Crystal of high-purity magnesium L-lactate

Abstract

A method of forming high purity L-magnesium lactate crystals from homogenous and non-homogenous decomposed organic waste is provided. The process provides magnesium L-lactate crystals with improved enantiomeric purity and total purity, which are particularly suitable for reuse in the production of new polylactic acid.

Description

[0001] This application is a divisional application of an invention patent application filed on January 19, 2022, with application number 202280009092.2 and invention name “Crystallization of High-Purity Magnesium L-Lactate”. Technical Field

[0002] The present invention relates to a method for crystallizing high-purity magnesium L-lactate from decomposed organic waste. Background Art

[0003] Lactic acid is the most widely occurring hydroxycarboxylic acid used in the food, chemicals, pharmaceutical and cosmetic industries. This naturally occurring organic acid can be prepared by chemical synthesis or microbial fermentation. When prepared by microbial fermentation, care should be taken to avoid endogenous reductions in pH caused by lactic acid formation in order to maintain the productivity of the microorganisms. A pH in the range of 5-7 is preferred and can be obtained by adding a base such as ammonium, sodium, potassium, magnesium or calcium hydroxide, which neutralizes the lactic acid, thereby producing a lactate. In order to convert the lactate into lactic acid, a re-acidification step using, for example, sulfuric acid can be performed.

[0004] About 60-80% of the cost of lactic acid production comes from downstream processes, including purification, concentration and separation of lactic acid / lactate from the fermentation broth. In addition, it is desirable to reduce or eliminate the production of by-products (eg, salts other than lactate).

[0005] Various methods for recovering and purifying lactic acid and / or lactate from fermentation broth have been proposed before. For example, Wang Yong et al. described a crystallization-based method for purifying magnesium lactate in "Efficient magnesium lactate production with in situ product removal by crystallization, Bioresource technology 198 (2015): 658-663". Crystallization was carried out at 42 ° C and no seed crystals were added. The fermentation medium used in the fermenter contained yeast extract, glucose, NaCl, sodium acetate, triammonium citrate, KH2PO4, MgSO4·7H2O and MnSO4·7H2O. The product concentration, productivity and yield of the fermentation coupled with in situ product removal (ISPR) reached 143 g L -1 , 2.41 g L -1 h -1 and 94.3%.

[0006] U.S. Pat. No. 9,689,007 describes a method for producing lactate or lactic acid from a "low-sugar" plant extract by fermentation, the method comprising: providing a fermentation medium comprising at least 25% by weight of a plant extract containing a fermentable carbohydrate, and fermenting the fermentation medium with a lactic acid-producing microorganism in the presence of a caustic magnesium salt to provide a fermentation broth containing up to 9.5% by weight of magnesium lactate at the end of the fermentation, the magnesium lactate being in a soluble form during and at the end of the fermentation. In order to achieve a magnesium lactate concentration of up to 9.5% by weight in the fermentation broth at the end of the fermentation, the fermentation medium comprising the plant extract preferably contains a fermentable carbohydrate concentration of up to 9.5% by weight.

[0007] U.S. Publication No. 2014 / 0012041 describes a method for preparing lactate, the method comprising: crystallizing an aqueous lactate solution containing formate, the amount of formate relative to the lactate being not less than 7.0 wt %; and recovering the lactate. The lactate concentration in the aqueous lactate solution is 10.0 to 30.0 wt %.

[0008] U.S. Publication No. 2017 / 0218408 describes a method for preparing a fermentation product including lactic acid, the method comprising: a) treating a lignocellulosic material in a granular state and having an average particle size of 0.1 to 250 mm with a caustic magnesium salt in the presence of water to provide a treated aqueous lignocellulosic material; b) saccharifying the treated aqueous lignocellulosic material in the presence of a hydrolytic enzyme to provide a saccharified aqueous lignocellulosic material containing fermentable carbohydrates and solid lignocellulosic components; c) simultaneously with step b), fermenting the saccharified aqueous lignocellulosic material in the presence of both a lactic acid-forming microorganism and a caustic magnesium salt to provide an aqueous fermentation broth containing magnesium lactate and solid lignocellulosic components; d) recovering magnesium lactate from the fermentation broth, wherein the saccharification and fermentation are performed simultaneously. The raw material of the method of U.S. Publication No. 2017 / 0218408 is a lignocellulosic material, which includes a material containing cellulose, hemicellulose and lignin, such as a material that can be derived from plant biomass. Preferred lignocellulosic materials are selected from wheat straw, bagasse, corn stalks and mixtures thereof.

[0009] WO Publication No. 2017 / 178426 describes a fermentation method for preparing magnesium lactate from a carbon source, the method comprising the following steps:

[0010] - providing a fermentation medium comprising a fermentable carbon source in a fermentation reactor,

[0011] - fermenting the fermentation medium in the presence of an alkaline magnesium salt using a lactic acid producing microorganism to provide a fermentation broth containing magnesium lactate, and

[0012] - recovering solid magnesium lactate from the fermentation broth containing magnesium lactate, wherein during at least 40% of the operating time of the fermentation process, the concentration of solid magnesium lactate in the fermentation broth is maintained in the range of 5-40% by volume, based on the solid magnesium lactate crystals in the total amount of the fermentation broth. Examples of fermentable carbon sources are C5 sugars, C6 sugars, oligomers thereof (e.g. dimers C 12 sugars) and / or their polymers.

[0013] WO Publication No. 2017 / 207501 describes a method for separating biomass from a solid fermentation product, wherein a slurry comprising biomass and solid fermentation product is provided to the top of a biomass separator unit, and an aqueous medium is provided to the bottom of the biomass separator unit, and a product stream comprising the solid fermentation product is discharged from the bottom of the biomass separator unit, and a waste stream comprising the biomass is discharged from the top of the biomass separation unit. The solid fermentation product is a fermentation product present in the aqueous medium at a concentration higher than its saturation concentration, and may be a crystalline product or an amorphous product.

[0014] The above purification and crystallization methods are designed for fermentation broths derived from substantially uniform biomass-based feed streams with low soluble and insoluble impurity content. However, it is necessary to utilize more available, cheaper heterogeneous feedstocks for fermentation, such as mixed food wastes from urban, industrial and commercial sources. These heterogeneous feedstocks contain impurities such as salts, lipids, proteins, coloring components and inert materials. Fermentation broths derived from such heterogeneous feedstocks cannot be effectively processed by currently available methods to obtain high purity L-lactate magnesium products in a cost-effective manner.

[0015] WO Publication No. 2020 / 110108 describes a method for separating and purifying magnesium lactate from a fermentation broth, the method comprising the following steps:

[0016] (a) providing a clarified fermentation broth from which insoluble impurities have been removed, which comprises magnesium lactate in soluble form obtained from a fermentation process, wherein the temperature of the fermentation broth is about 45° C. to about 75° C.;

[0017] (b) concentrating the clarified fermentation broth from step (a) to a lactate concentration of about 150 g / L to about 220 g / L;

[0018] (c) subjecting the concentrated clarified fermentation broth from step (b) to at least one cooling crystallization to obtain magnesium lactate crystals; and

[0019] (d) collecting the obtained magnesium lactate crystals.

