Purification of magnesium lactate from fermentation broth with high levels of impurities

Abstract

The present invention provides a method for efficiently purifying magnesium lactate from a fermentation broth derived from a heterogeneous raw material containing soluble and insoluble impurities. The fermentation broth having a large amount of impurities and containing soluble form of magnesium lactate is separated from the insoluble impurities, concentrated to a particularly high concentration of magnesium lactate at an elevated temperature, and then cooled by gradual and controlled cooling to form high purity magnesium lactate crystals.

Description

Technical Field

[0001] The present invention relates to a method for purifying magnesium lactate from a fermentation broth having a high content of impurities (including soluble and insoluble impurities) and containing magnesium lactate in a soluble form, the method comprising the steps of separating impurities, concentrating, crystallizing and purifying. Background Art

[0002] Lactic acid is the most widely occurring hydroxycarboxylic acid (Joglekar, HG, et al. "Comparative assessment of downstream processing options for lactic acid." Separation and Purification Technology 52.1 (2006): 1-17). It is a widely used chemical with applications in the food, chemical, pharmaceutical and cosmetic industries (Huang, H et al. (2004) A Hollow-Fiber Membrane Extraction Process for Recovery and Separation. Biochemistry and Biotechnology, 113). This naturally occurring organic acid can be produced by chemical synthesis or microbial fermentation. It has been found naturally or as a product of in situ microbial fermentation in many foods (e.g., yogurt, buttermilk and many other fermented foods) (Datta, R., et al. (2006) Lactic acid: recent advances in products, processes and technologies—a review, 1129 (May), 1119–1129).

[0003] When produced by microbial fermentation, the pH in the fermentation tank usually needs to be maintained at 5-7 during the fermentation process. Due to the production of lactic acid, the pH decreases, which is not ideal for the productivity of the microorganism. Adding alkali such as ammonium, sodium, potassium, magnesium or calcium hydroxide can maintain the pH value by neutralizing the lactic acid and forming lactate. In order to obtain crude lactic acid, a re-acidification step using, for example, sulfuric acid is usually implemented.

[0004] Compared with traditional petrochemical products, lactic acid fermentation based on renewable resources has received more and more attention over the years. However, in order to compete with traditional chemical production pathways, it is necessary to optimize the cost of biological-based lactic acid production. About 60-80% of the production costs come 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 generation of by-products (e.g., salts).

[0005] Various methods have been previously proposed to recover and purify lactic acid and / or lactate from fermentation broth.

[0006] For example, Wang Yong et al. described a crystallization-based magnesium lactate purification method in "Efficient magnesium lactate production with insitu product removal by crystallization", Bioresource technology 198 (2015): 658-663. Crystallization was performed at 42°C without adding seed crystals. The fermentation medium used in the fermenter contained yeast extract, glucose, NaCl, sodium acetate, triammonium citrate, KH 2 PO 4 MgSO 4 7H 2 O and MnSO 4 7H 2 The product concentration, productivity and yield of the fermentation combined with in situ product removal (ISPR) reached 143 g L -1 , 2.41 g L -1 h -1 and 94.3%.

[0007] U.S. Pat. No. 9,689,007 describes a method for producing lactate or lactic acid from a "low-sugar" plant extract by fermentation, comprising providing a fermentation medium comprising at least 25 wt.% of a plant extract containing a fermentable carbohydrate, and fermenting the fermentation medium by a lactic acid-producing microorganism in the presence of a caustic magnesium salt to provide a fermentation broth containing at most 9.5 wt.% 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 have a magnesium lactate concentration of at most 9.5 wt.% in the fermentation broth at the end of the fermentation, the fermentation medium containing the plant extract preferably contains a fermentable carbohydrate concentration of at most 9.5 wt.%.

[0008] US Publication No. 2014 / 0012041 describes a method for producing lactate, comprising: crystallizing an aqueous lactate solution containing not less than 7.0 wt % of formate relative to the lactate, and recovering the lactate. The lactate concentration in the aqueous lactate solution is 10.0 to 30.0 wt %.

[0009] 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 lignocellulosic aqueous material; b) saccharifying the treated lignocellulosic material in the presence of a hydrolytic enzyme to provide a saccharified lignocellulosic aqueous material comprising fermentable carbohydrates and a solid lignocellulose fraction; c) simultaneously with step b), fermenting the saccharified lignocellulosic aqueous material in the presence of both a lactic acid-forming microorganism and a caustic magnesium salt to provide an aqueous fermentation broth comprising magnesium lactate and a solid lignocellulose fraction; d) recovering magnesium lactate from the fermentation broth, wherein 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 can be derived from plant biomass. Preferred lignocellulosic materials are selected from the following groups consisting of: wheat straw; bagasse; corn straw; and mixtures thereof.

[0010] WO Publication No. 2017 / 178426 describes a fermentation method for producing magnesium lactate from a carbon source, comprising the steps of: - providing a fermentation medium containing a fermentable carbon source in a fermentation reactor; - fermenting the fermentation medium by a lactic acid-producing microorganism in the presence of an alkaline magnesium salt to provide a fermentation broth containing magnesium lactate, and - recovering solid magnesium lactate from the fermentation broth containing magnesium lactate, wherein the concentration of solid magnesium lactate in the fermentation broth is maintained in the range of 5-40% by volume during at least 40% of the operating time of the fermentation process, calculated as solid magnesium lactate crystals in the total fermentation broth. An example of a fermentable carbon source is C 5 Sugar, C 6 Sugars, their oligomers (e.g. dimer C 12 sugars) and / or their polymers.

[0011] 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, while a product stream comprising the solid fermentation product is extracted from the bottom of the biomass separator unit, and a waste stream comprising biomass is extracted from the top of the biomass separator unit. The solid fermentation product is a fermentation product that is present in an aqueous medium at a concentration higher than its saturation concentration, and can be a crystalline product or an amorphous product.

[0012] The above purification methods are designed for fermentation broths derived from substantially homogeneous biomass-based feed streams with low soluble and insoluble impurity content. However, there is a need to utilize more available and cheaper heterogeneous raw materials for fermentation, such as mixed food waste from municipal, industrial and commercial sources. These heterogeneous raw materials contain impurities such as salts, lipids, proteins, color components and inert materials. Fermentation broths derived from such heterogeneous raw materials cannot also be effectively processed by currently available methods to obtain a pure magnesium lactate product in a cost-effective manner.

[0013] There remains an unmet need for a simple, cost-effective method for purifying and isolating magnesium lactate with high recovery from fermentation broths derived from heterogeneous feedstocks having large mixed impurity contents. Summary of the invention

[0014] The present invention provides a method for separating and purifying magnesium lactate from a complex fermentation broth with a large amount of impurities, comprising the steps of separating insoluble impurities, concentrating, crystallizing and purifying. Advantageously, the use of a complex fermentation broth based on waste makes the method economically and environmentally beneficial.

[0015] The present invention is based in part on the unexpected discovery that magnesium lactate crystals with a purity of greater than 85%, greater than 92% or greater than 95% can be obtained from a complex, heterogeneous fermentation broth by a small number of purification process steps. In this method, a complex, heterogeneous fermentation broth having a large amount of impurities and containing magnesium lactate in soluble form is separated from insoluble impurities, concentrated at high temperature to a particularly high concentration of magnesium lactate, and then cooled by stepwise controlled cooling. Unexpectedly, this method produces high purity crystals in a cost-effective manner even if the fermentation broth contains a large amount of impurities.

[0016] The purification methods known in the art are designed for fermentation broths derived from substantially homogeneous biomass-based feed streams containing relatively small amounts of soluble and insoluble impurities. These known methods are not cost effective or are not suitable for fermentation broths derived from heterogeneous and complex feedstocks with high concentrations of soluble and insoluble impurities.

[0017] The present inventors have discovered a simple and economical method for obtaining high purity magnesium lactate crystals from a heterogeneous fermentation broth obtained from feedstocks containing high concentrations of soluble and insoluble impurities from municipal, industrial and commercial sources. The insoluble impurities may include organic-based impurities and inorganic-based impurities.

