Method of producing a c2-c6 hydroxycarboxylic acid

Abstract

Provided herein is a method of producing a C2-6 hydroxycarboxylic acid, comprising the steps of: (i) feeding a first composition comprising a C6 saccharide into a first reactor, wherein the first reactor is a continuous or semi-continuous reactor; (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the C6 saccharide to an intermediate product, wherein the intermediate product is an aldehyde; (iii) feeding a second composition comprising the intermediate product into a second reactor; and (iv) converting at least a portion of the intermediate product to the C2-6 hydroxycarboxylic acid.

Description

[0001] Methods

[0002] Field of the Invention

[0003] The present invention relates to novel methods for processing renewable biomass into high-value bio-based chemicals.

[0004] Background of the Invention

[0005] The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

[0006] Current petrochemical based production technologies are a major challenge to human and planetary health. Currently, more than 10% of fossil fuels extracted or produced are used to produce petrochemicals resulting in a massive climate impact. Some of these petrochemical derived products also contain carcinogenic and endocrine disrupting impurities which impact human bodies, resulting is risk of increased cancer, infertility, or developmental problems.

[0007] Current biobased chemical production technologies are plagued by several inefficiencies, particularly in the conversion of renewable biomass to high-value chemicals. These issues include (a) limited conversion efficiency, particularly in the upgrading of complex organic compounds (sugars, cellulose, hemicellulose) into target bio-based products or (b) low selectivity of existing catalytic processes, leading to unwanted by-products, decreased yields, and higher purification costs.

[0008] On the other hand, less toxic, biobased approaches face scalability limitations, with many being constrained to small-scale operations or facing prohibitive costs when scaled to industrial levels.

[0009] For example, glycolic acid is a key chemical used in industry, such as the cosmetic or cleaning industry. Particularly when used in the cosmetic industry, glycolic acid needs to be supplied in high purity and at low cost. Currently, commercial production of glycolic acid involves petrochemical feedstocks and / or employs toxic starting materials such as formaldehyde. Although it is technically possible to remove the unwanted impurities by purification, such purification steps lead to a significant added cost. Thus,such purified products cannot be supplied at a suitably low cost and are thus not suitable raw materials for certain industries.

[0010] Less toxic, biobased approaches to produce glycolic acid from renewable feedstocks have been explored, including fermentation approaches. However, the fermentation approaches known thus far either employ complex multi-pot fermentation strategies, use petrochemically derived starting materials, and / or there are still concerns with residual presence of highly toxic ethylene oxide or di- or tri-ethylene glycols and / or are not suitable for large scale industrial application.

[0011] There is therefore a need for new methods to convert biomass feedstock into high purity, high value chemicals. Ideally, such new methods are scalable to industrial scale.

[0012] Summary of the Invention

[0013] The inventors have now surprisingly found a new process for producing high purity and high value organic products using a renewable biomass feedstock.

[0014] Advantageously, the process of the invention enables high conversion rates of the starting biomass or saccharide, while avoiding the use of toxic feedstock and toxic chemicals, and reducing operating costs. Avoiding the use of toxic feedstock and chemicals used in traditional processes is a key advantage which enables a much safer overall process while ensuring the presence of no toxic impurities within the final organic product.

[0015] A further advantage of the process is that the dual-stage system (i.e. hydrothermal conversion and the further conversion) ensures high efficiency by maintaining separate optimal reaction conditions for each conversion stage, optimizing product yield while maintaining high selectivity. The process produces highly versatile intermediates which may be converted to useful organic products.

[0016] Advantageously, the process of the invention is scalable, e.g. to industrial scale.

[0017] The process of the invention is environmentally friendly due to the sustainable nature of the biomass or the saccharide used as starting feed, the high purity of the end organic products (thus avoiding wasteful purification steps which often use organic solvents), and the possibility of using low CO2 emitting reactors (e.g. reactors that use renewable energy and / or energy integration and / or heat recovery).According to the first aspect of the invention, there is provided a method of producing an organic product, comprising the steps of:

[0018] (i) feeding a first composition comprising biomass or a saccharide into a first reactor, wherein the first reactor is a continuous, semi-continuous or batch reactor;

[0019] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to an intermediate product;

[0020] (iii) feeding a second composition comprising the intermediate product into a second reactor; and

[0021] (iv) converting at least a portion of the intermediate product to the organic product.

[0022] According to the second aspect of the invention, there is provided an organic product or a composition comprising an organic product, wherein the organic product is obtainable (e.g. obtained) by the method of the first aspect of the invention.

[0023] According to a third aspect of the invention, there is provided a method of producing a C2 to C4 organic product, comprising the steps of:

[0024] (i) feeding a first composition comprising biomass or a saccharide into a first reactor, wherein the first reactor is a continuous, semi-continuous reactor or batch reactor; and

[0025] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to the C2 to C4 organic product.

[0026] According to a fourth aspect of the invention, there is provided a C2 to C4 organic product or a composition comprising a C2 to C4 organic product, wherein the C2 to C4 organic product is obtainable (e.g. obtained) by the method of the third aspect of the invention.

[0027] According to a fifth aspect of the invention, there is provided a composition comprising glycolic acid and glyceric acid.Detailed Description of the Invention

[0028] Unless indicated otherwise, all technical and scientific terms used herein will have their common meaning as understood by one of ordinary skills in the art to which this invention pertains.

[0029] The term "comprising", or variants thereof will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. References to "comprising" also encompass providing basis for "consisting".

[0030] The term "consisting" or variants thereof is to be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step or group of elements, integers or steps.

[0031] The term "wt%" is a commonly used abbreviation in the art and refers to the "weight %" with respect to the total weight of the material referred to, unless otherwise specified (e.g. the wt% may be in respect of dry weight in certain embodiments).

[0032] Where a numerical range is used, for example, "between 1 wt% and 10 wt%", the specified end points of the range are included in the claimed amount.

[0033] The term "about" includes ± 5% of the specified value. The term "about" includes the specified value.

[0034] According to the first aspect of the invention, there is provided a method of producing an organic product, the method comprising the steps of:

[0035] (i) feeding a first composition comprising biomass or a saccharide into (i.e. to) a first reactor, wherein the first reactor is a continuous, semi-continuous or batch reactor (such as continuous or semi-continuous reactor);

[0036] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to an intermediate product;

[0037] (iii) feeding a second composition comprising the intermediate product into (i.e. to) a second reactor; and

[0038] (iv) converting at least a portion of the intermediate product to the organic product.The method of the first aspect may be referred to herein as "the method of the invention", "the process of the invention", or the like.

[0039] For the avoidance of doubt, the skilled person will understand that references herein to methods or products of particular aspects of the invention (such as the first aspect of the invention) will include references to all embodiments and particular features thereof, which embodiments and particular features may be taken in combination to form further embodiments.

[0040] For the avoidance of doubt, the skilled person will understand that "at least a portion of the biomass or the saccharide" means "at least a portion of the biomass or at least a portion of the saccharide" or the like, throughout. Similarly, the skilled person will understand that step (i) comprises either feeding a first composition comprising biomass or feeding a first composition comprising a saccharide to the first reactor.

[0041] Hydrothermal conversion, e.g. steps Ci) and CH)

[0042] As used herein, when a composition is used in a continuous or semi-continuous reactor, the composition may be interchangeably referred to as a "feed" or a "stream".

[0043] The feed may comprise a solvent, such as water or an organic solvent (such as ethanol). In some embodiments, the first composition and / or (e.g. and) the second composition comprise water. In more particular embodiments, the method of the invention comprises only water as solvent, i.e. no organic solvents are used (e.g. less than 1 wt% of any composition used) in any of the steps of the method of the invention, e.g. steps (i) to (iv).

[0044] The method of the invention allows for the use of a wide range of feedstocks being processed in steps (i) and (ii), such as biomass or biomass constituents. A biomass constituent may be a saccharide.

[0045] As used herein, the term "biomass" includes organic matter, such as organic matter originating or derived from plants and / or animals. Examples of biomass include but are not limited to lignocellulose (also known as lignocellulosic biomass), cellulose, starch, glycerol, wood, wood residues, algae, energy crops, palm biomass, corn biomass, sugarcane biomass, agricultural residues including straw, and organic waste from industry, agriculture and households. The term "biomass" may be used interchangeably with "bio-feedstock" or "renewable biomass feedstock" and the like.In some embodiments, the first composition comprises biomass (i.e. the first composition comprising biomass or a saccharide is a first composition comprising biomass).

[0046] In some embodiments, the biomass comprises plant material, cellulose, lignocellulose, wood, algae, starch, agricultural waste, or mixtures of one or more thereof, such as cellulose, lignocellulose, and / or starch.

[0047] In particular embodiments, the biomass comprises lignocellulose or starch, such as lignocellulose.

[0048] In particular embodiments, the biomass comprises lignocellulose or cellulose.

[0049] In particular embodiments, the biomass comprises cellulose.

[0050] In particular embodiments, the biomass comprises starch.

[0051] In some embodiments, the biomass comprises unprocessed biomass or waste biomass.

[0052] The skilled person will understand that in embodiments wherein the first composition comprises biomass, in step (ii) at least a portion of the biomass is converted to the intermediate product. The conversion of the biomass to the intermediate product includes direct or indirect conversion. In other words, in some embodiments, step (ii) may comprise subjecting the first composition to hydrothermal conversion conditions to directly or indirectly convert at least a portion of the biomass to an intermediate product. An example of indirect conversion of the biomass into the intermediate product may be via another product, such as via a saccharide. The skilled person will understand that the "another product" may be formed in-situ and may be immediately converted into the intermediate product, i.e. without any isolation or purification steps.

[0053] Therefore, in some embodiments, the hydrothermal conversion conditions are suitable for converting both (a) the biomass into a saccharide and (b) the saccharide into the intermediate product.

