Process for producing regenerated lactate

Abstract

The present invention relates to a process for producing high purity magnesium L-lactate salt from decomposed organic waste and for enhancing the enantiomeric purity of the regenerated lactate salt.

Description

[Technical field]

[0001] The present invention relates to a process for producing magnesium L-lactate with high enantiomeric purity and low levels of non-lactate impurities.The present invention further relates to a process for increasing the enantiomeric purity of regenerated lactate, which comprises an enantiomeric mixture of L- and D-lactate. [Background technology]

[0002] Lactic acid fermentation Lactic acid fermentation, i.e., the production of lactic acid from carbohydrate sources via microbial fermentation, has attracted attention in recent years due to the ability to use lactic acid as a building block in the production of bioplastics. Lactic acid can be polymerized to form polylactic acid (PLA), a biodegradable and recyclable polyester that is considered a potential alternative to plastics produced from petroleum. PLA is used in the manufacture of a variety of products, including food packaging, consumables, textile fibers, and hygiene industries.

[0003] The production of lactic acid by fermentation bioprocessing is preferred over chemical synthesis methods for various considerations, including environmental concerns, cost, and the difficulty of producing enantiomerically pure lactic acid by chemical synthesis, and is desirable for most industrial applications. Conventional fermentation processes are typically based on anaerobic fermentation by lactic acid-producing microorganisms, which produce lactic acid as the main metabolic end product of carbohydrate fermentation. For the production of PLA, the lactic acid produced during fermentation is separated from the fermentation broth and purified by various processes, and the purified lactic acid is then subjected to polymerization.

[0004] Lactic acid has a chiral carbon atom and therefore exists in two enantiomeric forms, D- and L-lactic acid. To produce PLA suitable for industrial applications, the D- or L-lactic acid entering the production process must be highly purified to meet the specifications required for polymerization and reuse. Lactic acid bacteria that produce only the L-lactate enantiomer or only the D-lactate enantiomer are typically used to produce one separate enantiomer (L or D, respectively).

[0005] In currently available commercial processes, the carbohydrate source for lactic acid fermentation is typically a starch-containing renewable source, such as corn and cassava root. Additional sources, such as cellulose-rich sugarcane bagasse, have also been proposed. Typically, lactic acid-producing bacteria can utilize reducing sugars, such as glucose and fructose, but do not have the ability to degrade polysaccharides, such as starch and cellulose. Thus, to utilize such polysaccharides, the process requires the addition of glycolytic enzymes, typically combined with chemical treatment, to degrade the polysaccharides and release the reducing sugars.

[0006] An additional source of carbohydrates for lactic acid fermentation that has been proposed is complex organic waste, such as mixed food waste from municipal, industrial and commercial sources. Organic waste is advantageous because it is readily available and inexpensive compared to other carbohydrate sources for lactic acid fermentation.

[0007] Mixed food waste typically contains various ratios of reducing sugars (glucose, fructose, lactose, etc.), starch and lignocellulosic materials. Mixed food waste also contains endogenous D,L-lactic acid (e.g., from dairy products or natural degradation during transportation), one of which needs to be removed to utilize the waste as a substrate for producing optically pure lactic acid (L- or D-lactic acid). WO 2017 / 122197, assigned to the applicant of the present invention, discloses dual-acting lactic acid (LA)-utilizing bacteria genetically engineered to secrete polysaccharide-degrading enzymes such as cellulases, hemicellulases, and amylases that are useful for treating organic waste to eliminate lactic acid present in the waste and to degrade complex polysaccharides. WO 2020 / 208635, assigned to the applicant of the present invention, discloses systems and methods for treating organic waste, particularly mixed food waste, using D-lactate oxidase to eliminate D-lactate present in the organic waste.

[0008] Recycling of polylactic acid (PLA) PLA produced from renewable resources is an alternative to petroleum-based plastics and its use in the manufacture of products such as food packaging is continually growing. Due to the increasing presence of PLA in disposable end products, it is important to ensure that PLA is properly dealt with after disposal. Unlike thermoplastics such as polyethylene, polypropylene, polystyrene and poly(ethylene terephthalate), PLA is subject to thermal degradation. Therefore, when products containing PLA and mixtures of the aforementioned plastics are recycled, it is desirable to separate the PLA to avoid contamination of the recycling stream.

[0009] Recycling options for PLA include landfilling, composting, anaerobic digestion (biogas production), incineration, and chemical recycling of the components into monomers. Chemical recycling is preferred over other methods because the monomers can be reused in the production of new PLA.

[0010] One common form of PLA on the market is the copolymer PDLLA (poly(DL-)lactic acid), which is composed mainly of PLLA (made from L-lactic acid) and a small amount of PDLA (made from D-lactic acid). Most of the PLA plastics on the market contain a small amount of PDLA, which releases D-lactic acid when hydrolyzed. The hydrolyzed material may also contain an unknown amount of D-lactic acid formed by racemization during hydrolysis. Optical purity of greater than 99% is typically required for both D-lactic acid and L-lactic acid that enter the PLA production process. Therefore, the PLA regeneration process should address the issue of isomer separation. Chemical separation of the two enantiomers, usually using liquid or solid enantioselective membranes or high performance liquid chromatography (HPLC), is expensive.

[0011] Cam, Hyon and Ikada (1995) Biomaterials, 16(11):833-43 report the degradation of high molecular weight poly(L-lactide) in alkaline medium. The study tested the effect of molecular weight and morphology on hydrolysis. Degradation was carried out in 0.01 N NaOH solution at 37°C.

[0012] Siparsky, Voorhees, and Miao (1998) Journal of environmental polymer degradation, 6(1):31-41, report the hydrolysis of polylactic acid (PLA) and polycaprolactone (PCL) in aqueous acetonitrile solutions.

[0013] Xu, Crawford and Gorman (2011) Macromolecules, 44(12):4777-4782 report the effects of temperature and pH on the degradation of poly(lactic acid) brushes.

[0014] Chauliac (2013) "Development of a thermochemical process for hydrolysis of polylactic acid polymers to L-lactic acid and its purification using an engineered microbe", PhD dissertation, University of Florida, UMI number: 3583516, proposes a process for post-consumer use of PLA polymers. In this process, thermohydrolysis is the first step, followed by removal of D-LA from the hydrolyzed material, resulting in pure L-LA that can be redirected into the production of the polymer itself. Thermohydrolysis was carried out with water in the presence of NaOH. D-LA removal from the resulting syrup was achieved using Escherichia coli lacking all three identified L-lactate dehydrogenases.