[0018] Non-limiting examples of insoluble organic-based impurities include: microorganisms, fats and oils, lipids, aggregated proteins, bone fragments, hair, precipitated salts, cell debris, and residual unprocessed waste (e.g., food shells, seeds, insoluble food particles and fragments, etc.). Non-limiting examples of insoluble inorganic-based impurities include: plastics, glass, residues from food packaging, and sand. Non-limiting examples of soluble impurities include: seed fragments, salts, color components, etc.

[0019] According to some embodiments, the method of the present invention comprises maintaining the fermentation broth at a temperature of about 45-75° C. during the initial steps of separation and concentration, when the magnesium lactate is in a soluble form, so that substantially no crystals are formed before the fermentation broth is clarified from insoluble impurities and concentrated to the desired concentration.

[0020] The present inventors have found that the formation of magnesium lactate crystals during the fermentation process of heterogeneous feedstocks (e.g., mixed food waste from municipal, industrial, and commercial sources) and prior to clarification and concentration results in low-purity magnesium lactate crystals with a large amount of soluble and insoluble impurities (e.g., color components) incorporated therein, as well as undesirable polymorphic crystals. The low-purity magnesium lactate crystals would require additional processing steps and machinery for their purification, and are therefore not cost-effective or desirable.

[0021] According to some embodiments, the method of the present invention comprises concentrating the fermentation broth to a desired concentration of lactate of about 180 g / L-220 g / L; crystallizing the fermentation broth under controlled cooling to obtain magnesium lactate crystals; and collecting the obtained crystals. The remaining liquid after collecting the crystals (referred to herein as "mother liquor") can be recycled and subjected to additional crystallization. Therefore, in some embodiments, the method of the present invention further comprises concentrating the mother liquor and performing at least one additional crystallization. Without wishing to be bound by theory or mechanism of action, it can be expected that the magnesium lactate crystals obtained reach a high purity, due to the concentration of the fermentation broth and the conditions of the crystallization step, such as temperature, pH and cooling rate, so that magnesium lactate can form densely packed crystals and can exclude soluble impurities (such as color components), thereby obtaining magnesium lactate crystals with a high purity of more than about 93%.

[0022] The present inventors have found that concentrating the fermentation broth to different concentrations (lower or higher than the concentrations desired herein above) and / or utilizing different uncontrolled crystallization conditions, produces low purity magnesium lactate crystals having a large amount of soluble and insoluble impurities incorporated therein. The low purity magnesium lactate crystals obtained would require additional processing steps and machinery for their purification and are therefore not cost effective or desirable.

[0023] Therefore, the present invention provides an improved method for obtaining magnesium lactate from a heterogeneous fermentation broth using a raw material comprising high concentrations of soluble and insoluble impurities. The improved method is simple, cost-effective and results in high yields. Insoluble impurities can be removed before or after fermentation to produce lactate. According to some embodiments, it is more economical to separate most of the impurities (insoluble impurities) before fermentation. In some embodiments, after fermentation and production of lactate, remaining impurities can be removed by microfiltration.

[0024] Therefore, according to a first aspect, there is provided a method for separating and purifying magnesium lactate from a fermentation broth, comprising the steps of:

[0025] a) providing a clarified fermentation broth from which insoluble impurities have been removed, the clarified fermentation broth comprising magnesium lactate in soluble form as a result of the fermentation process, the temperature of the fermentation broth being from about 45° C. to about 75° C.;

[0026] b) concentrating the clarified fermentation broth from step (a) to a lactate concentration of about 150 g / L to about 220 g / L;

[0027] c) subjecting the concentrated clarified fermentation broth from step (b) to at least one cooling crystallization to obtain magnesium lactate crystals; and

[0028] d) collecting the obtained magnesium lactate crystals.

[0029] In some embodiments, the insoluble impurities include at least one of insoluble organic-based impurities, insoluble inorganic-based impurities, and soluble impurities.

[0030] In some embodiments, the temperature of the fermentation broth of step (a) is from about 55°C to about 65°C.

[0031] In some embodiments, the separation of insoluble impurities comprises at least one technique selected from the group consisting of filtration, centrifugation, flotation, sedimentation, flocculation, and decantation. In some embodiments, the separation of insoluble impurities comprises centrifugation. In some embodiments, the separation of insoluble impurities further comprises microfiltration. In some embodiments, the separation of insoluble impurities comprises centrifugation and microfiltration.

[0032] In some embodiments, the concentration of step (b) is carried out by evaporation, nanofiltration, reverse osmosis or a combination thereof. In some embodiments, the fermentation broth is concentrated to a lactate concentration of about 160 g / L to about 220 g / L in step (b). In some embodiments, the fermentation broth is concentrated to a lactate concentration of about 170 g / L to about 220 g / L in step (b). In some embodiments, the fermentation broth is concentrated to a lactate concentration of about 180 g / L to about 220 g / L in step (b).

[0033] In some embodiments, in step (c), at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 75° C. In some embodiments, in step (c), at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 70° C. In some embodiments, in step (c), at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 65° C.

[0034] In some embodiments, in step (c), at least one cooling crystallization step ends at a second temperature selected from the range of about 10 to about 1° C. In some embodiments, in step (c), at least one cooling crystallization step ends at a second temperature selected from the range of about 6 to about 2° C.

[0035] In some embodiments, in step (c), the cooling rate of at least one cooling crystallization is in the range of about 10 to about 0.5°C / h. In some embodiments, in step (c), the cooling rate of at least one cooling crystallization is in the range of about 5 to about 1°C / h.

[0036] In some embodiments, in step (c), the pH of the concentrated clarified fermentation broth is in the range of about 6 to about 7 prior to at least one cooling for crystallization.

[0037] In some embodiments, the magnesium lactate crystals obtained in step (d) are separated from the remaining liquid by a method selected from microfiltration and nanofiltration.

[0038] In some embodiments, the remaining liquid from step (d) is concentrated and then subjected to at least one additional crystallization to obtain additional magnesium lactate crystals. In some embodiments, the additionally obtained magnesium lactate crystals are separated from the liquid. In some embodiments, the obtained magnesium lactate crystals are combined with the additionally obtained magnesium lactate crystals to form combined magnesium lactate crystals.

[0039] In some embodiments, the method further comprises step (e): washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals. In some embodiments, step (e) comprises washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals using an organic solvent selected from the group consisting of ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate, and combinations thereof. In some embodiments, step (e) comprises washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals with an aqueous solution. In some embodiments, the specific temperature of the solvent or solution in step (e) is selected from about 0.5 to about 8°C.

[0040] In some embodiments, step (e) further comprises at least one finishing step selected from extraction, microfiltration, nanofiltration, activated carbon treatment, distillation, drying and grinding. In some embodiments, step (e) further comprises packaging for transportation purposes.

[0041] It is to be understood that any combination of the various aspects and embodiments disclosed herein is expressly included within the present disclosure.

[0042] Other embodiments and applicable scopes of the present invention will become apparent from the detailed description given below. However, it should be understood that the specific embodiments and specific examples, although indicating preferred embodiments of the present invention, are given by way of example only, because various changes and modifications within the spirit and scope of the present invention will be apparent to those skilled in the art based on the specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Some embodiments of the present invention are described herein with reference to the accompanying drawings. Figure 1 The drawings are for illustrative purposes only and do not attempt to show the structural details of the embodiments in more detail than is necessary for a basic understanding of the invention. For clarity, some objects depicted in the drawings are not drawn to scale.

[0044] Figure 1 : A schematic diagram of the method for separation and purification of magnesium lactate according to the present invention is depicted.

[0045] Figure 2A-2C : Depicting the separation of insoluble impurities according to some embodiments of the present invention: A separatory funnel ( Figure 2A ); Büchner filter (4μm-9μm cardboard filter ( Figure 2B )); and fat particles before separation from the fermentation broth ( Figure 2C ).

[0046] Figure 3A -E: Crystallization of magnesium lactate (B2): Magnesium lactate precipitate on the side of the flask ( Figure 3A ); Spontaneous precipitation of magnesium lactate ( Figure 3B ); Spherical magnesium lactate crystals ( Figure 3C ); recrystallization of spherical crystals ( Figure 3D ); and Büchner filtration to separate fine magnesium lactate crystals ( Figure 3E ).