[0054] In alternative embodiments, the hydrothermal conversion conditions used for converting (a) the biomass into a saccharide and (b) the saccharide into the intermediate product are different from each other (e.g. they comprise different temperatures, different pressures, and / or different residence times).In some embodiments, the first composition comprises a saccharide (i.e. the first composition comprising biomass or a saccharide is a first composition comprising a saccharide). The skilled person will understand that in such embodiments, step (ii) comprises the conversion of at least a portion of the saccharide to an intermediate product.

[0055] As used herein, the term "saccharide" includes monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

[0056] Monosaccharides may include simple sugars and their derivatives, such as glucose, glyceraldehyde, fructose, galactose, mannose, arabinose, xylose, ribose, erythrose, amino sugars (such as galactosamine, glucosamine, sialic acid, N-acetylglucosamine), sulfosugars (such as sulfoquinovose), and other derivatives (such as ascorbic acid, mannitol, glucuronic acid). A formula of a simple monosaccharide may be CnFhnOn, where the integer n is at least 3. Simple monosaccharides may be named generically based on the number of carbon atoms (represented by n), such as trioses (n = 3), tetroses (n=4), pentoses (n = 5), hexoses (n = 6), etc. Monosaccharides may be classified as a keto- or an aldo- monosaccharide. In some embodiments, the saccharide is a monosaccharide.

[0057] Disaccharide (also called a double sugar or biose) is the sugar formed when two monosaccharide units are joined by glycosidic linkage (for example by a dehydration reaction). Disaccharides may include sucrose, lactose, maltose, trehalose, cellobiose, chitobiose, kojibiose, nigerose, isomaltose, a,p-trehalose, p,p-trehalose, sophorose, laminaribiose, gentiobiose, trehalulose, turanose, maltulose, leucrose, isomaltulose, gentiobiulose, mannobiose, melibiose, allolactose, melibiulose, lactulose, rutinose, rutinulose, and xylobiose. In some embodiments, the saccharide is a disaccharide

[0058] Oligosaccharides are saccharide polymers containing a small number (typically three to ten) of monosaccharides units. Oligosaccharides may include maltodextrins, starches, raffinose, stachyose, fructo-oligosaccharides (FOS), arabino-oligosaccharides (AXOS), mannan oligosaccharides (MOS), galacto-oligosaccharides (GOS), amylose, amylopectin, maltotriose, and modified starches. Oligosaccharides may be linear or branched. In some embodiments, the saccharide is a oligosaccharide.

[0059] Oligosaccharides are a common component of fibre from plant tissue. Fructooligosaccharides (FOS), which are found in many vegetables, are oligosaccharidescomprising short chains of fructose molecules. FOS are present in Jerusalem artichoke, burdock, chicory, leeks, onions, and asparagus. FOS can also be synthesized by enzymes of the fungus Aspergillus niger acting on sucrose. Galacto-oligosaccharides (GOS), which also occur naturally, comprise short chains of galactose molecules. GOS is naturally found in soybeans and can be synthesized from lactose. Mannan oligosaccharides (MOS) are widely used in animal feed to improve gastrointestinal health. MOS are typically obtained from the yeast cell walls of Saccharomyces cerevisiae.

[0060] Polysaccharides are long-chain polymeric carbohydrates comprising monosaccharide units (typically more than 10) bound together by glycosidic linkages. Polysaccharides may include cellulose, hemicellulose, chitin, resistant starch (e.g. RS type 1, 2, 3, 4), etc. Polysaccharides may be linear or branched. In some embodiments, the saccharide is a polysaccharide, such as such as lignocellulose, cellulose or starch, for example cellulose.

[0061] In some embodiments, the saccharide is a Cs or Ce saccharide (i.e. a Cs saccharide or a Ce saccharide). The skilled person will understand that a Cs or Ce saccharide includes a Cs or Ce monosaccharide (e.g. a saccharide of formula CnFhnOn, wherein n is 5 or 6), Cs or Ce polysaccharide, Cs or Ce oligosaccharide, or Cs or Ce disaccharide.

[0062] As used herein, the terms Cs or Ce polysaccharide, oligosaccharide, or disaccharide refer to a polysaccharide, oligosaccharide, or disaccharide, each comprising Cs or Ce sugar units, as appropriate.

[0063] In some embodiments, the Cs or Ce polysaccharide, oligosaccharide, or disaccharide comprise greater than 60 % (such as greater than 80% or 90%) of the monomer units (i.e. monosaccharide units) being Cs or Ce monosaccharides, as appropriate.

[0064] In some embodiments, the monosaccharide or monosaccharide unit is of the formula CnFhnOn, wherein n is an integer of at least 3, such as from about 3 to about 9.

[0065] In some embodiments, the monosaccharide or monosaccharide unit is of the formula CnFhnOn, wherein n is an integer of at least 5, such as from about 5 to about 8.

[0066] In some embodiments, the monosaccharide or monosaccharide unit is of the formula CnFhnOn, wherein n is 5 or 6, such as 6.In some embodiments, the saccharide is a Cs or Ce monosaccharide. This means that the monosaccharide is of the formula CnFhnOn, wherein n is 5 or 6.

[0067] In some embodiments, the saccharide is a Cs monosaccharide. A Cs saccharide may also be referred to as a pentose.

[0068] In some embodiments, the Cs monosaccharide or Cs monosaccharide unit is at least one (e.g. is one) sugar selected from the group consisting of xylose, ribose, arabinose, ribulose and combinations of one or more thereof.

[0069] In some embodiments, the saccharide is a Ce monosaccharide. A Ce saccharide may also be referred to as a hexose.

[0070] In some embodiments, the Ce monosaccharide or Ce monosaccharide unit is at least one (e.g. is one) sugar selected from the group consisting of glucose, mannose, galactose, fructose, and combinations of one or more thereof.

[0071] In some embodiments, the monosaccharide or monosaccharide unit is xylose, arabinose, ribose, ribulose, glucose, galactose, mannose, or fructose.

[0072] In some embodiments, the saccharide is glucose.

[0073] In some embodiments, the first composition is a homogenous solution comprising the saccharide, such as wherein the saccharide is glucose.

[0074] For the avoidance of doubt, all isomers, including stereoisomers such as enantiomers and diastereomers, of the saccharides mentioned herein are intended to be included within the scope.

[0075] The saccharide may be obtained from biomass (such as the biomass as described herein). For example, in some embodiments, the method may comprise the pre-step of subjecting a composition (e.g. a "feed composition" or a "pre-composition") comprising biomass to hydrothermal conversion conditions to convert at least a portion of the biomass into the saccharide. The skilled person will understand that a "prestep" refers to a method step carried out prior to step (i). The conversion of the biomass into the saccharide, according to the pre-step, may be carried out in the first reactor (i.e. as described above in relation to the indirect conversion of the biomass into the intermediate product) or in a third reactor. The third reactor may be acontinuous, semi-continuous, or batch reactor (e.g. a continuous or semi-continuous reactor, such as continuous reactor).

[0076] In other words, in such embodiments, the method may comprise the steps and presteps of:

[0077] (i-a) feeding a composition (e.g. a feed composition) comprising biomass into a first reactor or a third reactor (e.g. third reactor);

[0078] (i-b) subjecting the composition comprising biomass to hydrothermal conversion conditions to convert at least a portion of the biomass to a saccharide (wherein step (i-b) is carried out in the first reactor or the third reactor, as appropriate);

[0079] (i) feeding a first composition comprising the saccharide into a (or the) first reactor; (ii) subjecting the first composition comprising the saccharide to hydrothermal conversion conditions to convert at least a portion of the saccharide to an intermediate product; the skilled person will understand that step (ii) is carried out in the first reactor;

[0080] (iii) feeding a second composition comprising the intermediate product into a second reactor; and

[0081] (iv) converting at least a portion of the intermediate product to the organic product.

[0082] In more particular such embodiments, pre-step (i-a) comprises feeding the composition into a (or the) first reactor, optionally wherein the first reactor is a continuous or semi-continuous reactor.

[0083] In some embodiments, the hydrothermal conversion conditions of pre-step (i-b) comprise subcritical water.

[0084] As used herein, the term "hydrothermal conversion" involves conducting a thermochemical conversion (such as in a reactor e.g. hydrothermal reactor) in liquid water at elevated temperature and wherein the pressure in the system is at or above the relevant saturated pressure, e.g. hydrothermal conversion includes applying specific heat and / or pressure conditions in subcritical or supercritical water. Advantageously, hydrothermal conversions can typically process high moisture content (such as >70 wt. %) biomass feedstock without the requirement for a dewatering or drying step. The terms "hydrothermal conversion" and "hydrothermal processing" may be used interchangeably.

[0085] Without wishing to be bound by theory, the supercritical and / or subcritical water is believed to act as a solvent, catalyst and / or reactant in the present invention.Advantageously, the hydrothermal conversion conditions as defined herein do not require any drying or de-watering step of the biomass or the saccharide, thus increasing the efficiency of the method of the invention. Further, the water medium used in the hydrothermal conditions enable easy integration of separation steps (e.g. after step (ii)), and removal of gaseous or solid unwanted by-products.

[0086] Step (ii) of the method of the present invention may be referred to herein as the "hydrothermal conversion" or the "hydrothermal conversion step". The skilled person will understand that step (ii) is carried out in the first reactor.

[0087] The features of various embodiments of "hydrothermal conversion" described herein may independently apply to both step (ii) and pre-step (i-b).

[0088] The hydrothermal conversion of the invention represents an efficient manner of breaking down complex biomass, complex saccharides, as well as simple saccharides into useful organic intermediates, i.e. the intermediate product, which may then be further converted into useful organic products.

