass into one or more sugars and partially converting it into alcohol (ethanol), without employing purification according to the present invention.

[0115] FIG. 9 represents, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass partially into one or more sugars and partially into alcohol (ethanol), modifying the method of FIG. 8 to employ purification according to the present invention.

[0116] FIG. 10 is a graph showing time (expressed in hours) on the horizontal axis and concentrations of furfural and 5-HMF (g / L) along the left vertical axis and ethanol (g / L) along the right vertical axis during simultaneous enzymatic hydrolysis and fermentation (SSCF) of pretreated biomass with purification according to the present invention.

[0117] FIG. 11 is a graph representing on the horizontal axis the concentration of ethanol (% by weight) in the aqueous reaction medium obtained at the end of the enzymatic hydrolysis and fermentation process of the pretreated biomass, on the vertical axis the energy consumption (MJ per kg of ethanol) and on the vertical axis the energy consumption (MJ per kg of ethanol) for separating the ethanol from the aqueous phase by distillation starting from said aqueous reaction medium.

[0118] 1 and 3 are highly schematic in order to make them easier to understand, and the reactors represented are therefore symbolic representations, not to scale, and do not presume their size and shape, nor do they show all the facilities necessary for their operation.

[0119] 4-9 represent block diagrams of the present methods, also highly simplified to make them easier to understand. They do not necessarily represent all steps / equipment required for the described methods, but rather highlight the most important steps / equipment / flows in the context of the present invention.

[0120] The reference numbers retain the same meaning from one figure to the next.

[0121] (Description of the embodiment) The present invention incorporates in a process for the conversion of lignocellulosic type biomass into one or more sugars or alcohols a treatment for the biochemical purification of sugar liquors containing C5 sugars and a lower content / proportion of C6 sugars, in order to reduce the content of C6 sugars in these liquors, and in fact even to eliminate C6 sugars, thereby obtaining a liquor "purified" with C5 sugars, from which advantages are obtained, in particular, for improving the yield of the conversion of biomass (more particularly into alcohol) or for obtaining sugars of higher quality / purity.

[0122] Specifically, in biomass processing methods, the present invention relates to methods that involve pretreatment of biomass prior to enzymatic hydrolysis, which pretreatment results in the production of a sugar liquor containing a mixture of C5 and C6 sugars.

[0123] An explanation is therefore given as follows: - First, with the help of Figures 1-3, the stage of purification of sugar liquor, - Then, with the aid of the following diagram, a method for the conversion of lignocellulosic biomass; producing these sugar liquors and incorporating this purification step to obtain benefits therefrom.

[0124] (Sugar liquor purification stage) This biochemical refining process involves contacting a sugar liquor containing C5 and C6 sugars (this liquor is obtained by processing lignocellulosic biomass-based materials and contains mainly C5 sugars) with microorganisms that selectively consume C6 sugars: the C5 sugars remain unmodified and substantially intact in the liquor, while the C6 sugars are gradually consumed by the microorganisms for their own growth and / or converted into other compounds, for example in the form of alcohol in the case of fermentation.

[0125] For example, the naturally occurring yeast Saccharomyces cerevisiae grows under aerobic conditions by consuming primarily C6 sugars, and produces ethanol under anaerobic conditions by consuming primarily C6 sugars.

[0126] The operating conditions of the treatment are adapted depending on the initial content of C6 sugars and the final content of C6 sugars that is acceptable (no C6 sugars or a content below a given value): temperature, pH, duration, aeration, choice and concentration of microorganisms.

[0127] (Example of purification of sugar liquor) (Example 1 (Comparative Example)) The starting point is an initial sugar liquor L0 obtained from biomass pretreated by acid impregnation of the biomass followed by steam explosion, according to the teachings of the above-mentioned patent FR 3 083 126. Reference will be made to this patent for further details.

[0128] Briefly, this pretreatment involves the impregnation of lignocellulosic biomass with an acidic liquor, followed by steam explosion of the impregnated biomass. At least a portion of the pretreated biomass undergoes a liquid / solid separation operation at the end of the pretreatment step, which includes contacting the pretreated lignocellulosic biomass with water, filtering, and optionally washing. To obtain liquor L0, 550 kg of the pretreated biomass is mixed with 1010 kg of water, then filtered and compressed. After filtration and compression, 885 kg of liquor L0 (also known as hydrolysate C5) is obtained. Due to the acidic conditions of the pretreatment, the pH of this liquor is 2.

[0129] The concentrations of the compounds of interest in this liquor L0 are given in Table 1 below, the concentrations being expressed in g per kg of liquor weight. It should be noted that the composition may contain very low contents of other impurities, for example of the acid or (inorganic) salt type, whose analysis was not attempted.

[0130] [Table 1]

[0131] It can be seen that 82% of the sugars in liquor L0 are C5 sugars, 18% are C6 sugars, and that 5-HMF and furfural, which are known to inhibit biochemical reactions that may subsequently occur on sugars (e.g., ethanol fermentation by yeast), are also present in much lower concentrations than the sugars.

[0132] The sugar liquor obtained from pretreated biomass generally contains a much higher amount of C5 sugars than C6 sugars, and in order to upgrade them, there is a need to separate the C5 sugars from the C6 sugars. In fact, currently available techniques (especially membrane filtration) are not very satisfactory because they are complex to implement and generally do not allow the desired level of C5 sugar purity to be achieved in the separated liquor.