[0047] Figure 4: Magnesium lactate crystals (B3): unwashed (lower left); washed with 200 mL of cold ethanol (top); and washed with 200 mL of cold water before drying (lower right).

[0048] Figure 5A -B: filtrate obtained after washing magnesium lactate crystals (B3) with ethanol: suspension obtained after washing crystals with ethanol ( Figure 5A ); and the filter cake after filtrate filtration ( Figure 5B ).

[0049] Figure 6 : Purity results of different magnesium lactate crystal fractions (B3).

[0050] Figure 7 : Solubility curves of pure magnesium lactate crystals and lactic acid (Sigma-Aldrich).

[0051] Figure 8 : Solubility curves of magnesium lactate and lactic acid (spherical crystals from B2).

[0052] Fig. 9 : Solubility curves of magnesium lactate and lactic acid (fine crystals from B2)

[0053] Fig.10 : TGA thermograms of three different magnesium lactate samples. DETAILED DESCRIPTION

[0054] The present invention provides a method for separating and purifying magnesium lactate crystals from a heterogeneous fermentation broth containing magnesium lactate in soluble form, the fermentation broth being obtained from a feedstock containing high concentrations of soluble and insoluble impurities from municipal, industrial and commercial sources. The method comprises the steps of separating insoluble impurities, concentrating, crystallizing and purifying.

[0055] Insoluble impurities can be removed before or after fermentation to produce lactate. According to some embodiments, separation of most of the insoluble impurities is performed after fermentation. For example, complex organic waste can be heat treated and directly pumped into a fermenter to produce lactic acid. After fermentation, centrifugation, such as a decanter centrifuge, removes most of the insoluble impurities. Clarification is then achieved by microfiltration.

[0056] According to other embodiments, the separation of insoluble impurities is carried out before fermentation. For example, in some embodiments, complex organic waste can be heat treated, followed by enzyme treatment, and then centrifuged (e.g., decanter centrifuge) to remove most of the insoluble impurities. The supernatant (still with some impurities) is pumped into a fermentor to produce lactic acid. After fermentation, the fermented liquid is clarified by ceramic membrane microfiltration.

[0057] In the lactic acid fermentation process described so far, the downstream processing method for separating lactic acid from the fermentation broth includes several steps. The first step generally involves removing insoluble particles (e.g., fat particles and oil) and separating cells and their fragments from the fermentation broth. Microfiltration and / or centrifugation are common techniques for this step. The second step is generally product separation or preliminary recovery, the purpose of which is to remove or separate extract components that are very different from the desired lactic acid product, such as salts and proteins. Common techniques for this step include ultrafiltration, solvent extraction, salt precipitation, and exclusion extraction. Further purification is usually required to remove contaminants with similar physical and chemical properties. These contaminants are generally the most challenging and costly to remove. This requires sensitive and complex techniques and equipment. Common techniques for this step include crystallization, distillation, nanofiltration, electrodialysis, and various chromatography methods (e.g., adsorption or ion exchange).

[0058] Water or other solvents are generally considered to be the main "impurities". Concentration or purification involves removing most of the solvent or capturing the carboxylic acid to achieve concentration. Usually after this step, the remaining impurities are removed. Common techniques for this step include evaporating the water (optionally under vacuum) and / or concentrating by reverse osmosis (RO) filtration. Other finishing steps may be applied, such as washing with an appropriate solvent, solvent extraction, drying, etc.

[0059] Purification methods known in the art are generally designed for fermentation broths derived from a substantially homogeneous biomass-based feed stream having a relatively low content of solid impurities, and some of the methods utilize crystallization and / or maintain the lactate in a particulate state during the fermentation step. 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 so as to produce a specific amount of magnesium lactate product at the end of the fermentation process. For example, U.S. Patent 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 at most 9.5% by weight of magnesium lactate at the end of the fermentation.

[0060] However, the known methods are not applicable or cost-effective for fermentation broths derived from more complex feedstocks, such as heterogeneous mixed food waste from municipal, industrial and commercial sources, which contain high levels of soluble and insoluble impurities. In addition, the known methods are not applicable to fermentation broths derived from complex feedstocks with a variety of possible initial fermentable carbohydrate concentrations, which result in fermentation broths with a variety of lactate concentrations.

[0061] Surprisingly, the present inventors have discovered a simple and economical method for obtaining high-purity magnesium lactate crystals from a heterogeneous fermentation broth obtained from a complex feedstock containing high concentrations of soluble and insoluble impurities. In addition, unlike other known methods, the present method can provide high-purity magnesium lactate crystals based on fermentation broths with a variety of initial lactate concentrations. Therefore, the present method is not limited or restricted by the source of the initial organic feedstock or the amount of fermentable carbohydrates in the initial organic feedstock.

[0062] Therefore, according to a first aspect, the present invention provides a method for separating and purifying magnesium lactate from a fermentation broth, comprising the following steps:

[0063] a) providing a clarified fermentation broth from which insoluble impurities have been removed, the clarified fermentation broth comprising magnesium lactate in soluble form as a result of the fermentation process, the temperature of the fermentation broth being from about 45° C. to about 75° C.;

[0064] b) concentrating the clarified fermentation broth of step (a) to a lactate concentration of about 150 g / L to about 220 g / L;

[0065] c) subjecting the concentrated clarified fermentation broth from step (b) to at least one cooling crystallization to obtain magnesium lactate crystals; and

[0066] d) collecting the obtained magnesium lactate crystals.

[0067] In some embodiments, a method for separating and purifying magnesium lactate from a fermentation broth comprises the steps of:

[0068] (a) providing a fermentation broth comprising magnesium lactate in soluble form as a result of a fermentation process, the temperature of the fermentation broth being from about 45° C. to about 75° C.;

[0069] (b) separating insoluble impurities from the fermentation broth to obtain a clarified fermentation broth;

[0070] (c) concentrating the clarified fermentation broth from step (b) to a lactate concentration of about 150 g / L to about 220 g / L;

[0071] (d) subjecting the concentrated clarified fermentation broth from step (c) to at least one cooling crystallization to obtain magnesium lactate crystals; and

[0072] (e) collecting the obtained magnesium lactate crystals.

[0073] As used herein, the term "fermentable carbohydrate" refers to carbohydrates that can be fermented by lactic acid producing microorganisms in a fermentation process. As used herein, the term "lactic acid" refers to a lactic acid having a chemical formula of CH 3 CH(OH)CO 2The magnesium salt form of lactic acid is called "magnesium lactate" and has the formula Mg(LA) 2 The term lactate can refer to the stereoisomers of lactate: L-lactate, D-lactate, or a combination thereof. In some exemplary embodiments, the lactate is L-lactate. In other embodiments, the lactate is D-lactate.

[0074] According to some embodiments, the fermentation liquid is a heterogeneous fermentation liquid. According to some embodiments, the fermentation liquid is derived from a fermentation process of an organic waste raw material comprising soluble and insoluble impurities. The organic waste raw material can be derived from the organic part of food garbage, which is selected from municipal, household, agricultural, industrial, commercial and hospital garbage, or a combination thereof. Organic waste can also come from animal and human excrement, vegetable and fruit residues, plants, cooked food, protein residues, slaughter waste and combinations thereof. Each possibility represents a separate embodiment of the present invention. Industrial organic food waste can include factory waste, such as byproducts, factory discards, market returns or inedible food parts (such as skin, fat, crust and peel) trimmings. Commercial organic food waste can include waste from shopping centers, restaurants, supermarkets, etc.

[0075] In some embodiments, the insoluble impurities include insoluble organic-based impurities and insoluble inorganic-based impurities.

[0076] Non-limiting examples of insoluble organic-based impurities include: microorganisms, fats, oils, lipids, aggregated proteins, bone fragments, hair, precipitated salts, cell debris, fibers (e.g., fruit and / or vegetable peels), unprocessed residual food scraps (e.g., food shells, seeds, food insoluble particles and fragments), and combinations thereof. Microorganisms may include lactic acid-producing microorganisms such as, but not limited to, yeasts, bacteria, and fungi. Each possibility represents a separate embodiment of the present invention.

[0077] Non-limiting examples of insoluble inorganic-based impurities include: plastic, glass, residues from food packaging, sand, and combinations thereof. Each possibility represents a separate embodiment of the present invention.

