Process for degrading a plastic product comprising at least one polyester

Abstract

This invention relates to a method for degrading plastic products, the method comprising carrying out an enzymatic hydrolysis polymerization step in a reaction medium containing a limited amount of soluble equivalent terephthalic acid in its main salt form under acidic conditions between pH 4 and 6.

Description

Technical Field

[0001] This invention relates to a method for degrading polyester-containing materials, such as plastic products, on an industrial or semi-industrial scale, wherein the plastic products are selected from plastics and / or fabrics comprising polyesters containing at least one terephthalic acid monomer. The method of the invention particularly includes carrying out an enzymatic hydropolymerization step under acidic conditions between pH 4 and 6 in a reaction medium containing a defined amount of a soluble equivalent of terephthalic acid in its predominant salt form. Preferably, this hydropolymerization step is preceded by a preliminary enzymatic hydropolymerization step carried out at a given adjusted pH between 6.5 and 10. The method of the invention is particularly suitable for degrading plastic products containing polyethylene terephthalate. The invention also relates to a method for generating monomers and / or oligomers from plastic products containing polyesters containing at least one terephthalic acid monomer. Prior Technology

[0002] Plastics are inexpensive and durable materials used to manufacture a wide variety of products for a broad range of applications (food packaging, textiles, etc.). As a result, plastic production has increased significantly over the past few decades. Furthermore, most plastics are used in single-use, disposable applications, such as packaging, agricultural films, disposable consumer goods, or short-lived products intended for disposal within one year of manufacture. Due to the durability of the polymers involved, large quantities of plastics accumulate in landfills and natural habitats worldwide, causing increasing environmental problems. For example, in recent years, polyethylene terephthalate (PET), an aromatic polyester derived from terephthalic acid and ethylene glycol, has been widely used in the manufacture of several consumer products, such as food and beverage packaging (e.g., bottles, conveniently sized soft drink bags, food pouches) or textiles, fabrics, rugs, carpets, etc.

[0003] Various solutions from plastic degradation to plastic recycling have been investigated to reduce the environmental and economic impacts associated with plastic waste accumulation. Mechanical recycling remains the most commonly used technology, but it faces several drawbacks. In practice, it requires extensive and costly sorting, and its use is degraded due to the total loss of molecular weight during the process and the uncontrolled presence of additives in the recycled products. Current recycling technologies are also expensive. Therefore, the recycled plastic products are generally not competitive with virgin plastic.

[0004] Recently, innovative methods for the enzymatic recycling of plastic products have been developed and described (e.g., WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265, WO 2017 / 198786, WO 2020 / 094661, and WO 2020 / 094646). In contrast to traditional recycling technologies, these enzymatic polymerization methods eliminate the need for expensive sorting and allow for the recovery of the chemical components of the polymer (i.e., monomers and / or oligomers). The resulting monomers / oligomers can be recycled, purified, and used to remanufacture plastic articles of equivalent quality to the original plastic articles, thus enabling the unlimited recycling of plastics. These methods are particularly suitable for recovering terephthalic acid and ethylene glycol from plastic products containing PET. In these methods, the formation of monomers and / or oligomers, especially terephthalic acid, causes a decrease in the pH of the reaction medium, which may be detrimental to the activity of degrading enzymes. Large amounts of alkali are used to maintain the pH and thus optimize enzyme activity. However, the use of strong acids to recover terephthalic acid by precipitation results in the formation of large quantities of almost worthless salts. Furthermore, the use of alkali and acid, and the lack of valuable salts, significantly impact the cost of these methods.

[0005] By working on this problem, the inventors have developed an optimized enzymatic method for degrading such plastic products, which requires low addition of alkali and acid during the process (and causes low salt formation), while maintaining satisfactory depolymerization yield from an economic and industrial perspective. Summary of the Invention

[0006] By working to improve methods for degrading materials containing polyesters, such as plastic products, the inventors have discovered the possibility of carrying out a depolymerization step in an acidic reaction medium at (or above) the saturation concentration of a soluble equivalent of terephthalic acid (TA) primarily in its salt form. The use of such a reaction medium eliminates the need for operators to adjust the pH during the acidic depolymerization step.

[0007] Therefore, the inventors' achievement lies in identifying specific conditions that enable a good balance between acceptable alkali consumption and depolymerization yield on an industrial scale. Specifically, the inventors have determined the equivalent TA saturation concentration to be achieved prior to the acidic depolymerization step to ensure an acidic pH between 4 and 6 during the acidic depolymerization step. This advantageously eliminates the need for any pH adjustment and thus alkali consumption during the acidic depolymerization step.

[0008] In this regard, one object of the present invention is to provide a method for degrading a material containing a polyester, such as a plastic product, the plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), wherein the method comprises a main step of enzymatic hydropolymerization of the at least one polyester at a pH between 4 and 6, wherein the main step of enzymatic hydropolymerization is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg, and more preferably at most 80 g / kg based on the total weight of the liquid phase of the reaction medium, and wherein at least 90%, preferably at least 95%, and more preferably at least 99% of the equivalent TA in the liquid phase of the reaction medium is in salt form.

[0009] Another object of the present invention is to provide a method for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA) in a reaction medium, wherein the method includes a preliminary depolymerization step of the at least one polyester carried out at a given pH between 6.5 and 10, preferably a preliminary enzymatic depolymerization step, and the main enzymatic depolymerization step carried out at a pH between 4 and 6.

[0010] Preferably, the pH of the initial depolymerization step is adjusted by adding alkali to the given pH, and the pH adjustment is stopped when the equivalent TA concentration in the liquid phase of the reaction medium reaches at least 5 g / kg, preferably at least 15 g / kg, more preferably at least 25 g / kg, and more preferably at most 110 g / kg, more preferably at most 100 g / kg based on the total weight of the liquid phase of the reaction medium.

[0011] Preferably, the method of the present invention includes: a. The initial depolymerization step is carried out at a given pH adjusted between 7.5 and 8.5 and at a temperature between 60°C and 72°C; and b. The main depolymerization step is carried out at a pH between 5.0 and 5.5 and at a temperature between 50°C and 65°C, wherein the pH is not adjusted. Each of the depolymerization steps includes contacting the plastic product with at least one enzyme capable of degrading the polyester, and wherein the pH adjustment in step (a) is stopped when the liquid phase of the reaction medium contains an equivalent TA concentration between 5 g / kg and 110 g / kg, preferably between 30 g / kg and 100 g / kg, and more preferably between 30 g / kg and 95 g / kg based on the total weight of the liquid phase of the reaction medium.

[0012] Another object of the present invention is to provide a reaction medium suitable for a method of degradation of plastic products comprising at least one polyester containing at least one monomer of terephthalic acid (TA), wherein the reaction medium contains at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg of equivalent TA in the liquid phase of the reaction medium based on the total weight of the liquid phase of the reaction medium, wherein at least 90%, preferably at least 95%, more preferably at least 99% of the equivalent TA is in salt form, and wherein at least one enzyme is capable of degrading the polyester. Implementation

[0013] definition In the context of this invention, "polyester-containing material" or "polyester-containing product" refers to a product comprising at least one polyester in a crystalline, semi-crystalline, or fully amorphous form, such as a plastic product. In one specific embodiment, polyester-containing material refers to any article made from at least one plastic material containing at least one polyester and possibly other substances or additives such as plasticizers, minerals, or organic fillers, such as plastic sheets, tubes, rods, profiles, molded parts, films, bulk materials, fibers, etc. In another specific embodiment, polyester-containing material refers to a plastic compound or plastic formulation suitable for manufacturing plastic products in a molten or solid state. In another specific embodiment, polyester-containing material refers to a fabric, textile, or fiber comprising at least one polyester. In another specific embodiment, polyester-containing material refers to plastic waste or fiber waste comprising at least one polyester. Specifically, polyester-containing material is a plastic product.