[0015] Wadso and Karlsson (2013) Polymer Degradation and Stability, 98(1):73-78 report two studies to measure the enthalpy of alkaline hydrolysis of polymers containing esters of carboxylic acids. Two materials were used: films of poly(vinyl acetate), PVAc, and fibers of poly(lactic acid), PLA. Degradation was carried out at 30°C using sodium hydroxide and potassium hydroxide.

[0016] Elsawy et al. (2017) Renewable and Sustainable Energy Reviews, 79:1346-1352 reviews the hydrolysis of polylactic acid (PLA) and its composites.

[0017] Motoyama et al. (2007) Polymer Degradation and Stability, 92(7):1350-1358 reports the effect of MgO catalyst on the depolymerization of poly-L-lactic acid to L,L-lactide.

[0018] WO 2015 / 112098 discloses a process for producing lactide from a plastic having polylactic acid (PLA-based plastic), which includes the steps of preparing a PLA-based plastic, accelerating the decomposition of polylactic acid in the plastic by alcoholysis or hydrolysis to provide a low molecular weight polylactic acid, and pyrolyzing the low molecular weight polylactic acid to provide lactide. The process also further includes minimizing the size of the PLA-based plastic after the preparation step, and purifying the lactide after pyrolysis of the low molecular weight polylactic acid.

[0019] US Patent No. 7,985,778 discloses a method for decomposing and recovering a synthetic resin having an ester bond in its structural structure by carrying out a hydrolysis treatment and a subsequent separation and recovery treatment. In the hydrolysis treatment, an article containing the decomposed and recovered synthetic resin is exposed to a water vapor atmosphere filled at a saturated water vapor pressure and below the treatment temperature or the melting point of the synthetic resin. The synthetic resin in the article to be treated is hydrolyzed by the water vapor generated at the treatment temperature to generate a decomposition product before being polymerized into a synthetic resin containing an ester bond. In the separation and recovery treatment, the decomposition product generated by the hydrolysis treatment is separated into a liquid component and a solid component and individually recovered.

[0020] US Patent No. 8,614,338 discloses a method for stereospecific chemical recycling of a mixture of polymers based on polylactic acid PLA, in order to reform its monomers or one of its derivatives. The method comprises the steps of placing the mixture of polymers in a suspension of lactate esters capable of dissolving the PLA fraction, followed by the separation of first the lactate esters, PLA and other dissolved impurities, and then the mixture of other polymers and impurities that are insoluble. The solution thus obtained, containing PLA, is then subjected to a catalytic depolymerization reaction by transesterification to form oligoesters. The depolymerization reaction by transesterification is then stopped at a given point in time to separate the residual lactate esters. The oligoesters thus obtained are then subjected to a cyclization reaction to produce lactides that are finally stereospecifically purified, so as to obtain a fraction of purified lactide with a meso-lactide content of 0.1% to 40%.

[0021] Nos. 8,431,683 and 8,481,675 disclose a process for recycling polymer blends that inevitably contain PLA, including grinding, pressing, dissolving the PLA in a solvent, removing undissolved contaminating polymer, alcoholysis depolymerization, and purification steps.

[0022] US Patent No. 8,895,778 discloses the depolymerization of spent polyesters such as polylactic acid. Ultrasonic implosion can be used to accelerate the depolymerization. The spent PLA was exposed to methanol as a suspension medium in the presence of organic or ionic salts of alkali metals such as potassium carbonate and sodium hydroxide as depolymerization catalysts to provide high yields and high quality lactic acid monomer.

[0023] US Patent Publication No. 2018 / 0051156 discloses a method for enhancing / promoting the depolymerization of a polymer (e.g., one that contains hydrolyzable bonds), which generally includes contacting a polymer that contains hydrolyzable bonds with a solvent and an alcohol to provide a polymer mixture in which the polymer is substantially dissolved, the contacting being carried out at a temperature at or below the boiling point of the polymer mixture. The resulting depolymerized polymer can be separated from them (e.g., including monomers and / or oligomers). Such a method can be carried out under relatively mild temperature and pressure conditions. In some embodiments, the polymer is poly(lactic acid).

[0024] WO 2021 / 165964, assigned to the applicant of the present invention, discloses industrial fermentation for the production of lactic acid from organic waste in combination with chemical recycling of polylactic acid to obtain lactic acid in high yields.

[0025] There is an unmet need for an economical and reliable process for the production of enantiomerically pure L-lactate from degraded waste containing both L- and D-lactate enantiomers. Summary of the Invention

[0026] The present invention provides high purity L-lactate monomer from lactic acid fermentation of organic waste and / or chemical hydrolysis of PLA. The present invention also provides a process for increasing the enantiomeric purity of lactate obtained from the recycling of organic waste and / or PLA waste.

[0027] The present invention is based in part on the unexpected discovery that the enantiomeric purity of L-lactate can be increased by carrying out ion exchange or exchange of lactate counterions in fermentation broth or PLA hydrolysis slurry containing various concentrations of D-lactate monomer, resulting in enantioselective precipitation of L-lactate, particularly magnesium L-lactate.The present invention thus allows for the recycling of waste from various sources, including waste containing endogenous D-lactate monomer, while avoiding the need for D-lactate utilization bacteria or enzymes to eliminate D-lactate monomer.The present invention conveniently produces L-lactate with enantiomeric purity of over 99%, which can be used for commercial production of PLA without additional processing for isomer separation.

[0028] According to the principles of the present invention, both the fermentation of organic waste and the hydrolysis of PLA are carried out in the presence of alkaline compounds. During fermentation, the pH in the fermenter drops due to the production of lactic acid, which negatively affects the productivity of the lactic acid producing microorganisms. For this reason, alkaline compounds, typically hydroxides of sodium, potassium, ammonium or magnesium, and mixtures or combinations thereof, are added to neutralize the pH, thereby forming lactate salts. The present invention discloses for the first time the use of ammonia water (aqua ammonia) derived from the anaerobic digestion of solid biomass waste from a fermentation process as a source of alkaline compounds during fermentation or PLA hydrolysis. Ammonia water derived from the solid biomass of a previous fermentation process is an excellent source of alkali to be added to adjust the pH of the fermentation broth to the desired value, while also allowing significant cost savings by removing the need for expensive alkaline compounds to be added. Furthermore, it provides for further recycling of the solid biomass obtained after lactic acid fermentation.