[0078] Non-limiting examples of soluble impurities include: water, solvents, polysaccharides, starch, cellulose, hemicellulose, lignin, salts, color components (eg, tannins, flavonoids, and carotenoids), and combinations thereof. Each possibility represents a separate embodiment of the present invention.

[0079] In some embodiments, the soluble and insoluble impurity content of the fermentation broth is the same as the soluble and insoluble impurity content of the raw material used for the fermentation process. In further embodiments, the soluble and insoluble impurity content of the fermentation broth is less than at least about 1 weight % compared to the soluble and insoluble impurity content of the raw material used for the fermentation process. In further embodiments, the soluble and insoluble impurity content of the fermentation broth is less than at least about 5 weight %, about 10 weight %, about 15 weight %, about 20 weight %, about 30 weight %, about 40 weight % or about 50 weight % compared to the soluble and insoluble impurity content of the raw material used for the fermentation process.

[0080] The present method can provide high purity magnesium lactate crystals based on fermentation broths with various initial lactate concentrations. In some embodiments, the fermentation broth in step (a) comprises an initial lactate concentration of about 50 to about 120 g / L.

[0081] In some embodiments, the fermentation broth in step (a) comprises magnesium lactate in soluble form, and at least one of insoluble organic-based impurities, insoluble inorganic-based impurities, and soluble impurities, as described herein above. In other embodiments, the fermentation broth in step (a) comprises magnesium lactate in soluble form and at least one of insoluble organic-based impurities (e.g., fats, lactic acid-producing microorganisms, oils, lipids, proteins, bone fragments, hair, precipitated salts, cell debris, and unprocessed residual food waste), insoluble inorganic-based impurities (e.g., plastics, glass, residues from food packaging, and sand), soluble impurities (e.g., polysaccharides, seed fragments, salts, and various color components), and combinations thereof.

[0082] In some embodiments, the dry matter content of the fermented liquid from step (a) is about 1 weight % to about 50 weight %. As used herein, the term "dry matter" refers to the insoluble organic and inorganic impurity content in the fermented liquid from step (a). In further embodiments, the dry matter content of the fermented liquid from step (a) is about 5 weight % to about 30 weight %. In some exemplary embodiments, the dry matter content of the fermented liquid from step (a) is about 10 weight % to about 25 weight %.

[0083] In some embodiments, at least about 50% by weight of the insoluble organic and / or inorganic-based impurities in the fermentation broth from step (a) are in particulate form. In further embodiments, at least about 60%, about 70%, about 80%, about 90%, or about 95% by weight of the insoluble organic and / or inorganic-based impurities in the fermentation broth from step (a) are in particulate form. In further embodiments, about 100% by weight of the insoluble organic and / or inorganic-based impurities in the fermentation broth from step (a) are in particulate form.

[0084] In further embodiments, the insoluble organic and / or inorganic based particles are characterized by having a particle size in the range of about 1 μm to about 5 mm. In still further embodiments, the insoluble organic and / or inorganic based particles are characterized by having a particle size in the range of about 1 μm to about 2 mm. In still further embodiments, the insoluble organic and / or inorganic based particles are characterized by having a particle size in the range of about 10 μm to about 1 mm.

[0085] As used herein, the term "particle size" refers to the length of a particle in its longest dimension. The particle has a shape selected from the group consisting of spherical, non-spherical, plate-like, plate-like, sponge-like, and combinations thereof.

[0086] In some embodiments, the fermentation broth of step (a) is at a temperature selected from about 45° C. to about 75° C. In further embodiments, the fermentation broth of step (a) is at a temperature selected from about 50° C. to about 70° C. In still further embodiments, the fermentation broth of step (a) is at a temperature selected from about 55° C. to about 65° C. In still further embodiments, the fermentation broth of step (a) is at a temperature selected from about 55° C. to about 60° C.

[0087] In some embodiments, when separation of insoluble impurities is performed after fermentation, the fermentation broth is at a temperature selected from about 45° C. to about 75° C. during separation. In further embodiments, the fermentation broth is at a temperature selected from about 50° C. to about 70° C. during separation. In still further embodiments, the fermentation broth is at a temperature selected from about 55° C. to about 65° C. during separation. In still further embodiments, the fermentation broth is at a temperature selected from about 55° C. to about 60° C. during separation.

[0088] In some embodiments, the fermentation broth during the concentration step is at a temperature selected from about 45° C. to about 75° C. In further embodiments, the fermentation broth during the concentration step is at a temperature selected from about 50° C. to about 70° C. In still further embodiments, the fermentation broth during the concentration step is at a temperature selected from about 55° C. to about 65° C. In still further embodiments, the fermentation broth during the concentration step is at a temperature selected from about 55° C. to about 60° C.

[0089] In some embodiments, the fermentation broth is maintained at a temperature selected from about 45°C to about 75°C. In further embodiments, the fermentation broth is maintained at a temperature selected from about 55°C to about 65°C.

[0090] The method of the present invention comprises maintaining the fermentation broth at a temperature of about 45-75° C., wherein the magnesium lactate is in a soluble form, until the cooling crystallization step, such that substantially no crystals are formed before the fermentation broth is clarified and concentrated to the desired concentration by removing insoluble impurities. In some embodiments, less than about 5% by weight of magnesium lactate crystals are formed before the cooling crystallization step. In further embodiments, less than about 4%, about 3%, about 2%, or about 1% by weight of magnesium lactate crystals are formed before the cooling crystallization step. Each possibility represents a separate embodiment of the present invention. In some embodiments, less than about 0.5% by weight of magnesium lactate crystals are formed before the cooling crystallization step.

[0091] Without wishing to be bound by any theory, it is expected that the removal of insoluble impurities and concentration of the fermentation broth should be carried out at a temperature of about 45-75°C, which is above the dissolution temperature of magnesium lactate, thereby maintaining magnesium lactate in a soluble form and preventing precipitation of magnesium lactate. The inventors surprisingly found that the formation of magnesium lactate crystals during the fermentation of heterogeneous raw materials and before clarification and concentration resulted in low-purity magnesium lactate crystals with a large amount of soluble and insoluble impurities (e.g., color components) incorporated therein, as well as undesirable polymorphic crystals. In addition, the inventors found that the formation of magnesium lactate crystals during clarification and / or concentration prior to crystallization resulted in low-purity magnesium lactate crystals with a large amount of soluble and insoluble impurities incorporated therein.

[0092] In some embodiments, the separation of insoluble particles comprises subjecting the fermentation broth comprising the soluble form of magnesium lactate to solid / liquid separation and / or liquid / liquid separation. In further embodiments, the solid / liquid and / or liquid / liquid separation provides a clarified magnesium lactate fermentation broth and a residue comprising insoluble impurities.

[0093] In some embodiments, solid / liquid separation comprises at least one technique selected from the group consisting of filtration, centrifugation, flotation, sedimentation, flocculation, and decantation. Each possibility represents a separate embodiment of the present invention. In some embodiments, liquid / liquid separation comprises at least one technique selected from the group consisting of centrifugation, filtration, mixer-settler, solvent extraction, and combinations thereof. In further embodiments, separation of insoluble particles comprises at least one technique selected from the group consisting of filtration, centrifugation, flotation, sedimentation, flocculation, decantation, and combinations thereof.

[0094] In some embodiments, separation of insoluble particles comprises centrifugation.

[0095] Filtration can be selected from ultrafiltration and microfiltration. In some embodiments, the separation of insoluble particles includes microfiltration. Microfiltration can be performed by at least one of the following methods: hollow fiber membrane, ceramic filter membrane, filter press or other methods known in the art. Each possibility represents a separate embodiment of the present invention.

[0096] In some embodiments, separation of insoluble particles comprises centrifugation and microfiltration.

[0097] In some embodiments, the concentration is carried out by removing water, filtering or by other methods known in the art. The removal of water can be carried out under reduced pressure (e.g., evaporation). Filtration can include nanofiltration or reverse osmosis. In some embodiments, the concentration is carried out by evaporation, nanofiltration, reverse osmosis or a combination thereof.

[0098] In some embodiments, concentration is performed by crystallization under reduced pressure in the crystallization vessel.

