CN117813389A

CN117813389A - Method for producing regenerated lactate

Info

Publication number: CN117813389A
Application number: CN202280051913.9A
Authority: CN
Inventors: T·沙皮拉; N·帕博; D·宾斯基
Original assignee: Three W Ltd
Current assignee: Three W Ltd
Priority date: 2021-08-03
Filing date: 2022-08-02
Publication date: 2024-04-02

Abstract

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

Description

Method for producing regenerated lactate

Technical Field

The present invention relates to a process for producing magnesium L-lactate having high enantiomeric purity and low content of non-lactate impurities. The invention also relates to a method for enriching the enantiomeric purity of regenerated lactate comprising an enantiomeric mixture of L-and D-lactate.

Background

Lactic acid fermentation

In recent years, lactic acid fermentation, i.e. the production of lactic acid from a carbohydrate source by microbial fermentation, has been of interest as lactic acid can be used as building block in the manufacture of bioplastic. Lactic acid can be polymerized to form biodegradable and recyclable polyesters, namely polylactic acid (PLA), which is considered a potential alternative to plastics made from petroleum. PLA is used to manufacture a variety of products including food packaging, disposable, textile and hygiene fiber, and the like.

The production of lactic acid by fermentation biological processes is preferred over chemical synthesis methods for various reasons including environmental issues, costs and the difficulty of producing enantiomerically pure lactic acid by chemical synthesis required for most industrial applications. Traditional fermentation processes are generally based on anaerobic fermentation of lactic acid producing microorganisms, which produce lactic acid as the main metabolic end product of carbohydrate fermentation. To produce PLA, lactic acid produced during fermentation is separated from the fermentation broth and purified by various processes, and then the purified lactic acid is polymerized.

Lactic acid has a chiral carbon atom and thus exists in two enantiomeric forms, namely D-lactic acid and L-lactic acid. In order to produce PLA suitable for industrial applications, the D-lactic acid or L-lactic acid entering the production process must be highly purified to meet the specifications required for polymerization and reuse. Lactic acid bacteria producing only the L-lactate enantiomer or only the D-lactate enantiomer are generally used in order to produce one individual enantiomer (L or D, respectively).

In currently available commercial processes, the carbohydrate source used for lactic acid fermentation is typically a renewable source containing starch, such as corn and tapioca root. Other sources, such as cellulose-rich bagasse, are also suggested. In general, lactic acid producing bacteria may 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, often in combination with chemical treatments, to degrade the polysaccharide and release the reducing sugar.

Another source of carbohydrates that has been suggested for lactic acid fermentation 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 less expensive than other carbohydrate sources used for lactic acid fermentation.

Mixed food waste typically includes varying proportions of reducing sugars (glucose, fructose, lactose, etc.), starch, and lignocellulosic material. Mixed food waste also contains endogenous D, L-lactic acid (e.g. from natural decomposition during dairy products or transportation), one of which needs to be removed in order to use the waste as a substrate for the production of optically pure lactic acid (L-or D-lactic acid). WO 2017/122197, assigned to the applicant of the present invention, discloses a dual-acting Lactic Acid (LA) utilizing bacterium that is genetically modified to secrete polysaccharide-degrading enzymes such as cellulases, hemicellulases and amylases, useful for treating organic waste to eliminate lactic acid present in the waste and degrade complex polysaccharides. WO 2020/208635, assigned to the applicant of the present invention, discloses a system and method for treating organic waste, in particular mixed food waste, using D-lactate oxidase, which eliminates the presence of D-lactate in the organic waste.

Polylactic acid (PLA) recycling

PLA produced from renewable resources is a substitute for petroleum-derived plastics, which is increasingly used in the manufacture of products such as food packaging. As PLA is increasingly present in disposable end products, it is important to ensure that PLA is adequately handled after disposal. Unlike thermoplastic resins such as polyethylene, polypropylene, polystyrene and polyethylene terephthalate, polylactic acid undergoes thermal degradation. Accordingly, when recycling products containing a mixture of PLA and the above-mentioned plastics, it is desirable to separate the PLA to avoid contamination of the recycled stream.

The recycling options for PLA include landfill, composting, anaerobic digestion (biogas production), incineration and chemical recovery into constituent monomers. Chemical recovery is preferred over other methods because the monomers can be reused in the production of new PLA.

One of the most common PLA forms on the market is the copolymer PDLLA (poly (D-L-) lactic acid), which consists mainly of PLLA (made of L-lactic acid) and a small amount of PDLA (made of D-lactic acid). A significant portion of the PLA plastics available on the market contain small amounts of PDLA, which upon hydrolysis release D-lactic acid. The hydrolyzed material may also contain an unknown amount of D-lactic acid formed by racemization during hydrolysis. Both D-lactic acid and L-lactic acid entering the PLA production process typically require optical purity in excess of 99%. Therefore, PLA recovery methods should solve the problem of isomer separation. Chemical separation of the two enantiomers is expensive and liquid or solid enantioselective membranes or High Performance Liquid Chromatography (HPLC) is typically used.

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 hydrolytic degradation. Degradation was performed in 0.01N NaOH solution at 37 ℃.

The hydrolysis of polylactic acid (PLA) and Polycaprolactone (PCL) in aqueous acetonitrile is reported by Sipassky, voorhes and Miao (1998) Journal of environmental polymer degradation,6 (1): 31-41.

Xu, crawford and Gorman (2011) Macromolecules,44 (12): 4777-4782 report the effect of temperature and pH on the degradation of polylactic acid brushes.

Chauliac (2013) "development of thermochemical processes and their purification to hydrolyze polylactic acid polymers to L-lactic acid using engineered microorganisms" (Development of a thermochemical process for hydrolysis of polylactic acid polymers to L-lactic acid and its purification using an engineered microbe), ph.d. paper, university of Florida, UMI Number:3583516, proposes a method of post-consumer use of PLA polymers. In this process, thermal hydrolysis is the first step, and then D-LA is removed from the hydrolyzed material to yield pure L-LA, which may be redirected into the production of the polymer itself. The thermal hydrolysis is carried out with water in the presence of NaOH. The removal of D-LA from the resulting syrup was achieved using E.coli (Escherichia coli) which lacks all three identified L-lactate dehydrogenases.