[0020] There remains an unmet need for a simple, cost-effective process for crystallizing high purity magnesium L-lactate salt from decomposed organic waste with high recovery yield. Summary of the invention

[0021] The present invention provides a method for preparing high purity L-lactate magnesium from fermentation broth or other organic waste decomposition products containing lactic acid and / or lactate. The method of the present invention includes evaporative crystallization, which can utilize fermentation broth or other organic waste decomposition products from a variety of different sources, making the method economically and environmentally beneficial. The method disclosed herein is suitable for feed batch production and continuous production in lactic acid recovery facilities.

[0022] The present invention is based in part on the unexpected discovery that high purity magnesium L-lactate crystals can be obtained from dispersions of decomposed organic wastes, such as lactic acid fermentation broths, without removing D-lactic acid during and / or after fermentation. The method involves the use of evaporative crystallization under specific conditions, which produces high purity magnesium L-lactate crystals after a single treatment despite the presence of significant amounts of impurities in the decomposed waste. Surprisingly, the method of the present invention can lead to improved enantiomeric separation even when using decomposed organic wastes containing up to 10% by weight of endogenous D-lactic acid. Thus, the method of the present invention is simple and economical, providing high purity magnesium L-lactate crystals even when using heterogeneous feedstocks from municipal, industrial and commercial sources containing high concentrations of soluble and insoluble impurities.

[0023] According to a first aspect, the present invention provides a method for forming high-purity magnesium L-lactate crystals from decomposed organic waste, the method comprising the following steps:

[0024] a. providing a clarified dispersion of decomposed organic waste comprising a concentration of about 50 to about 110 g / L of lactate;

[0025] b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0026] c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed L-lactate magnesium crystals;

[0027] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium L-lactate crystals; and

[0028] e. collecting the L-lactate magnesium crystals obtained in step (d),

[0029] wherein steps (b) to (d) are conducted at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar, including each value within the specified range.

[0030] According to one embodiment, the decomposed organic waste is obtained from a lactic acid fermentation process. According to another embodiment, the decomposed organic waste is obtained from lactic acid-containing waste. According to yet another embodiment, the decomposed organic waste is obtained from the hydrolysis of polylactic acid polymers.

[0031] According to a second aspect, the present invention provides a method for forming high-purity L-lactate magnesium crystals from a fermentation broth, the method comprising the following steps:

[0032] a. providing a clarified fermentation broth comprising lactate at a concentration of about 50 to about 110 g / L;

[0033] b. optionally concentrating the clarified fermentation broth of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0034] c. mixing the clarified fermentation broth of step (a) or the concentrated fermentation broth of step (b) to obtain a suspension containing seed L-lactate magnesium crystals;

[0035] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium L-lactate crystals; and

[0036] e. collecting the L-lactate magnesium crystals obtained in step (d),

[0037] wherein steps (b) to (d) are conducted at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar, including each value within the specified range.

[0038] According to a third aspect, the present invention provides a method for forming high-purity L-lactate magnesium crystals from decomposed organic waste, the method comprising the following steps:

[0039] a. providing a clarified dispersion of decomposed organic waste comprising a concentration of about 50 to about 110 g / L of lactate;

[0040] b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0041] c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed L-lactate magnesium crystals;

[0042] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium L-lactate crystals; and

[0043] e. collecting the L-lactate magnesium crystals obtained in step (d),

[0044] wherein steps (b) to (d) are carried out at a temperature of about 100° C. in the absence of vacuum.

[0045] According to certain embodiments, the clarified dispersion or clarified fermentation broth comprises decomposed organic waste or fermentation broth from which impurities have been removed by at least one of filtration, centrifugation, flotation, sedimentation, coagulation, flocculation and decantation. Each possibility represents an independent embodiment. According to other embodiments, the clarified dispersion or clarified fermentation broth comprises decomposed organic waste or fermentation broth from which impurities have been removed by filtration and / or centrifugation.

[0046] According to other embodiments, the organic waste comprises a carbohydrate source. According to other embodiments, the organic waste is selected from food waste, municipal food waste, residential food waste, agricultural waste, industrial food waste from food processing facilities, commercial food waste (from hospitals, restaurants, shopping centers, airports, etc.) and mixtures or combinations thereof. Each possibility represents an independent embodiment.

[0047] According to a particular embodiment, the decomposed organic waste comprises endogenous D-lactic acid. According to a particular embodiment, the decomposed organic waste comprises up to 10% by weight of endogenous D-lactic acid.

[0048] According to certain embodiments, step (b) is performed to a lactate concentration of about 100 to about 130 g / L, including each value within the specified range.

[0049] According to various embodiments, the mixing in step (c) is performed at a speed of about 50 to about 300 revolutions per minute (RPM), including each value within the specified range.

[0050] According to certain embodiments, the mixing in step (c) is performed for at least 1 hour. According to other embodiments, the mixing in step (c) is performed for about 1 to about 6 hours, including each value within the specified range.

[0051] According to other embodiments, steps (b) to (d) are performed at an elevated temperature in the range of about 50°C to about 80°C, including each value within the specified range. According to other embodiments, steps (b) to (d) are performed at a pressure of about 150 to about 250 mbar applied vacuum, including each value within the specified range. According to other embodiments, steps (b) to (d) are performed at a pressure of about 250 to about 350 mbar applied vacuum, including each value within the specified range.

[0052] According to certain embodiments, removing about 70% to about 90% of the water from the suspension in step (d) is performed at an evaporation rate of about 2 to about 5 weight % per hour, including each value within the specified range.

[0053] According to various embodiments, step (e) comprises filtration and / or centrifugation. According to certain embodiments, step (e) is performed at room temperature.

[0054] According to certain embodiments, the method further comprises a step (f) of washing the obtained magnesium L-lactate crystals. According to a specific embodiment, the washing of the obtained magnesium L-lactate crystals is carried out in a solvent selected from water, ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate and mixtures or combinations thereof. Each possibility represents an independent embodiment.

[0055] According to other embodiments, the method further comprises a step (g) of drying the magnesium L-lactate crystals to a loss on drying (LOD) % of about 10% to about 20%, including each value within the specified range. According to a specific embodiment, step (g) is carried out at an elevated temperature of about 50° C. to about 120° C., including each value within the specified range.

[0056] According to other embodiments, the obtained magnesium L-lactate crystals are dissolved and recrystallized by repeating steps (c) to (e). According to these embodiments, steps (c) to (e) are repeated, for example, 2 to 6 cycles, including each value within the specified range.

[0057] According to other embodiments, the recovery rate of the magnesium L-lactate crystals is at least 90%.

[0058] According to other embodiments, the obtained L-lactate magnesium crystals are characterized by a median particle size of less than 75 μm. According to certain embodiments, the obtained L-lactate magnesium crystals are characterized by a particle size distribution including a median particle size in the range of about 20 to about 100 μm, including each value in the specified range. According to other embodiments, the obtained L-lactate magnesium crystals are characterized by a median particle size greater than 75 μm. According to other embodiments, the obtained L-lactate magnesium crystals are characterized by a particle size distribution including a median particle size in the range of about 100 to about 300 μm, including each value in the specified range.

[0059] According to certain embodiments, the obtained L-lactate magnesium crystals contain less than 3% D-lactate magnesium. According to certain embodiments, the obtained L-lactate magnesium crystals contain less than 2% D-lactate magnesium. According to other embodiments, the obtained L-lactate magnesium crystals contain less than 1.5% D-lactate magnesium. According to other embodiments, the obtained L-lactate magnesium crystals contain less than 1% D-lactate magnesium.