[0133] For example, in the publication "Removal of Furfural and HMF from Monosaccharides by Nanofiltration and Reverse Osmosis Membranes" by Tielin Wang et al. (Journal of the Energy Institute, 91(2018), 473-480), it is concluded that the most effective membranes for separating 5-HMF and furfural from sugar liquor are Desal-5 DK and Alfa Laval-NF membranes (less than 2% retention for 5-HMF and furfural), but that they result in excessive sugar losses (2%-8% for glucose and 10%-20% for xylose).

[0134] A publication by Kuang Zhang et al., "Removal of the Fermentation Inhibitor, Furfural, Using Activated Carbon in Cellulosic-Ethanol Production" (Industrial & Engineering Chemistry Research, 2011, 50, 14055-14060), concludes, in part, that Norit_1240, a commercially available activated carbon from Norit, can selectively reduce the furfural concentration of a model sugar liquor solution from 4 g / L to 0 g / L, but does not selectively separate C6 sugars (in this example, glucose) from C5 sugars (in this example, xylose).

[0135] Example 2 (according to the present invention) The starting point is the sugar liquor L0 defined in Example 1. The fermentation of liquor L is carried out with the yeast Saccharomyces cerevisiae, a microorganism in its native version, which is genetically unmodified and exhibits the distinctive feature of preferentially consuming C6 sugars but not C5 sugars.

[0136] The yeast was inoculated at 0.5 g yeast per kg weight of solution, i.e., 60 g yeast per kg weight of C6 sugars. The experiment was carried out in a bioreactor at 33°C and pH 5.3 for 6 hours. The process was carried out by fermentation under anaerobic conditions to maximize the production of ethanol from the C6 sugars and no biomass was produced. The reaction can be carried out in batch mode, fed-batch mode, or continuous mode. They can then be separated and processed / upgraded separately.

[0137] The reactions resulting from the action of yeast are shown diagrammatically in Figure 1, which represents a bioreactor (1) with the following inputs: (2): yeast, (3): a base, for example of the NH4OH, KOH or NaOH type (to regulate the pH and maintain the reaction medium under the conditions necessary for the activity of the selected yeast); (4): Nutrients for yeast, (5): Liquor L0; containing C5 sugar (51), C6 sugar (52), 5-HMF (53), and furfural (54) in the aqueous phase. The exit products are as follows: (6): CO2 emissions in the gas phase; vented at the top of the bioreactor; evidence of yeast activity; (5'): Extraction of liquor L1; obtained from liquor L0 after the action of yeast on liquor L0, containing yeast (2), C5 sugar (51), 5-(hydroxymethyl)furfuryl alcohol (55), furfuryl alcohol (56), ethanol (57), and yeast (2).

[0138] The quantities of inputs (besides the concentrations indicated above) are specified as follows: In a stirred vessel, 985 kg of liquor L0 are mixed with: - 0.4 kg of urea (nitrogen requirement), - 0.5 kg of dried S. cerevisiae yeast, - 5 kg of yeast extract (nutrients), 9.1 kg of a 50% by weight KOH solution; the pH is adjusted to 5.3.

[0139] The concentrations of the compounds of interest in the mixture in the initial state are given in Table 2 below, the concentrations being expressed in g per kg of liquor weight. It should be noted that the composition may contain very low contents of other impurities of salt or acid type for which no analysis has been attempted.

[0140] [Table 2]

[0141] At the start of the reaction, the reaction medium contains: - 8.3 kg of C6 sugars (glucose + galactose + mannose), - 37.3 kg of C5 sugars (xylose + arabinose), - 0.4 kg of 5-HMF, - 0.2 kg of furfural.

[0142] The manner in which the fermentation is carried out is described in detail below.

[0143] Fermentation was continued for 6 hours, showing complete consumption of glucose, galactose, and mannose (C6 sugars, dashed lines). Arabinose and xylose (C5 sugars) were not consumed. Furfural and 5-HMF were consumed by the yeast, which detoxified the medium, producing furfuryl alcohol and 5-(hydroxymethyl)furfuryl alcohol (also known as 2,5-bis(hydroxymethyl)furan), which do not inhibit the yeast.

[0144] It was thus found that the initial liquor L0, composed of 45.6 kg of monomeric sugars (18% C6 sugars / 82% C5 sugars), could be purified in a few hours to give liquor L1, composed of 37.3 kg of monomeric sugars (0% C6 sugars and 100% C5 sugars).

[0145] Under anaerobic conditions at 33° C. and pH 5.3, yeast consumes C6 sugars (producing mainly ethanol) and consumes inhibitors (5-HMF and furfural) within 6 hours.

[0146] At the end of the reaction, the medium contains a liquor L1, the composition of which is given in Table 2 below, the concentration being expressed in g per kg of weight of medium.

[0147] [Table 3]

[0148] So after 6 hours of reaction we have: - 0 kg of C6 sugars (glucose + galactose + mannose); i.e., the consumption of C6 sugars is 100%; - 37.3 kg of C5 sugars (xylose + arabinose); i.e., the consumption of C5 sugars is only 1.6%. - 0 kg of 5-HMF; i.e., 5-HMF consumption is 100%. - 0 kg of furfural; i.e., furfural consumption is 100%; - 0.4 kg of 5-(hydroxymethyl)furfuryl alcohol, - 0.2 kg of furfuryl alcohol, - 2.9 kg of ethanol; i.e., the yield of ethanol / C6 sugars is 0.35 kg ethanol / kg C6 sugars .

[0149] The data in Table 2 and the graph in Figure 2 confirm that the yeast has no effect on the C5 sugars, whose content remains constant. On the other hand, the yeast consumes all of the C6 sugars and both of the inhibitors, converting them at least in part to alcohol (it is possible for the yeast to consume another part for its own growth). Treatment with yeast therefore gives excellent results: the liquor purified in C5 sugars no longer contains any C6 sugars, and the inhibitors are simultaneously and equally completely removed.