And Karlsson (2013) Polymer Degradation and Stability,98 (1): 73-78 report two studies measuring the enthalpy of alkaline hydrolysis of carboxylate-containing polymers. Two materials were used: polyvinyl acetate (PVAc) films and polylactic acid (PLA) fibers. Degradation was performed using sodium hydroxide and potassium hydroxide at 30 ℃.

Elsawy et al (2017) Renewable and Sustainable Energy Reviews,79:1346-1352 reviewed hydrolytic degradation of polylactic acid (PLA) and its composites.

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

WO 2015/112098 discloses a method for preparing lactide from a plastic with polylactic acid (PLA-based plastic), the method comprising preparing a PLA-based plastic, accelerating the decomposition of the polylactic acid in the plastic by alcoholysis or hydrolysis to provide low molecular weight polylactic acid, and thermally decomposing the low molecular weight polylactic acid to provide lactide. In addition, the method includes minimizing the size of the PLA-based plastic after the preparing step, and purifying the lactide after the thermal decomposition of the low molecular weight polylactic acid.

U.S. Pat. No. 7,985,778 discloses a method for decomposing and recovering a synthetic resin having an ester bond in the structure of a composition by performing a hydrolysis treatment and then a separation and collection treatment. In the hydrolysis treatment, an article containing a synthetic resin to be decomposed and recovered is exposed to a water vapor atmosphere filled under saturated water vapor pressure at a treatment temperature equal to or lower than the melting point of the synthetic resin. The synthetic resin in the article to be treated is hydrolyzed by the generated water vapor at the treatment temperature to generate decomposition products, and then polymerized into a synthetic resin containing ester bonds. The separation and collection process is a process in which the decomposition products produced by the hydrolysis process are separated into a liquid component and a solid component to be collected separately.

U.S.8,614,338 discloses a process for the stereospecific chemical recovery of a polymer mixture based on polylactic acid PLA, in order to reform one of its monomers or derivatives. The method comprises the steps of suspending the polymer mixture in a lactate ester capable of dissolving the PLA fraction, followed by first separating the lactate ester, PLA and other dissolved impurities, and second separating a mixture of other polymers and insoluble impurities. The solution containing PLA thus obtained is then subjected to a catalytic depolymerization reaction by transesterification in order to form an oligoester. The depolymerization reaction by transesterification is then stopped at a given moment and the residual lactate is separated. The oligoester thus obtained is then subjected to a cyclization reaction in order to produce lactide, which will eventually be stereospecifically purified, obtaining a purified lactide fraction having a meso-lactide content of 0.1% to 40%.

U.S.8,431,683 and U.S.8,481,675 disclose a method for recovering a polymer blend that necessarily contains PLA, comprising the steps of milling, compacting, dissolving in a solvent for PLA, removing undissolved contaminating polymer, alcoholysis depolymerization, and purification.

U.S.8,895,778 discloses depolymerization of polyesters such as post-consumer polylactic acid. Ultrasound induced implosion can be used to facilitate depolymerization. The post-consumer PLA is exposed to methanol as a suspension medium in the presence of an organic or ionic salt of an alkali metal, such as potassium carbonate and sodium hydroxide, as a depolymerization catalyst, providing high quality lactic acid monomer in high yield.

U.S.2018/0051156 discloses a process for enhancing/accelerating the depolymerization of polymers, such as those containing hydrolyzable bonds, which generally comprises contacting a polymer containing hydrolyzable bonds with a solvent and an alcohol to give a polymer mixture in which the polymer is substantially dissolved, wherein the contacting is conducted at a temperature equal to or below the boiling point of the polymer mixture. Depolymerized polymers (including, for example, monomers and/or oligomers) may be isolated therefrom. Such processes can be carried out under relatively mild temperature and pressure conditions. In certain embodiments, the polymer is polylactic acid.

WO 2021/165964 assigned to the applicant of the present invention discloses industrial fermentation for producing lactic acid from organic waste in combination with chemical recovery of polylactic acid to obtain lactic acid in high yield.

There remains an unmet need for an economically reliable process for producing enantiomerically pure L-lactate from waste of decomposition containing both the L-and D-lactate enantiomers.

Disclosure of Invention

The present invention provides high purity L-lactate monomers from lactic acid fermentation of organic waste and/or chemical hydrolysis of PLA. The invention also provides a method of enriching the enantiomeric purity of lactate obtained from the recovery of organic waste and/or PLA waste.

The present invention is based, in part, on the unexpected discovery that the enantiomeric purity of L-lactate can be enhanced by ion exchange or exchange of lactate counterions in a fermentation broth or PLA hydrolysis slurry containing various concentrations of D-lactate monomer, resulting in the enantioselective precipitation of L-lactate, particularly L-magnesium lactate salt. Thus, the present invention is capable of recovering waste from a variety of sources, including waste containing endogenous D-lactate monomers, while eliminating the need for D-lactate utilizing bacteria or enzymes to eliminate the D-lactate monomers. The present invention advantageously produces L-lactate having an enantiomeric purity of over 99%, which can be used in the commercial production of PLA without the need for additional isomer separation treatments.

In accordance with the principles of the present invention, both fermentation of the organic waste and hydrolysis of the PLA are carried out in the presence of alkaline compounds. During fermentation, the pH in the fermenter decreases due to the production of lactic acid, which has an adverse effect on the productivity of lactic acid producing microorganisms. Thus, a basic compound, typically sodium hydroxide, potassium hydroxide, ammonium hydroxide or magnesium hydroxide, and mixtures or combinations thereof, is added to neutralize the pH, thereby allowing lactate to form. The present invention discloses for the first time the use of anaerobically digested aqueous ammonia derived from solid biomass waste of a fermentation process as a source of alkaline compounds during fermentation or PLA hydrolysis. Ammonia from solid biomass of previous fermentation processes is an excellent source of alkalinity to be added to adjust the pH of the fermentation broth to the desired value while also providing significant cost savings by eliminating the need for expensive alkaline compounds to be added. Furthermore, it provides additional recycling of the solid biomass obtained after lactic acid fermentation.