[0029] An additional advantage of the process of the present invention arises from the use of regenerated salts from the previous acidification of lactate, which provide ion exchange or replacement of lactate counterions in the fermentation broth or PLA hydrolysis slurry. Typically, both the lactic acid fermentation process and the PLA degradation process produce lactate salts. To obtain polylactic acid, lactate salts need to be acidified to lactic acid monomers or methylated or acetylated in the presence of an acid. For this purpose, acids such as hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and mixtures or combinations thereof are used. During these processes, the lactate counterions and the acid anions precipitate and form salts. According to the principles of the present invention, the salts can be reused in subsequent processes after fermentation or PLA hydrolysis as ion sources for ion exchange or replacement of lactate counterions.

[0030] According to a first aspect, there is provided a process for enriching L-lactate enantiomers from an enantiomeric mixture derived from decomposed organic waste, the process comprising: (a) obtaining a degraded organic waste product containing an enantiomeric mixture of D- and L-lactate salts and counterions other than magnesium; (b) optionally performing at least one of the steps of neutralizing the D- and L-lactate salts and removing solid particles from the decomposed organic waste; and (c) adding a magnesium salt to the enantiomeric mixture of step (a) or (b), thereby precipitating L-lactate magnesium salt in high enantiomeric purity. Includes.

[0031] In one embodiment, the process provides an enrichment of the L-lactate enantiomer of up to 1% or more. In another embodiment, the process provides an enrichment of the L-lactate enantiomer of up to 5% or more. In yet another embodiment, the process provides an enrichment of the L-lactate enantiomer of up to 10% or more. In certain embodiments, the process provides an enrichment of the L-lactate enantiomer of up to 15%. In other embodiments, the process provides an enrichment of the L-lactate enantiomer of up to 20%. In yet other embodiments, the process provides an enrichment of the L-lactate enantiomer of up to 25%.

[0032] In certain embodiments, the decomposed organic waste is obtained from a lactic acid fermentation process. In further embodiments, the decomposed organic waste is obtained from a lactic acid-containing waste. In additional embodiments, the decomposed organic waste is obtained from the hydrolysis of polylactic acid polymers.

[0033] In various embodiments, the organic waste comprises a carbohydrate source. In 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, institutional food waste (from hospitals, restaurants, shopping centers, airports, etc.), and mixtures or combinations thereof. Each possibility represents a separate embodiment.

[0034] In a further embodiment, the decomposed organic waste is pretreated prior to step (a). In certain embodiments, the pretreatment comprises the removal of non-lactic acid containing impurities.

[0035] In accordance with the principles of the present invention, the decomposed organic waste contains endogenous D-lactate in an amount of up to 20 wt.%. In some embodiments, the enantiomeric mixture contains 20% or less D-lactate. In other embodiments, the enantiomeric mixture contains 10% or less D-lactate. In yet other embodiments, the enantiomeric mixture contains 5% or less D-lactate.

[0036] In certain embodiments, the counterion is selected from the group consisting of sodium, potassium and ammonium. Each possibility represents a separate embodiment. While the process of the present invention utilizes decomposed organic waste containing an enantiomeric mixture of D- and L-lactate salts and counterions other than magnesium, it is contemplated that magnesium ions may be present in the decomposed organic waste. Thus, according to various embodiments, the decomposed organic waste contains an enantiomeric mixture of D- and L-lactate salts, magnesium ions, and counterions other than magnesium.

[0037] In further embodiments, step (b) is performed which includes neutralizing the D- and L-lactate salts. Typically, the neutralization is performed at a pH of about 6.5 to about 7.5, including each value within the specified range. In one embodiment, the neutralization is performed in the presence of an acid selected from hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof. Each possibility represents a separate embodiment. In one embodiment, the neutralization is performed in the presence of sulfuric acid. In other embodiments, the neutralization is performed in the presence of a base selected from sodium, potassium, or ammonium hydroxides, and combinations thereof. Each possibility represents a separate embodiment.

[0038] In various embodiments, step (b) is performed which includes removing solid particles from the decomposed organic waste, where removing the solid particles includes solid-liquid separation.

[0039] In additional embodiments, step (c) is carried out at an elevated temperature, hi some embodiments, step (c) is carried out at a temperature in the range of 20° C. to 80° C., inclusive of each value within the specified range.

[0040] In certain embodiments, the magnesium salt in step (c) is added in solid form. In alternative embodiments, the magnesium salt in step (c) is added as an aqueous solution. In further embodiments, the magnesium salt in step (c) is added gradually. In other embodiments, the magnesium salt in step (c) is added in up to 20% excess. In further embodiments, the magnesium salt in step (c) is derived from the acidification, methylation or acetylation of a previous batch of magnesium L-lactate.

[0041] In certain embodiments, the magnesium salt in step (c) is magnesium sulfate.

[0042] In additional embodiments, the resulting magnesium L-lactate salt is separated by filtration or centrifugation. In further embodiments, the resulting magnesium L-lactate salt is subjected to subsequent purification. In other embodiments, the subsequent purification includes at least one of crystallization, recrystallization, fractionation, silica gel chromatography, preparative HPLC, and combinations thereof. Each possibility represents a separate embodiment.

[0043] In certain embodiments, subsequent purification includes washing the resulting magnesium L-lactate salt, for example with purified water, while in other embodiments, subsequent purification includes dissolving and recrystallizing the resulting magnesium L-lactate salt.

[0044] In one embodiment, the resulting magnesium L-lactate salt contains less than 3% magnesium D-lactate. In another embodiment, the resulting magnesium L-lactate salt contains less than 2% magnesium D-lactate. In yet another embodiment, the resulting magnesium L-lactate salt contains less than 1.5% magnesium D-lactate. In a particular embodiment, the resulting magnesium L-lactate salt contains less than 1% magnesium D-lactate.

[0045] In a further embodiment, the magnesium L-lactate salt obtained is crystalline magnesium L-lactate dihydrate.

[0046] In other embodiments, the resulting magnesium L-lactate is acidified to form L-lactic acid with at least one of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof. Each possibility represents a separate embodiment. In certain embodiments, the L-lactic acid is used for subsequent polylactic acid formation.

[0047] In some embodiments, the processes disclosed herein further include a step of increasing the purity of L-lactate from the decomposed organic waste.

[0048] According to another aspect, there is provided a process for increasing the purity of L-lactate from decomposed organic waste, the process comprising: (a) obtaining a degraded organic waste comprising L-lactate and a counterion other than magnesium; (b) optionally performing at least one of neutralizing the L-lactate salt and removing solid particles from the decomposed organic waste; and (c) adding magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating magnesium L-lactate salt in high purity. Includes.

[0049] According to yet another aspect, there is provided a process for producing magnesium L-lactate salt in high purity from decomposed organic waste, the process comprising: (a) obtaining a degraded organic waste comprising L-lactate and a counterion other than magnesium; (b) optionally performing at least one of neutralizing the L-lactate salt and removing solid particles from the decomposed organic waste; and (c) adding magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating magnesium L-lactate salt in high purity. Includes.