[0150] The fact that at least a portion of the C6 sugars were converted to ethanol is also highly advantageous because ethanol is a highly upgradeable product that can be produced in methods of processing lignocellulosic biomass.

[0151] From the data in the graph in Figure 2, it can also be observed that the duration of fermentation for completely consumed C6 sugars is 6 hours, which is a reasonable period and can be further shortened, especially by varying the amount of yeast added, or a reduced but non-zero content of C6 sugars is acceptable. Experiments have thus been successfully carried out with much shorter fermentation times, especially 30 minutes to 2 hours, for example, with a duration of about 1 hour.

[0152] FIG. 3 represents an alternative embodiment to FIG. 1: starting from the same liquor L0 as in FIG. 1 and Example 1, this time the fermentation of liquor L0 under aerobic conditions is carried out with the same microorganism as in Example 2, the yeast Saccharomyces cerevisiae, in its native version, which is genetically unmodified and which exhibits the distinctive feature of preferentially consuming C6 sugars but not C5 sugars.

[0153] The reaction obtained from the action of yeast is shown diagrammatically in FIG. 3, which represents a bioreactor (1) with the following inputs: (2): yeast, (3) a base, for example of the NH4OH, KOH or NaOH type (to regulate the pH and maintain the reaction medium under the conditions necessary for the activity of the selected yeast); (4): Nutrients for yeast, (5): Liquor L0; containing C5 sugars (51), C6 sugars (52), 5-HMF (53), furfural (54), and acetic acid (60) in the aqueous phase, and the outlet products are as follows: (6): CO2 emissions in the gas phase; vented at the top of the bioreactor; evidence of yeast activity; (5'): Extraction of liquor L1; obtained from liquor L0 after the action of yeast on liquor L0, containing propagated yeast (2), C5 sugar (51), 5-(hydroxymethyl)furfuryl alcohol (55) and furfuryl alcohol (56); (7): Supply of air under aerobic conditions.

[0154] It was therefore confirmed that the yeast had no effect on the C5 sugars, whose content remained constant. On the other hand, the yeast consumed all of the C6 sugars and both of the inhibitors (5-HMF and furfural), as well as acetic acid, converting it at least partially into alcohol (the yeast can consume another portion for its own growth). Treatment with yeast therefore gave excellent results: the liquor purified in C5 sugars no longer contained any C6 sugars, and the inhibitors were at the same time completely removed, while allowing the yeast to grow.

[0155] In conclusion, with regard to this purification step, it appears that success can be achieved in obtaining a liquor containing the type of sugars (C5 sugars) that one wishes to retain in purifying a sugar mixture, by selecting a selective microorganism that can also optionally consume / remove unwanted compounds / impurities in the sugar mixture, particularly inhibitors of biochemical reactions, such as furan derivatives. This can be easily achieved in a single step of aerobic fermentation, and the results are surprising, in some cases completely removing the compounds that one wishes to remove from the sugar liquor.

[0156] It is thereby possible to obtain a very pure C5 sugar liquor, with no or a very low content of C6 sugars, and with a purity that has not previously been possible to achieve by separation methods of the type of selective adsorption on zeolites, such as those described in the patents cited in the introduction to this patent application.

[0157] Furthermore, this is highly advantageous in that, rather than actually separating the two types of sugars, a very pure type of sugar is obtained and the other sugar (C6 sugar) is converted into an upgradeable product, such as ethanol. The combination of C5 sugars obtained by the method according to the present invention with the ethanol obtained from the conversion of C6 sugars offers several possibilities, particularly depending on the envisaged upgrading route and the ratio between the two types of sugars in the initial sugar liquor. It is therefore possible to subsequently separate the C5 sugars from the ethanol and obtain very pure C5 sugars on the one hand and ethanol on the other, which can be upgraded / used separately. It is also possible to keep them together for common upgrading. It is also possible to maintain a low content of ethanol together with the C5 sugars, benefiting from the antiseptic / antibacterial effect of alcohol on the sugars.

[0158] A method for the conversion of lignocellulosic biomass incorporating the steps of producing a sugar liquor and purifying said sugar liquor as described above. Three conversion methods are described below: - Method A: Conversion to alcohol (ethanol), - Method B: conversion to one or more sugars, and - "Hybrid" method C, which targets obtaining both an alcohol and one or more sugars.

[0159] Method A: Conversion of Biomass to Ethanol This is illustrated with the help of FIGS.

[0160] Figure 4 describes the conversion process without the purification steps described above. The reference symbols in the figure represent the following streams / devices / steps: (1): Biomass (2): Conditioning and pre-treatment (3): Pretreated biomass (3a): Pretreated biomass into the filtration tool (3b): Pretreated biomass for enzymatic hydrolysis (optional) (4): solid / liquid separation (e.g., belt filter or filter press); extracting the sugar liquor, with an optional washing step; (5): Water as a contact and / or cleaning fluid (6): Sugar liquor containing mainly C5 sugars (6a): Sugar liquor containing mainly C5 sugars for enzyme production (6b): Sugar liquor containing mainly C5 sugars for yeast propagation (7): Pretreated and washed biomass (8): Reactor for enzyme production (9): Fungal inoculation for enzyme production (e.g., Trichoderma reesei) (10): Enzyme cocktail (a mixture of one or more enzymes, particularly containing cellulase, β-glucosidase, xylanase, etc.) (11): Reactor for yeast propagation (12):Yeast (13): Yeast proliferation (14): Enzymatic hydrolysis reactor (15): Hydrolyzate (16): Fermentation reactor (17): Fermented must (wine) (18): Solid / liquid separation (e.g., filter press); with an optional step of washing the solid residue with a solvent (e.g., water). (19): Solid residue (mainly composed of lignin) (20): The liquid product of filtration, in this example, filtered wine (21): Separation of ethanol and water (e.g., distillation column, sieve) (22): Liquid residue (Venus) (23): Purified ethanol Throughout the text, and in particular in the description of the figures, the term reactor can be understood as a unit containing at least one reactor, without the necessity of there being only one single one of them, which is the same for all other devices, in particular filtration, solid / liquid separation, distillation columns and other types of tools (for the sake of simplicity).