An additional advantage of the process of the invention stems from the use of a previously acidified regenerated salt from lactate to provide ion exchange or exchange of lactate counter ions in the fermentation broth or PLA hydrolysis slurry. In general, both lactic acid fermentation processes and PLA-decomposition processes produce lactate. In order to obtain polylactic acid, it is necessary to acidify the lactate salt into lactic acid monomers, or to methylate or acetylate in the presence of an acid. Thus, acids such as hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and mixtures or combinations thereof are used. In these methods, the counterion of the lactate salt and the anion of the acid precipitate to form a salt. In accordance with the principles of the present invention, such salts can be reused in subsequent fermentation or PLA hydrolysis processes as an ion source for ion exchange or exchange of lactate counter ions.

According to a first aspect, there is provided a process for enriching an enantiomer of an L-lactate salt from a mixture of enantiomers derived from decomposed organic waste, the process comprising the steps of:

(a) Obtaining a decomposed organic waste comprising an enantiomeric mixture of D-lactate and L-lactate and a counter ion other than magnesium;

(b) At least one of optionally neutralizing the D-lactate and L-lactate and removing solid particles from the decomposed organic waste; and

(c) Adding a magnesium salt to the enantiomeric mixture of step (a) or (b) to precipitate a magnesium salt of L-lactate having an enriched enantiomeric purity.

In one embodiment, the method provides an enrichment of 1% or more of the L-lactate enantiomer. In another embodiment, the method provides an enrichment of 5% or more of the L-lactate enantiomer. In yet another embodiment, the method provides an enrichment of the L-lactate enantiomer of 10% or more. In particular embodiments, the method provides up to 15% enrichment of the L-lactate enantiomer. In other embodiments, the methods provide up to 20% enrichment of the L-lactate enantiomer. In other embodiments, the methods provide up to 25% enrichment of the L-lactate enantiomer.

In certain embodiments, the decomposed organic waste is obtained from a lactic acid fermentation process. In other embodiments, the decomposed organic waste is obtained from waste containing lactic acid. In other embodiments, the decomposed organic waste is obtained from hydrolysis of polylactic acid polymers.

In various embodiments, the organic waste comprises a source of carbohydrates. In other embodiments, the organic waste is selected from the group consisting of food waste, municipal food waste, residential food waste, agricultural waste, industrial food waste from food processing facilities, commercial food waste (from hospitals, restaurants, shopping centers, airports, and the like), and mixtures or combinations thereof. Each possibility represents a separate embodiment.

In other embodiments, the decomposed organic waste is pre-treated prior to step (a). In certain embodiments, the pretreatment comprises removing impurities comprising non-lactic acid.

In accordance with the principles of the present invention, the decomposed organic waste contains endogenous D-lactate in an amount of up to 20 weight percent (wt.%). In certain embodiments, the enantiomeric mixture comprises 20% or less of D-lactate. In other embodiments, the enantiomeric mixture comprises 10% or less of D-lactate. In other embodiments, the enantiomeric mixture comprises 5% or less of D-lactate.

In certain embodiments, the counterion is selected from sodium, potassium and ammonium. Each possibility represents a separate embodiment. Although the process of the present invention utilizes decomposed organic waste comprising enantiomeric mixtures of D-lactate and L-lactate and counter ions 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 comprises an enantiomeric mixture of D-lactate and L-lactate, magnesium ions, and counter ions other than magnesium.

In other embodiments, step (b) comprising neutralizing the D-lactate and L-lactate is performed. Typically, neutralization is carried out to 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 the group consisting of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof. Each possibility represents a separate embodiment. In one embodiment, neutralization is performed in the presence of sulfuric acid. In other embodiments, the neutralization is performed in the presence of a base selected from the group consisting of sodium hydroxide, potassium hydroxide, or ammonium hydroxide, and combinations thereof. Each possibility represents a separate embodiment.

In various embodiments, step (b) comprising removing solid particles from the decomposed organic waste is performed, and the removing of the solid particles comprises solid-liquid separation.

In other embodiments, step (c) is performed at an elevated temperature. In certain embodiments, step (c) is performed at a temperature of 20 ℃ to 80 ℃, including each value within the specified range.

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

In a particular embodiment, the magnesium salt in step (c) is magnesium sulfate.

In other embodiments, the resulting magnesium L-lactate salt is isolated by filtration or centrifugation. In other embodiments, the resulting magnesium L-lactate salt is subsequently purified. In other embodiments, the subsequent purification comprises at least one of crystallization, recrystallization, partitioning, silica gel chromatography, preparative HPLC, and combinations thereof. Each possibility represents a separate embodiment.

In certain embodiments, the subsequent purification comprises, for example, washing the resulting magnesium L-lactate salt with purified water. In other embodiments, the subsequent purification comprises dissolving and recrystallizing the resulting magnesium salt of L-lactate.

In one embodiment, the resulting magnesium L-lactate salt comprises less than 3% magnesium D-lactate. In another embodiment, the resulting magnesium L-lactate salt comprises less than 2% magnesium D-lactate. In yet another embodiment, the resulting magnesium L-lactate salt comprises less than 1.5% magnesium D-lactate. In certain embodiments, the resulting magnesium L-lactate salt comprises less than 1% magnesium D-lactate.

In other embodiments, the resulting magnesium L-lactate salt is crystalline magnesium L-lactate dihydrate.

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

In certain embodiments, the methods disclosed herein further comprise enriching the purity of the L-lactate from the decomposed organic waste.

According to another aspect, there is provided a method of enriching the purity of L-lactate from decomposed organic waste, the method comprising the steps of:

(a) Obtaining decomposed organic waste comprising L-lactate and counter ions other than magnesium;

(b) At least one of optionally 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 a magnesium L-lactate salt having an enriched purity.

According to yet another aspect, there is provided a method for producing magnesium L-lactate salt in high purity from decomposed organic waste, the method comprising the steps of:

(c) Adding magnesium salt to the decomposed organic waste of step (a) or (b) to precipitate magnesium salt of L-lactate in high purity.