[0014] In the context of this invention, the terms "plastic article" or "plastic product" are used to refer to any article or product comprising at least one polymer, such as plastic sheets, tubes, rods, profiles, molded parts, bulk materials, fibers, etc. Preferably, plastic articles are articles such as rigid or flexible packaging (bottles, trays, cups, etc.), agricultural films, bags and sacks, disposable articles or similar articles, carpet waste, textiles, fabrics, etc. Plastic articles may contain additional substances or additives, such as plasticizers, minerals, organic fillers, or dyes. In the context of this invention, plastic articles may comprise a mixture of semi-crystalline and / or amorphous polymers and / or additives.

[0015] "Polymer" refers to a compound or mixture of compounds whose structure consists of multiple repeating units (i.e., "monomers") linked by covalent chemical bonds. In the context of this invention, the term "polymer" refers to such compounds used to form plastic products.

[0016] The term "polyester" refers to a polymer containing ester functional groups in its main chain. Ester functional groups are characterized by carbon atoms bonded to three other atoms: single bonds to carbon, double bonds to oxygen, and single bonds to oxygen. The oxygen atom in the single bond is bonded to another carbon atom. Depending on the composition of its main chain, polyesters can be aliphatic, aromatic, or semi-aromatic. Polyesters can be homopolymers or copolymers. As an example, polyethylene terephthalate (PET) is a semi-aromatic copolymer composed of two monomers: terephthalic acid and ethylene glycol.

[0017] The term "depolymerization" in relation to polymers or plastic articles containing polymers refers to a method by which the polymer or at least one polymer of the plastic article is depolymerized and / or degraded to smaller molecules, such smaller molecules as monomers and / or oligomers and / or any degradation products.

[0018] According to the present invention, "oligomer" refers to a molecule containing 2 to about 20 monomer units. As an example, oligomers recovered from PET include methyl 2-hydroxyethyl terephthalate (MHET) and / or bis(2-hydroxyethyl terephthalate) (BHET) and / or 1-(2-hydroxyethyl terephthalate) and / or 4-methyl terephthalate (HEMT) and / or dimethyl terephthalate (DMT).

[0019] The terms "equivalent terephthalic acid" or "equivalent TA" are used to refer to any form of terephthalic acid molecule, that is... - The acid form of terephthalic acid corresponding to only the molecule of terephthalic acid (TAH 2), i.e., C 8H 6O 4, - The terephthalic acid molecule combines with one or more cations such as sodium, potassium, ammonium, or hydrated hydrogen (TAH-, TA2-) to form a terephthalic acid salt (hereinafter referred to as "TA salt" in this text). - Terephthalic acid molecules are contained in oligomers (and thus combined with other monomers), such as MHET. The oligomers may be in the form of salts, that is, combined with one or more cations (hereinafter referred to as "oligomer salts").

[0020] The term equivalent TA does not cover TA monomers contained in polymer articles of degradation methods.

[0021] In one embodiment of the present invention, the equivalent TA is entirely in salt form, that is, the equivalent TA corresponds to TA salt and / or oligomer salt.

[0022] According to the present invention, the "equivalent terephthalic acid concentration" or "equivalent TA concentration" in the liquid phase of the reaction medium refers to the amount of dissolved equivalent TA measured in the liquid phase, including, for example, dissolved TAH 2; the TA portion of soluble TA salts (TAH-, TA 2-), soluble MHET, or other soluble oligomers (including oligomers in salt form). The equivalent TA concentration can be measured by any means known to those skilled in the art, especially by HPLC. The equivalent TA concentration is expressed as g equivalent TA / kg of the liquid phase of the reaction medium (g / kg).

[0023] The term "reaction medium" refers to all units and compounds (including liquids, enzymes, polyesters, monomers and oligomers produced from the depolymerization of the polyester) present in the reactor during the depolymerization step, also known as reactor contents.

[0024] According to the present invention, "liquid phase of the reaction medium" refers to a reaction medium free of any solids and / or suspended particles. This liquid phase includes the liquid and all compounds dissolved therein (including enzymes, monomers, salts, etc.). This liquid phase can be separated from and recovered from the solid phase of the reaction medium using methods known to those skilled in the art, such as filtration, decantation, centrifugation, etc. In the context of the present invention, the liquid phase is particularly free of residual polyester (i.e., undegraded and insoluble polyester) and free of precipitated monomers.

[0025] The method of this invention, through optimization of enzymatic degradation methods for plastic products, has led the inventors to discover that by reducing alkali consumption while maintaining enzyme activity compatible with industrial performance, it is possible to avoid the formation of co-products (salts) and improve the economic returns of plastic product degradation methods. More specifically, the inventors have discovered that enzymatic hydropolymerization of polyesters can be carried out at an acidic pH without the addition of any alkali when the reaction medium already contains a certain amount of equivalent terephthalic acid in its salt form. The inventors have therefore developed a method in which the acidic enzymatic hydropolymerization step is carried out in a reaction medium containing a defined concentration of equivalent terephthalic acid in its predominant salt form. Advantageously, this acidic hydropolymerization step is carried out without any pH adjustment in the reaction medium. Advantageously, the method includes a preliminary step prior to the acidic hydropolymerization step, allowing the defined equivalent terephthalic acid concentration to be achieved in the reaction medium.

[0026] Therefore, one object of the present invention is to provide a method for degrading materials containing polyester, such as plastic products comprising at least one polyester containing at least one terephthalic acid monomer (TA), wherein the method comprises a main step of enzymatic hydropolymerization of the at least one polyester at a pH between 4 and 6, and wherein the enzymatic hydropolymerization step is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg based on the total weight of the liquid phase of the reaction medium, and wherein at least 90% of the equivalent TA is in salt form.

[0027] Preferably, at least 95% of the equivalent TA in the liquid phase of the reaction medium is in the form of salt, more preferably at least 96%, 97%, 98%, or 99%.

[0028] According to the present invention, the main depolymerization step (also referred to as the "acidic depolymerization step") is carried out at a pH between 4 and 6.

[0029] The reaction medium for the main depolymerization step includes the following: at least one plastic product containing at least one polyester containing at least one TA monomer; a liquid; at least one enzyme capable of degrading the at least one polyester; and a defined equivalent TA concentration in the liquid phase, mainly in salt form.

[0030] Advantageously, the pH of the main depolymerization step is not adjusted, that is, no alkali is added to the reaction medium to maintain the pH during the main depolymerization step.

[0031] In fact, the inventors have discovered that once the reaction medium reaches a specific equivalent TA concentration, primarily in salt form, the pH of the reaction medium is automatically maintained (i.e., no specific operation is required to maintain this pH). This is attributed to the physicochemical equilibrium in the solution prior to precipitation, which is related to the maximum concentration of TA in its acidic form (TAH₂). Under such acidic conditions, the liquid phase of the reaction medium is saturated with TA, and any additional terephthalic acid precipitates and is therefore insoluble. Consequently, any terephthalic acid precipitated in the reaction medium during the acidic depolymerization step does not affect the pH of the reaction medium.

[0032] According to the present invention, the main depolymerization step is carried out at a pH between 4 and 6. Preferably, the main depolymerization step is carried out at a constant pH or a target pH between 4 and 6. In the context of the present invention, "constant pH" means a given pH + / - 0.2, preferably a given pH + / - 0.1, and more preferably + / - 0.05.