[0161] The sequence of events in the method according to FIG. 4 is as follows: biomass (1) undergoes conditioning / pretreatment in unit (2) (optional mechanical comminution, dust removal, possible removal of metal parts, in this case, for example, impregnation with acidic liquor and cooking / steam explosion of pretreated biomass (3)). A portion of this pretreated biomass, stream (3a), exits a solid / liquid filtration tool (4), which also receives water (5) as contact and / or wash water. As a first step, the pretreated biomass is contacted with water to improve its filterability. The mixture is then filtered on a belt filter and washed with water. Another portion of the pretreated biomass, stream (3b), can be sent to an enzymatic hydrolysis reactor (14). This reactor (14) is also fed with stream (7), which is the solids obtained from the filtration in unit (4) and is therefore the washed solids pretreated biomass.

[0162] It should be noted that throughout this text, "solids" is opposed to "liquids," but it should be understood that any solids can still contain a certain percentage of liquid (and vice versa). This percentage of liquid in a solid can be assessed by measuring its dry matter (DM) content, which is measured according to standard ASTM E1756 - 08 (2015), "Standard Test Method for Determination of Total Solids in Biomass."

[0163] At the outlet of the reactor (14), a hydrolysate (sugar) stream (15) is available, which is then fed to a fermentation reactor (16) where it is converted into ethanol; at the outlet of the fermentation reactor (16), a fermented must is obtained. The fermented must, also known as wine, contains ethanol in water. A solid / liquid separation tool (18) separates the solid woody residue (19) from the liquid portion (20), the filtered wine. This filtered wine is conveyed to a separation tool (21) (distillation column) to obtain ethanol (23) and an aqueous liquid residue (known as vinasse).

[0164] At the outlet of the separation tool (4), the liquid portion (6) is an aqueous sugar liquor containing mainly C5 sugars. All or part of this portion, stream (6a), can be passed to a reactor (8) for the production of enzymes, resulting in an enzyme cocktail (10), which is then fed to an enzymatic hydrolysis reactor (14); this stream can then serve as a substrate for the growth and / or production of Trichoderma reesei-type microorganisms that produce this mixture of enzymes (10). All or part (6b) of this stream (6) can also be passed to a reactor (11) for the propagation of yeast (13), which is then fed to a fermentation reactor (16). Here again, the sugar liquor (6b) can serve as a propagation substrate for yeast, such as Saccharomyces, particularly Saccharomyces cerevisiae.

[0165] It should further be noted that the enzymatic hydrolysis operation (14) is preferably carried out in two stages: fed-batch liquefaction of the substrate and subsequent enzymatic hydrolysis in batch mode (possibly in two reactors in series or in the same reactor), working at the highest possible DM content and converting lignocellulosic substrates that may have complex rheology. Neutralization of the medium can be carried out before the enzymatic hydrolysis, for example by adding a basic solution in cases where the pretreatment is carried out under acidic conditions.

[0166] It should also be noted that enzymatic hydrolysis and fermentation can be carried out simultaneously (SSCF). If they are carried out one after the other, adjustment of the pH of the medium between units (14) and (16) can be performed.

[0167] It should also be noted that enzyme production and / or yeast propagation can take place on the site of biomass processing, as depicted in Figure 4. However, one or the other can also be performed off-site: ready-to-use enzymes or yeast can therefore be brought on-site. This explains why, depending on the choice made in this regard, the stream can be split into two streams (6a), (6b) (the distribution between the two streams can be equal or unequal, depending on the requirements) or can be used only for yeast propagation or only for enzyme production.

[0168] FIG. 5 represents the method of FIG. 4 but with modifications according to the invention and with the following additional reference numerals: (6a'): Sugar liquor containing only C5 sugars for enzyme production (6b'): Sugar liquor containing only C5 sugars for yeast propagation (6c'): Sugar liquor containing only C5 sugars for fermentation (24): Biochemical purification reactor (25): Yeast that consumes C6 sugars (26): Sugar liquor containing only C5 sugars, yeast, and ethanol (27): Solid / liquid separation (e.g., centrifuges, filters, or ultrafiltration units) (28): Recycled yeast that consumes C6 sugars (29): Sugar liquor containing only C5 sugars and optional ethanol (30): Separation of ethanol and C5 sugar liquor (e.g., stripper or evaporator); optional step (31): Stripped ethanol stream (32): Sugar liquor containing only C5 sugars

[0169] It should be noted that in Figure 5, pretreated biomass stream (3) is split into two streams: stream (3a) which exits tool (4) and stream (3b) which exits directly to enzymatic hydrolysis reactor (14). However, here, as in the case of the processes depicted in Figures 7 and 9 below, the relative proportions between streams (3a) and (3b) are variable.