According to another aspect, there is provided a process for producing magnesium L-lactate salt from decomposed organic waste, the process comprising the steps of:

(a) Decomposing the organic waste by performing at least one of fermentation of the organic waste using lactic acid producing microorganisms and hydrolysis of PLA in the presence of an alkaline compound to obtain decomposed organic waste comprising L-lactate and counterions other than magnesium;

(c) Adding a magnesium salt to the decomposed organic waste of step (a) or (b), thereby precipitating a magnesium salt of L-lactate.

In certain embodiments, the basic compound comprises NaOH, KOH, NH ₄ OH、Ca(OH) ₂ And at least one of mixtures or combinations thereof. Each possibility represents a separate embodiment. In other embodiments, the basic compound comprises Mg (OH) ₂ And/or MgCO ₃ And NaOH, KOH, NH ₄ OH、Ca(OH) ₂ And combinations of at least one of mixtures or combinations thereof. In other embodiments, the alkaline compound comprises NH derived from anaerobic digestion of solid biomass obtained from a previous batch of lactic acid fermentation ₄ OH. In various embodiments, the NH derived from anaerobic digestion of solid biomass ₄ OH is obtained by stripping.

In certain embodiments, the magnesium salt in step (c) is derived from the acidification, methylation or acetylation of the magnesium L-lactate of a previous batch of lactic acid fermentation. In other embodiments, the magnesium salt in step (c) results from the acidification, methylation or acetylation of the magnesium L-lactate of the previous batch PLA hydrolysis.

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

Drawings

FIG. 1 is a schematic illustration of a process according to certain embodiments of the invention.

Fig. 2 shows lactate concentration (+%) and% of D-lactate concentration (x) in solution during an exchange reaction of sodium lactate (NaLa) resulting from hydrolysis of PLA grade number 4032D, according to certain embodiments of the invention.

Detailed Description

The present invention provides a process for producing magnesium L-lactate from decomposed organic waste with high enantiomeric purity and reduced amounts of impurities. The invention also provides a method for enriching the enantiomers of L-lactate from a mixture of enantiomers of D-lactate and L-lactate and for enriching the purity of L-lactate from decomposed organic waste. The high purity magnesium L-lactate salt may be further used to produce new lactic acid based products.

The term "lactic acid" as used herein refers to a hydroxycarboxylic acid having the formula: CH (CH) ₃ CH(OH)CO ₂ H. The term lactic acid or lactate (unprotonated lactic acid) may refer to the stereoisomer (enantiomer) of lactic acid, L-lactic acid/L-lactate, D-lactic acid/D-lactate or a combination thereof. The term "enantiomer" as used herein refers to two stereoisomers of a compound that are non-superimposable mirror images of each other.

For most industrial applications, high purity L-lactic acid monomers are required in order to produce PLA with suitable properties. The process of the present invention is thus particularly directed to the production of L-lactate having enriched enantiomeric or chiral purity, which can be converted to L-lactate suitable for reuse without the elimination of D-lactate monomers.

One advantage resulting from the process of the present invention is the enantiomeric enrichment, which is particularly beneficial for the reuse of lactic acid. The enrichment of the L-lactate enantiomer by the method of the present invention is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or even more of the initial L-lactate content. Each possibility represents 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. The scope of the present invention includes reducing the D-lactate content by at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or even 100% of the initial D-lactate content by the methods disclosed herein. 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. In accordance with the principles of the present invention, the resulting L-magnesium lactate crystals comprise 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. Each possibility represents a separate embodiment.

Another advantage resulting from the process of the present invention is the enrichment of the purity of the L-magnesium lactate. Typically, the initial purity of lactate in the decomposed organic waste is low. There are many non-lactate impurities that are present in organic waste and carried to its decomposition products. Advantageously, the present invention provides crude L-magnesium lactate having a purity of at least 80% formed directly using the methods disclosed herein. Additional enrichment of purity can be performed by washing, crystallization or recrystallization methods to produce high purity L-magnesium lactate salt.

In accordance with the principles of the present invention, the decomposed organic waste used in the methods disclosed herein is any decomposition product of lactic acid-containing waste, such as, but not limited to, polylactic acid polymers hydrolyzed using basic compounds such as sodium hydroxide. According to further embodiments, the decomposed organic waste used in the methods disclosed herein is obtained from lactic acid fermentation of fermentable carbohydrates such as, but not limited to, those of organic waste. Organic waste materials 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, commercial food waste (from hospitals, restaurants, shopping centers, airports, etc.), and mixtures or combinations thereof. Each possibility represents a separate embodiment. The organic waste may also be derived from animal and human excreta, vegetable and fruit residues, plants, deli, protein residues, slaughter waste and the like residues and combinations thereof. Each possibility represents a separate embodiment. Industrial organic food waste may include plant waste such as byproducts, plant waste (e.g., expired products, defective products), market returns, or offcuts of non-edible food portions (e.g., skin, fat, hulls, and pericarp). Each possibility represents a separate embodiment. Commercial organic food waste may include waste from shopping centers, restaurants, supermarkets, and the like. Each possibility represents a separate embodiment.

According to certain aspects and embodiments, the organic waste comprises monosaccharides or disaccharides obtained as by-products from sugar production of beet or cane sugar, such as, but not limited to, fructose, molasses, or High Fructose Corn Syrup (HFCS) production. According to other aspects and embodiments, the organic waste includes starch and starch derivatives, such as refined glucose syrup resulting from hydrolysis of starch, which may be corn starch, tapioca starch, wheat starch, potato starch, etc. Each possibility represents a separate embodiment. The organic waste may also originate 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 from steeped wheat or corn. Paper sludge hydrolysate obtained by hydrolyzing paper sludge with cellulolytic enzymes, as well as dairy byproducts generated during cheese production and dairy beverage production including dairy beverage production such as lactose-free beverages, may also be used.