[0033] Preferably, the main depolymerization step is carried out at a pH between 4 and 5.5, more preferably between 4.5 and 5.5, and even more preferably between 5 and 5.5. Specifically, the main depolymerization step is carried out at pH 5.2 + / - 0.2, more preferably at pH 5.2 + / - 0.1. Alternatively, the main depolymerization step is carried out at pH 5.3 + / - 0.2, more preferably at pH 5.3 + / - 0.1. Alternatively, the main depolymerization step is carried out at pH 5.4 + / - 0.1, and alternatively at pH 5.45 + / - 0.05.

[0034] According to the invention, the main depolymerization step is carried out at a temperature between 40°C and 80°C, preferably between 50°C and 72°C, more preferably between 50°C and 65°C, and even more preferably between 50°C and 60°C. In one embodiment, the main depolymerization step is carried out between 55°C and 60°C or between 50°C and 55°C. In another embodiment, the main depolymerization step is carried out between 55°C and 65°C. In another embodiment, the main depolymerization step is carried out between 60°C and 72°C, preferably between 60°C and 70°C. In one embodiment, the main depolymerization step is carried out at 60°C + / - 1°C. In another embodiment, the main depolymerization step is carried out at 56°C + / - 1°C. In one embodiment, the temperature of the main depolymerization step is maintained below the Tg of the polyester of interest. In the context of this invention, "polyester of interest" refers to a polyester containing at least one terephthalic acid monomer (TA) targeted by a degradation method. Advantageously, the temperature is maintained at a given temperature + / - 1°C.

[0035] In one embodiment, the main depolymerization step is carried out at a pH between 5.0 and 5.5 and at a temperature between 50°C and 65°C.

[0036] According to the present invention, the main depolymerization step is carried out by contacting the plastic product with an enzyme capable of degrading the polyester (such as an enzyme belonging to category EC: 3.1.1). In a preferred embodiment, the enzyme is a depolymerase, more preferably an esterase, and even more preferably a lipase or keratinase.

[0037] The main depolymerization step is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg and at most 80 g / kg, more preferably at most 70 g / kg, based on the total weight of the liquid phase of the reaction medium, and wherein at least 90% of the equivalent TA in the liquid phase of the reaction medium is in salt form, preferably at least 95%, more preferably at least 96%, 97%, 98%, or 99%.

[0038] In one embodiment, the main depolymerization step is carried out in a reaction medium having an equivalent TA concentration in the liquid phase of the reaction medium between 20 g / kg and 80 g / kg, preferably between 30 g / kg and 80 g / kg, and more preferably between 30 g / kg and 70 g / kg, wherein at least 90%, preferably at least 95%, more preferably at least 96%, 97%, 98%, and 99% of the equivalent TA in the liquid phase of the reaction medium is in salt form.

[0039] To ensure that at least 90%, preferably at least 95%, 96%, 97%, 98%, or 99% of the equivalent TA in the liquid phase of the reaction medium is in salt form, a base may be introduced into the reaction medium prior to the main depolymerization step to form a TA salt (or oligomer salt) with the TA or oligomer. Any base known to those skilled in the art may be used. Specifically, the base is selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), or ammonia (NH₄OH). Advantageously, sodium hydroxide (NaOH) is preferred.

[0040] In one embodiment, the liquid phase contains an equivalent TA concentration of the reaction medium between 10 g / kg and 80 g / kg, and at least 90% of the equivalent TA is in salt form, and the main depolymerization step is carried out at a pH between 5 and 5.5.

[0041] In one embodiment, the equivalent TA concentration in the liquid phase of the reaction medium is between 10 g / kg and 60 g / kg, preferably between 20 g / kg and 50 g / kg, and more preferably between 30 g / kg and 50 g / kg, and at least 90% of the equivalent TA is in salt form, and the main depolymerization step is carried out at pH 5.25 + / - 0.1.

[0042] In another embodiment, the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 80 g / kg, preferably between 50 g / kg and 80 g / kg, and at least 90% of the equivalent TA is in salt form, and the main depolymerization step is carried out at pH 5.45 + / - 0.05.

[0043] In one embodiment, the primary depolymerization step is carried out at a pH between 5.0 and 5.5, and comprises an equivalent TA concentration in the liquid phase of a reaction medium between 5 g / kg and 110 g / kg, preferably between 30 g / kg and 100 g / kg, wherein at least 90% of the equivalent TA is in salt form. In a particular embodiment, the primary depolymerization step is carried out at a temperature between 50°C and 65°C.

[0044] In one particular embodiment, during the main depolymerization step, one or more additional polyesters and / or enzymes are added to the reaction medium.

[0045] In one embodiment, the preliminary depolymerization step is performed before the main depolymerization step to obtain the reaction medium for the main depolymerization step. This preliminary depolymerization step is carried out at a given pH between 6.5 and 10 by contacting a plastic product with a depolymerizing agent in the initial reaction medium. According to the invention, the preliminary step includes contacting the plastic product with a depolymerizing agent selected from chemical and / or biological depolymerizing agents. Therefore, the initial reaction medium (i.e., the reaction medium before the preliminary depolymerization step) comprises: at least one plastic product containing at least one polyester comprising at least one TA monomer, a liquid, and at least one depolymerizing agent. Advantageously, the initial reaction medium does not contain equivalent TA.

[0046] The purpose of this preliminary degradation step is to at least partially degrade polyesters containing at least one TA monomer in order to achieve the desired equivalent TA concentration in the reaction medium required to carry out the main depolymerization step.

[0047] In one embodiment, the depolymerizing agent used in the preliminary degradation step is a biodepolymerizing agent.

[0048] Preferably, the initial depolymerization step is an enzymatic depolymerization step, which is carried out by contacting the plastic product with at least one enzyme capable of degrading the polyester in the plastic product. Preferably, the depolymerizing agent is a depolymerase, more preferably an esterase, and even more preferably a lipase or keratinase.

[0049] During this initial depolymerization step, the pH of the reaction medium is adjusted to a given pH, + / - 0.5, by adding an alkali. Any alkali known to those skilled in the art can be used. Specifically, the pH can be adjusted by adding an alkali selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), or ammonia (NH₄OH) to the reaction medium. Advantageously, sodium hydroxide (NaOH) is used. Preferably, the pH is adjusted to a given pH + / - 0.1, more preferably + / - 0.05. In other words, an amount of alkali is added to the reaction medium to prevent any drop in pH below the given pH + / - 0.1, more preferably + / - 0.05. Adjusting the pH during this initial depolymerization step causes the formation of TA salts and / or oligomer salts in the reaction medium, thus resulting in at least 90%, preferably at least 95%, 96%, 97%, 98%, or 99% of the equivalent TA being in salt form.

[0050] In one embodiment, the given pH for the initial enzymatic hydrolysis polymerization step is between 6.50 and 10.00, preferably between 7.00 and 9.50, more preferably between 7.00 and 9.00, and even more preferably between 7.50 and 8.50. In a preferred embodiment, the given pH is greater than 7.00, more preferably greater than 7.50, and even more preferably pH 8.00 + / - 0.1.

[0051] In one particular embodiment, the initial depolymerization step is carried out using at least one degrading enzyme, and the given pH is the optimal pH of the at least one enzyme, + / - 0.5. "Optimal pH of the enzyme" refers to the pH at which the enzyme exhibits the highest degradation rate under given temperature conditions and in a given medium. Advantageously, the optimal pH of the enzyme is the optimal pH of the enzyme in the initial reaction medium.