[0060] According to other embodiments, the present invention also provides high purity magnesium L-lactate crystals obtainable by the methods disclosed herein.

[0061] According to other embodiments, the present invention provides a method for enriching L-lactate enantiomers from a mixture of enantiomers derived from decomposed organic waste, the method comprising the steps of:

[0062] a. providing a clarified dispersion of decomposed organic waste comprising a concentration of about 50 to about 110 g / L of lactate, wherein the lactate comprises a mixture of enantiomers of D- and L-lactate;

[0063] b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0064] c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed magnesium lactate crystals;

[0065] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium L-lactate crystals having enriched enantiomeric purity; and

[0066] e. collecting the L-lactate magnesium crystals obtained in step (d),

[0067] wherein steps (b) to (d) are conducted at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar, including each value within the specified range.

[0068] In one embodiment, the method is enriched in 1% or more of the L-lactate enantiomer. In another embodiment, the method is enriched in 5% or more of the L-lactate enantiomer. In yet another embodiment, the method is enriched in 10% or more of the L-lactate enantiomer. In a specific embodiment, the method is enriched in up to 15% of the L-lactate enantiomer. In other embodiments, the method is enriched in up to 20% of the L-lactate enantiomer. In other embodiments, the method is enriched in up to 25% of the L-lactate enantiomer.

[0069] It is to be understood that any combination of each of the aspects and embodiments disclosed herein is expressly included within the disclosure of the present invention.

[0070] From the detailed description given below, further embodiments and the full scope of applicability of the present invention will become apparent. However, it should be understood that the detailed description and specific examples, although indicating preferred embodiments of the present invention, are given by way of illustration only, because for those skilled in the art, various changes and modifications within the spirit and scope of the present invention will become apparent from the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The particle size distribution of magnesium L-lactate crystals obtained according to certain embodiments of the present invention is shown.

[0072] Figures 2A-2F Optical microscope images of magnesium L-lactate crystals retained on sieves with cutoff sizes of 710 μm (2A), 500 μm (2B), 300 μm (2C), 100 μm (2D), and 75 μm (2E) obtained according to certain embodiments of the present invention are shown. Figure 2F An optical microscope image of magnesium L-lactate crystals passing through a 75 μm sieve is shown.

[0073] Figure 3 The particle size distribution of magnesium L-lactate crystals obtained using cooling crystallization is shown.

[0074] Figures 4A-4F Optical microscope images of magnesium L-lactate crystals retained on sieves with cut-off sizes of 710 μm (4A), 500 μm (4B), 300 μm (4C), 100 μm (4D) and 75 μm (4E) obtained using cooling crystallization are shown. Figure 4F An optical microscope image of magnesium L-lactate crystals passing through a 75 μm mesh is shown.

[0075] Figure 5 The particle size distribution of magnesium L-lactate crystals obtained after recrystallization according to certain embodiments of the present invention is shown.

[0076] Figure 6 The particle size distribution of magnesium L-lactate crystals obtained using different evaporation rates is shown.

[0077] Figure 7 Particle size distribution of magnesium L-lactate crystals obtained from fed-batch constant volume crystallization according to certain embodiments of the present invention is shown.

[0078] Figure 8 An optical microscope image of magnesium L-lactate crystals obtained from fed-batch constant volume crystallization according to certain embodiments of the present invention is shown.

[0079] Fig. 9 The particle size distribution of magnesium L-lactate crystals obtained from fed-batch constant concentration crystallization according to certain embodiments of the present invention is shown.

[0080] Fig.10 An optical microscope image of magnesium L-lactate crystals obtained from fed-batch constant concentration crystallization according to certain embodiments of the present invention is shown.

[0081] Fig.11 Shown is the particle size distribution of magnesium L-lactate crystals obtained after recrystallization of magnesium lactate obtained from decomposed PLA 4032D with sodium hydroxide and counter ion replacement according to certain embodiments of the present invention.

[0082] Fig.12 An optical microscope image of L-magnesium lactate crystals obtained after recrystallization of magnesium lactate obtained from decomposed PLA 4032D with sodium hydroxide and counter ion replacement is shown according to certain embodiments of the present invention.

[0083] Fig.13 1 shows the particle size distribution of magnesium L-lactate crystals obtained after recrystallization of magnesium lactate obtained from decomposed PLA with sodium hydroxide and counter ion replacement according to certain embodiments of the present invention.

[0084] Fig.14 An optical microscope image of L-magnesium lactate crystals obtained after recrystallization of magnesium lactate obtained from decomposed PLA with sodium hydroxide and counter ion replacement is shown according to certain embodiments of the present invention.

[0085] Fig.15 The particle size distribution of magnesium L-lactate crystals obtained from the crystallization of magnesium L-lactate at 30°C is shown.

[0086] Fig.16 An optical microscope image of magnesium L-lactate crystals obtained from crystallization of magnesium L-lactate at 30° C. is shown. DETAILED DESCRIPTION

[0087] The present invention provides a method for forming magnesium L-lactate crystals from fermentation broth or other organic waste decomposition products that can be obtained from feedstocks containing high concentrations of soluble and insoluble impurities from municipal, industrial and commercial sources. The method disclosed for the first time herein provides L-lactate crystals that have high overall purity, high enantiomeric purity, can be easily handled due to the desired filterability and particle size distribution, and are particularly advantageous for subsequent polylactic acid formation.

[0088] According to certain aspects and embodiments, a dispersion or fermentation broth of a clarified decomposed organic waste is obtained, the clarified dispersion or fermentation broth comprising a concentration of about 50 to about 110 g / L of lactate ions, including each value within the specified range. Exemplary lactate concentrations include, but are not limited to, about 50, about 55, about 60, about 65, about 70, about 75, about 80, about 85, about 90, about 95, about 100, about 105, or about 110 g / L. Each possibility represents an independent embodiment.

[0089] According to certain embodiments, the dispersion is any decomposition product of lactic acid-containing waste, such as, but not limited to, polylactic acid polymers that undergo hydrolysis. According to other embodiments, a fermentation broth derived from an organic waste raw material is used. The organic waste raw material within the scope of the present invention can be obtained from any waste source, including but not limited to food waste, urban food waste, residential food waste, agricultural waste, industrial food waste from food processing facilities, commercial food waste (from hospitals, restaurants, shopping centers, airports, etc.) and mixtures or combinations thereof. Each possibility represents an independent embodiment. The organic waste can also be derived from animal and human excrement, vegetable and fruit residues, plants, cooked food, protein residues, slaughter waste and residues of combinations thereof. Each possibility represents an independent embodiment. Industrial organic food waste can include factory waste such as byproducts, factory waste, market returns or inedible food parts of the scraps (such as skin, fat, husk and peel). Each possibility represents an independent embodiment. Commercial organic food waste can include waste from shopping centers, restaurants, supermarkets, etc. Each possibility represents an independent embodiment.

[0090] According to various aspects and embodiments, the dispersion of the decomposed organic waste is the fermentation liquid obtained from the fermentation method of carbohydrate source.When using heterogeneous raw materials, the dispersion of the decomposed organic waste or the fermentation liquid usually comprise insoluble impurities based on organic matter, such as but not limited to microorganisms (such as lactic acid producing microorganisms, including such as yeast, bacteria and fungi), fats and oils, lipids, aggregated proteins, bone fragments, hair, precipitated salts, cell fragments, fibers (such as fruits and / or vegetable peels) and residual untreated waste (such as food shells, seeds, insoluble food particles and debris etc.).Every possibility represents an independent embodiment.Insoluble impurities based on inorganic matter include plastics, glass, food packaging residues, sand and combinations thereof.Every possibility represents an independent embodiment.