[0089] In some embodiments, the hydrothermal conversion conditions comprise a temperature between about 100 °C and about 500 °C, such as between about 300 °C and about 500 °C.

[0090] In some embodiments, the hydrothermal conversion conditions comprise a temperature of at most about 450 °C, such as at most about 400 °C, at most about 375 °C, at most about 350 °C, at most about 300 °C, or at most about 280 °C. Advantageously, the lower temperatures may be useful to avoid or minimise carbonisation, which would otherwise have a negative impact on the yield and thus overall efficiency and / or might lead to reactor fouling.

[0091] In more particular embodiments, the hydrothermal conversion conditions comprise a temperature between about 100 °C to about 450 °C, such as between about 150 °C and about 450 °C, between about 200 °C and about 450 °C, between 300 °C and about 420 °C, between 350 °C and about 420 °C, or between 375 °C and 400 °C.

[0092] In some embodiments, the hydrothermal conversion conditions comprise a pressure between 0.5 MPa and 30 MPa (i.e. from about 0.5 MPa to about 30 MPa).In some embodiments, the hydrothermal conversion conditions comprise a pressure of at least 10 MPa, such as at least 15 MPa or at least 20 MPa.

[0093] In some embodiments, the hydrothermal conversion conditions comprise a pressure of at most 30 MPa, such as at most 28 MPa, or at most 25 MPa.

[0094] In more particular embodiments, the hydrothermal conversion conditions comprise a pressure from about 1 MPa to about 30 MPa, such as from about 5 MPa to about 30 MPa, from about 10 MPa to about 30 MPa, or from about 20 MPa to about 30 MPa.

[0095] The residence time of the biomass or the saccharide in the relevant reactor may be any suitable length of time. Advantageously, the process of the invention allows for fast conversion time, and thus an efficient process which is particularly advantageous when applied at industrial scale (e.g. due to speed and lower cost). Therefore, in some embodiments, the hydrothermal conversion conditions comprise a residence time of the biomass or the saccharide of at most 60 s, such as at most 30 s, 20 s, 10 s, 7 s, 5 s, 4 s, 3 s, 2 s or 1 s, such as at most 30 s or 5 s, e.g. at most 5 s. The person skilled in the art will understand that "s" refers to seconds.

[0096] In some embodiments, the hydrothermal conversion conditions comprise a residence time of the biomass or the saccharide between about 0.05 s and about 30 s.

[0097] In more particular embodiments, the hydrothermal conversion conditions comprise a residence time of the biomass or the saccharide between about 0.05 s and about 20 s, such as between about 0.05 s and about 15 s, between about 0.5 s and about 10 s, between about 0.5 s and about 5 s, such as between about 0.5 s and about 3 s.

[0098] The reactants biomass or saccharide (e.g. glucose) may be used at any suitable starting concentration. In some embodiments, the first composition comprises a concentration of the biomass or saccharide (e.g. of the Ce saccharide such as glucose or starch) of at least 1 wt%, such as at least 5 wt%, at least 10 wt%, at least 15 wt% or at least 20 wt% (e.g. at least 10 wt%). Advantageously, a higher concentration allows for the overall process to be more suitable for industrial application. Surprisingly, the inventors have found that the hydrothermal conversion step of the method of the invention can be successfully carried out at high concentrations of the saccharide e.g. glucose, leading to a highly efficient process.For example, in some embodiments, the first composition comprises a concentration of the biomass or saccharide (e.g. glucose) between 1 and 25 wt%, such as between 5 and 20 wt%.

[0099] In some embodiments, the first composition comprises a concentration of the biomass or saccharide (e.g. glucose) between 10 and 30 wt%, such as between 12 and 30 wt%, between 15 and 30%, between 15 and 30 wt%, or between 15 and 25 wt%.

[0100] In some embodiments, step (ii) comprises contacting water at a sufficient temperature and a sufficient pressure with the first composition for a duration sufficient to convert at least a portion (such as at least 30 wt%, at least 50 wt% or at least 70 wt%) of the biomass or the saccharide into the intermediate product.

[0101] In some embodiments, step (ii) comprises contacting water (e.g. as a second stream) at a temperature of at least about 100 °C and a pressure of at least 0.5 MPa with the first composition (e.g. as a first stream) for a duration sufficient to convert at least a portion (such as at least 30 wt%, at least 50 wt% or at least 70 wt%) of the biomass or the saccharide into the intermediate product. The first stream may have any of the features described herein in relation to the hydrothermal conversion conditions, such as temperature and / or pressure and / or residence time.

[0102] For example, in a particular embodiment, step (ii) comprises contacting water (e.g. as a second stream) at a temperature between 150 °C and 400 °C (e.g. 350 °C to 400 °C) and a pressure from 0.5 MPa to 30 MPa (e.g. from 20 MPa to 30 MPa) with the first composition (e.g. as a first stream) for duration (i.e. residence time) of about 0.05 s to 20 s (e.g. from 0.5 s to 5 s), to convert at least a portion of the biomass or the saccharide into the intermediate product. Optionally, the at least a portion may be at least 30 wt%, at least 50 wt% or at least 70 wt% of the biomass or the saccharide, as appropriate.

[0103] In some embodiments, the hydrothermal conversion conditions comprise subcritical water and / or supercritical water.

[0104] In some embodiments, the hydrothermal conversion conditions comprise subcritical water. In particular such embodiments, the first composition comprises biomass.

[0105] In some embodiments, the hydrothermal conversion conditions comprise supercritical water. In particular such embodiments, the first composition comprises a saccharide.In some embodiments, the hydrothermal conversion conditions comprise subcritical and supercritical water. In particular such embodiments, the first composition comprises biomass and step (ii) comprises conversion of the biomass to the intermediate product, optionally via a second intermediate product which may be a saccharide.

[0106] A subcritical fluid is a fluid that is under pressure greater than atmospheric pressure and at temperatures above the usual boiling point of the fluid at atmospheric pressure (1 atm). Subcritical water is liquid water under pressure greater than 1 atm (i.e. 0.1 MPa), and at temperatures above the usual boiling point of water (100 °C). It may also be referred to as "pressurized hot water". At a subcritical state, water is maintained in liquid form by applying pressure. Therefore, the liquid water is in equilibrium with vapor at the saturated vapor pressure.

[0107] In some embodiments, the hydrothermal conversion conditions comprise subcritical water.

[0108] A supercritical fluid is a fluid (such as water) at a temperature above its critical temperature and at a pressure above its critical pressure. A supercritical fluid exists at or above its "critical point," the point of highest temperature and pressure at which the liquid and vapor (gas) phases can exist in equilibrium with one another. Above critical pressure and critical temperature, the distinction between liquid and gas phases disappears. As used herein, "supercritical water" indicates water which would be supercritical if present in pure form under a given set of temperature and pressure conditions. For example, "supercritical water" indicates water present at a temperature of at least about 374° C. and a pressure of at least about 22.1 MPa, whether the water is pure water, or present as a mixture (e.g. water and ethanol, water and CO2, etc).

[0109] In some embodiments, the hydrothermal conversion conditions comprise supercritical water.

[0110] In some embodiments, the hydrothermal conversion conditions comprise subcritical and / or (e.g. and) supercritical water. The skilled person will understand that in embodiments where both supercritical and subcritical water are used, the supercritical water and subcritical water are used sequentially, e.g. to each target solubilisation and / or reaction of different components of the starting biomass or saccharide.Step (ii) is carried out in the first reactor, i.e. the subjecting of step (ii) is (i.e. is carried out) in the first reactor. The first reactor may be continuous, semi-continuous or batch reactor.

[0111] In some embodiments, the first reactor is a continuous or semi-continuous reactor, such as a continuous reactor. Advantageously, the use of a continuous reactor enables ultra-short residence times (such as those described herein), the use of reactors of smaller dimensions, faster conversion times leading to higher productivity, and easier energy integration.

[0112] As used herein, the terms "continuous reactor" and "flow reactor" may be used interchangeably, and refer to reactors which employ continuous flow technology to execute chemical reactions continuously. For example, reagents are continuously added to a flow reactor vessel inlet whilst the output is constantly collected at the reactor outlet, to create a continuously flowing stream of reactants and outputs. A flow reactor can provide chemical manufacturers with a more versatile and efficient reactor than batch alternatives.

[0113] As used herein, "continuous" indicates a process which is uninterrupted for its duration, or a process which is only momentarily interrupted, paused or suspended relative to the duration of the process.

[0114] Particular examples of continuous reactors are plug flow reactors. In some embodiments, step (ii) (i.e the hydrothermal conversion) is carried out in a plug flow reactor, i.e. the first reactor is a continuous reactor, e.g. a plug flow reactor. The plug flow reactor may have at least two (e.g. two) separate input streams each at a specific temperature and pressure, e.g. the first input stream and the second input stream.

[0115] In some embodiments, the first input stream may comprise supercritical and / or (e.g. or) subcritical water. The skilled person will understand that in embodiments where the first input stream comprises supercritical water and subcritical water, the method comprises one or more step (such as a step) wherein supercritical water and subcritical water are used sequentially.

[0116] In particular such embodiments, the first input stream may comprise (e.g. be at) a temperature between about 100 °C and about 500 °C and a pressure of between about 0.5 MPa and about 30 MPa (e.g. from 10 MPa to 30 MPa, such as from 20 MPa to 30MPa). The first stream may have any of the other temperatures and pressures described herein in relation to the hydrothermal conditions.

[0117] In some embodiments, the second input stream may comprise the first composition, i.e. the first composition comprising the biomass or the saccharide.

[0118] In particular such embodiments, the first input stream may comprise (e.g. be at) a temperature between about 20 °C and about 500 °C (such as between about 100 °C and about 500 °C) and a pressure of between about 0.1 MPa and about 30 MPa (such as between about 0.5 MPa and about 30 MPa).