[0052] In one embodiment, the preliminary depolymerization step is performed at a temperature between 50°C and 80°C, preferably between 55°C and 75°C, between 55°C and 72°C, between 60°C and 72°C, more preferably 65°C ± 5°C, more preferably ± 2°C, or ± 1°C. In one embodiment, the temperature is maintained between 55°C and 70°C, between 55°C and 65°C, preferably at 60°C, ± 5°C, more preferably ± 2°C, or ± 1°C. In one embodiment, the temperature is maintained between 60°C and 80°C, between 65°C and 75°C, preferably at 72°C, ± 5°C, more preferably ± 2°C, or ± 1°C. In one embodiment, the preliminary depolymerization step is performed at 60°C ± 5°C, more preferably ± 2°C, or ± 1°C. In one embodiment, the temperature of the initial depolymerization step is maintained below the Tg of the polyester of interest. Advantageously, the temperature is maintained at a given temperature + / - 1°C.

[0053] Therefore, one object of the present invention is to provide a method for degrading plastic products comprising at least one polyester, wherein the method is carried out in a reaction medium and comprises: a. The preliminary depolymerization step, as described above, is carried out at a given pH adjusted to between 6.5 and 10 ± 0.5; and b. The main depolymerization steps, as described above, are carried out at a pH between 4 and 6 + / - 0.5. Two of the depolymerization steps involve contacting the plastic product with at least one enzyme capable of degrading the polyester.

[0054] According to this embodiment, the transfer from the preliminary depolymerization step to the main depolymerization step is carried out by pH adjustment to stop the preliminary depolymerization step.

[0055] Preferably, the pH in step (a) is adjusted until the equivalent TA concentration in the liquid phase of the reaction medium is at least 5 g / kg, more preferably at least 15 g / kg, and even more preferably at least 25 g / kg based on the total weight of the liquid phase of the reaction medium. Preferably, the pH adjustment in step (a) is stopped when the equivalent TA concentration in the reaction medium reaches at most 110 g / kg, and more preferably at most 100 g / kg.

[0056] In one embodiment, the pH adjustment of the initial depolymerization step is stopped when the equivalent TA concentration in the liquid phase of the reaction medium is between 15 g / kg and 110 g / kg, preferably between 30 g / kg and 100 g / kg, and more preferably between 30 g / kg and 95 g / kg. Specifically, when the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 40 g / kg, 30 g / kg and 50 g / kg, 30 g / kg and 60 g / kg, 30 g / kg and 70 g / kg, 30 g / kg and 80 g / kg, 30 g / kg and 90 g / kg, 40 g / kg and 50 g / kg, 40 g / kg and 60 g / kg, 40 g / kg and 70 g / kg, 40 g / kg and 80 g / kg, 40 g / kg and 90 g / kg, 40 g / kg and 95 g / kg, 50 g / kg and 60 g / kg, 50 g / kg and 70 g / kg, 50 g / kg and 80 g / kg, 50 g / kg and 90 g / kg, 50 g / kg and 95 g / kg, 6 ... When the pH adjustment of the initial depolymerization step is between 70 g / kg, 60 g / kg and 80 g / kg, 60 g / kg and 90 g / kg, 60 g / kg and 95 g / kg, 70 g / kg and 80 g / kg, 70 g / kg and 90 g / kg, 70 g / kg and 95 g / kg, 80 g / kg and 90 g / kg, 80 g / kg and 95 g / kg, and 90 g / kg and 95 g / kg, stop.

[0057] Alternatively, in order to measure or monitor the equivalent TA concentration in the reaction medium, it is possible to monitor the amount of alkali added to the reaction medium during the initial depolymerization step to neutralize the generated TA and thereby adjust the pH. Therefore, according to the present invention, during the initial depolymerization step, tracking the amount of alkali added to the reaction medium can be used instead of monitoring the equivalent TA concentration in the reaction medium.

[0058] Therefore, in one embodiment, the pH of the preliminary depolymerization step is adjusted (e.g., by adding alkali during the preliminary depolymerization step) until the amount of alkali added to the liquid phase of the reaction medium reaches at least 2 g / kg, preferably at least 12 g / kg, based on the total weight of the liquid phase of the reaction medium. Preferably, the pH adjustment of the preliminary depolymerization step is stopped when the amount of alkali added to the reaction medium reaches at most 65 g / kg, preferably at most 53 g / kg, based on the total weight of the liquid phase of the reaction medium. In one embodiment, the pH adjustment of the preliminary depolymerization step is stopped when the amount of alkali added to the reaction medium is between 2 g / kg and 65 g / kg, preferably between 12 g / kg and 53 g / kg. In one embodiment, when the content is between 12 g / kg and 15 g / kg, between 12 g / kg and 20 g / kg, between 12 g / kg and 30 g / kg, between 12 g / kg and 40 g / kg, between 12 g / kg and 50 g / kg, between 12 g / kg and 60 g / kg, between 15 g / kg and 20 g / kg, between 15 g / kg and 30 g / kg, between 15 g / kg and 40 g / kg, between 15 g / kg and 50 g / kg, between 15 g / kg and 53 g / kg, between 15 g / kg and 60 g / kg, between 15 g / kg and 65 g / kg, between 20 g / kg and 30 g / kg, between 20 g / kg and 40 g / kg, between 20 g / kg and 50 g / kg, between 20 g / kg and 53 g / kg, between 20 g / kg and 60 g / kg, 20 Between 30 g / kg and 65 g / kg, between 30 g / kg and 40 g / kg, between 30 g / kg and 50 g / kg, between 30 g / kg and 53 g / kg, between 30 g / kg and 60 g / kg, between 30 g / kg and 65 g / kg, between 40 g / kg and 50 g / kg, between 40 g / kg and 53 g / kg, between 40 g / kg and 60 g / kg, between 40 g / kg and 65 g / kg, between 45 g / kg and 53 g / kg, between 45 g / kg and 60 g / kg, between 45 g / kg and 65 g / kg, between 50 g / kg and 53 g / kg, between 50 g / kg and 60 g / kg, between 50 g / kg and 65 g / kg, between 53 g / kg and 60 g / kg, between 53 g / kg and 65 ... When the amount of alkali added to the reaction medium is between 30 g / kg and 95 g / kg, especially between 30 g / kg and 40 g / kg, between 30 g / kg and 50 g / kg, the pH adjustment of the initial depolymerization step is stopped. In a specific embodiment, when the amount of alkali added is between 30 g / kg and 95 g / kg, particularly between 30 g / kg and 40 g / kg, between 30 g / kg and 50 g / kg, the pH adjustment of the initial depolymerization step is stopped.Between 60 g / kg and 30 g / kg, between 70 g / kg and 30 g / kg, between 80 g / kg and 30 g / kg, between 90 g / kg and 40 g / kg, between 50 g / kg and 40 g / kg, between 70 g / kg and 40 g / kg, between 80 g / kg and 40 g / kg, between 90 g / kg and 40 g / kg, between 95 g / kg and 50 g / kg, between 70 g / kg and 50 g / kg, between 80 g / kg and 50 g / kg, between 90 g / kg and 50 g / kg, between 95 g / kg and 50 g / kg, between 70 g / kg and 60 g / kg, between 80 g / kg and 60 g / kg, between 90 g / kg and 60 g / kg, between 95 g / kg and 50 g / kg. When the equivalent TA concentration in the liquid phase of the reaction medium is between 12 g / kg and 53 g / kg, between 12 g / kg and 45 g / kg, between 12 g / kg and 38 g / kg, especially between 12 g / kg and 15 g / kg, between 12 g / kg and 20 g / kg, between 12 g / kg and 30 g / kg, between 12 g / kg and 40 g / kg, between 12 g / kg and 50 g / kg, between 15 g / kg and 20 g / kg, between 15 g / kg and 30 g / kg, between 15 g / kg and 38 g / kg, between 15 g / kg and 38 g / kg, between 15 g / kg and 38 g / kg, 15 g / kg and 38 g / kg, 15 g / kg and 38 g / kg, 15 g / kg and 38 g / kg, 15 g / kg and 38 g / kg, 15 g / kg and 38 g / kg, 15 g / kg and 30 ... Between 15 g / kg and 50 g / kg, between 15 g / kg and 53 g / kg, between 20 g / kg and 30 g / kg, between 20 g / kg and 38 g / kg, between 20 g / kg and 40 g / kg, between 20 g / kg and 45 g / kg, between 20 g / kg and 50 g / kg, between 20 g / kg and 53 g / kg, between 30 g / kg and 38 g / kg, between 30 g / kg and 40 g / kg, between 30 g / kg and 45 g / kg, between 30 g / kg and 50 g / kg, between 30 g / kg and 53 g / kg, between 40 g / kg and 50 g / kg, between 40 g / kg and 53 g / kg, between 45 g / kg and 50 g / kg, between 45 g / kg and 53 g / kg, between 50 ...When the amount of alkali added to the reaction medium is between 53 g / kg and 53 g / kg, the pH adjustment of the initial depolymerization step is stopped.