According to various aspects and embodiments, the decomposed organic waste comprises fermentation broth obtained from a fermentation process of a carbohydrate source. When using heterogeneous raw materials, the decomposed organic waste or fermentation broth typically contains insoluble organic-based impurities such as, but not limited to, microorganisms (e.g., lactic acid producing microorganisms including, for example, yeast, bacteria, and fungi), fats and oils, lipids, aggregated proteins, bone fragments, hair, precipitated salts, cell fragments, fibers (e.g., fruit and/or vegetable peels), and residual untreated waste (e.g., food casings, seeds, insoluble food particles, and scraps, etc.). Each possibility represents a separate embodiment. Non-limiting examples of insoluble inorganic-based impurities include plastics, glass, residues from food packaging, sand, and combinations thereof. Each possibility represents a separate embodiment.

Although not required, the decomposed organic waste may be further pretreated prior to use of the method of the invention. Suitable pretreatments include, but are not limited to, filtration, ultrafiltration, nanofiltration, reverse Osmosis (RO) filtration, solvent extraction, rejection extraction, salt precipitation, crystallization, distillation, evaporation, electrodialysis, and various types of chromatography (e.g., adsorption or ion exchange). Each possibility represents a separate embodiment.

The decomposed waste may contain D-lactate and L-lactate in various concentrations. The process of the present invention advantageously provides high purity magnesium L-lactate even when the initial concentration of D-lactate and L-lactate monomers is as low as 10%. Typically, the initial concentration of D-lactate and L-lactate monomers is in the range of about 20% to about 50%, including each value within the specified range. The ratio of D-lactate to L-lactate monomers in the decomposed waste may vary with the endogenous D-lactate content and the formation of racemic lactic acid that occurs during decomposition. Typically, the ratio of D-to L-lactate monomer 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.

Referring now to the drawings, FIG. 1 illustrates an operational scenario for producing L-magnesium lactate according to certain embodiments of the present invention. Lactic acid fermentation is performed. Has the following componentsOrganic waste such as municipal waste, food waste and agricultural waste serve as substrates for fermentation of L-lactic acid by L-lactic acid producing microorganisms such as Bacillus coagulans (Bacillus coagulans). Endogenous decreases in pH occur due to the formation of L-lactic acid. Thus, the fermentation process is carried out in the presence of an alkaline substance to adjust the pH during fermentation. The alkaline material neutralizes the pH, resulting in the formation of L-lactate ions and counterions. The decomposition of the organic waste typically involves an alkaline material selected from sodium hydroxide, potassium hydroxide or ammonium hydroxide, thereby producing sodium, potassium or ammonium counterions, respectively, in the decomposed waste. Thus, the use of sodium hydroxide results in the formation of sodium lactate with sodium as the counter ion, while the use of ammonium hydroxide results in the formation of ammonium lactate with ammonium as the counter ion. Advantageously, the alkaline substance added to the lactic acid fermentation is ammonia water (amonia water or aqua amonia). The use of ammonia enables additional recycling of the waste remaining after the fermentation process. This mode of operation is referred to as "reverse flow" in which the source of the basic compound used in the production of lactic acid in one batch is obtained in the production of lactic acid in the previous batch. In particular, biomass derived from the fermentation may be reused as a side stream (# 2: anaerobically fermented organics and fatty acids) as the main stream of lactic acid production continues to downstream processing for lactate purification and separation. In this side stream, anaerobic digestion is performed to produce biogas (mainly methane) as a main product. When the biomass remaining after anaerobic digestion is concentrated, it can be used to produce ammonia, for example by stripping. The aqueous ammonia may then be used in a subsequent fermentation process to adjust the pH. This mode of operation is cost effective because it can reduce the cost of expensive alkaline compounds that neutralize the pH during fermentation. As an additional ammonia source, the protocol shows that by using, for example, mg (OH) ₂ For lactate counter ion (NH) in fermentation broth ₄ ⁺ ) The ion exchange or exchange step is performed to provide additional ammonia that can be recycled back to the subsequent fermentation batch. Additional uses of biomass remaining after fermentation are supplementing low nutrient content recycle streams such as, but not limited to, waste paper waterSolution, yeast lysate and milk product water.

According to certain aspects and embodiments, the decomposed organic waste may optionally be neutralized using acids or bases known in the art. Typically, neutralization is carried out to a pH of about 6.5 to 7.5, including any values therebetween. One skilled in the art will appreciate that neutralization is performed by adding an acid when the pH of the decomposed organic waste is alkaline. 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, when the pH of the decomposed organic waste is acidic, neutralization is performed by adding a base. Suitable bases include, but are not limited to, sodium hydroxide, potassium hydroxide, or ammonium hydroxide, and combinations thereof. Each possibility represents a separate embodiment.

In case the decomposed organic waste contains PLA waste particles that cannot be hydrolyzed or impurities containing non-lactic acid, they can be separated from the decomposed organic waste by a solid-liquid separation technique such as filtration or decantation. Each possibility represents a separate embodiment.

In accordance with the principles of the present invention, ion exchange is then performed by adding a magnesium salt to result in precipitation of a magnesium salt of L-lactate having enriched total and enantiomeric purity. It should be understood that the ion exchange of the present invention may be complete, i.e., the counter ion derived from the basic species is not magnesium, or partial, i.e., two or more basic species are used, one of which contains magnesium ions and the other contains cations other than magnesium. The magnesium salt used for ion exchange may 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 ions at a concentration of about 50 to about 500g/L, including each value within the specified range. Exemplary magnesium ion concentrations include, but are not limited to, about 75g/L to about 400g/L, about 100g/L to about 300g/L, or about 150g/L to about 250g/L, including each value within the specified ranges. Each possibility represents a separate embodiment. In certain embodiments, the magnesium salt is added stepwise while mixing.

In certain aspects and embodiments, the magnesium salt is derived from the acidification, methylation or acetylation of the lactate salt of the previous batch. According to these embodiments, the salt is a regenerated salt, giving additional cost-savings advantages. In general, the process of the invention produces magnesium lactate salt as the final product. However, to obtain polylactic acid, the lactic acid may be hydrochlorinated 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. After addition of the acid, the magnesium ions may precipitate with the anions of the acid to form magnesium salts, which may be used for subsequent ion exchange in accordance with the principles of the present invention. In the case where the lactate product undergoes methylation or acetylation, these processes are also typically performed in the presence of an acid, resulting in precipitation of magnesium salts, which can be used in subsequent ion exchange processes.