[0119] As used herein, "batch reactor" refers to a chemical reactor in which a non-continuous reaction is conducted, i.e. one where the reactants, products and solvent do not flow in or out of the reaction vessel during the reaction until the target reaction conversion is achieved. An example of a batch reactor is a continuously stirred tank reactor.

[0120] As used herein, "semi-continuous" refers to a modified batch reactor such that the reactor allows reactant addition and / or product removal during the reaction, e.g. the reactor allows partial filling of reactants with the flexibility of adding more as time progresses and / or wherein the targeted products are removed continuously as they are formed using suitable separation techniques, such as precipitation, solvent extraction or ion exchange resin. "Semi-continuous" and "semi-batch" may be used interchangeably.

[0121] In some embodiments, the method further comprises a step of recycling into the first reactor a stream comprising unreacted biomass or saccharide, e.g. a stream comprising biomass or saccharide (such as those defined herein) remaining in solution following steps (ii), (iv), or subsequent steps such as purification steps after step (iv). Advantageously, this would increase the conversion of the starting material (the biomass or the saccharide), thus increasing the overall yield of the process.

[0122] Advantageously, the hydrothermal conversion does not require use of transition metal catalysts or organic solvents. Therefore, the process is less costly and more environmentally friendly than traditional synthetic chemistry alternatives.

[0123] Therefore, in some embodiments, step (ii) is carried out in the substantial absence of a transition metal catalyst and / or (e.g. or) organic solvents. For example, the first composition comprises less than 10 ppm transition metal and / or less than 1 wt%organic solvent (for the avoidance of doubt, this includes 0 ppm and 0 wt%). In more particular embodiments, substantially no transition metal (e.g. less than 10 ppm) and / or substantially no organic solvent is introduced in the first reactor (e.g. any input stream introduced in the first reactor comprises less than 1 wt% organic solvent).

[0124] In some embodiments, step (ii) is carried out in the substantial absence of exogenous acid (such as the first composition comprises less than 1 wt% of exogenous acid (for the avoidance of doubt, this includes 0 wt%)).

[0125] As used herein, exogenous acid refers to an acid that has been introduced as a reagent to the process. By "substantial absence of exogenous acid", it is intended that no acid (such as less than 1 wt% of exogenous acid in the first composition (for the avoidance of doubt, this includes 0 wt%)) other than acid that may be naturally occurring in the biomass and / or the saccharide of the first composition is required to be added to the input stream or reactor to aid the reaction.

[0126] The output stream of step (ii) comprises the intermediate product (which is the desired product of the hydrothermal conversion of step (ii)). The (crude) output stream of step (ii) may be referred to as a "third composition", i.e. the third composition comprises the intermediate product as defined herein.

[0127] The intermediate product refers to an organic molecule, and may include a molecule comprising one to six carbons in its skeleton, i.e. a Ci to Ce molecule (which may be referred to as a "Ci to Ce intermediate product" or the like).

[0128] In some embodiments, the intermediate product is an aliphatic product (i.e. an aliphatic molecule). The skilled person will understand than an aliphatic molecule refers to a non-aromatic molecule (i.e. the intermediate product does not comprise an aromatic ring). The aliphatic molecule may be saturated or unsaturated, straight-chain or branched-chain. In particular embodiments, the aliphatic molecule is saturated.

[0129] In some embodiments, the intermediate product is a C2, C3 or C4 molecule. The skilled person will understand that a C2, C3 or C4 molecule refers to a molecule comprising from 2 to 4 carbon atoms, such as 2 (i.e. C2), 3 (i.e. C3), or 4 (i.e. C4) carbon atoms in its skeleton (or backbone). The backbone may be linear or branched. In some embodiments, each carbon atom is substituted with H and one or more functional groups independently selected from the group consisting of halo, hydroxy, amino and carboxyl.In some embodiments, the intermediate product is a C2 molecule (i.e. comprises only two carbons in its skeleton).

[0130] In some embodiments, the intermediate product is a C3 molecule (i.e. comprises only three carbons in its skeleton).

[0131] In some embodiments, the intermediate product is a C4 molecule (i.e. comprises only four carbons in its skeleton).

[0132] The C2 molecule, C3 molecule and C4 molecule may each comprise one or more functional groups independently selected from the group consisting of halo, hydroxy, amino and carboxyl.

[0133] In some embodiments, the intermediate product comprises an aldehyde group (e.g. the intermediate product is an aldehyde). An aldehyde is a compound containing the functional group -C(O)H. Advantageously, the intermediate product comprising an aldehyde is a versatile intermediate due to the reactivity of the aldehyde group. Additionally, advantageously, the method of the invention allows for the fast production of (e.g. unstable) aldehyde intermediates, which may then be immediately converted to stable, useful products, e.g. in step (iv). The intermediate aldehyde may be obtained in step (ii) in the absence of toxic or otherwise unwanted by-products, due to the advantageous hydrothermal conditions and feedstock used in steps (i) and (ii).

[0134] In some embodiments, the intermediate product does not comprise a nitrile group, i.e. the intermediate product molecule does not comprise a nitrile substituent. "Nitrile group" may be used interchangeably with "cyano". A nitrile group may be represented as -CN where the carbon atom is triple bonded to the nitrogen atom.

[0135] In some embodiments, the intermediate product is glycolaldehyde. Glycolaldehyde (CH2(OH)C(O)H) may be represented by the structural formula:

[0136]

[0137] ° . Glycolaldehyde is a relatively unstable aldehyde, which is advantageously obtained in in the absence of toxic or otherwise unwanted by-products due to the advantageous hydrothermal conditions and feedstock used in steps (i) and (ii). Glycolaldehyde is a versatile intermediate and may be further converted into valuable organic products such as glycolic acid.In some embodiments, the intermediate product is obtained in the substantial absence of toxic impurities. In other words, the output stream of step (ii), i.e. the third composition comprising the intermediate product, comprises substantially no toxic impurities. The skilled person will be able to determine what "substantially no" means, depending on the particular toxic impurity.

[0138] In particular such embodiments, the third composition comprises less than 3 wt% (e.g. less than 2 wt%) of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, oxalic acid and formic acid.

[0139] In more particular such embodiments, the third composition comprises less than 1 wt% (such as less than 0.5 wt% or 0.1 wt%; for the avoidance of doubt, this includes 0 wt%) of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, oxalic acid and formic acid.

[0140] In some embodiments, the third composition comprises less than 3 wt% (e.g. less than 1 wt%) of each of formaldehyde and hydrogen cyanide.

[0141] In some embodiments, in step (ii), the at least a portion is at least 50 wt% of the biomass or the saccharide, such as at least 60 wt%, 70 wt%, 80 wt% or 90 wt%; i.e. at least 50 wt% such as at least 60 wt%, 70 wt% , 80 wt% or 90 wt% of the biomass or the saccharide is converted into the intermediate product. In more particular embodiments, in step (ii), substantially all the biomass or the saccharide is converted into the intermediate product. As used herein, "substantially all" refers to at least 90 wt%, such as at least 95 wt%.

[0142] The method of the invention allows for a high conversion of the feedstock biomass or saccharide into the intermediate product.

[0143] Therefore, in some embodiments, the output stream of step (ii) (i.e. the third composition) comprises at least 1 wt% intermediate product, such as at least 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, or 50 wt%, wherein the wt% is with respect to the total weight of the third composition.

[0144] In some embodiments, the output stream of step (ii) (i.e. the third composition) comprises at least 10 wt% intermediate product (as defined herein), such as at least 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or 90 wt%, wherein thewt% is with respect to the dry mass of the third composition, i.e. the solvent present in the third composition is disregarded.

[0145] In a particular embodiment, wherein the intermediate product is glycolaldehyde, the output stream composition of step (ii) (i.e. the third composition) comprises at least 10 wt% glycolaldehyde, such as at least 20 wt%, 30 wt%, 40 wt%, or 50 wt%, wherein the wt% is with respect to the total weight of the third composition.

[0146] In a particular embodiment, wherein the intermediate product is glycolaldehyde, the output stream composition of step (ii) (i.e. the third composition) comprises at least 10 wt% glycolaldehyde, such as at least 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or 90 wt%, wherein the wt% is with respect to the dry mass of the third composition, i.e. the solvent present in the third composition is disregarded.

[0147] The process of the invention allows the desired reaction to proceed with minimal gasification of the feedstock, and therefore the majority of the feedstock is converted to the desired intermediate product. Therefore, in some embodiments, step (ii) comprises at most 10 wt% gasification of the biomass or the saccharide, such as at most 5 wt% or 2 wt%, i.e. at most 10 wt%, 5 wt% or 2 wt% of the biomass or the saccharide is gasified in steps (ii) to (iv).

[0148] Second stage conversion, e.g. steps (iii) and (iv)

[0149] The intermediate product obtained in step (ii) may be (e.g. is) subjected to further processing, e.g. in steps (iii) and (iv), in order to convert at least a portion of the intermediate product to the organic product.

[0150] In step (iii), the second composition comprising the intermediate product is fed into the second reactor. The skilled person will understand that the second composition comprises the intermediate product obtained in step (ii) and as defined herein and that the converting of step (iv) occurs in the second reactor.

[0151] The second reactor may be a continuous reactor, a semi-continuous reactor, ora batch reactor. In some embodiments, the second reactor is a continuous or semi-continuous reactor, such as a continuous reactor. In some embodiments, the second reactor is a semi-continuous reactor or a batch reactor.The first and second reactors may be the same reactor, part of the same reactor (e.g. the first and second reactor are two different stages (or parts) of the same reactor) or may be different reactors.