[0170] It is also envisaged, according to one embodiment of the invention, that after the initial passage of the entire pretreated biomass stream (3) through the tool (4), the solid portion is separated and sent to the hydrolysis reactor (14): there is only one stream (3) / (3a) entering the tool (4) in its entirety, and no stream (3b): the reactor (14) is no longer fed with stream (3b). This embodiment is more particularly recommended for the case of the production of sugars (FIG. 7) than for the case of the production of alcohols (FIG. 5) or of sugars and alcohols (FIG. 9).

[0171] This scenario without stream (3b) therefore also falls within the scope of the present invention, whether it relates to a process for the production of alcohols, sugars or alcohol / sugar hybrids.

[0172] The ethanol (31)-rich stream can be introduced, separately or in admixture with the filtered wine, at the inlet of the section for ethanol and water separation (21) or into the fermenter (16). The operating conditions of the stripper can be adjusted to produce a C5 sugar-rich stream and an ethanol-rich stream.

[0173] The resulting ethanol (31) can also be recycled to the pretreatment stage (2) or to the stage of filtration and washing of the biomass (4).

[0174] The sugar liquor stream (32), containing only C5 sugars, can be used for enzyme production, yeast propagation or as a substrate in fermentation.

[0175] In this example, stream (6) contains more C5 sugars than C6 sugars and is purified in the following way: it is introduced into a biochemical purification reactor (24), which may include a preliminary neutralization step of the liquor (6), for example with a basic solution of sodium or potassium hydroxide, in the case where the biomass has been pretreated under acidic conditions. The reactor (24) is also fed with microorganisms (25), particularly yeast, which exhibit the distinctive feature of consuming only C6 sugars. At the outlet of the reactor (24), a sugar liquor stream (26), depleted in C6 sugars, is available. A solid / liquid separation tool (27) allows the recovery of solids (28), which include insoluble yeast, which can be recycled in whole or in part to the reactor (24). The separated liquid portion (29) is therefore a C5 sugar liquor, free of microorganisms, low in or no C6 sugars, and possibly containing ethanol, the product of the conversion of the C6 sugars by yeast. This portion (29) is sent to a separation tool (30), which separates the sugars from the ethanol, if present in a measurable content in portion (29). The separated sugar liquor (32) can then be used in different ways: all or a portion in the form of stream (6a') can be sent to enzyme production (8), all or a portion in the form of stream (6b') can be sent to yeast propagation (11) for the fermentation of biomass (as in the method of FIG. 4), and all or a portion in the form of stream (6c') can be sent to fermentation reactor (16). Ethanol stream (31) can be, for a part, sent to fermentation reactor (16) (either during fermentation or added to the stream exiting reactor (16)) or can alternatively be added to stream (20) at the inlet of ethanol separation device (21). The relative proportions of streams (6a'), (6b') and (6c') can be adjusted, especially if yeast propagation and / or enzyme production is performed in situ or ex situ (in which case streams (6a') and / or (6b') are not present).In all cases, an additional proportion of ethanol (6c') is added to the ethanol product leaving the fermenter (16) at or downstream of the fermenter (16) (the terms "upstream" and "downstream" are understood in this text according to the general direction of the biomass through the on-board installation).

[0176] By incorporating biochemical purification of the mixture of sugars (6), it is ultimately possible to increase the amount of ethanol produced for a given amount of biomass and therefore its conversion yield.

[0177] (Method B: Conversion of biomass to sugars) This is illustrated by FIGS.

[0178] Figure 6 shows a process without purification according to the present invention. It is important in this example that there is no fermentation to stop the biomass conversion at the stage of sugar production. In comparison with Figure 4, sugar liquor (20), consisting mainly of C6 sugars, is therefore the first end product to be upgraded; stream (6a) can be used to act as a substrate for enzyme growth and / or production in reactor (8) (if the enzyme is generated in situ); stream (6b) is the second end product to be upgraded, a liquor of mainly C5 sugars, but still containing C6 sugars.

[0179] Figure 7 illustrates a process incorporating the purification of sugar liquor according to the present invention into the process of Figure 6: reactors / tools (24), (27), and (30) of the process of Figure 5 are operated in the same manner, except that they are reconstituted. In this example, sugar liquor (6), containing primarily C5 sugars, is purified after yeast purification and separation to give liquor (32), which is split in part into C5 sugar stream (6a') to serve as a substrate for enzyme growth / production in reactor (8) and, if enzyme production occurs in situ, split in whole or in part into stream (6d'), which is purified C5 sugar liquor, which can be upgraded as is. This C5 sugar liquor, designated (6d'), is highly pure, purer than the liquor of stream (6b) of the process of Figure 6; it can therefore be used as is.

[0180] "Hybrid" Method C: Conversion of Biomass to Ethanol and One or More Sugars This is illustrated by FIGS.

[0181] The method according to Figure 8 does not use the purification according to the present invention, which is important in this example to produce sugars and ethanol in parallel. In comparison to the method of Figure 4, where the focus is on producing ethanol, in this example both of the following are available: - production of ethanol; this is the stream (23) obtained in the same way as in the process of FIG. 4, and - Production of mainly C5 sugars: this is stream (6d) obtained from stream (6) as in the process in Figure 4. This stream (6d) can be part of stream (6) or the whole of this stream (if the enzymes are produced ex situ and / or the yeasts are propagated ex situ, or if the use of other external sources is preferred for the growth / propagation of the microorganisms / enzyme production).