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. In accordance with the principles of the present invention, magnesium salts include any hydrate or anhydrous form, such as, but not limited to MgCl ₂ ·×H ₂ O (where x=0-6), mgCO ₃ ·×H ₂ O (where x=0, 1, 2, 3 or 5), mgSO ₄ ·×H ₂ O (where x=0-11), mg ₃ (PO ₄ ) ₂ ·×H ₂ O (where x=0, 5, 8 or 22), mgHPO ₄ ·×H ₂ O (where×=0 or 3), mg (H ₂ PO ₄ ) ₂ ·×H ₂ O (where x=0, 2 or 4), mg (OH) ₂ Etc. Each possibility represents a separate embodiment. In one embodiment, magnesium sulfate (e.g., magnesium sulfate heptahydrate) is added.

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

The scope of the invention includes adding magnesium salts at room temperature or at elevated temperature. Each possibility represents a separate embodiment. Suitable temperatures include the range of 20℃to 80℃such as about 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃. Each possibility represents a separate embodiment.

The magnesium L-lactate salt thus obtained may be further subjected to downstream purification processes. It has also surprisingly been found that a simple purification to increase the enantiomeric purity of magnesium L-lactate is, for example, washing the crude magnesium L-lactate salt with purified water. The scope of the present invention includes additional purification steps such as crystallization, recrystallization, partitioning, silica gel chromatography, preparative HPLC, and combinations thereof. Each possibility represents a separate embodiment. A re-acidification step may also be performed to obtain crude L-lactic acid, followed by a purification step to obtain purified L-lactic acid. The 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.

Purification methods may include extraction, electrodialysis, adsorption, ion exchange, crystallization, and combinations of these methods. Several methods are reviewed, for example, in Ghaffar et al, (2014) Journal of Radiation Research and Applied Sciences,7 (2): 222-229, and Lvopez-Garz, et al, (2014) Biotechnol adv.,32 (5): 873-904. Alternatively, recovery and conversion of lactic acid to lactide in a single step (Dusselie et al, (2015) Science,349 (6243): 78-80) may be used.

A specific downstream purification process for purifying magnesium lactate by crystallization is described in co-pending patent application WO 2020/110108 assigned to the applicant of the present invention. The purification method comprises the following steps:

-providing a clear solution containing magnesium lactate at a temperature of 45 ℃ to 75 ℃;

-concentrating the solution to a lactate concentration of 150-220g/L;

-subjecting said concentrated solution to at least one cooling crystallization to obtain magnesium lactate crystals; and

-collecting the magnesium lactate crystals obtained.

In certain embodiments, the solution is provided at a temperature of 55 ℃ to 65 ℃, including each value within the specified range.

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

The at least one cooling crystallization may begin at a first temperature in the range of 50 to 75 ℃, including each value in the specified range. In certain embodiments, the at least one cooling crystallization starts at a first temperature in the range of 50 to 70 ℃, including each value in the specified range. In other embodiments, the at least one cooling crystallization starts at a first temperature in the range of 50 to 65 ℃, including each value in the specified range.

The at least one cooling crystallization step may end at a second temperature in the range of 10 to 1 ℃, including each value in the specified range. In certain embodiments, the at least one cooling crystallization ends at a second temperature in the range of 6 to 2 ℃, including each value in the specified range.

The cooling rate of the at least one cooling crystallization may be in the range of 10 to 0.5 ℃/h, including each value within the specified range. In certain embodiments, the cooling rate is in the range of 5 to 1 ℃/h, including each value within the specified range.

The pH of the concentrated mixture may be adjusted to a range of 6 to 7, including each value therebetween, prior to the cooling crystallization.

The obtained magnesium lactate crystals may be separated from the remaining liquid by microfiltration or nanofiltration. The remaining liquid may undergo concentration and then at least one additional cooling crystallization to obtain additional magnesium lactate crystals. After separating the magnesium lactate crystals from the liquid, they may be washed with an aqueous solution or with an organic solvent such as ethanol or acetone and purified. 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.

Although the process disclosed herein primarily contemplates the enrichment of the L-lactate enantiomer from an enantiomeric mixture comprising D-lactate and L-lactate derived from decomposed organic waste, the present invention also contemplates the enrichment of the D-lactate enantiomer.

Thus, according to certain aspects and embodiments, the present invention provides a method for enriching D-lactate enantiomers from an enantiomeric mixture derived from decomposed organic waste, the method comprising the steps of:

(c) Adding a magnesium salt to the enantiomeric mixture of step (a) or (b) to precipitate a magnesium salt of D-lactate having an enriched enantiomeric purity.

According to certain aspects and embodiments, the present invention provides a method for producing a magnesium D-lactate salt in high purity from decomposed organic waste, the method comprising the steps of:

(a) Obtaining decomposed organic waste comprising D-lactate and counter ions other than magnesium;

(b) At least one of optionally neutralizing the D-lactate and removing solid particles from the decomposed organic waste; and

(c) Adding magnesium salt to the decomposed organic waste of step (a) or (b) to precipitate D-magnesium lactate salt in high purity.

The term "about" as used herein and in the appended claims means ± 10%.

As used herein and in the appended claims, no particular number of a reference includes a plurality of reference unless the context clearly dictates otherwise. Thus, for example, 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 the term "or" is generally employed in its sense including "and/or" unless the context clearly dictates otherwise.

The following examples are provided to more fully illustrate certain embodiments of the invention. However, they should in no way be construed as limiting the broad scope of the invention. Many variations and modifications of the principles disclosed herein may be readily devised by those skilled in the art without departing from the scope of the invention.

Examples

Example 1

Alkaline pyrolysis of PLA pellets using sodium hydroxide

To a 250ml three-necked flask equipped with a condenser and thermometer was added 50g PLA pellets (Ingeo ^TM Biopolymers 4032D,NatureWorks LLC.). 150ml of 5M NaOH was added and the flask was heated to 80℃and the pH was found to be 13.5.