[0152] The duration of step (iv) may be any suitable length of time. Advantageously, the process of the invention allows for fast conversion time, and thus an efficient process which is particularly advantageous when applied at industrial scale (e.g. due to speed and lower cost). Therefore, in some embodiments, step (iv) is of a duration of at most 24 hours, such as at most 6 hours, at most 1 hour, at most 30 minutes, at most 10 minutes, such as at most 5 minutes.

[0153] In some embodiments, step (iv) does not comprise fermentation.

[0154] In some embodiments, step (iv) does not comprise hydrothermal conditions.

[0155] In some embodiments, the converting in step (iv) comprises converting at least 50 wt% of the intermediate product to the organic product, such as at least 60 wt%, 70 wt%, 80 wt% or 90 wt% of the intermediate product. In more particular embodiments, in step (iv), substantially all the intermediate product is converted into the organic product. As used herein, "substantially all" refers to at least 90 wt%, such as at least 95 wt%.

[0156] In some embodiments, the converting in step (iv) comprises a catalysed conversion.

[0157] In some embodiments, the converting in step (iv) comprises an oxidation of the intermediate product, such as an enzyme-catalysed oxidation or a photo-oxidation. In particular such embodiments, the second reactor may be a bubble column reactor (i.e. a reactor comprising a gas distributor; the gas may be air or oxygen). As used herein, "oxidation" includes both direct or indirect oxidation of the intermediate product.

[0158] In particular embodiments wherein step (iv) comprises an oxidation of the intermediate product, step (iv) is carried out for a duration of at most 24 hours, such as at most 6 hours. In more particular embodiments wherein step (iv) comprises an oxidation of the intermediate product, step (iv) does not comprise (e.g. does not require) fermentation or the use of any microorganism.

[0159] In some embodiments, the oxidation of the intermediate product comprises contacting the intermediate product with water, wherein the water comprises more than 7 mg / Loxygen (i.e. more than 7 mg oxygen per liter of water), such as more than 8 mg / L, 10 mg / L or more than 20 mg / L.

[0160] In some embodiments, step (iv) comprises sparging oxygen or air (e.g. air) through the composition comprising the intermediate product.

[0161] Advantageously, step (iv) may be run under pressure to reduce reaction times. Accordingly, in some embodiments, step (iv) comprises a pressure of above atmospheric pressure (e.g. above 0.15 MPa, above 0.2 MPa, above 0.5 MPa, or above 1 MPa). In more particular embodiments wherein step (iv) comprises an oxidation of the intermediate product, step (iv) comprises contacting the intermediate product with water, wherein the water is at a pressure of above atmospheric pressure (e.g. above 0.15 MPa, above 0.2 MPa, above 0.5 MPa, or above 1 MPa). The water may comprise any oxygen content, including those described above.

[0162] In particular embodiments, the converting in step (iv) is in the presence of oxygen (e.g. pressurised oxygen). The skilled person will understand that "pressurised oxygen" includes oxygen at a pressure of above atmospheric pressure (e.g. above 0.15 MPa, above 0.2 MPa, above 0.5 MPa, or above 1 MPa).

[0163] In some embodiments, step (iv) comprises the use of air to pressurise the second reactor such that the amount of oxygen present in the second reactor is higher than the amount of oxygen required for stoichiometric oxidation of the intermediate product (or other suitable reactant). In particular such embodiments, the second reactor is a batch reactor and / or (e.g. and) the temperature of (e.g. inside of) the second reactor is at most 50 °C (such as between about 20 °C and about 50 °C).

[0164] In some embodiments, the converting in step (iv) comprises an enzyme-catalysed, metal-catalysed (e.g. transition metal-catalysed), photo-catalysed, or photo-oxidation conversion (i.e. step (iv) may comprise contacting the intermediate product with an enzyme, a metal catalyst, or a photocatalyst, or subjecting the intermediate product to UV radiation).

[0165] In some embodiments, step (iv) may comprise contacting the intermediate product with an enzyme (e.g. to convert at least a proportion of the intermediate product to the organic product).Without wishing to be bound by theory, it is considered that enzymes are advantageous catalysts for use in step (iv) (for example for the conversion of glycolaldehyde to glycolic acid), particularly when used as isolated catalysts in 'cell-free manufacturing', because they can be highly selective towards the desired reaction. For example, certain enzymes will only oxidize certain functional groups (such as the aldehyde group) and hence selectively produce the desired organic products (such as glycolic acid).

[0166] Therefore, in some embodiments, step (iv) may comprise contacting the intermediate product with an enzyme, such as wherein the enzyme has oxidative activity of an aldehyde group. By an "enzyme having oxidative activity of an aldehyde group", it is intended that one or more (such as one) enzyme is used to convert at least a portion of any aldehyde functional groups present in the intermediate product to carboxylic acid or hydroxy functional groups.

[0167] In some embodiments, the enzyme is not comprised in a host cell, i.e. the enzyme is an isolated enzyme.

[0168] In some embodiments, the enzyme is selected from the group consisting of an aldehyde oxidase (e.g. EC 1.2.3.1), xanthine oxidase (e.g. EC 1.17.3.2) and glyoxal oxidase (e.g. EC 1.2.3.15).

[0169] In some embodiments, step (iv) does not comprise the use of (such as the addition into the reactor of) a co-factor, such as nicotinamide adenine dinucleotide (NAD) and / or nicotinamide adenine dinucleotide phosphate (NADP). Such embodiments are advantageous because co-factors are costly and require regeneration.

[0170] In some embodiments, step (iv) comprises the use of at least two enzymes, such as only two enzymes, (e.g. for the conversion of at least a portion of the intermediate product to the organic product). The at least two enzymes may be two different (e.g. types of) enzymes. The at least two enzymes may belong to different EC numbers.

[0171] In some embodiments, step (iv) is carried out in a cell-free environment. Such embodiments may be referred to as "cell-free manufacturing" or the like. A cell-free environment is intended to mean that there is substantially no need for intact living cells (e.g. to perform the catalysis) in the reaction environment. This manufacturing method may eliminate the toxicity and metabolic burden associated with traditional cell-based methods.Without wishing to be bound by theory, it is considered that 'cell-free manufacturing' is advantageous compared to fermentation using whole microbes because using isolated enzymes prevents reactions between the intermediate product (such as glycolaldehyde) and any contaminating enzymes or metabolic products. Furthermore, enzymes can be optimized through structural modifications to make them more efficient and robust catalysts. Finally, they can be produced in genetically engineered (recombinant) host microbes from sustainable sugar feedstocks.

[0172] In some embodiments, the enzyme-catalysed process comprises the use of a glycolaldehyde dehydrogenase, such as EC number 1.2.1.21.

[0173] Advantageously, the method of the invention does not require a fermentation step, which is usually associated with long residence times (e.g. at least 24 hours) and thus higher costs. Additionally, further advantages of not relying on fermentation are that no microorganisms are required, no concerns over contamination with other microbes, less complex reaction medium, easy separation, less variable and hence more reliable process. Therefore, in some embodiments, the converting of step (iv) does not comprise fermentation, i.e. comprises substantially no fermentation. In more particular embodiments, the method of the invention comprises substantially no (i.e. does not comprise) fermentation.

[0174] In some embodiments, step (iv) comprises photo-catalysed conversion (i.e. step (iv) may comprise subjecting the intermediate product (e.g. the second composition) to UV radiation). In some embodiments, the photo-catalysed conversion comprises subjecting a second composition comprising the intermediate product to UV radiation for a sufficient duration to convert at least a portion of the intermediate product to the organic product. The UV radiation may comprise UVC radiation, such as UV radiation having a wavelength of from about 200 nm to about 280 nm, such as about 254 nm.

[0175] In some embodiments, step (iv) comprises subjecting the intermediate product (e.g. the second composition) to UV radiation (e.g. UVA radiation having a wavelength of from about 315 nm to about 400 nm, such as about 380 nm) and a suitable catalyst or photosensitiser (e.g. a titanium, copper or iron catalyst, such as TiO?).

[0176] Advantageously, the photo-catalysed conversion using UV radiation leads to high selectivity towards the organic product (e.g. glycolic acid). A further advantage of theuse of UV radiation is sterilisation of the organic products, potentially giving a much longer shelf life to the end product.

[0177] In some embodiments, in step (iv), the at least a portion is at least 50 wt% of the intermediate product, such as at least 60 wt%, 70 wt%, 80 wt% or 90 wt%; i.e. at least 50 wt% such as at least 60 wt%, 70 wt%, 80 wt% or 90 wt% of the intermediate product is converted into the organic product. In more particular embodiments, in step (iv), substantially all the intermediate product is converted into the organic product. As used herein, "substantially all" refers to at least 90 wt%, such as at least 95 wt%.

[0178] End products

[0179] In some embodiments, the organic product (which may also be referred herein as the "end product") is selected from the group of organic acid, organic alcohol, organic aldehyde, organic ketone, and organic amine.

[0180] In some embodiments, the organic product is an aliphatic product (i.e. an aliphatic molecule). The skilled person will understand than an aliphatic molecule refers to a non-aromatic molecule (i.e. the intermediate product does not comprise an aromatic ring). The aliphatic molecule may be saturated or unsaturated, straight-chain or branched-chain. In particular embodiments, the aliphatic molecule is saturated.

[0181] In more particular embodiments, both the intermediate product and the organic product are aliphatic molecules, such as saturated molecules.

[0182] In some embodiments, the organic product is at least a C2 organic product (e.g. is a C2 organic product).

[0183] In some embodiments, the organic product is a C2-6 organic product. As used herein, a C2-6 organic product is an organic product that comprises from 2 to 6 carbon atoms in its skeleton. In more particular embodiments, the organic product is a C2-4 organic product (i.e. it comprises from 2 to 4 carbon atoms in its skeleton).

[0184] In some embodiments, the organic product is an organic acid and / or an organic alcohol, such as an organic acid.