[0099] In some embodiments, the fermentation broth is concentrated to a lactate concentration of about 160 g / L to about 220 g / L. In further embodiments, the fermentation broth is concentrated to a lactate concentration of about 170 g / L to about 220 g / L. In further embodiments, the fermentation broth is concentrated to a lactate concentration of about 180 g / L to about 220 g / L. In further embodiments, the fermentation broth is concentrated to a lactate concentration of about 150 g / L to about 195 g / L. Still in further embodiments, the fermentation broth is concentrated to a lactate concentration of about 155 g / L to about 190 g / L. In further embodiments, the fermentation broth is concentrated to a lactate concentration of about 160 g / L to about 185 g / L. Still in further embodiments, the fermentation broth is concentrated to a lactate concentration of about 175 g / L to about 185 g / L.

[0100] The present inventors surprisingly found that concentrating a heterogeneous fermentation broth to different concentrations, i.e., less than about 150 g / L lactate or more than about 220 g / L lactate, resulted in the formation of low-purity magnesium lactate crystals during the crystallization process. The low-purity magnesium lactate crystals exhibited a large amount of impurities incorporated therein. Such low-purity magnesium lactate crystals would require additional processing steps and machinery for their purification, and therefore separation and purification of magnesium lactate from the above heterogeneous fermentation broth is not cost-effective or desirable, as described above.

[0101] In some embodiments, the initial pH of the concentrated clarified fermentation broth, prior to at least one cooling crystallization, is in the range of about 6 to about 7. Depending on the initial pH of the concentrated clarified fermentation broth, the pH can be adjusted by adding a base or an acid.

[0102] The acid may contain H 2 SO 4 or other acids known in the art. The base may be selected from caustic salts, such as but not limited to caustic magnesium salts, caustic sodium salts, caustic potash salts, caustic calcium salts and caustic ammonium salts. Non-limiting examples of caustic salts may be selected from MgO, Mg(OH) 2 MgCO 3 Mg(HCO 3 )2 、Ba(OH) 2 , NaOH, Na 2 CO 3 、NaHCO 3 , KOH, K 2 CO 3 , KHCO 3 , CaO, Ca(OH) 2 、CaCO 3 NH 4 OH, (NH 4 ) 2 CO 3 Each possibility represents a separate embodiment of the present invention.

[0103] In some embodiments, at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 75°C, which is higher than the dissolution temperature of magnesium lactate, so that magnesium lactate remains in a soluble form. In further embodiments, at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 70°C. In still further embodiments, at least one cooling crystallization is initiated at a first temperature selected from the range of about 50 to about 65°C.

[0104] In some embodiments, at least one cooling crystallization step ends at a second temperature selected from the range of about 15 to about 0.5° C. In further embodiments, at least one cooling crystallization step ends at a second temperature selected from the range of about 10 to about 1° C. In still further embodiments, at least one cooling crystallization step ends at a second temperature selected from the range of about 6 to about 2° C.

[0105] In some embodiments, the cooling rate of at least one cooling crystallization is in the range of about 50 to about 0.1°C / h. In further embodiments, the cooling rate of at least one cooling crystallization is in the range of about 10 to about 0.5°C / h. In some exemplary embodiments, the cooling rate of at least one cooling crystallization is in the range of about 5 to about 1°C / h.

[0106] Magnesium lactate crystals are obtained during and / or after cooling crystallization. The inventors have found that the specific conditions of controlled crystallization, i.e., initial temperature, final temperature, pH and cooling rate, as described above, enable the formation of high-purity magnesium lactate crystals. The high-purity magnesium lactate crystals are characterized by having a densely packed configuration, which enables them to exclude soluble impurities, such as color components, during the crystallization process. Crystallization under uncontrolled conditions results in the formation of low-purity magnesium lactate crystals.

[0107] After cooling and crystallization, the obtained magnesium lactate crystals are collected and separated from the remaining mother liquor. As used herein, the term "mother liquor" refers to the liquid remaining after the magnesium lactate crystals are crystallized. In some embodiments, the obtained magnesium lactate crystals are separated from the remaining liquid by a method selected from microfiltration, nanofiltration or another method known in the art.

[0108] In some embodiments, to obtain additional magnesium lactate crystals, the remaining liquid (mother liquor) is concentrated and then subjected to at least one additional cooling crystallization. In some embodiments, the additional concentration conditions are the same as the conditions of the first concentration step, as described above. In further embodiments, the conditions of at least one additional cooling crystallization are the same as the conditions of the first cooling crystallization.

[0109] In some embodiments, to obtain additional magnesium lactate crystals, at least one additional cooling crystallization is performed by recycling the remaining liquid (mother liquor) back to the crystallizer. In further embodiments, to obtain additional magnesium lactate crystals, at least one additional cooling crystallization is performed by placing the remaining liquid (mother liquor) in an additional separate crystallizer.

[0110] In some embodiments, the remaining liquid (mother liquor) undergoes at least two additional concentration and cooling crystallization cycles. In further embodiments, the remaining liquid (mother liquor) undergoes at least 3, at least 4, at least 5 or at least 10 additional concentration and cooling crystallization cycles. Each possibility represents a separate embodiment of the present invention.

[0111] In some embodiments, additional magnesium lactate crystals are separated from the remaining liquid (mother liquor) by the methods set forth herein above. In further embodiments, the magnesium lactate crystals obtained by the first cooling crystallization are combined with additional magnesium lactate crystals from at least one additional cooling crystallization to form combined magnesium lactate crystals. In still further embodiments, additional magnesium lactate crystals from additional concentration and cooling crystallization cycles are collected and combined with previously obtained magnesium lactate crystals to form combined magnesium lactate crystals.

[0112] In some embodiments, the method of the present invention further comprises a washing and / or purification step, comprising washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals. In a further embodiment, the washing and / or purification step comprises washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals with an organic solvent or an aqueous solution. In some embodiments, the organic solvent is selected from: ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate and combinations thereof. Each possibility represents a separate embodiment of the present invention. The aqueous solution may comprise water.

[0113] In some embodiments, the organic solvent or aqueous solution in the washing and / or purification step has a specific temperature selected from about 0.5 to about 15° C. In further embodiments, the organic solvent or aqueous solution has a specific temperature selected from about 0.5 to about 8° C.

[0114] In some embodiments, the washing and / or purification step further comprises at least one finishing step selected from extraction, microfiltration, nanofiltration, activated carbon treatment, distillation, drying and grinding. In further embodiments, the washing and / or purification further comprises packaging for transport purposes.

[0115] In some embodiments, after the washing and / or purification steps, the resulting magnesium lactate crystals are characterized by having a high purity of more than about 85% by weight. In further embodiments, the resulting magnesium lactate crystals are characterized by having a high purity of more than about 90%, about 92%, about 94% by weight, about 95% by weight, about 96% by weight, about 97% by weight, about 98% by weight, or about 99% by weight. In some embodiments, the magnesium lactate crystals contain less than about 15% by weight of soluble impurities. In further embodiments, the magnesium lactate crystals contain less than about 10% by weight, about 9% by weight, about 8% by weight, about 7% by weight, about 6% by weight, about 5% by weight, about 4% by weight, about 3% by weight, about 2% by weight, or less than about 1% by weight of soluble impurities.

[0116] Now refer to Figure 1 . Figure 1 Schematic diagram of a preferred embodiment of magnesium lactate recovery and purification. Figure 1 As a result of the fermentation process, the fermentation broth 11 containing magnesium lactate in soluble form enters the magnesium lactate recovery and purification process 101. In some embodiments, the fermentation broth is maintained at a temperature of at least about 45° C. to about 75° C. The insoluble impurities including insoluble organic and inorganic-based impurities (e.g., particles) are separated from the fermentation broth 11 using a separation step 12, thereby forming a clarified fermentation broth. The separation of insoluble particles from the fermentation broth in the separation step 12 can utilize centrifugation and / or microfiltration.

[0117] The clarified fermentation broth is then concentrated by evaporation to a lactate concentration of about 160 g / L to about 220 g / L in a concentration step 13. The concentrated fermentation broth enters a crystallization step 14 and undergoes a first crystallization to obtain magnesium lactate crystals. In order to obtain densely packed crystals with high purity, crystallization is started at a first temperature selected from the range of about 50 to about 65° C., a cooling rate of about 5 to about 1° C. / h, and ends at a second temperature selected from the range of about 5 to about 2° C. The initial pH of the clarified fermentation broth (at the beginning of the crystallization step) is in the range of about 6 to about 7.