[0050] According to a further aspect, there is provided a process for producing L-lactate magnesium salt from decomposed organic waste, the process comprising: (a) decomposing the organic waste by performing at least one of organic waste fermentation using a lactic acid producing microorganism and PLA hydrolysis in the presence of an alkaline compound to obtain a decomposed organic waste containing L-lactate and a counterion other than magnesium; (b) optionally performing at least one of neutralizing the L-lactate salt and removing solid particles from the decomposed organic waste; and (c) adding a magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating L-lactate magnesium salt. Includes.

[0051] In some embodiments, the alkaline compound includes at least one of NaOH, KOH, NH4OH, Ca(OH)2, and mixtures or combinations thereof. Each possibility represents a separate embodiment. In other embodiments, the alkaline compound includes a combination of Mg(OH)2 and / or MgCO3 with at least one of NaOH, KOH, NH4OH, Ca(OH)2, and mixtures or combinations thereof. In further embodiments, the alkaline compound includes NH4OH from anaerobic digestion of solid biomass obtained from a batch prior to lactic acid fermentation. In various embodiments, the NH4OH from anaerobic digestion of solid biomass is obtained by gas stripping.

[0052] In some embodiments, the magnesium salt in step (c) is derived from acidification, methylation or acetylation of a batch of magnesium L-lactate prior to lactic acid fermentation, while in other embodiments, the magnesium salt in step (c) is derived from acidification, methylation or acetylation of a batch of magnesium L-lactate prior to PLA hydrolysis.

[0053] Other objects, features and advantages of the present invention will become apparent from the following description, examples and drawings. [Brief description of the drawings]

[0054] [Figure 1] Schematic of a process according to certain embodiments of the present invention. [Diagram 2] % lactate (●) and D-lactate (×) concentrations of solution during the exchange reaction of sodium lactate (NaLa) produced from hydrolyzing PLA grade no. 4032D, according to certain embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] The present invention provides a process for producing magnesium L-lactate salt with high enantiomeric purity and low amounts of impurities from degraded organic waste. The present invention further provides a process for enriching the L-lactate enantiomer from an enantiomeric mixture of D- and L-lactate salts and increasing the purity of the L-lactate salt from degraded organic waste. The high purity magnesium L-lactate salt can further be used to produce new lactic acid-based products.

[0056] As used herein, the term "lactic acid" refers to a hydroxycarboxylic acid having the following chemical formula: CH3CH(OH)CO2H. The term lactic acid or lactate (unprotonated lactic acid) may refer to the stereoisomers (enantiomers) of lactic acid: L-lactic acid / L-lactate, D-lactic acid / D-lactate, or combinations thereof. As used herein, the term "enantiomers" refers to two stereoisomers of a compound that are non-superimposable mirror images of one another.

[0057] In most industrial applications, high purity L-lactate monomer is required to produce PLA with suitable properties. Therefore, the process of the present invention is particularly directed to producing L-lactate with high enantiomeric or chiral purity that can be converted to L-lactate suitable for reuse without the need to remove D-lactate monomer.

[0058] One advantage resulting from the process of the present invention is enantioenrichment, which is particularly advantageous for recycling lactic acid. The enrichment of L-lactate enantiomers by the process of the present invention is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or more of the initial L-lactate content. Each possibility represents a separate embodiment. For example, for an initial enantiomeric mixture containing 90% L-lactate and 10% D-lactate, a 10% enrichment results in a magnesium lactate salt containing 99% L-lactate and 1% D-lactate. Reduction of D-lactate content by the processes disclosed herein of at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or even up to 100% of the initial D-lactate content is within the scope of the present invention. Each possibility represents a separate embodiment. For example, for an initial enantiomeric mixture containing 90% L-lactate and 10% D-lactate, a 50% reduction in D-lactate content results in a magnesium lactate salt containing 95% L-lactate and 5% D-lactate. The resulting magnesium L-lactate crystals contain less than 3% magnesium D-lactate, less than 2% magnesium D-lactate, less than 1.5% magnesium D-lactate, or less than 1% magnesium D-lactate, according to the principles of the present invention. Each possibility represents a separate embodiment.

[0059] An additional advantage resulting from the process of the present invention is the improved purity of magnesium L-lactate. Typically, the initial purity of lactate salt in the decomposed organic waste is low. There are many non-lactate impurities present in the organic waste that are carried over to its decomposition products. Advantageously, the present invention provides at least 80% purity of crude magnesium L-lactate directly formed using the process disclosed herein. Further improvement of purity can be affected by washing, crystallization or recrystallization processes to obtain high purity magnesium L-lactate salt.

[0060] According to the principles of the present invention, the decomposed organic waste used in the processes disclosed herein is the decomposition product of any lactic acid-containing waste, such as, but not limited to, polylactic acid polymers subjected to hydrolysis using an alkaline compound, e.g., sodium hydroxide. According to additional embodiments, the decomposed organic waste used in the processes disclosed herein is obtained from lactic acid fermentation of fermentable carbohydrates, such as, but not limited to, those derived from organic waste. Organic waste feedstocks within the scope of the present invention may be derived from any waste source, including, but not limited to, food waste, municipal food waste, residential food waste, agricultural waste, industrial food waste from food processing facilities, institutional food waste (from hospitals, restaurants, shopping centers, airports, etc.), and mixtures or combinations thereof. Each possibility represents a separate embodiment. Organic waste may further be derived from residues such as animal and human waste, fruit and vegetable residues, plants, prepared foods, protein residues, slaughterhouse waste, and combinations thereof. Each possibility represents a separate embodiment. Industrial organic food waste may include factory waste such as by-products, factory rejects (e.g., expired products, defective products), store returns, or inedible food parts (such as skins, fats, shells, and peels) trimmings. Each possibility represents a separate embodiment. Industrial organic food waste may include waste from shopping malls, restaurants, supermarkets, etc. Each possibility represents a separate embodiment.

[0061] According to certain aspects and embodiments, the organic waste includes mono- or disaccharides obtained from sugar beet or cane sugar as a by-product of sugar manufacturing, such as, but not limited to, the production of fructose, molasses, or high fructose corn syrup (HFCS). According to other aspects and embodiments, the organic waste includes starch and starch derivatives, such as refined glucose syrup derived from the hydrolysis of starch, which may be corn starch, tapioca starch, wheat starch, potato starch, and the like. Each possibility represents a separate embodiment. The organic waste may further come from by-products of wine or beer production, such as, but not limited to, yeast autolysates and hydrolysates, as well as plant protein hydrolysates, animal protein hydrolysates, and soluble by-products of wheat or corn steeping. Paper sludge hydrolysate obtained by hydrolyzing paper sludge with cellulolytic enzymes may also be used, as well as dairy by-products produced during cheese production and dairy beverage production, e.g., for milk-based beverages, including lactose-free beverages.