[0059] Therefore, in one embodiment, the pH of the preliminary depolymerization step is adjusted by adding NaOH until the amount of NaOH added to the liquid phase of the reaction medium reaches at least 2 g / kg, more preferably at least 12 g / kg, based on the total weight of the liquid phase of the reaction medium. Preferably, the pH adjustment of the preliminary depolymerization step is stopped when the amount of NaOH added to the reaction medium reaches at most 45 g / kg, more preferably at most 38 g / kg, based on the total weight of the liquid phase of the reaction medium. In one embodiment, the pH adjustment of the preliminary depolymerization step is stopped when the amount of NaOH added to the reaction medium is between 2 g / kg and 45 g / kg, preferably between 12 g / kg and 38 g / kg. Specifically, the alkali used for pH adjustment is sodium hydroxide (NaOH), and the pH adjustment of the preliminary depolymerization step is stopped when the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 95 g / kg, and when the amount of NaOH added to the reaction medium is between 12 g / kg and 38 g / kg.

[0060] Alternatively, the pH of the initial depolymerization step is adjusted by adding KOH until the amount of KOH added to the liquid phase of the reaction medium reaches at least 3 g / kg, more preferably at least 17 g / kg, based on the total weight of the liquid phase of the reaction medium. More preferably, the pH adjustment of the initial depolymerization step is stopped when the amount of KOH added to the reaction medium reaches at most 65 g / kg, more preferably at most 53 g / kg, based on the total weight of the liquid phase of the reaction medium. In one embodiment, the pH adjustment of the initial depolymerization step is stopped when the amount of KOH added to the reaction medium is between 3 g / kg and 65 g / kg, preferably between 17 g / kg and 53 g / kg.

[0061] Advantageously, the pH adjustment of the preliminary depolymerization step is stopped when at least 5%, preferably at least 10%, and more preferably at least 20% of the polyester of interest introduced into the initial reaction medium depolymerizes. Specifically, the pH adjustment of the preliminary depolymerization step is stopped when at most 70%, preferably at most 60%, of the polyester of interest introduced into the initial reaction medium depolymerizes into monomers and / or oligomers. In another embodiment, the pH adjustment of the preliminary depolymerization step is stopped when at most 50%, preferably at most 40%, and more preferably at most 30%, of the polyester of interest introduced into the initial reaction medium depolymerizes. Specifically, the pH adjustment of the preliminary depolymerization step is stopped when the polyester of interest introduced into the initial reaction medium depolymerizes between 20% and 70%, preferably between 40% and 70%, and more preferably between 50% and 60%.

[0062] In one embodiment, when the equivalent TA concentration in the liquid phase of the reaction medium is between 5 g / kg and 110 g / kg, preferably between 30 g / kg and 100 g / kg, the pH adjustment in the initial depolymerization step is stopped, and the subsequent main depolymerization step is carried out at a pH between 5.0 and 5.5.

[0063] In one embodiment, when the equivalent TA concentration in the liquid phase of the reaction medium is between 5 g / kg and 60 g / kg, preferably between 20 g / kg and 50 g / kg, and more preferably between 30 g / kg and 50 g / kg, the pH adjustment in the preliminary depolymerization step is stopped, and the main depolymerization step is carried out at pH 5.25 + / - 0.10.

[0064] In one embodiment, when the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 110 g / kg, preferably between 50 g / kg and 110 g / kg, and more preferably between 50 g / kg and 95 g / kg, the pH adjustment in the preliminary depolymerization step is stopped, and the main depolymerization step is carried out at pH 5.45 + / - 0.05.

[0065] In one embodiment, when the amount of NaOH added to the liquid phase containing the reaction medium is between 2 g / kg and 45 g / kg, the pH adjustment of the preliminary depolymerization step is stopped, and the subsequent main depolymerization step is carried out at a pH between 5.0 and 5.5.

[0066] In one embodiment, when the amount of NaOH added to the liquid phase of the reaction medium is between 2 g / kg and 25 g / kg, preferably between 8 g / kg and 20 g / kg, and more preferably between 12 g / kg and 20 g / kg, the pH adjustment of the preliminary depolymerization step is stopped, and the main depolymerization step is carried out at pH 5.25 + / - 0.10.

[0067] In one embodiment, when the amount of NaOH added to the liquid phase of the reaction medium is between 12 g / kg and 45 g / kg, preferably between 20 g / kg and 45 g / kg, and more preferably between 20 g / kg and 38 g / kg, the pH adjustment of the preliminary depolymerization step is stopped, and the main depolymerization step is carried out at pH 5.45 + / - 0.05.

[0068] In one embodiment, the method of the present invention includes: a. The initial depolymerization step is carried out at a given pH adjusted between 7.5 and 8.5 and at a temperature between 60°C and 72°C; and b. The main depolymerization step is carried out at a pH between 5.0 and 5.5 and a temperature between 50°C and 65°C, wherein the pH is not adjusted. Each depolymerization step includes contacting the plastic product with at least one enzyme capable of degrading the polyester, and wherein the pH adjustment in step (a) is stopped when the liquid phase of the reaction medium contains an equivalent TA concentration between 5 g / kg and 110 g / kg, preferably between 30 g / kg and 100 g / kg, and more preferably between 30 g / kg and 95 g / kg. Alternatively, the main depolymerization step is carried out at a pH between 5.0 and 5.5 and at a temperature between 65°C and 72°C, wherein the pH is not adjusted. Preferably, the pH adjustment in the preliminary depolymerization step (a) is carried out by adding NaOH, and the pH adjustment is stopped when the amount of NaOH added to the liquid phase of the reaction medium contains an amount between 2 g / kg and 45 g / kg, preferably between 5 g / kg and 40 g / kg, and more preferably between 12 g / kg and 38 g / kg. In one embodiment, when the liquid phase containing the reaction medium has an equivalent TA concentration between 30 g / kg and 50 g / kg, the pH adjustment in step (a) is stopped, and step (b) is performed at pH 5.25 ± 0.1. Alternatively, when the liquid phase containing the reaction medium has an equivalent TA concentration between 50 g / kg and 110 g / kg, preferably between 50 g / kg and 95 g / kg, the pH adjustment in step (a) is stopped, and step (b) is performed at pH 5.45 ± 0.05.

[0069] In one particular embodiment, if the pH decreases below the target pH during the main depolymerization step, alkali may sometimes be added to raise the pH back to the target pH. This target pH should preferably be defined before carrying out the main depolymerization step. Specifically, a target pH between 4 and 6, + / - 0.5, preferably + / - 0.2 or + / - 0.1 is included.

[0070] In one particular embodiment, the method of the present invention may include a step between the preliminary depolymerization step and the main depolymerization step, wherein a base or acid is added to the reaction medium to achieve the target pH of the main depolymerization step.