[0185] As used herein, the term "organic acid" refers to organic compounds with acidic properties. Particular organic acids that may be mentioned include carboxylic acids (compounds comprising the functional group -COOH). Typically, organic acids are weakacids that do not dissociate completely in water. In some embodiments, the organic acid is selected from the group consisting of glyceric acid, glyoxylic acid, oxalic acid, and lactic acid.

[0186] In some embodiments, the organic acid is a carboxylic acid. In some embodiments, the carboxylic acid is a Ci-6 carboxylic acid, e.g. a C2 carboxylic acid. A C1-6 carboxylic acid is a carboxylic acid that comprises from 1 to 6 carbon atoms (e.g. from 2 to 4 carbon atoms).

[0187] As used herein, the term "organic alcohol" refers to an organic compound comprising at least one hydroxy functional group. In some embodiments, the organic alcohol is a C1-6 alcohol, e.g. a C2 alcohol. A C1-6 alcohol is an alcohol that comprises from 1 to 6 carbon atoms (e.g. from 2 to 4 carbon atoms, which may be referred to as a C2-4 alcohol). The alcohol may be linear or branched and / or the one or more hydroxy groups may be independently present on any of the carbon atoms (including di- and tri-substitution).

[0188] In some embodiments, the organic acid or organic alcohol is a hydroxycarboxylic acid. A hydroxycarboxylic acid is a carboxylic acid that is substituted with one or more hydroxy (-OH) groups. As hydroxycarboxylic acid contains both a hydroxy group and a carboxylic acid group, it may be classified as an organic acid or an organic alcohol.

[0189] In some embodiments, the carboxylic acid is a C2-6 hydroxycarboxylic acid, such as a C2 hydroxycarboxylic acid. A C2-6 hydroxycarboxylic acid is a hydroxycarboxylic acid that comprises from 2 to 6 carbon atoms (e.g. from 2 to 4 carbon atoms, which may be referred to as a C2-4 hydroxycarboxylic acid).

[0190] In a particular embodiment, the hydroxycarboxylic acid is glycolic acid. Glycolic acid O

[0191] may be represented by the structural formula

[0192]

[0193] In some embodiments, the organic acid is an amino acid.

[0194] In some embodiments, the organic product is an organic aldehyde, such as a C2 to C4 aldehyde, e.g. glyoxal.

[0195] Further method stepsIn some embodiments, the method further comprises the pre-step of converting biomass, such as waste biomass, into the saccharide. The biomass may have any of the features described above, for example the biomass may comprise lignocellulosic material or cellulose, such as cellulose.

[0196] In some embodiments, the biomass and / or the saccharide is not petrochemically-derived, e.g. less than 1 wt% of the first composition is petrochemically derived (for the avoidance of doubt, this includes 0 wt%). In more particular embodiments, the method does not comprise feeding any composition into the first and second reactor, wherein the composition is more than 1 wt% petrochemically-derived.

[0197] In some embodiments, the method further comprises a step of rapid pressure let down (also known as a flash) between steps (ii) and (iii). The rapid pressure let down is advantageous for industrial applicability and environmental benefits (e.g. due to better heat energy recovery) and may be further advantageous due to removal of unwanted volatile by-products such as formaldehyde.

[0198] In some embodiments, the method further comprises a purification step after step (ii), such as between steps (ii) and (iii), to purify (e.g. increase the purity of) the intermediate product. Therefore, in some embodiments, the second composition comprises the intermediate product obtained from the purification step (rather than the intermediate product obtained in the crude composition (i.e. the output stream) of step (ii)).

[0199] The purification step may comprise any of the purification techniques known in the art, for example separation, solvent extraction, crystallization, distillation or reactive distillation, to purify (i.e. to increase the purity of) the intermediate product. In some embodiments, the purification step comprises salt formation and / or (e.g. or) ion exchange separation.

[0200] In some embodiments, the method further comprises a purification step after step (iv), to purify (e.g. increase the purity of) the organic acid or organic alcohol. The purification step may have any of the features described above for the purification step of the intermediate product (e.g. salt formation or ion exchange separation).

[0201] In more particular embodiments, the purification step comprises salt formation (particularly in embodiments wherein the organic product is an organic acid). For example, the purification step may comprise reacting the organic acid with a base(such as an inorganic base, e.g. an inorganic hydroxide) to form a salt. Advantageously, the salt may enable facile purification through standard techniques such as filtration.

[0202] In some embodiments, the purification step may comprise (e.g. be) in situ purification, such as the purification step is carried out in the first or second reactor, such as in the second reactor.

[0203] In some embodiments, the method may comprise a step of separating the output stream obtained in step (ii), e.g. the output stream obtained in step (ii) (i.e. the third composition) may be split into: a first stream comprising the intermediate product, a second stream comprising unreacted biomass or saccharide (i.e. a recycle stream), further streams comprising by-products (such as a third stream comprising a byproduct).

[0204] In particular such embodiments, the method comprises recirculating (i.e. feeding) the second stream into the first reactor.

[0205] In particular embodiments, the by-product of the third stream may be the C2 to C4 organic product of the third aspect of the invention, e.g dihydroxyacetone.

[0206] In some embodiments, the organic product (e.g. organic acid) is obtained in the substantial absence of toxic impurities, i.e. the organic product in step (iv) is obtained as a fourth composition comprising the organic product, and the fourth composition comprises less than 1 wt% of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, and formic acid (for the avoidance of doubt, this includes 0 wt%). In embodiments wherein the second reactor is a continuous or semi-continuous reactor, the fourth composition may be the output stream of the second reactor.

[0207] In some embodiments, the method comprises substantially no (such as no) purification step between steps (ii) and (iii), i.e. the output stream of the first reactor represents the second composition which is used in step (iii). The skilled person will understand that, in such embodiments, "substantially no purification step" refers to no purification step that will significantly alter the composition of the output stream, such as no purification step that will alter the composition of more than 80 wt% of the output stream, such as more than 90 wt% or 95 wt%.In some embodiments, the output stream of step (ii) may be at a pH of less than 7, such as a pH of less than 6. In such embodiments, the method further comprising a neutralising step between step (ii) and (iii), wherein the pH of the output stream of step (ii) or the pH of the second composition (e.g. the second composition) is increased to about pH 6 to pH 8, such as to about pH 7. The pH of 6 to 8 (or pH 7) may be maintained in the neutral range (i.e. pH 6 to 8, such as about pH 7) for the duration of steps (iii) and (iv).

[0208] In other words, in some embodiments, the pH of the second composition is in the neutral range (i.e. pH 6 to 8, such as about pH 7) and the pH is maintained in the neutral range throughout steps (iii) and (iv).

[0209] Therefore, in some embodiments, the method comprises a step of neutralisation throughout step (iii) such that the pH of the second composition is maintained at from about pH 6 to about pH 8, such as about pH 7 throughout step (iii). The neutralisation may be continuous neutralisation throughout step (iii).

[0210] Advantageously, maintaining a neutral pH in step (iii) (e.g. in steps (iii) and (iv)) is associated with higher yields of the acid organic product (e.g. C2-6 hydroxycarboxylic acid).

[0211] Advantageously, the method of the invention allows for high conversion of the feedstock (i.e. biomass or saccharide) into the organic product. Therefore, in some embodiments, the conversion efficiency of the biomass or the saccharide is at least 50%, such as at least 60%, at least 70%, at least 80% or at least 90%. For the avoidance of doubt, the conversion efficiency refers to the percentage of feedstock that is consumed in the method of the invention during steps (i) to (iv).

[0212] Advantageously, the method of the invention allows for high yield of the intermediate product and the organic product. For the avoidance of doubt, the yield is calculated with respect to the moles of starting biomass or saccharide and moles of the intermediate product or organic product, as appropriate.

[0213] Therefore, in some embodiments, the yield of the intermediate product (e.g. glycolaldehyde) is at least 40%, such as at least 50%, such as at least 60%, at least 70%, at least 80% or at least 90%.In some embodiments, the yield of the organic product (e.g. glycolic acid) is at least 40%, such as at least 50%, such as at least 60%, at least 70%, at least 80% or at least 90%. The yield of the organic product is calculated with respect to the starting biomass or saccharide, i.e. calculated over steps (i) to (iv).

[0214] Overall, advantageously, the process of the invention is highly selective towards the desired organic product, with minimal over reaction of the intermediate product, or production of undesired by products. Therefore, in some embodiments, the crude composition obtained in step (iv) comprises the organic product, wherein the purity of the organic product in the crude composition is at least 50%, such as at least 80% 90%, 95% (wherein the purity percentages are with respect to the dry mass of the fourth composition, i.e. the solvent present in the crude composition is disregarded).

[0215] In particular such embodiments, e.g. where the organic product is glycolic acid, the overall method is highly selective towards glycolic acid, such that essentially no undesired byproducts are obtained in step (iv), e.g. substantially no (e.g. less than 1 wt%, or less than 0.5 wt%, or less than 0.1 wt% of each of (for the avoidance of doubt, this includes 0 wt%)) glyoxylic acid, oxalic acid, glyoxal, formic acid or formaldehyde are obtained in the output steam of step (iv).

[0216] Advantageously, the method of the invention yields high concentration of the intermediate product in the crude composition of step (ii) and / or of the end product in the crude composition of step (iv) (e.g. in the output streams of the first and / or second reactor, in embodiments where the first and / or second reactors is / are continuous or semi-continuous reactor(s)). For instance, glycolaldehyde and / or glycolic acid may be obtained at a concentration of at least 1 g / L or 10 g / L per hour.

[0217] In some embodiments, the method of the first aspect is used to obtain the composition of the fifth aspect of the invention.