[0118] During the crystallization process, densely packed crystals are formed, which are able to exclude soluble impurities, thereby producing high purity, for example, purity exceeding 94%. The high purity crystals contain less than about 6% by weight of soluble impurities.

[0119] At the end of the crystallization step 14, the magnesium lactate crystals obtained are separated from the remaining mother liquor by filtration in a crystal collection step 15.

[0120] The remaining mother liquor is passed through a recycling step 151 into a crystallizer for at least one further crystallization step 14. In step 15, the magnesium lactate crystals obtained in at least one further crystallization are separated from the remaining mother liquor and combined with the crystals obtained in the first crystallization.

[0121] The combined crystals are subjected to a purification step 16, which comprises washing with an organic solvent selected from the group consisting of ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate, combinations thereof or other suitable solvents known in the art.

[0122] The purified crystals undergo a final finishing step 17, which comprises at least one further finishing step selected from extraction, microfiltration, nanofiltration, activated carbon treatment, distillation, drying and grinding. The further finishing step may comprise the preparation of the purified crystals for packaging and transport.

[0123] The term "about" means ±10%, ±5%, ±1%, or ±0.1% of the specified value.

[0124] However, throughout the description and claims of the specification, the words “comprise”, “include”, “contain” and “including” mean “including but not limited to”, and are not intended to (and do not) exclude other parts, additives, components, integers or steps.

[0125] As used herein, the singular forms "a", "an" and "the" include the plural forms unless the context clearly indicates otherwise. Thus, for example, reference to "a polysaccharide" includes a combination of polysaccharides.

[0126] The following examples are presented to more fully illustrate some embodiments of the present invention. However, they should never be construed 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.

[0127] Example

[0128] Example 1: Removal of insoluble impurities and microfiltration

[0129] The purpose of this step is to separate insoluble impurities from the fermentation broth to reduce the potential for fouling in further downstream processing steps.

[0130] All of the following examples used two fermentation broths containing magnesium lactate (referred to as B2 and B3) containing different initial lactate concentrations (Table 1 below). Both fermentation broths were derived from commercial food waste, where source-sorted food waste from restaurants was combined with factory waste from bakeries. The commercial food waste was shredded, heat-treated, and fermented using lactic acid-producing microorganisms. After fermentation, each fermentation broth contained magnesium lactate, insoluble organic-based impurities, insoluble inorganic-based impurities, and soluble impurities.

[0131] The fermentation broth contains about 20% by weight of insoluble impurities. The insoluble organic and inorganic based impurities contain particles having an average particle size of about 1 μm to about 2 mm.

[0132] Table 1: Overview of different fermentation broths

[0133] sample Fermentation Broth Lactate concentration (g / L) B2 <![CDATA[Mg(LA) 2 ]]> 78.9 B3 <![CDATA[Mg(LA) 2 ]]> 85.5

[0134] Lactate concentration was determined using an HPLC detector (UV-VIS and RID, Agilent 1260 Infinity).

[0135] Insoluble impurities are removed from the fermentation broth using a separatory funnel and a Büchner filter (4-9 μm cardboard filter, Pall K250) mounted on a vacuum pump. In order to keep the magnesium lactate in a soluble form, the temperature of the fermentation broth should be maintained at 55-60° C. during the removal of insoluble impurities. Once clogged, replace the filter with a new one. Microfiltration can also be performed using a flat plate filter (Buon Vino Mini Jet filter) with a 0.5 μm cardboard membrane.

[0136] The fermentation broth initially contains a yellow oily phase (caused by insoluble organic-based particles) that may clog the filter. Use a separatory funnel ( Figure 2A , 2C ) helps to separate the fat particles from the fermentation broth. This method is used for fermentation broths B2 and B3. The oil phase is present in the top layer, while the magnesium lactate aqueous solution is present in the bottom layer.

[0137] The fermentation broth was filtered to obtain a clear, dark and diluted lactate solution. The initial concentrations of B2 and B3 were 78.9 g / L and 85.8 g / L lactate, respectively. After filtration, the lactate concentration of B2 was 75.7 g / L and that of B3 was 82.9 g / L.

[0138] Without wishing to be bound by any theory or mechanism, it is expected that the removal of insoluble particles (e.g., fat particles) prior to crystallization is critical because they can disturb the crystal lattice and thereby reduce the purity and alter the polymorphism of the resulting lactic acid crystals. Additionally, it is important to perform the removal of these particles at a temperature above the dissolution temperature of magnesium lactate (in the above examples, between 55-60° C.). Otherwise, magnesium lactate may precipitate and impair the crystallization process.

[0139] To obtain higher combined yields, a two-step filtration process (diafiltration) can be performed.

[0140] No traces of magnesium lactate were detected in the fat particles, indicating that there was no quality loss during the filtration process.

[0141] Example 2: Concentration

[0142] The purpose of this step is to concentrate the clarified fermentation broth obtained after separation of insoluble impurities.

[0143] The clarified B2 and B3 obtained in Example 1 were concentrated to 220 g / L and 175.9 g / L of lactate, respectively.

[0144] Concentrate by evaporation. Use a rotary evaporator ( R-100, Büchi) is evaporated at a temperature of about 60° C. The concentration step can also be carried out in the crystallization vessel.

[0145] When an evaporation temperature of 80°C was attempted, the magnesium lactate crystals obtained after crystallization were not densely packed crystals of the preferred polymorphic form.

[0146] Without wishing to be bound by any theory or mechanism, it is conceivable that concentrated fermentation broth has a better yield during crystallization. Since the solubility of magnesium lactate at 20°C is 100 g / L (SDS of magnesium lactate, Jost Chemicals), significant mass loss occurs in the mother liquor after crystallization due to the dissolution of magnesium lactate crystals in the mother liquor. The concentration of saturated fermentation broth reduces the volume of the mother liquor and therefore reduces the loss of magnesium lactate. This makes evaporation necessary to obtain a reasonable process yield.

[0147] It was observed that concentrating the clarified fermentation broth to a lactate concentration below 150 g / L or above 220 g / L resulted in the formation of low purity magnesium lactate crystals having an undesirable spherical shape and containing a large amount of soluble impurities (e.g., color components, resulting in a brown color) incorporated therein. This process has a low yield.

[0148] For example, when the clarified B3 was concentrated to 140 g / L of lactate, a yield of 46.5% was obtained, and the obtained crystals exhibited an undesirable spherical shape and brown color, indicating the presence of a large amount of soluble impurities incorporated into the crystals.

[0149] Example 3: Crystallization process of magnesium lactate (B2) - (Comparative Example)

[0150] Several crystallization experiments were carried out on the concentrated clarified B2 obtained in Example 2. The experiments were carried out in 500 and 2000 mL Radleys Reactor-Ready TM The experiment was carried out in a laboratory reactor and the temperature was controlled using a Huber Petit Fleur thermostat.

[0151] As described in Example 2 above, in order to reduce the amount of mother liquor that can dissolve the resulting crystals, evaporation must be performed to increase the crystallization yield. During the evaporation process, magnesium lactate precipitation can be seen on the side of the flask ( Figure 3A ).

[0152] The concentrated clarified B2 obtained in Example 2 contained 220 g / L of lactate. The pH of the concentrated clarified B2 was about 7. The concentrated clarified fermentation broth was crystallized by two methods described in the following sections.

[0153] First method

[0154] After evaporation, the crystallization of magnesium lactate was carried out using the first method:

[0155] 1. The concentrated microfiltrate was cooled at room temperature without controlling the cooling rate. Magnesium lactate spontaneously crystallized into undesirable spherical crystals ( Figure 3B ).

[0156] 2. Separate from step 1 ( Figure 3C ) and dried at 70° C. This fraction was used for solubility determination.

[0157] 3. Part of the spherical crystals obtained from step 1 were separated and recrystallized by dissolving the crystals at 60°C to a concentration of 219.8 g / L ( Figure 3D ).

[0158] 4. Cool the solution to 16-17°C without controlling the cooling rate.