[0062] According to various aspects and embodiments, the decomposed organic waste comprises a fermentation broth obtained from a fermentation process of a carbohydrate source. When using a heterogeneous feedstock, the decomposed organic waste or fermentation broth typically comprises insoluble organic impurities, such as, but not limited to, microorganisms (e.g., lactic acid-producing microorganisms, including, e.g., yeasts, bacteria, and fungi), fats and oils, lipids, aggregated proteins, bone chips, hair, precipitated salts, cellular debris, fibers (e.g., fruit and / or vegetable peels), and residual unprocessed waste (e.g., food shells, seeds, insoluble food particles and debris, etc.). Each possibility represents a separate embodiment. Non-limiting examples of insoluble inorganic impurities include plastic, glass, residues from food packaging, sand, and combinations thereof. Each possibility represents a separate embodiment.

[0063] Although not required, the decomposed organic waste can be further pretreated prior to using the process of the present invention. Suitable pretreatments include, but are not limited to, filtration, ultrafiltration, nanofiltration, reverse osmosis (RO) filtration, solvent extraction, repulsive extraction, salting-out precipitation, crystallization, distillation, evaporation, electrodialysis, and various types of chromatography (e.g., adsorption or ion exchange). Each possibility represents a separate embodiment.

[0064] The degraded waste may contain various concentrations of D- and L-lactate. The process of the present invention advantageously provides high purity magnesium L-lactate even when the initial concentration of D- and L-lactate monomers is as low as 10%. Typically, the initial concentration of D- and L-lactate monomers is in the range of about 20% to about 50%, including each value within the range specified. The ratio of D- and L-lactate monomers in the degraded waste may vary depending on the endogenous D-lactate content and the racemic lactic acid formation that occurs during degradation. Typically, the ratio of D-lactate monomers to L-lactate monomers includes, but is not limited to, 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, 14:86, 15:85, 16:84, 17:83, 18:82, 19:81, or 20:80. Each possibility represents a separate embodiment.

[0065] Referring now to the drawings, FIG. 1 shows an operational scheme for the production of magnesium L-lactate according to one particular embodiment of the present invention. Lactic acid fermentation is carried out. Organic waste, such as municipal waste, food waste and agricultural waste, serves as a substrate for L-lactic acid fermentation by L-lactic acid producing microorganisms, e.g., Bacillus coagulans. Due to the formation of L-lactic acid, an endogenous pH drop occurs. For this reason, the fermentation process is carried out in the presence of an alkaline substance to regulate the pH during fermentation. The alkaline substance neutralizes the pH, resulting in the formation of L-lactate ions and counterions. The decomposition of organic waste typically involves an alkaline substance selected from sodium hydroxide, potassium hydroxide or ammonium hydroxide, thereby generating sodium, potassium or ammonium counterions, respectively, with the decomposed waste. Thus, the use of sodium hydroxide results in the formation of sodium lactate with the counterion sodium, and the use of ammonium hydroxide results in the formation of ammonium lactate with the counterion ammonium. Advantageously, the alkaline substance added to the lactic acid fermentation is ammonia water or aqua ammonia. The use of ammonia water allows further recycling of the waste material remaining after the fermentation process. This mode of operation is called "counterflow" where the source of alkaline compounds used in the production of one batch of lactic acid is obtained from the production of a previous batch of lactic acid. In particular, while the main stream of lactic acid production continues to the downstream lactate purification and separation process, the biomass from the fermentation can be reused as a side stream (#2: anaerobically fermentable organic matter and fatty acids). In this side stream, anaerobic digestion is carried out, producing biogas (mainly methane) as the main product. If the biomass remaining after anaerobic digestion is concentrated, it can be used to generate ammonia water, for example by gas stripping. The ammonia water can then be used in the subsequent fermentation process to adjust the pH. This mode of operation is cost-effective as it makes it possible to reduce the cost of expensive alkaline compounds to neutralize the pH during fermentation.As a source of additional ammonia water, the scheme can be implemented by, for example, adding the lactate counterion (NH4) in the fermentation broth by using Mg(OH)2. + ) to provide additional ammonia water that can be refluxed to a subsequent fermentation batch. An additional use for the biomass remaining after fermentation is to supplement recycle streams with low nutrient content, such as, but not limited to, wastepaper hydrolysates, yeast lysates, and dairy waters.

[0066] According to certain aspects and embodiments, the decomposed organic waste may be neutralized, in some cases, using an acid or base known in the art. Typically, neutralization is performed at a pH of about 6.5 to 7.5, including any value therebetween. It will be appreciated by those skilled in the art that if the pH of the decomposed organic waste is basic, neutralization is performed by the addition of an acid. Suitable acids include, but are not limited to, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof. Each possibility represents a separate embodiment. Alternatively, if the pH of the decomposed organic waste is acidic, neutralization is performed by the addition of a base. Suitable bases include, but are not limited to, sodium, potassium, or ammonium hydroxides, and combinations thereof. Each possibility represents a separate embodiment.

[0067] If the degraded organic waste contains particles of PLA waste or non-lactic acid-containing impurities that have failed to hydrolyze, they may be separated from the degraded organic waste by solid-liquid separation techniques such as, for example, filtration or decantation. Each possibility represents a separate embodiment.

[0068] In accordance with the principles of the present invention, ion exchange is then performed by addition of a magnesium salt, resulting in precipitation of magnesium salt of L-lactate with high overall and enantiomeric purity. It should be understood that the ion exchange of the present invention can be completed, i.e., two or more alkaline substances are used, where the counter ion from the alkaline substance is other than magnesium, or is partial, i.e., one contains magnesium ion and the other contains a cation other than magnesium. The magnesium salt used for ion exchange can be added in solid form or as an aqueous solution. Each possibility represents a separate embodiment. When the magnesium salt is added as an aqueous solution, typically the aqueous solution contains magnesium ion at a concentration ranging from about 50 to about 500 g / L, including each value within the specified range. Representative magnesium ion concentrations include, but are not limited to, about 75 g / L to about 400 g / L, about 100 g / L to about 300 g / L, or about 150 g / L to about 250 g / L, including each value within the specified range. Each possibility represents a separate embodiment. In some embodiments, the magnesium salt is added gradually while mixing.