[0182] The process of Figure 9 incorporates the process of Figure 8 with a refinement according to the invention: the reactors / tools (24), (27), and (30) described above are re-entered, resulting in the production of a C5 sugar refined stream (32) and a stream (6d') which constitutes all or part of the liquor (32) and constitutes a C5 sugar refined sugar liquor, and which can be directly upgraded in parallel with the production of ethanol (23). The ethanol stream (31) obtained from the separation (30) can be re-injected into the fermenter (16), as in the case of the process of Figure 5, or downstream of the fermenter (16), either as a mixture with the stream leaving the fermenter (16), or upstream of the device (21) for separating ethanol from water (distillation column). A doubly beneficial situation thus exists in this example: both an improved ethanol yield and an improved quality / purity of the C5 sugar liquor.

[0183] From these various embodiments of the invention, all its advantages can be seen as follows:

[0184] A lignocellulosic sugar hydrolysate consisting of a mixture of sugars having 6 and 5 carbon atoms is purified to give a hydrolysate containing only sugars having 5 carbon atoms.

[0185] The use of this "pure" mixture of C5 sugars is beneficial for many chemical (catalytic conversion of xylose to xylitol) or biochemical (e.g., propagation of yeast, induction of fungi to produce enzymes) conversion applications.

[0186] Complex and expensive physical separation of C5 and C6 sugars (eg, by nanofiltration, membranes, ion exchange resins, zeolites, etc.) is therefore avoided.

[0187] A lignocellulosic sugar hydrolysate consisting of a mixture of sugars having 6 and 5 carbon atoms is purified to give a hydrolysate containing only sugars having 5 carbon atoms, but also containing some compounds described as inhibitors, such as furfural or 5-(hydroxymethyl)furfural (5-HMF); these two compounds are inhibitors of, for example, fermentation reactions.

[0188] In the case of using the yeast S. cerevisiae to carry out the biochemical purification of a mixture of sugars under anaerobic conditions, consumption of C6 sugars produces ethanol, which can be recovered and incorporated into biomass conversion processes.

[0189] In the case where the yeast S. cerevisiae is used to carry out the biochemical purification of a sugar mixture under aerobic conditions, consumption of C6 sugars results in the generation of additional microorganisms (yeast growth), which can be recovered and incorporated into the process for biomass conversion.

[0190] Under aerobic conditions, the yeast S. cerevisiae is also able to consume acetic acid from the medium, which is also an inhibitor of the fermentation reaction or the growth of the fungus T. reesei.

[0191] Biochemical purification is carried out on clear media; it is easy to separate the microorganisms by solid / liquid separation, e.g., centrifugation or ultrafiltration membranes, and remove and recycle the microorganisms.

[0192] The resulting ethanol can advantageously be used in a process for the production of 2G sugars: A portion of the ethanol can be used in pretreatment (2), - a portion of the ethanol can additionally or alternatively be used as a washing fluid for the filtration stage (4), - Part of the ethanol can additionally or instead be used as a fluid for washing the remaining unconverted solid residue, which makes it possible to increase the NCV (acronym: net calorific value) of the solid residue, which can then be incinerated in a boiler for cogeneration to produce electricity and steam, or to extract the soluble fraction therefrom for better upgrading (fuel-based or bioproducts); A portion of the ethanol can additionally or alternatively be incorporated into the reaction medium of the enzymatic hydrolysis reactor (14), thereby making it possible to limit the risk of contamination.

[0193] The refined sugar and ethanol separation step (30) is carried out to concentrate the sugars, for example to a content of 50 g / kg, which is even more advantageous since this sugar liquor is used for enzyme production and yeast propagation. The refinement step is therefore fully integrated into the production of ethanol and / or 2G sugars.

[0194] Examples using biomass conversion methods Example 3 Conforming to Method A for Conversion of Biomass to Ethanol In comparison with the method of FIG. 4, it is done according to the method of FIG.

[0195] In this example, the reaction is carried out in an SSCF, with step (14) (enzymatic hydrolysis) and step (16) (ethanol fermentation) taking place in one and the same reactor, at a temperature of 33°C and a pH of 5.3 under anaerobic conditions. In this example according to the invention, step (30) of separating ethanol from the C5 liquor is not carried out. In this scheme according to the invention, the purification in step (24) makes it possible to reduce the concentration of 5-HMF present at the start of the reaction (from 2.80 g / L to 0.56 g / L) and the concentration of furfural (from 1.60 g / L to 0.32 g / L). This purification also produces ethanol from C6 sugars (2.84 g / L).

[0196] These compounds are inhibitors for the yeast Saccharomyces cerevisiae, so ethanol production undergoes a delay, or even inhibition, of fermentation activity in the method of Figure 4 without sugar purification: specifically, the fermentation reaction time is lengthened or the yeast may not even be fermented.

[0197] After 144 hours of reaction, the ethanol titer of the ethanol produced according to the method of FIG. 5 in accordance with the present invention is 52.4 g / L compared to 49.3 g / L for the method of FIG.

[0198] The difference in ethanol titer is even greater before 50 hours of reaction. For example, after 42 hours of fermentation, the present invention makes it possible to go from 33.8 g / L to 45.9 g / L of ethanol. This can be observed from the graph in Figure 10, which represents the change in concentration (g / L) of different compounds during the reaction of SSCF (simultaneous enzymatic hydrolysis and fermentation): - Curve C10: Change in 5-HMF content by applying the method of Figure 4 (without purification) Curve C11: Change in 5-HMF content by applying the method of FIG. 5 (with purification) - Curve C20: Change in furfural content by applying the method of Figure 4 (without purification) - Curve C21: Change in furfural content by applying the method of Figure 5 (with purification) - Curve C30: Change in ethanol content by applying the method of Figure 4 (without purification) - Curve C31: Change in ethanol content by applying the method of Figure 5 (with purification).