[0071] Alternatively or additionally, the depolymerizing agent in the preliminary depolymerization step may be a chemical depolymerizing agent. In this case, pH adjustment is not required during the preliminary depolymerization step, and the preliminary depolymerization step is carried out until the equivalent TA concentration in the liquid phase of the reaction medium reaches at least 5 g / kg, preferably at least 15 g / kg, and more preferably at least 25 g / kg based on the total weight of the liquid reaction medium.

[0072] According to the present invention, the preliminary depolymerization step and the main depolymerization step are preferably carried out at the same temperature. In one embodiment, the two steps are carried out at 60°C + / - 5°C, preferably + / - 2°C or + / - 1°C. In another embodiment, the two steps are carried out at 56°C + / - 5°C, preferably + / - 2°C or + / - 1°C.

[0073] In another embodiment, the primary depolymerization step is carried out directly using a reaction medium containing a defined equivalent concentration of TA (primarily in salt form), i.e., without a preliminary depolymerization step. Any method known to those skilled in the art can be used to prepare the reaction medium for the primary depolymerization step containing a defined equivalent concentration of TA, primarily in salt form.

[0074] In one embodiment, the defined equivalent concentration of TA in the reaction medium, which is mainly in salt form, can be achieved by adding TA (TA salt and / or oligomer salt) in salt form to the reaction medium prior to the main depolymerization step, for example by adding disodium terephthalate C8H4Na2O4, dipotassium terephthalate C8H4K2O4, diammonium terephthalate C8H12N2O4, monosodium terephthalate C8H5NaO4, monopotassium terephthalate C8H5KO4 and / or monoammonium terephthalate C8H10NO4.

[0075] Alternatively or otherwise, the limited equivalent concentration of TA in the reaction medium, which is mainly in salt form, can be achieved by adding TA in both acidic and basic forms to the reaction medium to produce TA salts.

[0076] Preferably, a TA salt (and / or an oligomer salt and / or TA in both its acidic and basic forms, respectively) is added prior to the main depolymerization step to achieve an equivalent TA concentration in the liquid phase of the reaction medium of at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg, and more preferably at most 80 g / kg, and more preferably at most 70 g / kg, based on the total weight of the liquid phase of the reaction medium, and at least 90% of the equivalent TA in the liquid phase is in salt form.

[0077] In one embodiment, a TA salt (and / or an oligomeric salt and / or TA in both its acidic and basic forms, respectively) is added to achieve an equivalent TA concentration in the liquid phase of the reaction medium, comprising between 20 g / kg and 80 g / kg, preferably between 30 g / kg and 80 g / kg, and more preferably between 30 g / kg and 70 g / kg, and at least 90% of the equivalent TA in the liquid phase is in salt form.

[0078] In one embodiment, a TA salt (and / or an oligomer salt and / or TA in both its acidic and basic forms, respectively) is added to achieve an equivalent TA concentration in the liquid phase of the reaction medium, comprising between 10 g / kg and 80 g / kg, preferably between 30 g / kg and 80 g / kg, and at least 90% of the equivalent TA in the liquid phase is in salt form, and the main depolymerization step is carried out at a pH between 5 and 5.5.

[0079] In one embodiment, a TA salt (and / or an oligomeric salt and / or TA in both its acidic and basic forms, respectively) is added to achieve an equivalent TA concentration in the liquid phase of the reaction medium comprising between 10 g / kg and 60 g / kg, preferably between 20 g / kg and 50 g / kg, and more preferably between 30 g / kg and 50 g / kg, and at least 90% of the equivalent TA in the liquid phase is in salt form, and the main depolymerization step is carried out at pH 5.25 + / - 0.1.

[0080] In another embodiment, a TA salt (and / or an oligomeric salt and / or TA in both its acidic and basic forms, respectively) is added to achieve an equivalent TA concentration in the liquid phase of the reaction medium, comprising between 30 g / kg and 80 g / kg, preferably between 50 g / kg and 80 g / kg, and at least 90% of the equivalent TA in the liquid phase is in salt form, and the main depolymerization step is carried out at pH 5.45 + / - 0.05.

[0081] In one embodiment, the TA salt and / or oligomer salt added to the reaction medium are recovered from the preceding chemical and / or enzymatic depolymerization steps as defined above (or in WO 2020 / 094661), preferably by adjusting the pH to between 6.5 and 10 by adding a base. The TA salt can be recovered using any purification method, such as the method described in WO 2020 / 094661, and is to be added to the reaction medium of the main depolymerization step.

[0082] In one embodiment, the reaction medium for the main depolymerization step is prepared by adding an additional TA salt (and / or oligomer salt and / or TA in both its acidic and basic forms, respectively) to the reaction medium and performing a preliminary depolymerization step as described above to induce TA formation, thereby achieving a target equivalent TA concentration in the reaction medium, and at least 90% of the equivalent TA in the liquid phase is in salt form.

[0083] According to the present invention, at least the primary depolymerization step and, where appropriate, the preliminary depolymerization step are carried out by contacting a plastic product comprising at least one polyester containing at least one TA monomer with at least one enzyme capable of degrading the polyester. In one embodiment, the enzymatic depolymerization steps are carried out by contacting a plastic product comprising at least one polyester containing at least one TA monomer with at least one microorganism exhibiting and secreting the enzyme capable of degrading the polyester.

[0084] In one embodiment, the at least one enzyme exhibits polyester degradation activity at a pH between 4 and 10, particularly between 4 and 9. In another embodiment, the at least one enzyme has an optimal pH between 6.5 and 10, particularly between 6.5 and 9, and still exhibits polyester degradation activity at a pH between 4 and 6, preferably between 5 and 5.5, and / or at the pH of the main depolymerization step.

[0085] In the context of this invention, "polyester degradation activity" can be evaluated by any method known to those skilled in the art. Specifically, "polyester degradation activity" can be evaluated by: measuring the depolymerization activity of a particular polyester, measuring the degradation rate of a solid polyester compound dispersed in an agar plate, measuring the depolymerization activity of the polyester in a reactor, measuring the quantity of depolymerization products (EG, TA, MHET, etc.) released, and mass measuring the polyester.

[0086] In one embodiment, the enzyme system exhibiting polyester degradation activity is selected from polymerase degraders, preferably from esterases. In a preferred embodiment, the enzyme system is selected from lipases or keratinases.

[0087] In a particular embodiment, the enzyme is an esterase. Specifically, the esterase is a keratinase, preferably derived from keratinases selected from the following microorganisms: *Thermobifida cellulosityca*, *Thermobifida halotolerans*, *Thermobifida fusca*, *Thermobifida alba*, *Bacillus subtilis*, *Fusarium solani pisi*, *Humicola insolens*, *Sirococcus conigenus*, *Pseudomonas mendocina*, *Thielavia terrestris*, *Saccharomonospora viridis*, *Thermomonospora curvata*, or any functional variant thereof. In another embodiment, the keratinase system is selected from metagenomic libraries, such as LC-keratinase described in Sulaiman et al., 2012, or esterases described in EP3517608, or any functional variants thereof, including depolymerases listed in WO 2021 / 005198, WO 2018 / 011284, WO 2018 / 011281, WO 2020 / 021116, WO 2020 / 021117, or WO 2020 / 021118. In another specific embodiment, the esterase system is preferably derived from lipases of Ideonella sakaiensis or any functional variants thereof, including lipases described in WO 2021 / 005199. In another specific embodiment, the depolymerase is a keratinase derived from a specific humic fungus, such as the keratinase mentioned in Uniprot A0A075B5G4, or any functional variant thereof. In another embodiment, the depolymerase is selected from commercial enzymes, such as Novozym 51032, or any functional variant thereof.