[0069] In certain aspects and embodiments, the magnesium salt is derived from the acidification, methylation or acetylation of lactate salt from a previous batch. According to these embodiments, the salt is a regenerated salt, thereby providing the additional advantage of cost reduction. Typically, the process of the present invention produces magnesium lactate salt as the final product. However, to obtain polylactic acid, the lactate salt may be acidified for polymerization using, for example, hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and mixtures or combinations thereof. Each possibility represents a separate embodiment. Following the addition of the acid, the magnesium ions can precipitate together with the anions of the acid to form magnesium salts that can be used for subsequent ion exchange according to the principles of the present invention. When the lactate product undergoes methylation or acetylation, these processes are also typically carried out in the presence of an acid, thereby resulting in the precipitation of magnesium salts that can be used in subsequent ion exchange processes.

[0070] Magnesium salts within the scope of the present invention include, but are not limited to, magnesium chloride, magnesium carbonate, magnesium sulfate, magnesium phosphate, magnesium hydroxide, and the like. Each possibility represents a separate embodiment. Magnesium salts according to the principles of the present invention include any hydrated or anhydrous form, including, but not limited to, MgCl2·xH2O (x=0-6), MgCO3·xH2O (x=0, 1, 2, 3, or 5), MgSO4·xH2O (x=0-11), Mg3(PO4)2·xH2O (x=0, 5, 8, or 22), MgHPO4·xH2O (x=0 or 3), Mg(H2PO4)2·xH2O (x=0, 2, or 4), Mg(OH)2, and the like. Each possibility represents a separate embodiment. In one embodiment, magnesium sulfate (e.g., magnesium sulfate heptahydrate) is added.

[0071] In some aspects and embodiments, the magnesium salt is added in a stoichiometric amount. In other aspects and embodiments, the magnesium salt is added in excess. Up to a 20% excess of magnesium salt may be added in accordance with the principles of the present invention.

[0072] Addition of the magnesium salt at room temperature or at elevated temperatures is within the scope of the present invention. Each possibility represents a separate embodiment. Suitable temperatures include in the range of 20° C. to 80° C., for example, about 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., or 80° C. Each possibility represents a separate embodiment.

[0073] The thus obtained magnesium L-lactate salt may be further subjected to downstream purification processes. One simple purification method, which has surprisingly been found to improve the enantiomeric purity of magnesium L-lactate, is to wash the crude magnesium L-lactate salt, for example, using purified water. Additional purification steps, such as crystallization, recrystallization, fractionation, silica gel chromatography, preparative HPLC, and combinations thereof, are within the scope of the present invention. Each possibility represents a separate embodiment. A re-acidification step may also be performed to obtain crude L-lactate, followed by a purification step to obtain purified L-lactate. Re-acidification may be performed as known in the art, for example, by using at least one of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof. Each possibility represents a separate embodiment.

[0074] Purification processes may include extraction, electrodialysis, adsorption, ion exchange, crystallization, and combinations of these methods. Some methods are reviewed, for example, in Ghaffar et al. (2014) Journal of Radiation Research and Applied Sciences, 7(2):222-229; and Lopez-Garzon et al. (2014) Biotechnol Adv., 32(5):873-904. Alternatively, one-step recovery and conversion of lactic acid to lactide may be used (Dusselier et al. (2015) Science, 349(6243):78-80).

[0075] A particular downstream purification process for purifying magnesium lactate via crystallization is described in co-pending patent application WO 2020 / 110108, assigned to the applicant of the present invention. The purification process comprises the following steps: - providing a clarified solution comprising magnesium lactate at a temperature between 45°C and 75°C; - concentrating the solution to a concentration of 150-220 g / L lactate; - carrying out at least one cooling crystallization of the concentrated solution to obtain magnesium lactate crystals; and - recovering the resulting magnesium lactate crystals. Includes.

[0076] In some embodiments, the solution is provided at a temperature between 55° C. and 65° C., inclusive, each value within the specified range.

[0077] Concentration of the solution may be performed by evaporation, nanofiltration, reverse osmosis, or a combination thereof. Each possibility represents a separate embodiment. In some embodiments, the solution is concentrated to a concentration of 160-220 g / L lactate, e.g., 170-220 g / L lactate, or 180-220 g / L lactate, inclusive of each value within the specified range.

[0078] At least one cooling crystallization may be initiated at a first temperature within the range of 50-75° C., inclusive, within the specified range. In some embodiments, at least one cooling crystallization is initiated at a first temperature within the range of 50-70° C., inclusive, within the specified range. In additional embodiments, at least one cooling crystallization is initiated at a first temperature within the range of 50-65° C., inclusive, within the specified range.

[0079] At least one cooling crystallization step may be terminated at a second temperature in the range of 10 to 1° C., inclusive, within the specified range. In some embodiments, at least one cooling crystallization is terminated at a second temperature in the range of 6 to 2° C., inclusive, within the specified range.

[0080] The cooling rate of at least one cooling crystallization may be in the range of 10 to 0.5° C. / hour, inclusive, within the specified range. In some embodiments, the cooling rate is in the range of 5 to 1° C. / hour, inclusive, within the specified range.

[0081] Prior to cooling crystallization, the pH of the concentrated mixture may be adjusted to within the range of 6 to 7, including every value therebetween.

[0082] The resulting magnesium lactate crystals may be separated from the remaining liquid by microfiltration or nanofiltration. The remaining liquid may be subjected to concentration followed by at least one additional cooling crystallization to obtain additional magnesium lactate crystals. Following separation from the liquid, the magnesium lactate crystals may be washed and purified with an aqueous solution or an organic solvent such as ethanol or acetone. Further processing of the magnesium lactate crystals may include at least one of extraction, microfiltration, nanofiltration, activated carbon treatment, drying and grinding. Each possibility represents a separate embodiment.

[0083] Although the process disclosed herein is primarily contemplated for enriching the L-lactate enantiomer from an enantiomeric mixture containing D- and L-lactate derived from decomposed organic waste, enrichment of the D-lactate enantiomer is also contemplated by the present invention.

[0084] Thus, according to certain aspects and embodiments, the present invention provides a process for enriching D-lactate enantiomers from an enantiomeric mixture derived from degraded organic waste, the process comprising: (a) obtaining a degraded organic waste product containing an enantiomeric mixture of D- and L-lactate salts and counterions other than magnesium; (b) optionally performing at least one of the steps of neutralizing the D- and L-lactate salts and removing solid particles from the decomposed organic waste; and (c) adding a magnesium salt to the enantiomeric mixture of step (a) or (b), thereby precipitating D-lactate magnesium salt in high enantiomeric purity. Includes.