[0091] The non-limiting examples of soluble impurities include water, solvents, polysaccharides, starch, cellulose, hemicellulose, lignin, seed fragments, salts, coloring components (e.g., tannic acids, flavonoids, and carotenoids) and combinations thereof. Each possibility represents an independent embodiment. Typically, the soluble and insoluble impurity content of the dispersion or fermentation liquid is the same as the soluble and insoluble impurity content of the organic waste raw material. In certain embodiments, the soluble and insoluble impurity content of the dispersion or fermentation liquid is at least about 1 weight % lower than the soluble and insoluble impurity content of the organic waste raw material. In other embodiments, the soluble and insoluble impurity content of the dispersion or fermentation liquid is at least about 5 weight %, about 10 weight %, about 15 weight %, about 20 weight %, about 30 weight %, about 40 weight % or about 50 weight % lower than the soluble and insoluble impurity content of the organic waste raw material. Each possibility represents an independent embodiment.

[0092] According to the principle of the present invention, in order to obtain a dispersion or fermented liquid of clarified decomposed waste material, the insoluble impurities are removed. The impurities can be removed before and / or after the waste material decomposition or fermentation to produce a clarified liquid. According to certain embodiments, the separation of insoluble impurities is carried out before decomposition or fermentation. For example, in certain embodiments, complex organic waste can be heat treated, then enzyme treated, and then the main body of insoluble impurities can be removed with a centrifuge such as a decanter centrifuge. The supernatant (which still has some impurities) is pumped into a container or fermentor tank for lactic acid production.

[0093] According to various embodiments, separation of most of the insoluble impurities is carried out after decomposition or fermentation. Clarification can be achieved by at least one of filtration, centrifugation, flotation, sedimentation, coagulation, flocculation and decantation. Each possibility represents an independent embodiment. Typically, the clarified dispersion or fermentation broth comprises a decomposed organic waste dispersion or fermentation broth that has been used to remove insoluble impurities by filtration (e.g., microfiltration) and / or centrifugation.

[0094] Although it is not necessary to obtain a clarified dispersion or fermented liquid according to the principles of the present invention, other impurity removal steps may be adopted. This includes, for example, product separation or initial recovery, so as to remove or separate extract components significantly different from the required lactic acid product, such as salts and proteins, using, for example, ultrafiltration, solvent extraction, salt precipitation and exclusion extraction. Every possibility represents an independent embodiment. Crystallization, distillation, evaporation, nanofiltration, reverse osmosis (RO) filtration, solvent extraction, electrodialysis and various types of chromatography (such as adsorption or ion exchange) may be used to further purify, to remove pollutants with similar physical and chemical properties. Every possibility represents an independent embodiment.

[0095] Purification methods known in the art are generally designed for fermentation broths derived from substantially uniform biomass-based feed streams having relatively low solid impurity content, and some of the methods utilize crystallization during the fermentation step and / or maintain the lactate in a particulate state. In addition, some known methods are designed to use a specific amount of carbohydrates in the feed stream at the beginning of the fermentation process, thereby producing a specific amount of magnesium lactate product at the end of the fermentation process. For example, U.S. Pat. No. 9,689,007 specifies that the fermentation medium should contain at least 25% by weight of a plant extract containing fermentable carbohydrates at the beginning of the process, and that the fermentation broth should contain up to 9.5% by weight of magnesium lactate at the end of the fermentation.

[0096] Although the present invention is capable of producing high purity L-lactate magnesium from a uniform biomass-based feedstock stream, it is advantageous that it is also capable of producing high purity L-lactate magnesium from more complex feedstocks such as heterogeneous mixed food wastes containing high levels of soluble and insoluble impurities from urban, industrial and commercial sources. In addition, known methods are not suitable for fermentation broths derived from complex feedstocks having a wide range of possible initial fermentable carbohydrate concentrations, resulting in fermentation broths having a wide range of lactate concentrations. Unexpectedly, the inventors have discovered a simple and economical method for obtaining high purity L-lactate magnesium crystals, which can be derived from heterogeneous fermentation broths obtained from complex feedstocks containing a wide range of initial fermentable carbohydrate concentrations. Therefore, the present method is not constrained or limited by the source of the initial organic feedstock or the amount of fermentable carbohydrates in the initial organic feedstock.

[0097] Advantageously, the present invention enables the production of high purity magnesium L-lactate crystals from heterogeneous raw materials with high yield and enantiomeric separation. Unexpectedly, it is now disclosed for the first time that high purity magnesium L-lactate crystals can be obtained from decomposed organic waste containing endogenous D-lactic acid. Typically, organic waste contains endogenous D-lactic acid, L-lactic acid or both L- and D-lactic acid, which originates from, for example, natural fermentation processes, such as in dairy products. Advantageously, the present invention enables the production of high purity magnesium L-lactate crystals from decomposed organic waste containing up to 10% by weight endogenous D-lactic acid.

[0098] According to the principles of the present invention, after obtaining a dispersion or fermentation broth of a clarified decomposed organic waste material from which insoluble impurities have been removed, the concentration of lactate ions is optionally increased to a range of about 100 to about 150 g / L, including each value within the specified range. Preferably, lactate ions are concentrated to a concentration of about 100 to about 130 g / L, including each value within the specified range. After concentration, exemplary concentrations of lactate include, but are not limited to, about 100, about 105, about 110, about 115, about 120, about 125, about 130, about 135, about 140, about 145, or about 150 g / L. Each possibility represents an independent embodiment. Advantageously, the present invention discloses that a much lower lactate concentration of about 100 to about 150 g / L can be used as an initial concentration before crystallization, thereby reducing costs and improving efficiency. The lactate concentration method is carried out at a high temperature of about 50° C. to about 90° C. and a pressure of about 80 to about 300 mbar applied with a vacuum, including each value within the specified range.

[0099] Then, by mixing the clarified or concentrated dispersion or fermentation broth at a high temperature of about 50°C to about 90°C and applying a vacuum to a pressure of about 80 to about 300 mbar to form a seed L-lactate magnesium crystal, including each value in the specified range. Typically, the dispersion or fermentation broth is mixed with a speed in the range of about 50 to about 300 rpm (RPM) using a mixer or homogenizer, including each value in the specified range. Exemplary mixing speeds include but are not limited to about 50RPM, about 75RPM, about 100RPM, about 125RPM, about 150RPM, about 175RPM, about 200RPM, about 225RPM, about 250RPM, about 275RPM or about 300RPM. Each possibility represents an independent embodiment. According to certain embodiments, the mixing is carried out for at least 1 hour, at least 2 hours, at least 3 hours, at least 4 hours, at least 5 hours, at least 6 hours or longer. Each possibility represents an independent embodiment. It is contemplated that the methods disclosed herein may further include adding exogenous magnesium L-lactate seeds to facilitate the crystallization process.

[0100] After the formation of the seed magnesium L-lactate crystals, about 70% to about 90% of the water, including each value in the specified range, is removed from the suspension at an elevated temperature of about 50° C. to about 90° C. and a vacuum is applied to a pressure of about 80 to about 300 mbar. Typically, at least about 70%, about 75%, about 80%, about 85%, or about 90% of the water is removed at this stage.