[0159] 5. Separate the obtained Mg(LA) from the mother liquor using Buchner filtration 2 Crystal( Figure 3E ).

[0160] result:

[0161] A total of 102 g of Mg(LA) was obtained from step 5 2 , the dry matter content was 64.8% w / w, which corresponds to 58.8 g lactate. The yield was 60.8%.

[0162] Second method

[0163] Next, the crystallization of magnesium lactate was performed using the second method. The same steps as the first crystallization method (same steps 1-5 as the first method) were used, and the mother liquor obtained was subsequently concentrated and crystallized, thereby allowing a higher overall yield. The following additional steps were performed:

[0164] 6. Concentrate the mother liquor using rotary evaporation and then perform the same crystallization step as above. During crystallization, cool the concentrated mother liquor to 2°C.

[0165] 7. The crystals obtained from the first crystallization and the mother liquor crystallization were dried at 70°C and ground into fine powder.

[0166] result:

[0167] The total combined yield of the method was 78.7%. The crystals obtained from the mother liquor crystallization contained more visible brown components than the crystals obtained from the first crystallization, which indicated that a larger amount of impurities were incorporated into the crystals.

[0168] Example 4: Crystallization process of magnesium lactate (B3)

[0169] Using Radleys Reactor-Ready TM The laboratory reactor and the Huber Petit Fleur thermostat regulated and controlled the crystallization of the concentrated clarified B3 obtained in Example 2. As described above, the lactate concentration of the concentrated clarified B3 was 175.9 g / L. The pH of the concentrated clarified B3 was about 7. The concentrated clarified fermentation broth was crystallized by two methods described in the following sections.

[0170] First method:

[0171] 1. The concentrated microfiltrate was added to the reactor at 60°C and cooled to 2°C at a rate of 2°C / h in a controlled manner.

[0172] 2. The polymorphs formed during the crystallization process (at 54°C, 20°C and 2°C) were determined using a polarized light microscope. Mg(LA) had already started to form at 54°C. 2 crystals and the desired densely packed crystal form is obtained. During cooling, the size of the crystals increases.

[0173] 3. The obtained crystals were separated from the mother liquor using Buchner filtration. The dry mass content of the crystals at this stage was 81.3% w / w.

[0174] 4. The obtained crystals were then dried at 70° C. and ground. The dry matter content increased to 88% w / w, while the remaining 12% w / w could be attributed to residual water.

[0175] 5. Additional final finishing steps are optional, such as washing the obtained crystals with a suitable solvent, for purification, drying and grinding.

[0176] result:

[0177] The crystallization yield obtained was 58.5%, which is almost the same as the yield obtained in the crystallization of B2 (Example 3, the yield of the first method was 60.8%). Because the crystallization and cooling process were controlled, no undesirable crystal form (spherical crystals) was observed.

[0178] Second method:

[0179] Next, the crystallization of magnesium lactate was performed using the second method. The same steps as the first crystallization method (same as steps 1-5 in the first method) were used, and the mother liquor obtained was subsequently concentrated and crystallized, thus allowing a higher combined total yield of 65.4%.

[0180] Three fractions of crystals obtained from the initial solution were separated from the mother liquor and used to find the most suitable washing liquid or solvent. The purpose of this step in the experiment was to improve the purity of the crystals and remove any remaining impurities. These fractions were subjected to the following treatments:

[0181] Mg(LA) 2 Crystal, no cleaning

[0182] Mg(LA) washed with 200 mL cold ethanol (2°C) 2 Crystal

[0183] Mg(LA) washed with 200 mL cold water (2°C) 2 Crystal

[0184] result

[0185] Clear differences in color between the different fractions can be seen. Crystals washed with water or ethanol are whiter and cleaner than unwashed crystals. Crystals washed with water partially dissolved, and a lactate loss of 9.9 g / L was measured in the wash water. After drying at 70°C, the crystals became solid again ( Figure 4 ).

[0186] Wash Mg(LA) with cold ethanol 2 After crystallization, the filtrate obtained (ethanol remaining after washing) contained two fractions in the form of suspension ( Figure 5A ). The suspension was filtered using a Buchner filter to obtain a thin cake ( Figure 5B ). The lactate concentration of the filtrate was 2.9 g / L. The suspension may be a mixture of impurities and salts that are poorly soluble in ethanol.

[0187] All three fractions were dried (70°C), ground, and their purity was determined by weight (the difference between the weight and the value measured on HPLC for the same sample) and quantitative peak area. The purity of the ethanol-washed crystals was as high as 97% ( Figure 6 Rinsing with water had no benefit on purity (72%). For crystals that were not rinsed at all, purity was lowest (65%).

[0188] Example 5: Crystallization solubility of magnesium lactate

[0189] The purpose of this experiment was to determine the appropriate solubility curve, as this will be a key tool in developing an effective crystallization method. The solubility of magnesium lactate was determined in water. The effect of temperature on solubility was estimated by evaluating the solubility at several temperatures. Three different types of Mg(LA) were analyzed. 2 sample:

[0190] 1. Magnesium lactate from Sigma-Aldrich

[0191] 2. Magnesium lactate from B2 (spherical crystals, Example 3 - Step 2)

[0192] 3. Magnesium lactate from B2 (fine crystals, after recrystallization of spherical crystals, Example 3 - Step 3-5).

[0193] The solubility of magnesium lactate in water at different temperatures was determined using the following method:

[0194] 1. A 5 mL Eppendorf tube filled with water (approximately 0.5 mL) was cooled to 10°C and placed in an Eppendorf Thermomixer.

[0195] 2. Add excess dry Mg(LA) 2 And mix for at least 2 hours.

[0196] 3. Repeat step 2 for each tube until the product no longer dissolves.

[0197] 4. Allow the undissolved fraction to pellet or, if necessary, centrifuge briefly.

[0198] 5. Collect 20 μL of supernatant using a positive displacement pipette and dilute with 980 μL RO water. Dilution is necessary to avoid recrystallization / solidification during HPLC.

[0199] 6. Filter the diluted sample using a 0.2 μm PES filter and then perform HPLC.

[0200] 7. Determine the mg concentration of lactate by HPLC.

[0201] 8. Increase the temperature from 10 to 60 °C and repeat steps 1-6 for each temperature.

[0202] result

[0203] Magnesium lactate from Sigma-Aldrich

[0204] Pure Mg(LA) from Sigma-Aldrich was analyzed 2 Crystal( Figure 7 ). The solubility at 20°C is 74.1 g / L, which is much lower than the data obtained from the literature. The samples from Sigma-Aldrich are anhydrous and hydrous Mg(LA) 2 mixture, resulting in a lower solubility than anhydrous Mg(LA) 2 The solubility of anhydrous compounds in water is generally higher than in the hydrated form. Anhydrous compounds can be obtained by removing water molecules from the crystal structure.

[0205] Magnesium lactate from B2 (spherical crystals and fine powder)

[0206] The solubility of the two types of crystals in water was analyzed. 2 Spherical crystals were obtained by precipitation ( Figure 8 ). Fine crystals were obtained after recrystallization of spherical crystals ( Fig. 9 ).

[0207] Due to different polymorphisms, the solubility of fine crystals (at 20°C: 72.4 g / L Mg(LA) 2 ) is lower than spherical crystals (at 20℃: 78.2g / L Mg(LA) 2 Without wishing to be bound by any theory or mechanism, it is expected that the most stable polymorphic form of any material is the one with the lowest chemical potential. Spherical crystals may contain some impurities because they are formed by uncontrolled precipitation. These impurities may enter the crystal lattice and reduce the stability of the structure (affecting the chemical potential).

[0208] Spherical crystals were found (at 60°C: 90.0 g / L Mg(LA) 2 ) over time than fine Mg(LA) 2 Crystals (at 60°C: 99.7 g / L Mg(LA) 2 )'s solubility is reduced.

[0209] Example 6: Thermogravimetric analysis (TGA)

[0210] The purpose of this experiment is to obtain information about the thermal degradation of Mg(LA) 2 More information on the crystal composition and to investigate whether the crystals produced during crystallization were in the dihydrate form (i.e., Mg(LA) 2 ·2H 2 O) assumption.