[0085] According to other aspects and embodiments, the present invention provides a process for producing high purity D-lactate magnesium salt from decomposed organic waste, the process comprising: (a) obtaining a degraded organic waste containing D-lactate and a counterion other than magnesium; (b) optionally performing at least one of neutralizing the D-lactate salt and removing solid particles from the decomposed organic waste; and (c) adding magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating D-lactate magnesium salt in high purity. Includes.

[0086] As used in this specification and the appended claims, the term "about" refers to ±10%.

[0087] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to "a counterion" includes a plurality of such counterions unless the context clearly dictates otherwise. It should be noted that the term "and" or "or" is generally used in the sense of including "and / or" unless the context clearly dictates otherwise.

[0088] The following examples are presented to more fully illustrate certain embodiments of the present invention. However, they should in no way be construed as limiting the broad scope of the present invention. Those skilled in the art can easily devise many variations and modifications of the principles disclosed herein without departing from the scope of the present invention.

[0089] Working Example Example 1 Alkaline thermohydrolysis of PLA pellets using sodium hydroxide 50 g of PLA pellets (Ingeo™ biopolymer 4032D, NatureWorks LLC.) were added to a 250 ml three-neck flask equipped with a condenser and a thermometer. 150 ml of NaOH 5M was added and the flask was heated to 80° C. (the measured pH was 13.5).

[0090] After 3.5 hours of rapid digestion, the lactate concentration reached 320 g / L with little further increase in lactate concentration over time. After 21.5 hours, the lactate concentration stopped increasing (final concentration of 340 g / L) and the reaction was cooled to room temperature.

[0091] The PLA residue was filtered using a sintered glass funnel resulting in a clear solution, with the final pH measured at 12.9, suitable for further PLA degradation.

[0092] The solution was neutralized with concentrated H2SO4, after which 280 ml of magnesium sulfate heptahydrate solution (300 g / L) was added dropwise with stirring. The formed MgLa2·2H2O precipitate was filtered using a sintered glass funnel, washed with acetone and dried at 80 °C to a final weight of 64 gr. The filtrate was added dropwise with stirring to 500 ml of acetone, after which it was stirred for another hour. The formed precipitate was filtered using a sintered glass funnel, washed with acetone and dried at 80 °C. Yield: 74%.

[0093] Example 2 MgLa 2 ·2H 2 Recycling of PLA through O-precipitation In a suitable stainless steel vessel, PLA (2 kg) obtained from 4032D PLA pellets or regenerated from cafeteria waste was added to a stirred 5 M sodium hydroxide solution (4 L) and heated to 90 °C until the lactate concentration reached about 30%. The solution was cooled to room temperature, filtered (0.45 μm cutoff) from the insoluble residue, and the pH of the filtrate was neutralized to 6.5-7.0 using concentrated sulfuric acid. A significant portion (>85%) of the lactate was then recovered as solid MgLa2·2H2O by exchange reaction at 20-80 °C with 0-20% excess MgSO4·xH2O (x=0-11) added portionwise to the mixed solution. The precipitated solid was then filtered off and washed once with RT water to give crude MgLa2·2H2O with a typical purity of >80%. Rinsing the crude magnesium lactate once with water successfully improved the purity to >95%. This exchange procedure was also applied to a commercial NaLa solution containing 2.4% D-lactate. The concentration of the D-lactate enantiomers was measured using chiral HPLC separation. Surprisingly, the protocol resulted in a decrease in the ratio of D-lactate to L-lactate. In a separate experiment, the aforementioned protocol was followed to extract MgLa2 from a 30% w / w sodium lactate solution obtained from the degradation of NatureWorks 4032D PLA pellets. Both the lactate concentration and the % of D-lactate were measured separately using HPLC. As can be seen in Figure 2, the total lactate concentration in the solution decreased from 30% to 4%, while the % of D-lactate (of the total lactate content) in the solution increased from 2.4% to 6.3%. This increase in the % of D-lactate in solution gives improved enantiomeric purity of the precipitated MgLa2, which contains less D enantiomer than the initial D enantiomer content. The results are summarized in Table 1A-B.

[0094] [Table 1]

[0095] [Table 2]

[0096] Thus, the results show that the process of the present invention increases the enantiomeric purity of the lactate salt by selectively precipitating magnesium L-lactate crystals, which leads to an increased concentration of D-lactate salt in the solution. The magnesium lactate obtained by this process is particularly suitable for repolymerization of the regenerated lactate salt into PLA.

[0097] Example 3 Recycling of organic waste in lactic acid fermentation process Mixed food waste is degraded by lactic acid fermentation in the presence of NaOH or NH4OH as pH-adjusting alkaline compounds. The fermentation broth thus obtained contains lactate ions and sodium or ammonium counterions. The broth is allowed to cool to room temperature, followed by filtration to remove any undissolved material. Lactate is then recovered as solid MgLa2·2H2O by exchange reaction at 20-80 °C with 0-20% excess of MgSO4·xH2O (x=0-11) added to the mixed solution. The lactate concentration and % of D-lactate are measured separately using HPLC. The precipitated solid is then filtered off and washed with water, typically to give crude MgLa2·2H2O. In some cases, the crude magnesium lactate is rinsed with RT water and subjected to subsequent recrystallization.

[0098] Example 4 L-Lactate Concentrate Ammonium lactate solutions, either commercially purchased or sourced from food waste fermentation broth, had an initial lactate concentration of 30%. Approximately 250 g of the solution was transferred to a 1 L three-neck round bottom flask equipped with a condenser and mechanical stirrer. The solution was heated to 70°C and the initial pH of 5.5 was adjusted to 7.2 by addition of ammonium hydroxide. 1.1 molar equivalents of MgSO4 were added in 8 equal portions over 1.5 hours, resulting in the precipitation of magnesium lactate. The mixture was stirred for an additional 2 hours and then filtered using a P3 sintered glass funnel. The filtered precipitate was washed with 1 weight equivalent of cold water and dried at 70°C. Lactate concentration and % D-lactate were measured separately using HPLC. The results are summarized in Tables 2A-B.

[0099] [Table 3]

[0100] [Table 4]

[0101] The results show that the process of the present invention increases the enantiomeric purity of the L-lactate salt. Advantageously, a greater than 50% reduction in D-lactate content was achieved even when using NH4La derived from food waste fermentation, which contains significant amounts of impurities.