[0199] From this graph it can be seen that at time t=0, the purification of C5 sugars makes it possible to reduce the load of inhibitors: furfural, 5-HMF, and after 50 hours of reaction, the ethanol productivity is much higher with the purification according to the invention. At the end of the reaction, the amount of ethanol produced is greater.

[0200] Furthermore, this increase in ethanol concentration makes it possible to reduce the energy consumption required for the distillation step in column (21) that separates the ethanol from the water.

[0201] If a reaction time of 144 hours is chosen, the energy gain is 4.5%. If a reaction time of 42 hours is chosen, the energy gain is 21%.

[0202] This is shown in FIG. 11, which represents the energy required (MJ) per kg of ethanol present in the feed of a distillation column depending on the ethanol concentration of the solution to be separated, recovering a rich stream at the top of the distillation with 94% by weight of ethanol and a stream containing 0.02% by weight of ethanol at the bottom of the column, and is taken from the publication by Vane, LM, "Separation Technologies for the Recovery and Dehydration of Alcohols from Fermentation Broths", Biofuels, Bioproducts and Biorefining, Society of Chemical Industry, London, UK, 2(6):553-588 (2008). [Brief explanation of the drawings]

[0203] [Figure 1] 1 is a highly schematic representation of a reactor for carrying out purification step d) of the treatment method according to the invention, showing the compounds of interest entering and leaving the reactor. [Figure 2]1 is a graph representing on the horizontal axis the duration (in hours) of the purification step d) of the method according to the invention and on the vertical axis the change in concentration (in g / kg reaction medium) of the compounds of the sugar mixture treated according to the invention. [Figure 3] 1 is a highly schematic representation of a reactor for carrying out the purification step d) of the treatment method according to the invention, showing the compounds of interest entering and leaving the reactor under aerobic conditions so as to allow the growth of microorganisms (yeasts). [Figure 4] 1 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with a view to converting the lignocellulosic biomass into alcohol (ethanol) without employing purification according to the present invention. [Figure 5] 1 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with a view to converting the lignocellulosic biomass to alcohol (ethanol), modified from the method of FIG. 4 to employ purification according to the present invention. [Figure 6] 1 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass into one or more sugars, without employing purification according to the present invention. [Figure 7] 6 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass into one or more sugars, modified from the method of FIG. 6 to employ purification in accordance with the present invention. [Figure 8] 1 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass in terms of converting the lignocellulosic biomass partially into one or more sugars and partially into alcohol (ethanol), without employing purification according to the present invention. [Figure 9] 10 depicts, in block diagram form, a method for the treatment of lignocellulosic biomass with respect to converting the lignocellulosic biomass partially into one or more sugars and partially into alcohol (ethanol), modified from the method of FIG. 8 to employ purification according to the present invention. [Figure 10]1 is a graph depicting time (expressed in hours) on the horizontal axis and concentrations of furfural and 5-HMF (g / L) along the left vertical axis and ethanol (g / L) along the right vertical axis during simultaneous enzymatic hydrolysis and fermentation (SSCF) of pretreated biomass with purification according to the present invention. [Figure 11] 1 is a graph representing on the horizontal axis the concentration of ethanol (% by weight) of the aqueous reaction medium obtained at the end of the enzymatic hydrolysis and fermentation process of the pretreated biomass, on the vertical axis the energy consumption (MJ per kg weight of ethanol) and on the vertical axis the energy consumption (MJ per kg weight of ethanol) for separating the ethanol from the aqueous phase by distillation starting from said aqueous reaction medium.

Claims

1. 1. A method for the treatment of lignocellulosic biomass, comprising the steps of: a) a stage of pretreatment of the biomass (2), which comprises the digestion of the biomass, possibly followed by steam explosion, to obtain a pretreated biomass (3); b) a first stage of solid / liquid separation: separation of all or part (3a) of the pretreated biomass (3) obtained in stage a) into a first solid fraction (7) of the pretreated biomass and a first liquid fraction (6), the first liquid fraction (6) comprising, in particular in an aqueous phase, a mixture of compounds comprising C5 sugars having 5 carbons and C6 sugars having 6 carbons, the weight content of C5 sugars being higher than the weight content of C6 sugars, c) a step of enzymatic hydrolysis (14) of the first solid fraction (7) of pretreated biomass obtained in step b), obtaining a hydrolysate (15) in the form of one or more sugars, including C6 sugars having six carbons, d) a step of purification (24) of the first liquid portion obtained in step b), by contacting the first liquid portion (6) with a first microorganism, which consumes essentially only C6 sugars among the sugars of said portion, to obtain a purified liquid portion (26) containing C5 sugars but depleted in C6 sugars, e) a second stage of solid / liquid separation (27); separation of the purified liquid fraction (26) obtained in stage d) containing C5 sugars but depleted in C6 sugars; obtaining a second solid fraction (28) containing the first microorganism and a second liquid fraction (29) containing C5 sugars but depleted in C6 sugars.

2. 2. The method according to claim 1, characterized in that only a first portion (3a) of the pretreated biomass (3) obtained in step a) is conveyed to a first stage b) of solid / liquid separation, and a second portion (3b) of the pretreated biomass (3) is conveyed directly to an enzymatic hydrolysis stage c).

3. 3. The method according to claim 1 or 2, characterized in that it also comprises a step f) of fermentation (16) by a third microorganism of the hydrolysate in the form of one or more sugars obtained in step c), in order to obtain a fermented biomass (17) containing at least one alcohol, in particular ethanol.

4. 4. The method according to claim 3, wherein the enzymatic hydrolysis step c) and the fermentation step f) are carried out simultaneously.

5. 5. The method according to claim 1, wherein at least a portion of the second solid fraction (28) containing the first microorganism obtained in step e) is recycled to step d) of the purification (24).