[0101] During these steps, the temperature is about 50°C, about 55°C, about 60°C, about 65°C, about 70°C, about 75°C, about 80°C, about 85°C or about 90°C. Each possibility represents an independent embodiment. The application of vacuum can be performed as known in the art, using, for example, a rotary evaporator to a pressure of about 80, about 85, about 90, about 95, about 100, about 105, about 110, about 115, about 120, about 125, about 130, about 135, about 140, about 145, about 150, about 155, about 160, about 165, about 170, about 175, about 180, about 185, about 190, about 195, about 200, about 210, about 220, about 230, about 240, about 250, about 260, about 270, about 280, about 290, about 300, about 310, about 320, about 330, about 340, about 350, about 360, about 370, about 380, about 390, about 400, about 410, about 420, about 430, about 440, about 450, about 460, about 470, about 480, about 490, about 500, about 510, about 520, about 530, about 540, about 550 , about 205, about 210, about 215, about 220, about 225, about 230, about 235, about 240, about 245, about 250, about 255, about 260, about 265, about 270, about 275, about 280, about 285, about 290, about 295, about 300, about 305, about 310, about 315, about 320, about 325, about 330, about 335, about 340, about 345 or about 350 mbar. Each possibility represents an independent embodiment. Alternatively, during these steps, the temperature is about 100° C. and no vacuum is applied.

[0102] According to certain aspects and embodiments, the evaporation rate is in the range of about 2 to about 5% weight loss per hour, including each value within the specified range. Without being bound by any theory or mechanism of action, at this evaporation rate, the obtained magnesium L-lactate crystals exhibit optimal filterability, total purity and enantiomeric purity.

[0103] Then the obtained L- lactate magnesium crystals are collected and separated from the remaining mother liquor. The term "L- lactate magnesium" used herein refers to a magnesium salt of a hydroxycarboxylic acid (CH3CH(OH)CO2H) having the formula Mg(LA)2. The term "L- lactate magnesium" refers to any solvate and / or polymorph of Mg(LA)2, including but not limited to Mg(LA)2 dihydrate. The term "mother liquor" used herein refers to the liquid remaining after the crystallization of L- lactate magnesium crystals. In certain embodiments, the obtained L- lactate magnesium crystals are separated from the remaining liquid by a method selected from microfiltration, nanofiltration, centrifugation or other methods known in the art. Each possibility represents an independent embodiment. In certain embodiments, the method of the present invention further includes a cleaning and / or purification step, which includes cleaning and / or purifying the obtained L- lactate magnesium crystals. Cleaning can be performed using an organic solvent or an aqueous solution. Each possibility represents an independent embodiment. In certain embodiments, the organic solvent includes one or more of ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate and a combination thereof. Each possibility represents an independent embodiment. The aqueous solution comprises water. It is now disclosed for the first time that washing the L-lactate magnesium crystals with water further improves the enantiomeric purity. Without being bound by any theory or mechanism of action, it is believed that the D-lactate magnesium crystals adhere to the surface of the L-lactate magnesium crystals, thereby washing with water to obtain better enantiomeric purity. Therefore, the present invention also provides a method for improving the enantiomeric purity of L-lactate magnesium crystals, the method comprising washing the L-lactate magnesium crystals obtained by crystallizing L-lactate magnesium at high temperature and reduced pressure with an aqueous solution. In certain embodiments, the method comprises reducing the percentage of D-lactate magnesium in the L-lactate magnesium crystals by at least 50% (w / w). Preferably, washing is carried out at room temperature, for example at about 10°C, about 15°C, about 20°C, about 25°C or about 30°C. Each possibility represents an independent embodiment.

[0104] In certain embodiments, the cleaning and / or purification step also includes at least one of a polishing step, extraction, microfiltration, nanofiltration, activated carbon treatment, distillation, and grinding. Each possibility represents an independent embodiment. In other embodiments, the method of the present invention also includes drying to achieve a desired loss on drying % (LOD). Exemplary LOD values ​​include, but are not limited to, about 10% to about 20%, including each value within the specified range.

[0105] According to the principles of the present invention, the method disclosed herein may also include dissolving the collected L-lactate magnesium crystals in a suitable solvent and recrystallizing them at an elevated temperature of about 50° C. to about 90° C. and applying a vacuum to a pressure of about 80 to about 300 mbar, including each value within the specified range, as described in detail above. This dissolution and recrystallization can be performed as needed for additional cycles, such as at least one additional cycle, at least 2, at least 3, at least 4, at least 5, at least 6 or at least 10 additional cycles to obtain the desired crystal purity. Each possibility represents an independent embodiment. However, it should be understood that due to the improved purity of the obtained L-lactate magnesium crystals, a single cycle as disclosed herein is sufficient.

[0106] The recovery rate of the obtained L-lactate magnesium crystals is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95% or higher. Each possibility represents an independent embodiment. The L-lactate magnesium crystals obtained by the method disclosed herein can be further acidified into lactic acid for subsequent reuse.

[0107] In certain embodiments, the obtained L-lactate magnesium crystals have a high purity of at least about 85 wt%, about 90%, about 92%, about 94 wt%, about 95 wt%, about 96 wt%, about 97 wt%, about 98 wt%, or about 99 wt%. Each possibility represents an independent embodiment. According to these embodiments, the L-lactate magnesium crystals contain less than about 15 wt%, such as about 10 wt%, about 9 wt%, about 8 wt%, about 7 wt%, about 6 wt%, about 5 wt%, about 4 wt%, about 3 wt%, about 2 wt%, about 1 wt% or less impurities. Each possibility represents an independent embodiment.

[0108] In other embodiments, the obtained L-lactate magnesium crystals contain less than 3%, for example about 2.9%, about 2.8%, about 2.7%, about 2.6%, about 2.5%, about 2.4%, about 2.3%, about 2.2%, about 2.1%, about 2.0%, about 1.9%, about 1.8%, about 1.7%, about 1.6%, about 1.5%, about 1.4%, about 1.3%, about 1.2%, about 1.1%, about 1% or less D-lactate magnesium. Each possibility represents an independent embodiment. Therefore, the method of the present invention also provides enantiomeric enrichment for enriching L-lactate enantiomers from enantiomeric mixtures of D- and L-lactate monomers. This enrichment is particularly beneficial for the reuse of lactic acid. By the method of the present invention, the enrichment of L-lactate enantiomer is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or even more of the initial L-lactate content. Each possibility represents an independent embodiment. For example, for the initial enantiomeric mixture containing 90% L-lactate and 10% D-lactate, 10% enrichment produces a magnesium lactate salt containing 99% L-lactate and 1% D-lactate. Within the scope of the present invention, by the method disclosed herein, D-lactate content is reduced by at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or even 100% of the initial D-lactate content. Each possibility represents an independent embodiment. For example, for an initial enantiomeric mixture containing 90% L-lactate and 10% D-lactate, a 50% reduction in the D-lactate content produces a magnesium lactate salt containing 95% L-lactate and 5% D-lactate.