[0102] Example 5 L-Lactate enrichment by ion exchange followed by recrystallization The ammonium lactate solution sourced from food waste fermentation broth had a starting lactate concentration of 29%. Approximately 250 g of the solution was transferred to a 1 L three-neck round bottom flask equipped with a condenser and mechanical stirrer. The solution was heated to 70°C and the initial pH of 5.7 was adjusted to 7.3 by addition of ammonium hydroxide. 1.1 molar equivalents of MgSO4 were added in 8 equal portions over 1.5 hours, resulting in the precipitation of magnesium lactate. The mixture was stirred for an additional 4 hours and then filtered using a P3 sintered glass funnel. The filtered precipitate was washed with 1 weight equivalent of cold water and dried at 70°C. The dried magnesium lactate precipitate was then redissolved in water to a concentration of 8.4% lactate. 5% w / w activated carbon was added and the solution was stirred overnight. The activated carbon was filtered off and the clear solution was transferred to a 0.5 L reactor preheated to 70°C and stirred at 300 RPM. The solution was concentrated in vacuum to remove 75% of the water, resulting in the crystallization of magnesium lactate. The crystals were then collected and filtered using a sintered glass funnel. The resulting crystals were washed with cold water and dried at 70° C. The results are summarized in Tables 3A to 3D.

[0103] [Table 5]

[0104] [Table 6]

[0105] [Table 7]

[0106] [Table 8]

[0107] After recrystallization, the magnesium lactate crystals contain less than 1% D-lactate salt, making them particularly suitable for reuse in the formation of new polylactic acid.

[0108] The foregoing description of specific embodiments will so fully reveal the general nature of the invention that others, by applying current knowledge, may easily modify and / or adapt such specific embodiments for various applications without undue experimentation and without departing from the general concept, and therefore such adaptations and modifications should and are intended to be understood within the meaning and range of equivalents of the embodiments of the present disclosure. It should be understood that the phraseology or terminology employed herein is for purposes of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a wide variety of alternative forms without departing from the spirit and scope of the invention, as set forth by the following claims.

Claims

1. A process for concentrating L - lactate enantiomers from an enantiomeric mixture derived from decomposed organic waste, comprising: (a) obtaining a decomposed organic waste containing an enantiomeric mixture of D - and L - lactates and a counter ion other than magnesium; (b) optionally performing at least one of the steps of neutralizing said D - and L - lactates and removing solid particles from said decomposed organic waste; and (c) adding a magnesium salt to said enantiomeric mixture of step (a) or (b), thereby precipitating magnesium L - lactate salt with high enantiomeric purity comprising a process.

2. The process according to claim 1, comprising concentrating L - lactate enantiomers by 1% or more, preferably 5% or more, more preferably 10% or more.

3. The process according to claim 1, wherein said decomposed organic waste is obtained from a lactic acid fermentation process or said decomposed organic waste is obtained from the hydrolysis of a polylactic acid polymer.

4. The process according to claim 1, wherein said decomposed organic waste is pretreated before step (a) to remove non - lactic acid - containing impurities.

5. The process according to claim 1, wherein said enantiomeric mixture contains 20% or less of D - lactate or said counter ion is selected from the group consisting of sodium, potassium, and ammonium.

6. Step (b) including the step of neutralizing said D - and L - lactates is performed. Preferably, the step of neutralizing said D - and L - lactates includes the addition of an acid selected from hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof, or the step of neutralizing said D - and L - lactates includes the addition of a base selected from hydroxides of sodium, potassium, or ammonium, and combinations thereof. The process according to claim 1.

7. Step (b) including the step of removing solid particles from said decomposed organic waste is performed, and the removal of solid particles includes solid - liquid separation. The process according to claim 1.

8. Step (c) is carried out at a high temperature within the range of 20 °C to 80 °C, or the magnesium salt in step (c) is added in solid form, or the magnesium salt in step (c) is added as an aqueous solution, or the magnesium salt in step (c) is added in a maximum of 20% excess, or the magnesium salt in step (c) is magnesium sulfate, the process according to claim 1.

9. The obtained magnesium L-lactate salt is separated by filtration or centrifugation, preferably, the obtained magnesium L-lactate salt is subjected to subsequent purification, more preferably, the subsequent purification includes at least one of crystallization, recrystallization, fractionation, silica gel chromatography, and preparative HPLC, or the subsequent purification includes the step of washing the obtained magnesium L-lactate salt with purified water, the process according to claim 1.

10. The obtained magnesium L-lactate salt contains less than 3% magnesium D-lactate, preferably, less than 2% magnesium D-lactate, more preferably, less than 1.5% magnesium D-lactate, and most preferably, less than 1% magnesium D-lactate, the process according to claim 1.

11. The obtained magnesium L-lactate salt is crystalline magnesium L-lactate dihydrate, or the obtained magnesium L-lactate is acidified with at least one of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof to form L-lactic acid and is used for subsequent polylactic acid formation, or the process further includes the step of increasing the purity of the L-lactate from the decomposed organic waste, the process according to claim 1.

12. A process for producing a high-purity magnesium L-lactate salt from decomposed organic waste, comprising: (a) obtaining decomposed organic waste containing an L-lactate and a counter ion other than magnesium; (b) optionally performing at least one of the step of neutralizing the L-lactate and the step of removing solid particles from the decomposed organic waste; and (c) adding a magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating a high-purity magnesium L-lactate salt comprising Process

13. A process for producing magnesium L-lactate from decomposed organic waste, comprising: (a) decomposing the organic waste by performing at least one of organic waste fermentation using lactic acid-producing microorganisms and PLA hydrolysis in the presence of an alkali compound to obtain decomposed organic waste containing L-lactate and counterions other than magnesium; (b) optionally performing at least one of the steps of neutralizing the L-lactate and removing solid particles from the decomposed organic waste; and (c) adding a magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating magnesium L-lactate comprising a process

14. wherein the alkali compound comprises at least one of NaOH, KOH, NH ４ OH, Ca(OH) ２ , and mixtures or combinations thereof, or the alkali compound comprises a combination of Mg(OH)2 and / or MgCO3 and at least one of NaOH, KOH, NH4OH, Ca(OH)2, and mixtures or combinations thereof, or the alkali compound comprises NH4OH derived from anaerobic digestion of solid biomass obtained from a batch prior to lactic acid fermentation, preferably, the NH4OH is obtained by gas stripping, the process according to claim 13.

15. The process according to claim 13, wherein the magnesium salt in step (c) is derived from acidification, methylation or acetylation of magnesium L-lactate in a batch prior to lactic acid fermentation, or wherein the magnesium salt in step (c) is derived from acidification, methylation or acetylation of magnesium L-lactate in a batch prior to PLA hydrolysis.

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