6. the second liquid portion (29) obtained in step e) containing C5 sugars but depleted in C6 sugars contains alcohol, in particular ethanol, obtained by total or partial conversion of C6 sugars under the action of the first microorganism; and 6. The method according to claim 1, wherein in step g) the second liquid portion is separated (30) into a third liquid portion rich in sugars (32) and a fourth liquid portion rich in alcohols (31), in particular by evaporation or stripping.

7. 7. The method according to claims 3 and 6, characterized in that all or part of the fourth liquid part (31) containing alcohol obtained in step g) is sent to step f) of the fermentation (16) or all or part of said fourth liquid part is mixed with the fermented biomass (17) containing at least one alcohol obtained at the end of the fermentation step f).

8. 8. The method according to claim 1, further comprising a step h) of producing an enzyme (8) from a second microorganism, in particular a fungus, using said enzyme to ensure the enzymatic hydrolysis of step c), and sending all or part (6a') of the second liquid portion (29) obtained in step e) containing C5 sugars but depleted in C6 sugars or the sugar-rich third liquid portion (32) obtained in step g) to step h) as a substrate for the growth of the second microorganism and / or the production of the enzyme.

9. 5. The method according to claim 3 or 4, characterized in that it comprises a step i) of propagation (11) of a third fermentation microorganism, ensuring the fermentation of step f) using said microorganism, in particular yeast, and sending all or part (6b') of the second liquid part (29) containing C5 sugars but depleted of C6 sugars obtained in step e) or the sugar-rich third liquid part (32) obtained in step g) to step i) as a substrate for the propagation of said third microorganism.

10. 10. The method according to any one of claims 1 to 9, characterized in that all or part (6c') of the second liquid part (29) containing C5 sugars but depleted of C6 sugars obtained in step e) or the sugar-rich third liquid part (32) obtained in step g) is sent to step f) of fermentation (16).

11. 11. The method according to any one of claims 1 to 10, characterized in that the first liquid portion (6) obtained in step b) also contains furfural and that the first microorganism also consumes the furfural, in particular by converting it at least in part into alcohol, in particular furfuryl alcohol.

12. 12. The method according to claim 1, wherein the first liquid portion (6) obtained in step b) also contains 5-(hydroxymethyl)furfural 5-HMF, and wherein the first microorganism also consumes the 5-(hydroxymethyl)furfural, in particular at least in part by converting the 5-(hydroxymethyl)furfural into 5-(hydroxymethyl)furfuryl alcohol.

13. 13. The method according to any one of claims 1 to 12, characterized in that the first microorganism used in step d) and optionally the third microorganism used in step i) are selected from yeasts, bacteria and fungi, preferably from yeasts in the genus Saccharomyces, in particular from the species Saccharomyces cerevisiae, or bacteria in the genus Corynebacterium.

14. 9. The method according to claim 8, characterized in that the second microorganism is chosen from fungi, in particular filamentous fungi, preferably from the genus Trichoderma, in particular Trichoderma reesei.

15. 15. The method according to any one of claims 1 to 14, wherein the pretreatment (2) of the biomass in step a) comprises the following substeps: a1) sub-step of impregnation of the biomass (1) with a liquor, in particular an acidic liquor; obtaining an impregnated biomass; a2) A sub-step of digesting the impregnated biomass, possibly with steam explosion; obtaining a pretreated biomass (3).

16. 5. The method of claim 3 or 4, further comprising the steps of: a separation step j), in particular by distillation (21); separation of the fermented biomass obtained in step f) in the form of alcohol (20); optionally a solid / liquid separation step k) of the fermented biomass, carried out before or after said separation step j).

17. 1. An on-board installation for the processing of lignocellulosic biomass, comprising: a) a unit for the pretreatment of biomass (2); including a device for digesting the biomass, possibly with steam explosion; obtaining pretreated biomass; b) a first unit for solid / liquid separation (4), which in particular comprises a filtering device; separating all or part (3a) of the pretreated biomass (3) obtained in unit a) into a first solid fraction (7) of the pretreated biomass and a first liquid fraction (6), which first liquid fraction (6) comprises, in particular in an aqueous phase, a mixture of compounds comprising C5 sugars having 5 carbons and C6 sugars having 6 carbons, the weight content of C5 sugars being higher than the weight content of C6 sugars; c) a unit for enzymatic hydrolysis (14) of the first solid fraction (7) of pretreated biomass obtained in step b), obtaining a hydrolysate (15) in the form of one or more sugars, including C6 sugars having six carbons; - d) a unit for the purification (24) of said first liquid portion (6), which is brought into contact with a first microorganism which consumes essentially only C6 sugars among the sugars of said portion, to obtain a purified liquid portion (26) containing C5 sugars but depleted in C6 sugars; e) a second unit for solid / liquid separation (27), which in particular comprises at least one filtration or centrifugation device; separating the purified liquid fraction (26) obtained in unit d) containing C5 sugars but depleted in C6 sugars; obtaining a second solid fraction (28) containing the first microorganisms and a second liquid fraction (29) containing C5 sugars but depleted in C6 sugars.

18. the second liquid portion (29) obtained in unit e) containing C5 sugars but depleted of C6 sugars contains alcohol, in particular ethanol, obtained by total or partial conversion of the C6 sugars under the action of the first microorganism; and 18. The loading facility according to claim 17, characterized in that it comprises a unit g) for separation (30) of the second liquid portion into a third liquid portion (32) rich in sugars and a fourth liquid portion (31) rich in alcohols, said separation unit g) comprising at least one device for evaporation or stripping.

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