[0218] According to a second aspect of the invention, there is provided an organic product or a composition comprising an organic product, wherein the organic product is obtainable (e.g. obtained) by the method of the first aspect of the invention. For the avoidance of doubt, the organic product and the composition of the second aspect may have any of the features of the first aspect of the invention, including combinations thereof.

[0219] In some embodiments, the composition is a cosmetic composition, optionally further comprising a diluent, carrier and / or adjuvant, as known to those skilled in the art.According to a third aspect of the invention, there is provided a method of producing a C2 to C4 organic product, comprising the steps of:

[0220] (i) feeding a first composition comprising biomass or a saccharide into a first reactor; and

[0221] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to the C2 to C4 organic product.

[0222] The C2 to C4 product may have any of the features of the intermediate product of the first aspect of the invention.

[0223] In particular embodiments, the C2 to C4 product comprises (e.g. is) a ketone and / or (e.g. and) a hydroxy group.

[0224] In more particular embodiments, the C2 to C4 organic product is a C3 organic alcohol, such as dihydroxyacetone.

[0225] According to a fourth aspect of the invention, there is provided a C2 to C4 organic product or composition comprising a C2 to C4 organic product, wherein the C2 to C4 organic product is obtainable (e.g. obtained) by the method of the third aspect of the invention. For the avoidance of doubt, the C2 to C4 organic product and the composition of the fourth aspect may have any of the features of the first and third aspects of the invention, including combinations thereof.

[0226] According to a fifth aspect of the invention, there is provided a composition comprising glycolic acid and glyceric acid. The composition of the fifth aspect is obtainable (e.g. obtained) by the method of the first aspect of the invention, such as wherein the method comprises substantially no purification step between steps (ii) or (iii).

[0227] Advantageously, the composition of the fifth aspect of the invention is a valuable composition, useful in specialised applications (such as in the cosmetic industry). Additionally, the composition may be efficiently obtained using the method of the invention, at least because no significant separation is required between steps (ii) and (iii). Additional further benefits when using the method of the invention to obtain the composition of the fifth aspect is the lack of toxic impurities, advantageous carbon footprint, low process complexity and great process reliability.In an alternative fifth aspect of the invention, there is provided the use of the composition of the fifth aspect in a non-therapeutic method (e.g. cosmetic method).

[0228] In some embodiments, the composition comprises between 30 and 80 wt% glycolic acid, such as between 40 and 80 wt%, or between 50 and 80 wt%.

[0229] In some embodiments, the composition comprises between 5 and 20 wt% glyceric acid, such as between 5 and 10 wt% or between 10 and 20 wt%.

[0230] In some embodiments, the composition comprises (i) between 30 and 80 wt% glycolic acid and (ii) between 5 and 20 wt% glyceric acid.

[0231] In some embodiments, the composition further comprises between 0 and 30 wt% dihydroxyacetone, such as between 0 and 20 wt% or 0 and 10 wt%.

[0232] In some embodiments, the composition further comprises between 0 and 30 wt% gluconic acid, such as between 0 and 20 wt% or 0 and 10 wt%.

[0233] In some embodiments, the composition comprises one or more of glycolaldehyde, glyceraldehyde and glucose. In particular such embodiments, the composition comprises at most 10 wt% (such as at most 5 wt%) of each of glycolaldehyde, glyceraldehyde and glucose.

[0234] In some embodiments, the composition comprises a molar ratio of glycolic acid to glyceric acid between 1:1 and 20:1, such as between 1.5:1 and 16:1.

[0235] Embodiments of the invention are exemplified in the following numbered paragraphs.

[0236] Paragraph 1. A method of producing an organic product, comprising the steps of:

[0237] (i) feeding a first composition comprising biomass or a saccharide into a first reactor, wherein the first reactor is a continuous, semicontinuous or batch reactor (such as continuous or semi-continuous reactor);

[0238] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to an intermediate product;

[0239] (iii) feeding a second composition comprising the intermediate product into a second reactor; and

[0240] (iv) converting at least a portion of the intermediate product to the organic product.Paragraph 2. The method of paragraph 1, wherein the biomass or a saccharide is a saccharide, i.e. the first composition comprises a saccharide.

[0241] Paragraph 3. The method of paragraph 2, further comprising a pre-step of:

[0242] (i-b) subjecting a composition comprising biomass to hydrothermal conversion conditions to convert at least a portion of the biomass into the saccharide.

[0243] Paragraph 4. The method of paragraph 1, wherein the biomass or a saccharide is biomass, i.e. the first composition comprises biomass.

[0244] Paragraph 5. The method of any one of the preceding paragraphs, wherein the first reactor is a continuous reactor or semicontinuous reactor, such as continuous reactor.

[0245] Paragraph 6. The method of any one of the preceding paragraphs, wherein the second reactor is a (i) batch, continuous or semicontinuous reactor, such as continuous reactor; or (ii) batch or continuous reactor.

[0246] Paragraph 7. The method of paragraph 1, wherein the hydrothermal conversion conditions comprise a temperature between 100 °C and 500 °C, such as 300 °C to 500 °C, 350 °C to 500 °C, or 350 °C to 400 °C (e.g. 300 °C to 500 °C).

[0247] Paragraph 8. The method of any one of the preceding paragraphs, wherein the hydrothermal conversion conditions comprise a pressure between 0.5 MPa and 30 MPa, such as 10 MPa to 30 MPa, or 20 MPa to 30 MPa.

[0248] Paragraph 9. The method of any one of the preceding paragraphs, wherein the hydrothermal conversion conditions comprise a residence time of the biomass or the saccharide between 0.05 s and 20 s, such as between 0.5 s to 10 s, or between 0.5 s to 5s.

[0249] Paragraph 10. The method of any one of the preceding paragraphs, wherein step (ii) comprises contacting water at a temperature of at least about 100 °C and a pressure of at least 0.5 MPa with the first composition for a duration sufficient to convert at least a portion of the biomass or the saccharide into the intermediate product.

[0250] Paragraph 11. The method of any one of the preceding paragraphs, wherein the hydrothermal conversion conditions comprise subcritical water.Paragraph 12. The method of any one of the preceding paragraphs, wherein the hydrothermal conversion conditions comprise supercritical water.

[0251] Paragraph 13. The method of any one of the preceding paragraphs, wherein step (ii) is carried out in the substantial absence of a transition metal catalyst and / or organic solvent.

[0252] Paragraph 14. The method of any one of the preceding paragraphs, wherein the biomass comprises plant material, cellulose, lignocellulose, wood, algae, starch, agricultural waste, or mixtures of one or more thereof.

[0253] Paragraph 15. The method of any one of the preceding paragraphs, wherein the saccharide is a Cs or Ce saccharide.

[0254] Paragraph 16. The method of paragraph 15, wherein the saccharide is a Ce monosaccharide, such as wherein the Ce monosaccharide is selected from the group consisting of glucose, mannose, galactose, fructose, and combinations thereof.

[0255] Paragraph 17. The method of paragraph 16, wherein the Ce monosaccharide is glucose.

[0256] Paragraph 18. The method of any one of the preceding paragraphs, wherein the intermediate product is a C2, C3 or C4 molecule.

[0257] Paragraph 19. The method of any one of the preceding paragraphs, wherein the intermediate product comprises an aldehyde group.

[0258] Paragraph 20. The method of any one of the preceding paragraphs, wherein the intermediate product does not comprise a nitrile group.

[0259] Paragraph 21. The method of any one of the preceding paragraphs, wherein the intermediate product is glycolaldehyde.

[0260] Paragraph 22. The method of any one of the preceding paragraphs, wherein the intermediate product is obtained in the substantial absence of toxic impurities, such as wherein the output stream of step (ii) comprises less than 3 wt % (e.g. less than 2 wt% or less than 1 wt%), such as less than 1 wt% of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, oxalic acid and formic acid.Paragraph 23. The method of any one of the preceding paragraphs, wherein the converting in step (iv) comprises an oxidation reaction (e.g. in the presence of oxygen (e.g. pressurised oxygen)), such as an enzyme-catalysed oxidation or photooxidation.

[0261] Paragraph 24. The method of any one of the preceding paragraphs, wherein the converting in step (iv) comprises contacting the intermediate product with an enzyme, a metal catalyst, or a photocatalyst, or subjecting the intermediate product to UV radiation.

[0262] Paragraph 25. The method of any one of the preceding paragraphs, wherein step (iv) comprises contacting the intermediate product with an enzyme having oxidative activity of an aldehyde group, such as in the presence of oxygen (e.g. pressurised oxygen).

[0263] Paragraph 26. The method of any one of the preceding paragraphs, wherein step (iv) is carried out in a cell-free environment.

[0264] Paragraph 27. The method of any one of paragraphs 1 to 24, wherein step (iv) comprises subjecting the intermediate product to UV radiation, such as UV radiation having a wavelength of about 254 nm.

[0265] Paragraph 28. The method of any one of the preceding paragraphs, wherein the organic product is selected from the groups consisting of organic acid, organic alcohol, organic aldehyde, organic ketone, and organic amine, such as wherein the organic product is an organic acid or organic alcohol.

[0266] Paragraph 29. The method of paragraph 28, wherein the organic acid or organic alcohol is a hydroxycarboxylic acid.

[0267] Paragraph 30. The method of paragraph 29, wherein the hydroxycarboxylic acid is glycolic acid.

[0268] Paragraph 31. The method of any one of the preceding paragraphs, wherein the biomass or the saccharide is not petrochemically-derived, such as less than 1 wt% of the first composition is petrochemically derived.Paragraph 32. The method of any one of the preceding paragraphs, wherein the method further comprises a step of rapid pressure let down (also known as a flash) between steps (ii) and (iii).

[0269] Paragraph 33a. The method of any one of the preceding paragraphs, wherein the method further comprises a purification step after step (ii), such as between steps (ii) and (iii), optionally wherein the purification step comprises solvent extraction, crystallization, distillation and / or reactive distillation.