[0088] In another specific embodiment, the enzyme is selected from enzymes that have at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% similarity to the full-length amino acid sequence described in SEQ ID N°1 and / or the full-length amino acid sequence described in SEQ ID N°3 and exhibit polyester degradation activity, especially PET degradation activity.

[0089] In one embodiment, the enzyme is selected from enzymes having PET degradation activity (PET enzymes) and / or enzymes having MHET degradation activity (MHET enzymes).

[0090] In the context of this invention, "MHET degradation activity" can be assessed by any method known to those skilled in the art. As an example, "MHET degradation activity" can be assessed by measuring the MHET degradation activity rate, which is determined by measuring the amount of depolymerization products (ethylene glycol EG and TA) released.

[0091] In one embodiment, the MHET enzyme may be a self-degrading polymerase, preferably selected from esterases. In one embodiment, the MHET enzyme may be selected from lipases or keratinases. In another embodiment, the MHET enzyme may be selected from enzymes belonging to category EC: 3.1.1.102.

[0092] In one specific embodiment, the MHET enzyme is selected from MHET enzymes isolated from or derived from *Sakai osakaensis*, such as those disclosed in Yoshida et al., 2016, or any functional variant thereof. In another specific embodiment, the MHET enzyme is selected from enzymes having at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity with the full-length amino acid sequence described in SEQ ID NO2.

[0093] In one particular embodiment, PET enzyme and MHET enzyme are included in a multi-enzyme system, particularly a two-enzyme system, such as the Osaka Sakai PET enzyme / MHET enzyme system disclosed by Knott et al. 2020.

[0094] In one embodiment, the enzyme is selected from enzymes that have an optimal pH between 4 and 6 and / or exhibit polyester degradation activity at a pH between 4 and 6.

[0095] In one embodiment, the main depolymerization step and the preliminary enzymatic depolymerization step are carried out by contacting a plastic product containing at least one polyester with at least two enzymes, preferably with at least two enzymes exhibiting polyester degradation activity, wherein: - At least the first enzyme exhibits polyester degradation activity at a pH between 6.5 and 10, preferably at the pH of the initial enzymatic hydrolysis polymerization step, and - At least the second enzyme, unlike the first enzyme, exhibits polyester degradation activity at a pH between 4 and 6, preferably at the pH of the main depolymerization step.

[0096] In one embodiment, both steps are carried out by contacting a plastic product containing at least one polyester with at least two enzymes, preferably with at least two enzymes exhibiting polyester degradation activity, wherein: - At least the first enzyme exhibits polyester degradation activity at a pH between 6.5 and 10, preferably at the pH of the initial enzymatic hydrolysis polymerization step, and - At least the second enzyme, unlike the first enzyme, exhibits this activity at a pH between 4 and 10.

[0097] In one specific embodiment, the plastic product comprises PET, and both steps are carried out by contacting the plastic product comprising at least PET with at least two enzymes, preferably at least one PET enzyme and at least one MHET enzyme. In one embodiment, the preliminary depolymerization step is carried out by contacting the plastic product comprising at least one polyester with at least one PET enzyme, and the main depolymerization step is carried out by contacting with at least one MHET enzyme. In one embodiment, the preliminary depolymerization step is carried out by contacting the plastic product comprising at least one polyester with at least one PET enzyme, and during the main depolymerization step, at least one MHET enzyme is added in addition to the PET enzyme. In one specific embodiment, the preliminary depolymerization step is carried out by contacting the plastic product comprising at least one polyester with at least one PET enzyme, and during the main depolymerization step, at least one MHET enzyme is added in addition to the PET enzyme.

[0098] MHET enzyme can be added simultaneously with PET enzyme. Alternatively or additionally, MHET enzyme can be added after PET enzyme, for example, once the polyester has been at least partially degraded by PET enzyme.

[0099] In one embodiment, the plastic product is simultaneously contacted with both PET enzyme and MHET enzyme. In another embodiment, the plastic product is first contacted with PET enzyme, and then MHET enzyme is introduced into the reaction medium after PET enzyme.

[0100] In certain embodiments, the simultaneous use of PET enzyme and MHET enzyme during the preliminary depolymerization step and / or the main depolymerization step can cause a synergistic effect, resulting in a depolymerization rate higher than the sum of the depolymerization rates obtained using only PET enzyme and only MHET enzyme.

[0101] In one embodiment, the enzyme used in the preliminary depolymerization step and / or the main depolymerization step is selected from enzymes that have at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identity with the full-length amino acid sequence described in SEQ ID n°1 and / or SEQ ID n°3, and the MHET enzyme of SEQ ID n°2.

[0102] Enzymes can be in soluble or solid form, such as powder. Specifically, they can bind to cell membranes or lipid vesicles, or to synthetic carriers such as glass, plastics, polymers, filter membranes, and membranes, for example, in the form of beads, tubes, plates, and the like. Enzymes can be in isolated or purified form. Preferably, the enzymes of the present invention are derived from microbial expression, production, secretion, isolation, or purification. Enzymes can be purified by techniques known in the art and stored under conventional techniques. Enzymes can be further modified to improve, for example, their stability, activity, and / or adsorption on polymers. For example, enzymes are formulated with stabilizing and / or dissolving components, such as water, glycerol, sorbitol, dextrins, including maltodextrin and / or cyclodextrins, starch, propylene glycol, salts, etc.

[0103] In another embodiment, one or both steps of depolymerization are performed by at least one microorganism that exhibits and secretes a depolymerase. In the context of this invention, the enzyme may be secreted in a culture medium or secreted toward the cell membrane of the microorganism, wherein the enzyme may be immobilized. The microorganism may synthesize the depolymerase naturally, or it may be a recombinant microorganism in which a recombinant nucleotide sequence encoding the depolymerase has been inserted, for example, into a vector. For example, a nucleotide molecule encoding the depolymerase of interest is inserted into a vector, such as a plastid, recombinant virus, bacteriophage, free genome, artificial chromosome, or similar vector. Host cell conversion and suitable culture conditions for the host are well known to those skilled in the art.

[0104] Recombinant microorganisms can be used directly. Alternatively or additionally, the recombinant enzyme can be purified from the culture medium. For this purpose, any commonly used isolation / purification method can be used, such as salting out, thermal shock, gel filtration, hydrophobic interaction chromatography, affinity chromatography, or ion exchange chromatography. In certain embodiments, microorganisms known to synthesize and secrete the polymerase of interest can be used.

[0105] According to the present invention, several enzymes and / or several microorganisms may be used together or sequentially during different depolymerization steps.

[0106] According to the present invention, the amount of enzyme in a reaction medium comprising between 0.1 mg / g and 15 mg / g of target polyester, preferably between 0.1 mg / g and 10 mg / g of target polyester, more preferably between 0.1 mg / g and 5 mg / g of target polyester, and even more preferably between 0.5 mg / g and 4 mg / g of target polyester. Preferably, the amount of enzyme in the reaction medium is at most 4 mg / g, more preferably at most 3 mg / g, and more preferably at most 2 mg / g of target polyester. When at least one PET enzyme and at least one MHET enzyme are used, the amount of PET enzyme in the reaction medium comprising between 0.1 mg / g and 10 mg / g of target polyester, preferably between 0.1 mg / g and 5 mg / g of target polyester, and more preferably between 0.5 mg / g and 4 mg / g of target polyester, and the amount of MHET enzyme in the reaction medium comprising between 0.1 mg / g and 5 mg / g of target polyester, preferably between 0.1 mg / g and 2 mg / g of target polyester.