[0211] Thermal analysis was performed using a TA Instruments TGA Q500. The following samples were analyzed:

[0212] Pure Mg(LA) from Sigma Aldrich 2

[0213] Mg(LA) from B3 before washing 2 (Example 4)

[0214] After washing with ethanol, Mg(LA) from B3 2 (Example 4)

[0215] A small amount of each sample was placed on an aluminum pan. The maximum sample weight was 1 g. The heating rate was 10°C / min, ranging from 50°C to 800°C. Nitrogen was used as carrier gas in TGA analysis.

[0216] result

[0217] In the TGA thermograms of the three samples, three transitions can be seen ( Fig.10 ):

[0218] Between 100℃ and 200℃

[0219] Between 325℃ and 350℃

[0220] Between 350℃ and 450℃

[0221] The first transition at 100°C–200°C is attributed to the evaporation of unbound water and the release of hydrated water. This transition accounts for approximately 15% of the total sample weight and is supported by theoretical calculations based on the Mg(LA) 2 ·2H 2 The quality of water in the quality of O.

[0222]

[0223] The second and third transitions at 325℃-450℃ are attributed to Mg(LA) 2 The generated lactic acid burns. Since the carrier gas is N 2 , so lactic acid may burn to carbon instead of carbon oxides. This transformation accounts for about 68% of the total weight of the sample, which is consistent with the Mg(LA) 2 ·2H 2The theoretical amount of lactic acid in O is relatively small:

[0224]

[0225] At the end of the experiment, Mg(LA) 2 ·2H 2 About 17% of the total initial amount of O remained, which is consistent with the 2 ·2H 2 The MgO content in O corresponds to:

[0226]

[0227] Based on the TGA results, it can be concluded that the generated Mg(LA) 2 The samples purchased from Sigma-Aldrich were all in the dihydrate form.

[0228] Example 7: Large-Scale Separation and Purification

[0229] The aim of this experiment was to purify magnesium lactate on a large scale from fermentation broth derived from decaying food waste and residues of: bananas, oranges, apples (with plastic stickers), potatoes, cabbage, cucumbers, carrots, tomatoes, tofu, rice, bread, milk, cheese (3% fat content) and sunflower oil, as well as water.

[0230] The food waste is chopped, heat treated and fermented using lactic acid producing microorganisms. After fermentation, the fermentation broth contains magnesium lactate, insoluble organic-based impurities, insoluble inorganic-based impurities and soluble impurities. The volume of the fermentation broth is about 1000 liters and contains an initial concentration of 76.3 g / L of lactate.

[0231] Insoluble impurities were removed from the fermentation broth by separating the solids using a decanter, followed by separation of fats / greases by liquid-liquid centrifugation and finally by microfiltration through a ceramic membrane. The temperature of the purified fermentation broth was maintained at 55-60°C. The purified fermentation broth was then concentrated by evaporation to a lactate concentration of 216.8 g / L and subjected to cooling crystallization under controlled conditions, similar to the crystallization conditions shown in Example 4: the concentrated purified fermentation broth was added to a crystallization reactor at 60°C and cooled to 2°C in a controlled manner at a rate of 2°C / h. The resulting crystals were separated from the mother liquor, washed with cold ethanol, dried and ground. A high purity of 98.6% was obtained.

[0232] The description of the foregoing specific embodiments will so fully reveal the general nature of the invention that others can easily modify and / or change the various applications of such specific embodiments by applying current knowledge without undue experimentation and without departing from the general concepts, and therefore, such changes and modifications should and are intended to be understood as being within the meaning and range of equivalents of the disclosed embodiments. It should be understood that the wording or terminology employed herein is for descriptive purposes and not limiting. The means, materials and steps for performing the various disclosed functions may take a variety of alternative forms without departing from the invention.

Claims

1. A method for separating and purifying magnesium lactate from a fermentation broth obtained from a fermentation process of an organic waste feedstock, the method comprising the steps of: (a) providing a clarified fermentation broth from which insoluble impurities have been removed, the clarified fermentation broth comprising magnesium lactate in soluble form as a result of the fermentation process, the temperature of the fermentation broth being between 45°C and 75°C; (b) concentrating the clarified fermentation broth in step (a) to a lactate concentration of 150 g / L to 220 g / L; (c) subjecting the concentrated clarified fermentation broth from step (b) to at least one cooling crystallization to obtain magnesium lactate crystals, wherein the cooling rate of the at least one cooling crystallization is in the range of 5 to 1° C. / h; and (d) collecting the obtained magnesium lactate crystals.

2. The method according to claim 1, wherein the insoluble impurities include at least one of insoluble organic-based impurities, insoluble inorganic-based impurities and soluble impurities.

3. The method according to claim 1 or 2, wherein the temperature of the fermentation broth in step (a) is 55°C to 65°C.

4. The method according to claim 1 or 2, wherein the separation of insoluble impurities comprises at least one technique selected from the group consisting of filtration, centrifugation, flotation, sedimentation, flocculation and decantation.

5. A process according to claim 4, wherein the separation of insoluble impurities is carried out by centrifugation.

6. The method according to claim 4, wherein the separation of insoluble impurities further comprises microfiltration.

7. The method according to claim 6, wherein the separation of insoluble impurities comprises centrifugation and microfiltration.

8. The method according to claim 1 or 2, wherein the concentration of step (b) is carried out by evaporation, nanofiltration, reverse osmosis or a combination thereof.

9. The method according to claim 1 or 2, wherein in step (b) the fermentation broth is concentrated to a lactate concentration of 160 g / L to 220 g / L.

10. The method according to claim 9, wherein in step (b) the fermentation broth is concentrated to a lactate concentration of 170 g / L to 220 g / L.

11. The method according to claim 10, wherein in step (b) the fermentation broth is concentrated to a lactate concentration of 180 g / L to 220 g / L.

12. The method according to claim 1 or 2, wherein in step (c), the at least one cooling crystallization is initiated at a first temperature selected from the range of 50 to 75°C.

13. The method according to claim 12, wherein in step (c), the at least one cooling crystallization is initiated at a first temperature selected in the range of 50 to 70°C.

14. The method according to claim 13, wherein in step (c), the at least one cooling crystallization is initiated at a first temperature selected in the range of 50 to 65°C.

15. The method according to claim 1 or 2, wherein in step (c), the at least one cooling crystallization step is ended at a second temperature selected in the range of 10 to 1°C.

16. The method according to claim 15, wherein in step (c), the at least one cooling crystallization is ended at a second temperature selected in the range of 6 to 2°C.

17. The method according to claim 1 or 2, wherein in step (c), the cooling rate of the at least one cooling crystallization is 2°C / h.

18. The method according to claim 1 or 2, wherein in step (c), the pH of the concentrated clarified fermentation broth is in the range of 6 to 7 before the at least one cooling crystallization.

19. The process according to claim 1 or 2, wherein the magnesium lactate crystals obtained in step (d) are separated from the remaining liquid by a process selected from microfiltration and nanofiltration.

20. A process according to claim 19, wherein the remaining liquid from step (c) is concentrated and then subjected to at least one further crystallization to obtain further magnesium lactate crystals.

21. The process according to claim 20, wherein the magnesium lactate crystals further obtained are separated from the liquid.

22. The method according to claim 21, wherein the magnesium lactate crystals obtained from claim 19 are combined with the magnesium lactate crystals additionally obtained from claim 21, thereby forming combined magnesium lactate crystals.

23. The method according to claim 1 or claim 22, further comprising the step (e): washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals.

24. The method according to claim 23, wherein step (e) comprises washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals using an organic solvent selected from the group consisting of ethanol, propanol, isobutanol, cyclohexane, acetone, ethyl acetate and combinations thereof.

25. The method according to claim 23, wherein step (e) comprises washing and / or purifying the obtained magnesium lactate crystals or the combined magnesium lactate crystals with an aqueous solution.

26. The process according to any one of claims 24-25, wherein the specific temperature of the solvent or solution in step (e) is selected from 0.5 to 8°C.

27. The method according to claim 23, wherein step (e) further comprises at least one finishing step selected from the group consisting of extraction, microfiltration, nanofiltration, activated carbon treatment, distillation, drying and grinding.

28. The method of claim 23, wherein step (e) further comprises packaging for shipping purposes.

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