[0109] In various embodiments, the obtained L-lactate magnesium crystals are characterized by a median particle size of less than 75 μm. In other embodiments, the obtained L-lactate magnesium crystals are characterized by a median particle size greater than 75 μm. The term "particle size" as used herein refers to the length of a particle (i.e., crystal) in its shortest dimension. The particles have a shape selected from spherical, non-spherical, rectangular, flake, platelet, sponge-like, and combinations thereof. Each possibility represents an independent embodiment. Preferably, the obtained L-lactate magnesium crystals are characterized by a particle size distribution that may be a unimodal particle size distribution, a bimodal particle size distribution, or a trimodal particle size distribution, wherein the median particle size is in the range of about 20 to about 100 μm or about 100 to about 300 μm, including each value within the specified range. The terms "median" or "d" as used herein are interchangeable. 50” refers to the particle size when the cumulative distribution percentage based on volume reaches 50%. In other words, the median particle size represents a value, wherein half of the particles have a diameter smaller than this value, and half of the particles have a diameter larger than this value. Therefore, the median particle size of the obtained magnesium L-lactate crystals is usually about 25, about 50, about 75, about 100, about 125, about 150, about 175, about 200, about 225, about 250, about 275 or about 300 μm. Each possibility represents an independent embodiment.

[0110] Although the methods disclosed herein are primarily contemplated for the production of high purity L-lactate magnesium crystals, the same methods can also be used to produce high purity D-lactate magnesium crystals.

[0111] Therefore, according to certain aspects and embodiments, the present invention provides a method for forming high-purity magnesium D-lactate crystals from decomposed organic waste, the method comprising the following steps:

[0112] a. providing a clarified dispersion of decomposed organic waste comprising a concentration of about 50 to about 110 g / L of lactate;

[0113] b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0114] c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed D-lactate magnesium crystals;

[0115] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium D-lactate crystals; and

[0116] e. collecting the D-magnesium lactate crystals obtained in step (d),

[0117] wherein steps (b) to (d) are conducted at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar, including each value within the specified range.

[0118] According to other aspects and embodiments, the present invention provides a method for enriching D-lactate enantiomers from a mixture of enantiomers derived from decomposed organic waste, the method comprising the steps of:

[0119] a. providing a clarified dispersion of decomposed organic waste comprising a concentration of about 50 to about 110 g / L of lactate, wherein the lactate comprises a mixture of enantiomers of D- and L-lactate;

[0120] b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L;

[0121] c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed magnesium lactate crystals;

[0122] d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain magnesium D-lactate crystals having enriched enantiomeric purity; and

[0123] e. collecting the D-magnesium lactate crystals obtained in step (d),

[0124] wherein steps (b) to (d) are conducted at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar, including each value within the specified range.

[0125] As used herein, the term "about" refers to ± 10% of a given value.

[0126] Throughout the present specification and claims, the words "comprise" and "comprising" and variations thereof mean "including but not limited to", and are not intended to (and do not) exclude other parts, additives, components, integers or steps.

[0127] As used herein, the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. Thus, for example, reference to "a solvent" includes combinations of solvents known in the art.

[0128] As used herein, the term "and" or "or" includes "and / or" unless the context clearly dictates otherwise.

[0129] In order to more fully illustrate certain embodiments of the present invention, the following examples are provided. However, they should never be interpreted as limiting the broad scope of the present invention. Without departing from the scope of the present invention, those skilled in the art can easily design many variations and modifications of the principles disclosed herein.

[0130] Example

[0131] Example 1.

[0132] Fermentation of mixed food waste feedstock was performed using magnesium hydroxide as an alkaline agent, which was added to maintain the pH in the range of 5-7. The fermentation broth containing lactate was centrifuged and filtered to produce a transparent supernatant with a lactate concentration of 75 g / L. The supernatant was maintained at 60°C and a vacuum of 180 mbar until the lactate concentration was 120 g / L. The concentrated supernatant was stirred at 200 RPM for 4 hours under the same conditions to allow seed crystals to form, and then concentrated again to remove 80% of the water. The concentrate was cooled to 25°C and filtered using a Buchner funnel equipped with No. 3 Whatman filter paper. The resulting crystals were washed with acetone and dried at 80°C. The yield of the preparation was 70% by weight and the content was 97.4%. Although the D / L-lactate ratio in the supernatant was 3.7% / 96.3% at the start, the D / L-lactate ratio of the mother liquor was 8.6% / 91.4%, and the resulting D / L-lactate ratio in the magnesium lactate crystals was 1.2% / 98.8%. Surprisingly, washing the magnesium lactate crystals with water further improved the enantiomeric purity. Without being bound by any theory or mechanism of action, it is believed that the D-lactate crystals adhered to the surface of the L-lactate crystals, thereby washing with water resulted in better enantiomeric purity.

[0133] Example 2.

[0134] The particle size distribution of magnesium L-lactate crystals prepared as described in Example 1 was evaluated using a series of sieves with the following cut-off sizes: 75 μm, 100 μm, 300 μm and 710 μm. The resulting particle size distribution is presented in Figure 1 and Table 1.

[0135] Table 1.

[0136] Sieve retention value [μm] weight% 710 0.16 500 1.13 300 9.91 100 56.41 75 13.71 0 18.68

[0137] The crystals were observed under an optical microscope. Figures 2A-2F The crystals were shown to exhibit a relatively uniform shape, with characteristic crystal faces.

[0138] Example 3.

[0139] Crystals prepared as described in Example 1 and characterized as described in Example 2 were compared with crystals obtained by concentrating a clarified fermentation broth having a lactate concentration of 98 g / L at 60°C to a lactate concentration of 215 g / L. The concentrate was cooled to 20°C at a rate of 2°C / min, the crystals were filtered and washed with cold water (5°C). The particle size distribution of the crystals obtained by the method described in this example was Figure 3 and Table 2, the optical microscope images of the crystals are shown in Figures 4A-4F middle.

[0140] Table 2.

[0141] Sieve retention value [μm] weight% 710 0.02 500 0.05 300 0.03 100 2.26 75 18.26 0 79.37

[0142] Example 4.

[0143] Fermentation of mixed food waste feedstock was performed using magnesium hydroxide as an alkaline agent, which was added to maintain the pH in the range of 5-7. The fermentation broth containing lactate was centrifuged and filtered to produce a transparent supernatant with a lactate concentration of 78 g / L. The supernatant was maintained at 60°C and a vacuum of 200 mbar until the lactate concentration was 122 g / L. The concentrated supernatant was stirred at 200 RPM for 4 hours under the same conditions to allow seed crystals to form, and then concentrated again to remove 80% of the water. The concentrate was cooled to 25°C and filtered using a Buchner funnel equipped with No. 3 Whatman filter paper. The resulting crystals were washed with acetone and water and dried at 80°C. The yield of the preparation was 74% by weight and the content was 96.0%. Although the D / L-lactate ratio in the supernatant was 3.1% / 96.9% at the beginning, the D / L-lactate ratio of the mother liquor was 8.3% / 91.7%, and the D / L-lactate ratio obtained in the magnesium lactate crystals was 1.6% / 98.4%. The obtained magnesium lactate crystals were redissolved to a final concentration of 110 g / L, the solution was treated with activated carbon to remove colored impurities and filtered. The clear solution was stirred at 200 RPM at 60°C for 6 hours to allow seed formation, and then concentrated again to remove 80% of the water. The concentrate was cooled to 30°C and filtered using a Buchner funnel equipped with No. 3 Whatman filter paper. The obtained crystals were washed with acetone and water and dried at 70°C. The yield of the preparation was 66% by weight and the content was 98.4%. Although the D / L-lactate ratio in the recrystallization solution was 1.6% / 98.4% at the beginning, the D / L-lactate ratio of the mother liquor was 5.3% / 94.7%, and the D / L-lactate ratio obtained in the magnesium lactate crystals was 0.8% / 99.2%.