[0270] Paragraph 33b. The method of any one of the preceding paragraphs, wherein the method further comprises a purification step after step (iv), such as wherein the purification step comprises salt formation and / or (e.g. or) ion exchange separation.

[0271] Paragraph 34. The method of any one of the preceding paragraphs, wherein the organic product is obtained in the substantial absence of toxic impurities, such as wherein the output stream of step (iv) comprises less than 3 wt% (e.g. less than 2 wt% or less than 1 wt%), such as less than 1 wt% of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, and formic acid.

[0272] Paragraph 35. The method of any one of the preceding paragraphs, wherein the conversion efficiency of the biomass or the saccharide is at least 50%, at least 60%, at least 70%, at least 80%, such as at least 90%.

[0273] Paragraph 36. The method of any one of the preceding paragraphs, wherein the yield of the intermediate product is at least 40%, such as at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%.

[0274] Paragraph 37. The method of any one of the preceding paragraphs, wherein the yield of the organic product is at least 40%, such as at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%.

[0275] Paragraph 38. The method of any one of the preceding paragraphs, wherein in step (ii), the at least a portion of the biomass or the saccharide is at least at least 50 wt%, such as at least 60 wt%, 70 wt%, 80 wt%, 90 wt%, or substantially all.

[0276] Paragraph 39. The method of any one of the preceding paragraphs, wherein in step (iv), the at least a portion of intermediate product is at least at least 50 wt%, such as at least 60 wt%, 70 wt%, 80 wt%, 90 wt%, or substantially all.Paragraph 40. An organic product, or a composition comprising an organic product, wherein the organic product is obtainable by the method of paragraphs 1 to 39.

[0277] Paragraph 41. The composition of paragraph 40 wherein the composition is a cosmetic composition.

[0278] Paragraph 42. A method of producing a C2 to C4 organic product, comprising the steps of:

[0279] (i) feeding a first composition comprising biomass or a saccharide into a first reactor, wherein the first reactor is a continuous or semi-continuous reactor; and

[0280] (ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the biomass or the saccharide to the C2 to C4 organic product.

[0281] Paragraph 43. The method of paragraph 42, wherein the C2 to C4 organic product is a C2 to C4 organic alcohol, such as a C3 organic alcohol.

[0282] Paragraph 44. The method of paragraph 42, wherein the C2 to C4 organic product is dihydroxyacetone.

[0283] Paragraph 45. The method of any one of paragraphs 42 to 44, having any one of the features of paragraphs 1 to 39.

[0284] Paragraph 46. A composition comprising the C2 to C4 organic product obtainable by the method of paragraphs 42 to 45.

[0285] Paragraph 47. A composition comprising between 30 and 80 wt% glycolic acid and between 5 and 20 wt% glyceric acid.

[0286] Paragraph 48. A composition of paragraph 47, further comprising between 0 and 30 wt% dihydroxyacetone; and / or between 0 and 30 wt% gluconic acid.

[0287] Paragraph 49. A composition of paragraph 47 or 48, having any one of the features of paragraphs 1 to 46.

[0288] Paragraph 50. A method of any one of paragraphs 1 to 45 to obtain a composition of any one of paragraphs 47 to 49.Examples

[0289] The present invention is illustrated by way of the following examples, which are not intended to be limiting on the overall scope of the invention.

[0290] Example 1: Conversion of glucose feedstock into glycolic acid via glycolaldehyde

[0291] Glucose to olvcolaldehvde (i.e. steps (I) and (ID)

[0292] An experiment was set up using glucose as the feedstock where it was solubilized in water at roughly 40 wt% and introduced into a continuous hydrothermal reactor where it mixes with a stream of heated and pressurized water giving an overall mixed temperature of 383°C, pressure of 241 bar (24.1 MPa) and a concentration of 12 wt% glucose.

[0293] Residence time was precisely controlled to roughly 1.3 seconds by depressurization in a flash vessel where the outputs were collected and analysed using HPLC.

[0294] A yield of 48.3% was obtained for glycolaldehyde and 16% for di hydroxyacetone (DHA).

[0295] Glycolaldehyde to glycolic acid (UV route), i.e. steps fill) and (iv)

[0296] Glycolaldehyde was prepared in water at a concentration of 1 g / l. 700ml of the mixture was poured into a 1 litre bioreactor. Air was pumped into the medium using two spargers ensuring maximal aeration of 2 litres per minute. A UV light source of 254nm was encased in a transmissible glass tubing and immersed in the bioreactor ensuring equal illumination of light throughout the vessel. Water was regularly topped up to maintain liquid level. A temperature and pH probe were used to monitor the reaction and the conversion rate.

[0297] At a temperature of 30°C, a conversion of >50% into glycolic acid was obtained after 24 hours.

[0298] Glycolaldehyde to glycolic acid (enzymatic route) i.e. steps fill) and (iv)

[0299] Test enzymes (xanthine oxidase and glyoxal oxidase) were mixed with water at approximately 5 micromolar concentration in separate 1 ml reaction tubes along withperoxidase mediated indicator (horseradish peroxidase enzyme, 0.6 micromole of 4-aminoantipyrine and 0.6 micromole of Dihydrate (N-Ethyl-N-(2-hydroxy-3-sulfopropyl)-m-toluidine)), and 0.1 mmol phosphate buffer.

[0300] For the xanthine oxidase reaction, glycolaldehyde was added to 20 mmol to start the reaction. For the glyoxal oxidase reaction, hydrogen peroxide was first added to a concentration of 0.5 micromolar to activate the enzyme, and then glycolaldehyde was added to 20 mmol. Both reactions were tracked by following absorbance at 555nm using a spectrophotometer.

[0301] For the xanthine oxidase reaction there was no reading until the addition of the glycolaldehyde at which point the absorbance rapidly increased to the maximum for the machine.

[0302] For the glyoxal oxidase reaction, there was no absorbance reading until the hydrogen peroxide was added at which point a low absorbance reading was observed (0.35), and then following the addition of the glycolaldehyde a large absorbance reading was observed (8.35).

[0303] Both of these results suggest high conversion to glycolic acid.

Claims

Claims1. A method of producing a C2-6 hydroxycarboxylic acid, comprising the steps of:(i) feeding a first composition comprising a Ce saccharide into a first reactor, wherein the first reactor is a continuous or semi-continuous reactor;(ii) subjecting the first composition to hydrothermal conversion conditions to convert at least a portion of the Ce saccharide to an intermediate product, wherein the intermediate product is an aldehyde;(iii) feeding a second composition comprising the intermediate product into a second reactor; and(iv) converting at least a portion of the intermediate product to the C2-6 hydroxycarboxylic acid.

2. The method of claim 1, wherein the first composition comprises a concentration of the Ce saccharide between 1 and 25 wt%, such as between 5 and 20 wt%.

3. The method of any one of the preceding claims, wherein the hydrothermal conversion conditions comprise a temperature between 100 °C and 500 °C, such as between about 300 °C and about 500 °C.

4. The method of any one of the preceding claims, wherein the hydrothermal conversion conditions comprise a pressure between 0.5 MPa and 30 MPa, such as between 10 MPa and 30 MPa, or between 20 MPa and 30 MPa.

5. The method of any one of the preceding claims, wherein the hydrothermal conversion conditions comprise a residence time of the Ce saccharide between 0.05 s and 20 s, such as between 0.5 s to 10 s, or between 0.5 s to 5s.

6. The method of any one of the preceding claims, wherein the hydrothermal conversion conditions comprise subcritical water and / or supercritical water.

7. The method of any one of the preceding claims, wherein the method comprises substantially no (such as no) purification step between steps (ii) and (iii).

8. The method of any one of the preceding claims, further comprising :a neutralising step between step (ii) and (iii) such that the pH of the second composition is from about pH 6 to about pH 8, such as about pH 7; and / orneutralisation (e.g. continuous neutralisation) throughout step (iii) such that the pH of the second composition is maintained at from about pH 6 to about pH 8, such as about pH 7, throughout step (iii).

9. The method of any one of the preceding claims, wherein step (ii) is carried out in the substantial absence of a transition metal catalyst and / or organic solvent.

10. The method of any one of the preceding claims, wherein the intermediate product is obtained in the substantial absence of toxic impurities, such as wherein the output stream of step (ii) comprises less than 3 wt%, such as less than 1 wt%, of each of formaldehyde, hydrogen cyanide, monochloroacetic acid, glycolonitrile, oxalic acid and formic acid.

11. The method of any one of the preceding claims, wherein the converting in step (iv) comprises contacting the intermediate product with an enzyme, a metal catalyst, or a photocatalyst, or subjecting the intermediate product to UV radiation.

12. The method of any one of the preceding claims, wherein step (iv) comprises contacting the intermediate product with an enzyme, such as an enzyme having oxidative activity of an aldehyde group.

13. The method of claim 12, wherein step (iv) is carried out in a cell-free environment.

14. The method of any one of claims 1 to 11, wherein step (iv) comprises subjecting the intermediate product to UV radiation, such as UV radiation having a wavelength of about 254 nm.

15. The method of any one of the preceding claims, wherein the first and second reactors are the same reactor.

16. The method of any one of the preceding claims, wherein the first reactor is a continuous reactor, optionally wherein the second reactor is a batch or semi-continuous reactor.

17. The method of any one of the preceding claims, wherein the Ce saccharide is a Ce monosaccharide, such as glucose.

18. The method of any one of claims 1 to 16, wherein the Ce saccharide is a Ce polysaccharide, such as starch.

19. The method of any one of the preceding claims, wherein the intermediate product is glycolaldehyde.

20. The method of any one of the preceding claims, wherein the C2-6 hydroxycarboxylic acid is glycolic acid.

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