After 3.5 hours of rapid degradation, the lactate concentration reached 320g/L, with only a small further increase in lactate concentration over time. After 21.5 hours, the lactate concentration stopped increasing (final concentration 340 g/L) and the reaction was cooled to room temperature.

The PLA residue was filtered with a sintered glass funnel to yield a clear solution. The final pH was measured to be 12.9, which is suitable for additional PLA degradation.

Subjecting the solution to concentrated H ₂ SO ₄ Neutralization, then 280ml of magnesium sulfate heptahydrate solution (300 g/L) were added dropwise while stirring. Filtration of formed MgLa using sintered glass funnel ₂ ·2H ₂ The O precipitate was washed with acetone and dried at 80℃to a final weight of 64gr. The filtrate was added dropwise to 500ml of acetone while stirring, and stirring was then continued for 1 hour. The precipitate formed was filtered using a sintered glass funnel, washed with acetone and dried at 80 ℃. Yield is as follows: 74%.

Example 2

₂ ₂ Recycling of PLA by MgLa.2HO precipitation

PLA (2 kg) obtained from 4032D PLA pellets or recovered from cafeteria waste was added to a stirred 5M sodium hydroxide solution (4L) and heated to 90 ℃ in a suitable stainless steel container until the lactate concentration reached about 30%. The solution was allowed to cool to RT, undissolved residue was filtered off (0.45 μm cut-off) and the pH of the filtrate was neutralized to 6.5-7.0 using concentrated sulfuric acid. Then, by adding 0-20% excess MgSO to the mixed solution in portions at 20-80 DEG C ₄ ·×H ₂ O (X=0-11) to carry out exchange reaction, and the majority of the reaction is carried out>85%) recovery of lactate to solid MgLa ₂ ·2H ₂ O. The precipitated solid is then filtered off and washed once with RT water, usually to give purity>80% of crude MgLa ₂ ·2H ₂ O. Rinsing the crude magnesium lactate once with water generally increases the purity to>95%. This exchange step was also applied to a commercial NaLa solution containing 2.4% D-lactate. Chiral HPLC separation was used to measure the concentration of the D-lactate enantiomer. Surprisingly, the protocol results in a reduction in the ratio of D-lactate to L-lactate. In another experiment MgLa was extracted from a 30% w/w sodium lactate solution obtained from degradation of Nature's 4032D PLA pellets according to the protocol described above ₂ . Lactate concentration and% D-lactate were measured separately using HPLC. As can be seen in fig. 2, the total lactate concentration in the solution was reduced from 30% to 4%, while the% of D-lactate (in total lactate content) in the solution was increased from 2.4% to 6.3%. This enrichment of the% of D-lactate in the solution increases the precipitated MgLa ₂ Enantiomer purity of the precipitated MgLa ₂ The D enantiomer content of (c) is lower than the initial D enantiomer content. The results are summarized in tables 1A-1B.

₂ Table 1A. Overall extraction yield and purity of MgLa obtained:

TABLE 1B enantiomerically pureDegree:

thus, the results demonstrate that the process of the present invention increases the enantiomeric purity of lactate by selectively precipitating magnesium L-lactate crystals, resulting in an increased concentration of D-lactate in solution. The magnesium lactate obtained by this method is particularly suitable for repolymerisation of regenerated lactate to PLA.

Example 3

Recycling of organic waste in lactic acid fermentation process

In NaOH or NH as basic compounds for regulating pH ₄ In the presence of OH, the mixed food waste is decomposed by lactic acid fermentation. The fermentation broth thus obtained contains lactate ions and sodium or ammonium counter ions. The broth was allowed to cool to RT and then filtered to remove undissolved material. Then, by adding excess MgSO of 0-20% to the mixed solution at 20-80deg.C ₄ ·×H ₂ O (X=0-11) is subjected to exchange reaction, and lactate is recovered into solid MgLa ₂ ·2H ₂ O. Lactic acid was recovered as solid mgla2.2h2o by exchange reaction with 0-20% excess MgSO 4.xh2o (x=0-11) at 20-80 ℃. Lactate concentration and% D-lactate were measured separately using HPLC. The precipitated solid is then filtered off and washed with water, typically to give crude MgLa ₂ ·2H ₂ O. Optionally, the crude magnesium lactate is rinsed with RT water and subjected to subsequent recrystallization.

Example 4

L-lactate enrichment

Ammonium lactate solution, commercially purchased or derived from food waste fermentation broth, was adjusted to an initial concentration of 30% lactate. About 250g of the solution was transferred to a condenser equippedAnd a mechanical stirrer in a 1L three-necked round bottom flask. The solution was heated to 70 ℃ and the initial pH of 5.5 was adjusted to 7.2 by the addition of ammonium hydroxide. 1.1 molar equivalents of MgSO were added in 8 aliquots over 1.5h ₄ Resulting in precipitation of magnesium lactate. The mixture was stirred for an additional 2h 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 ℃. Lactate concentration and% D-lactate were measured separately using HPLC. The results are summarized in tables 2A-2B.

₂ Table 2A. Overall extraction yield and purity of MgLa obtained:

table 2B. Enantiomeric purity:

the results show that the process of the invention improves the enantiomeric purity of the L-lactate. Advantageously, even when NH derived from fermentation of food waste containing significant amounts of impurities is utilized ₄ In the case of La, a reduction of more than 50% in the D-lactate content was also achieved.

Example 5

L-lactate enrichment by ion exchange and subsequent recrystallization

The ammonium lactate solution from the food waste broth was adjusted to the starting concentration of 29% lactate. About 250g of the solution was transferred to a 1L three-necked round bottom flask equipped with a condenser and mechanical stirrer. The solution was heated to 70 ℃ and the initial pH of 5.7 was adjusted to 7.3 by the addition of ammonium hydroxide. 1.1 molar equivalents of MgSO were added in 8 aliquots over 1.5h ₄ Resulting in precipitation of magnesium lactate. The mixture was stirred for an additional 4h and then filtered using a P3 sintered glass funnel. The filtered precipitate was washed with 1 weight equivalent of cold water and at 70℃And (5) drying. 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 0.5L reactor preheated to 70 ℃ and stirred at 300 RPM. The solution was concentrated in vacuo to remove 75% of the water, resulting in crystallization of magnesium lactate. The crystals were then harvested and filtered using a sintered glass funnel. The crystals obtained were washed with cold water and dried at 70 ℃. The results are summarized in tables 3A-3D.