[0144] Example 5.

[0145] The particle size distribution of the magnesium L-lactate crystals prepared as described in Example 4 was evaluated as described in Example 2. The obtained particle size distribution was presented in Figure 5 and Table 3.

[0146] Table 3.

[0147]

[0148]

[0149] As is apparent from these results, the crystals obtained by the method of the present invention as described in Examples 1 and 4 are much larger than the crystals obtained by the cooling crystallization method as described in Example 3. Specifically, most of the crystals obtained by the method of the present invention are larger than 100 microns, whereas the crystals obtained by the cooling crystallization method are smaller than 75 microns. In addition, the crystals obtained by the cooling crystallization method show very few characteristic crystal faces and are mainly in the form of aggregates.

[0150] Example 6.

[0151] In order to study the influence of the evaporation rate on the properties of the magnesium lactate crystals obtained, three crystallization experiments, designated "slow", "medium" and "fast", were carried out under different crystallization conditions as detailed in Table 4. The experiments were carried out on clarified liquors originating from lactic acid fermentation experiments as described in Examples 1 and 4.

[0152] Table 4.

[0153]

[0154] Four different parameters were evaluated: a) Cake moisture - measured after initial filtration and before water washing. Cake moisture is an indicator of filterability, so lower values ​​indicate that more mother liquor was removed in the filtration; b) Crystal purity - measured using HPLC; c) Yield - (corrected for crystal purity); and d) % of D-lactate - measured using HPLC. The results are presented in Table 5.

[0155] Table 5.

[0156]

[0157] The medium evaporation rate showed the best results in terms of filterability, with 4-5% less water compared to the slow or fast evaporation rates. This rate also produced crystals with the highest purity and lowest % D-lactate. A trend towards a decrease in the overall yield of crystallization at high evaporation rates was detected.

[0158] The crystals obtained from the experiments were also evaluated by inductively coupled plasma (ICP) elemental analysis. The results are presented in Table 6.

[0159] Table 6.

[0160] element slow medium quick Al 8.33 1.69 3.32 Ca 1065 368 495 Cl 1099.04 574.16 808.85 K 646 269 377 Mn 7.76 8.31 8.62 Na 591 282 372 P 391 90 128 S 98.0 40.2 54.3 Zn 5.7 4.4 3.8

[0161] These results show that moderate evaporation rate crystallization is superior in removing elemental impurities during crystallization. Specifically, the concentrations of calcium as well as chloride, potassium, sodium, and phosphorus were significantly reduced by moderate rate crystallization compared to crystallization at slow or fast evaporation rates. The particle size distribution of the resulting crystals was also evaluated using sieves with different cutoff values. The results show that moderate rate crystallization formed the largest crystals, with >75% of the crystals being larger than 100 μm. The results are shown in Figure 6 It should be noted, however, that particle size distributions based on sieving are less accurate due to the tendency of crystals to form clusters.

[0162] In summary, these results show that the moderate rate of crystallization produced the highest quality magnesium lactate crystals.

[0163] Example 7.

[0164] The lactic acid fermentation broth is centrifuged and filtered to produce 1kg of a transparent supernatant containing 7% lactate. The supernatant is concentrated to 12% lactate using a rotary evaporator, removing 42% by weight. The concentrate obtained is transferred to a 0.5L reactor preheated to 70°C and stirred at 300RPM. The supernatant is decremented at a rate of 7,65 or 135g / h in a vacuum (315, 280 or 250 mbar). After removing 80% by weight, crystals are harvested and filtered using a sintered glass funnel. The crystals obtained are washed with cold water and dried at 70°C. As illustrated in Example 6, the medium crystallization rate in which evaporation is performed at an evaporation rate of 2.4-4.8% by weight per hour during 8-16h provides the best results.

[0165] Example 8.

[0166] A constant mass feed batch crystallization was performed. The lactic acid fermentation broth was centrifuged and filtered to produce 2 kg of a transparent supernatant containing 7% lactate. 20% of the supernatant (0.4 kg) was added to a 0.5 L reactor preheated to 85 ° C and stirred at 300 RPM. The remaining 80% (1.6 kg) was added to a separate container heated to 60 ° C and connected to the reactor using a peristaltic pump. The supernatant was reduced at a rate of 80 g / h under vacuum (280 mbar). During evaporation, the supernatant was added at the same rate. The internal temperature was maintained at 70 ° C during crystallization. After 20h, all the supernatant had been added, and the crystals were subsequently harvested and filtered using a sintered glass funnel. The resulting crystals were washed with cold water and dried at 70 ° C. Yield: 57%, content: 98.6%, % D-lactate: 3.8%, original D-lactate%: 7.0%. The particle size distribution of the crystals was characterized by sieving. The results are shown in Figure 7 The crystals were observed under an optical microscope. Figure 8An image of crystals retained on a 50 μm mesh is shown.

[0167] Example 9.

[0168] The feed batch crystallization of constant concentration is carried out. The lactic acid fermentation broth is centrifuged and filtered to produce 2kg of transparent supernatant with a lactic acid concentration of 70g / L. 50% of the supernatant (1kg) is concentrated to a lactic acid concentration of 120g / L using a rotary evaporator. The obtained concentrate is transferred to a 0.5L reactor preheated to 80°C and stirred at 300RPM. The remaining 50% (1kg) supernatant is added to a separate container heated to 60°C and connected to the reactor using a peristaltic pump. The concentrate is decremented at a rate of 100g / h under vacuum (180 mbar) until a total concentration factor of 80% (200g) is reached. The internal temperature is maintained at 58°C during crystallization. The supernatant is then added at a rate of 80g / h while maintaining an evaporation ratio of 80%. After 12.5h, all supernatants have been added. The reactor is then placed at 60°C and stirred at atmospheric pressure for 7h. Harvest crystals and filter using a sintered glass funnel. The obtained crystals were washed with cold water and dried at 70°C. Yield: 43%, content: 96.3%. The particle size distribution of the crystals was characterized by sieving. The results are shown in Fig. 9 The crystals were observed under an optical microscope. Fig.10 An image of crystals retained on a 25 μm mesh is shown.

[0169] Example 10.

[0170] Magnesium lactate dihydrate is obtained as follows: polylactic acid (PLA 4032D) is decomposed using sodium hydroxide to obtain a sodium lactate slurry. As described in WO 2021 / 165964, sodium ions are replaced with magnesium ions by adding magnesium sulfate. Magnesium lactate dihydrate is then added to a three-necked round-bottom flask equipped with a condenser and dissolved in deionized water (DW) at 100°C. Any undissolved impurities are filtered out using a sintered glass funnel. The resulting 580g clear solution (10.7% lactic acid) was transferred to a 0.5L reactor preheated to 100°C. The solution was allowed to boil and water was evaporated within 20h, removing a total of 320g. The crystals were then harvested and filtered with a sintered glass funnel. The resulting crystals were dried at 70°C. Yield: 57.5%, content: 97.0%, D-lactate%: 0.5%, original crystal content: 86.4%; original D-lactate%: 1.5%. The particle size distribution of the crystals was characterized by sieving. The results are shown in Fig.11 The crystals were observed under an optical microscope. Fig.12 An image of crystals retained on a 200 μm mesh is shown.