Table 3A. Lactate concentration and D-lactate content in the post-exchange solution:

table 3B. Purity, D-lactate content and yield of precipitate after exchange:

table 3C lactate concentration and D-lactate content in solution after recrystallization:

table 3D. Purity of precipitate after recrystallization, D-lactate content and yield:

the recrystallized magnesium lactate crystals contain less than 1% D-lactate and are therefore particularly suitable for reuse in the formation of new polylactic acid.

The foregoing description of the specific embodiments reveals the general nature of the invention sufficiently that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and therefore such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for performing the various disclosed functions may take a variety of alternative forms without departing from the spirit and scope of the invention as described by the following claims.

Claims

1. A process for the enrichment of the enantiomers of L-lactate from a mixture of enantiomers derived from decomposed organic waste, said process comprising the steps of:

2. The method of claim 1, comprising enantiomerically enriching L-lactate by 1% or more.

3. The method of claim 2, comprising enantiomerically enriching the L-lactate by 5% or more.

4. A process according to claim 3, which comprises enantiomerically enriching the L-lactate by 10% or more.

5. The method according to any one of claims 1 to 4, wherein the decomposed organic waste is obtained from a lactic acid fermentation process.

6. The method according to any one of claims 1 to 4, wherein the decomposed organic waste is obtained from hydrolysis of polylactic acid polymer.

7. The method of any one of claims 1 to 6, wherein the decomposed organic waste is pre-treated to remove impurities comprising non-lactic acid prior to step (a).

8. The method of any one of claims 1 to 7, wherein the enantiomeric mixture comprises 20% or less D-lactate.

9. The method of any one of claims 1 to 8, wherein the counterion is selected from sodium, potassium and ammonium.

10. The method according to any one of claims 1 to 9, wherein step (b) comprising neutralizing the D-lactate and L-lactate is performed.

11. The method of claim 10, wherein neutralizing the D-lactate and L-lactate comprises adding an acid selected from the group consisting of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, sulfuric acid, and combinations thereof.

12. The method of claim 10, wherein neutralizing the D-lactate and L-lactate comprises adding a base selected from the group consisting of sodium hydroxide, potassium hydroxide, or ammonium hydroxide, and combinations thereof.

13. The method according to any one of claims 1 to 12, wherein step (b) comprising removing solid particles from the decomposed organic waste is performed, and the removal of solid particles comprises solid-liquid separation.

14. The process according to any one of claims 1 to 13, wherein step (c) is carried out at an elevated temperature in the range of 20 ℃ to 80 ℃.

15. The process of any one of claims 1 to 14, wherein the magnesium salt in step (c) is added in solid form.

16. The process of any one of claims 1 to 14, wherein the magnesium salt in step (c) is added as an aqueous solution.

17. The process of any one of claims 1 to 16, wherein the magnesium salt in step (c) is added in an excess of up to 20%.

18. The process of any one of claims 1 to 17, wherein the magnesium salt in step (c) is magnesium sulfate.

19. The method of any one of claims 1 to 18, wherein the resulting magnesium L-lactate salt is isolated by filtration or centrifugation.

20. The process of claim 19, wherein the resulting magnesium L-lactate salt is subjected to subsequent purification.

21. The method of claim 20, wherein subsequent purification comprises at least one of crystallization, recrystallization, partitioning, silica gel chromatography, and preparative HPLC.

22. The method of claim 20, wherein the subsequent purification comprises washing the resulting magnesium L-lactate salt with purified water.

23. The method of any one of claims 1 to 22, wherein the resulting magnesium L-lactate salt comprises less than 3% magnesium D-lactate.

24. The method of claim 23, wherein the resulting magnesium L-lactate salt comprises less than 2% magnesium D-lactate.

25. The method of claim 24, wherein the resulting magnesium L-lactate salt comprises less than 1.5% magnesium D-lactate.

26. The method of claim 25, wherein the resulting magnesium L-lactate salt comprises less than 1% magnesium D-lactate.

27. The process of any one of claims 1 to 26, wherein the resulting magnesium L-lactate salt is crystalline magnesium L-lactate dihydrate.

28. The method of any one of claims 1-27, wherein the resulting 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 used in subsequent polylactic acid formation.

29. The method of any one of claims 1 to 28, further comprising enriching the purity of the L-lactate from the decomposed organic waste.

30. A method of enriching L-lactate purity from decomposed organic waste, the method comprising the steps of:

31. A process for producing magnesium L-lactate in high purity from decomposed organic waste, the process comprising the steps of:

32. A process for producing magnesium L-lactate from decomposed organic waste, the process comprising the steps of:

(a) Decomposing the organic waste by performing at least one of fermentation of the organic waste using lactic acid producing microorganisms and hydrolysis of PLA in the presence of an alkaline compound to obtain decomposed organic waste comprising L-lactate and counter ions other than magnesium;

33. The method of claim 32, wherein the basic compound comprises NaOH, KOH, NH ₄ OH、Ca(OH) ₂ And at least one of mixtures or combinations thereof.

34. The method of claim 32, wherein the basic compound comprises Mg (OH) ₂ And/or MgCO ₃ And NaOH, KOH, NH ₄ OH、Ca(OH) ₂ And combinations of at least one of mixtures or combinations thereof.

35. The method of claim 32, wherein the alkaline compound comprises NH derived from anaerobic digestion of solid biomass obtained from a previous batch of lactic acid fermentation ₄ OH。

36. The method of claim 35, wherein theThe NH is ₄ OH is obtained by stripping.

37. The process of any one of claims 32 to 36, wherein the magnesium salt in step (c) is derived from acidification, methylation or acetylation of magnesium L-lactate of a previous batch of lactic acid fermentation.

38. The method of any one of claims 32 to 36, wherein the magnesium salt in step (c) is derived from the acidification, methylation or acetylation of a previous batch of PLA-hydrolyzed magnesium L-lactate.