[0171] Example 11.

[0172] Magnesium lactate dihydrate is obtained as follows: polylactic acid (tableware waste) is decomposed using sodium hydroxide to obtain a sodium lactate slurry. As described in WO 2021 / 165964, sodium ions are replaced with magnesium ions by adding magnesium sulfate. Magnesium lactate dihydrate is then added to a three-necked round-bottom flask equipped with a condenser and dissolved in DW at 100°C. Any undissolved impurities are filtered out using a sintered glass funnel. The resulting 500g clear solution (8.8% LA) was transferred to a 0.5L reactor preheated to 100°C. The solution was allowed to boil and water was evaporated within 29h, removing a total of 336g. The crystals were then harvested and filtered with a sintered glass funnel. The resulting crystals were washed with cold water and dried at 70°C. Yield: 70.7%, content: 98.0%, D-lactate%: 0.6%, original crystal content: 82.1%, original D-lactate%: 3.8%. The particle size distribution of the crystals was characterized by sieving. The results are shown in Fig.13 The crystals were observed under an optical microscope. Fig.14 An image of crystals retained on a 300 μm mesh is shown.

[0173] Comparative Example

[0174] Magnesium lactate dihydrate is obtained from lactic acid fermentation broth using evaporative crystallization at 30°C. Specifically, the lactic acid (LA) fermentation broth is centrifuged and filtered to produce 1 kg of a transparent supernatant containing 7% LA. The supernatant is maintained at 30°C and a vacuum is applied at 30-40 mbar until a lactic acid concentration of 12% is reached. The concentrated supernatant is transferred to a 0.5L reactor preheated to 30°C and stirred at 300RPM, and then vacuum concentrated again (35-40 mbar) to remove 77% of the water. The crystals are then harvested and filtered using a sintered glass funnel. Original D-lactate %: 6.8%, D-lactate % in mother liquor: 6.0%, yield: 88%, content: 84.6%. The resulting crystals are washed with cold water and dried at 70°C. The yield is reduced to 54%, and the content is increased to 99.8%. Thus, in contrast to the crystallization of magnesium L-lactate at a temperature in the range of about 50-100° C. according to an embodiment of the present invention, crystallization at 30° C. does not result in an increase in the D-lactate content in the mother liquor compared to the initial value. Instead, the D-lactate content in the mother liquor is reduced, resulting in crystals having the same ratio of D-lactate to L-lactate as the initial filtered fermentation broth. Furthermore, the resulting crystals are very small and are considered less suitable for new PLA production ( Figure 15-16 ).

[0175] The description of the above specific embodiments fully reveals the overall nature of the present invention, so that others can easily modify and / or rewrite such specific embodiments to adapt to various applications by applying current knowledge without excessive experimentation and without departing from the overall concept, and therefore, such adaptations and modifications should and are intended to be understood as being within the meaning and equivalent scope of the disclosed embodiments. It should be understood that the phrases or terms used herein are for the purpose of description rather than limitation. Without departing from the present invention, the means, materials and steps for performing the various functions disclosed may take various alternative forms.

Claims

1. A method for enriching an L-lactate enantiomer from an enantiomeric mixture comprising a D-lactate monomer and an L-lactate monomer, the method comprising the steps of: a. providing a clarified dispersion of an organic waste material comprising a mixture of enantiomers of D-lactate and L-lactate at a concentration of about 50 to about 110 g / L; b. optionally concentrating the clarified dispersion of step (a) to a lactate concentration of about 100 to about 150 g / L; c. mixing the clarified dispersion of step (a) or the concentrated clarified dispersion of step (b) to obtain a suspension containing seed magnesium lactate crystals; d. removing from the suspension of step (c) about 70% to about 90% of the water to obtain L-lactate magnesium crystals having enriched enantiomeric purity; and e. collecting the L-lactate magnesium crystals having an enriched enantiomeric purity obtained in step (d), wherein steps (b) to (d) are performed at an elevated temperature in the range of about 50°C to about 90°C and under an applied vacuum at a pressure of about 80 to about 300 mbar.

2. The method of claim 1, wherein the clarified dispersion derived from organic waste comprises a clarified fermentation broth obtained from a fermentation process of a carbohydrate source.

3. The method of claim 2, wherein the clarified fermentation broth comprises a fermentation broth from which impurities have been removed using at least one of filtration, centrifugation, flotation, sedimentation, coagulation, flocculation, and decantation.

4. The method of claim 1, wherein the organic waste comprises waste containing lactic acid.

5. The method of any one of claims 1 to 4, wherein step (b) is performed to a lactate concentration of about 100 to about 130 g / L.

6. The method of any one of claims 1 to 5, wherein the mixing in step (c) is performed at a speed of about 50 to about 300 revolutions per minute (RPM).

7. The method according to any one of claims 1 to 6, wherein the mixing in step (c) is performed for at least 1 hour.

8. The method of any one of claims 1 to 7, wherein steps (b) to (d) are performed at an elevated temperature ranging from about 50°C to about 80°C.

9. The process of any one of claims 1 to 8, wherein steps (b) to (d) are performed under applied vacuum to a pressure of about 150 to about 250 mbar.

10. The process of any one of claims 1 to 9, wherein step (d) is performed at an evaporation rate of about 2 to about 5 weight % per hour.

11. The method according to any one of claims 1 to 10, wherein step (e) comprises filtration and / or centrifugation.

12. The method according to any one of claims 1 to 11, wherein step (e) is performed at room temperature.

13. The method according to any one of claims 1 to 12, further comprising the step (f) of washing the obtained magnesium L-lactate crystals.

14. The method according to claim 13, wherein the washing of the obtained magnesium L-lactate crystals is carried out in a solvent selected from water, ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate, and mixtures or combinations thereof.

15. The method according to any one of claims 1 to 14, further comprising the step (g) of drying the magnesium L-lactate crystals to a loss on drying (LOD) % of about 10% to about 20%.

16. The method of claim 15, wherein drying is performed at an elevated temperature of about 50°C to about 120°C.

17. The process according to any one of claims 1 to 16, wherein the obtained magnesium L-lactate crystals having enriched enantiomeric purity are dissolved and recrystallized by repeating steps (c) to (e).

18. The process according to any one of claims 1 to 17, wherein the recovery of magnesium L-lactate crystals having enriched enantiomeric purity is at least 90%.

19. The process according to any one of claims 1 to 18, wherein the obtained magnesium L-lactate crystals having enriched enantiomeric purity are characterized by a median particle size of less than 75 μm.

20. The process of any one of claims 1 to 18, wherein the obtained magnesium L-lactate crystals having enriched enantiomeric purity are characterized by a median particle size greater than 75 μm.

21. The process of claim 20, wherein the resulting magnesium L-lactate crystals having enriched enantiomeric purity are characterized by a particle size distribution comprising a median particle size in the range of about 100 to about 300 μm.

22. The process according to any one of claims 1 to 21, wherein the obtained L-lactate magnesium crystals with enriched enantiomeric purity contain less than 3% D-lactate magnesium, preferably less than 2% D-lactate magnesium, more preferably less than 1.5% D-lactate magnesium and most preferably less than 1% D-lactate magnesium.

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