[0107] According to one embodiment of the present invention, the method of the present invention includes: a. A preliminary depolymerization step is carried out by contacting the plastic product with at least one PET enzyme at a given pH adjusted between 7.5 and 8.5 and a temperature between 60°C and 72°C; and b. The main depolymerization step is carried out by contacting the plastic product with at least one PET enzyme and, if applicable, at least one MHET enzyme at a pH between 5.0 and 5.5 and a temperature between 50°C and 65°C, wherein the pH is not adjusted. When the liquid phase of the reaction medium contains an equivalent TA concentration between 30 g / kg and 95 g / kg, the pH adjustment in step (a) is stopped. Depending on the circumstances, one or more additional amounts of enzyme (PET enzyme and / or MHET enzyme) may be added to the reaction medium during the main depolymerization step.

[0108] According to one embodiment of the present invention, the method of the present invention includes: a. A preliminary depolymerization step is carried out by simultaneously contacting the plastic product with at least one PET enzyme and at least one MHET enzyme at a given pH adjusted between 7.5 and 8.5 and a temperature between 60°C and 72°C; and b. The main depolymerization step is carried out at a pH between 5.0 and 5.5 and a temperature between 50°C and 65°C, wherein the pH is not adjusted. When the liquid phase of the reaction medium contains an equivalent TA concentration between 30 g / kg and 95 g / kg, the pH adjustment in step (a) is stopped. Depending on the circumstances, one or more additional amounts of enzyme (PET enzyme and / or MHET enzyme) may be added to the reaction medium during the main depolymerization step.

[0109] Advantageously, the PET enzyme is selected from enzymes that have at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% homology with the full-length amino acid sequence described in SEQ ID N°1 and / or SEQ ID N°3 and exhibit polyester degradation activity, and the MHET enzyme is selected from enzymes that have at least 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% homology with the full-length amino acid sequence described in SEQ ID N°2. Chemical depolymerization agent

[0110] In one embodiment, the preliminary depolymerization step includes or comprises a chemical depolymerization step, which is carried out by contacting a plastic product comprising at least one polyester with at least one chemical agent.

[0111] In one embodiment, the chemical agent is a catalyst. The chemical agent can be selected from any catalyst known to those skilled in the art for its strength in degrading and / or depolymerizing the target polyester. Advantageously, the catalyst is selected from metallic catalysts or stabilizers and non-toxic hydrosilanes (PMHS, TMDS), such as commercially available B(C6F5)3 and [Ph3C+, B(C6F5)4-] catalysts. Specifically, the catalyst is selected from alkoxides, carbonates, acetates, hydroxides, alkali metal oxides, alkaline earth metals, calcium oxide, calcium hydroxide, calcium carbonate, sodium carbonate, iron oxides, zinc acetate, and zeolites. In some embodiments, the catalyst comprises at least one of germanium compounds, titanium compounds, antimony compounds, zinc compounds, cadmium compounds, manganese compounds, magnesium compounds, cobalt compounds, silicon compounds, tin compounds, lead compounds, and aluminum compounds. Specifically, the catalyst includes germanium dioxide, cobalt acetate, titanium tetrachloride, titanium phosphate, tetrabutyl titanium dioxide, tetraisopropoxide titanium, tetran-propoxide titanium, tetraethoxy titanium, tetramethoxy titanium, tetra(acetylene) titanium complex, tetra(2,4-hexanedione) titanium complex, tetra(3,5-heptadecyl) titanium complex, dimethoxybis(acetylene) titanium complex, diethoxybis(acetylene) titanium complex, diisopropoxybis(acetylene) titanium complex, din-propoxybis(acetylene) titanium complex, dibutoxybis(acetylene) titanium complex, titanium dihydroxydiglycolate, titanium dihydroxydiglycolate, titanium dihydroxydilactic acid, titanium dihydroxydi(2- Titanium hydroxypropionate, titanium lactate, titanium octyl glycol, titanium dimethoxybis(triethanolamine), titanium diethoxybis(triethanolamine), titanium dibutoxybis(triethanolamine), titanium hexamethyl distitanate, titanium hexaethyl distitanate, titanium hexapropyl distitanate, titanium hexabutyl distitanate, titanium isophenyl distitanate, titanium octamethyl tritiate, titanium octaethyl tritiate, titanium octapropyl tritiate, titanium octabutyl tritiate, titanium octaphenyl tritiate, titanium hexyloxy distitanate, zinc acetate, manganese acetate, methyl silicate, zinc chloride, lead acetate, sodium carbonate, acidic sodium carbonate, acetic acid, sodium sulfate, potassium sulfate, zeolite, lithium chloride, magnesium chloride, ferric chloride, zinc oxide, magnesium oxide, calcium oxide, barium oxide, antimony dioxide, and antimony triacetate, at least one of these.

[0112] Alternatively or otherwise, the catalyst is selected from nano-type examples.

[0113] Alternatively, the chemical agent is an acid or base catalyst capable of breaking polymer bonds, specifically ester bonds. Specifically, the chemical agent involved in breaking ester bonds is a mixture of a hydroxide and an alcohol capable of dissolving the hydroxide. The hydroxide is selected from alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide, preferably from sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, ammonium hydroxide, and tetraalkylammonium hydroxide, and the alcohol is selected from linear, branched, cyclic alcohols, or combinations thereof, preferably linear C1-C4 alcohols selected from methanol, ethanol, propanol, and butanol.

[0114] In one specific embodiment, the chemical agent is a mixture of a nonpolar solvent (i.e., a swelling agent) capable of swelling the polyester and a reagent capable of breaking or hydrolyzing ester bonds, wherein the swelling agent is preferably a chlorinated solvent selected from dichloromethane, dichloroethane, tetrachloroethane, chloroform, carbon tetrachloride, and trichloroethane. In another specific embodiment, the chemical agent is an acid selected from ethylene glycol, hydrochloric acid, sulfuric acid, or Lewis acid.

[0115] In one embodiment, the method of the present invention is carried out using plastic products from plastic waste collection and / or post-industrial waste. More specifically, the method of the present invention can be used to degrade consumer plastic waste, including plastic bottles, plastic trays, plastic bags, plastic packaging, soft plastics and / or hard plastics, and even plastic waste contaminated with food residues, surfactants, etc. Alternatively or additionally, the method of the present invention can be used to degrade used plastic fibers, such as fibers from textiles, fabrics, and / or industrial waste. More specifically, the method of the present invention can be used for PET plastic and / or PET fiber waste, such as PET fibers from textiles, fabrics, and / or tires.

[0116] According to the present invention, the plastic product comprises at least one polyester selected from the following: poly(ethylene terephthalate) (PET), poly(propylene terephthalate) (PTT), poly(butyl terephthalate) (PBT), poly(ethyl isosorbide terephthalate) (PEIT), butyl adipate terephthalate (PBAT), poly(cyclohexyl dimethyl terephthalate) (PCT), glycosylated poly(ethylene terephthalate) (PETG), poly(butyl succinate-co-butyl terephthalate) (PBST), poly(butyl succinate / butyl terephthalate / butyl isophthalate)-co-(lactic acid ester) (PBSTIL), and blends / mixtures of these polymers, preferably selected from poly(ethylene terephthalate) (PET).

[0117] In one embodiment, the plastic product comprises at least one amorphous polyester targeted by the degradation method.

[0118] In one embodiment, the plastic product comprises at least one crystalline polyester and / or at least one semi-crystalline polyester targeted by the degradation method. In the context of this invention, "semi-crystalline polyester" refers to a partially crystalline polyester in which crystalline and amorphous regions coexist. The crystallinity of a semi-crystalline polyester can be assessed by various analytical methods and typically ranges from 10% to 90%. For example, differential scanning calorimetry (DSC) or X-ray diffraction can be used to determine the crystallinity of the polymer.

[0119] In one embodiment, the plastic product comprises crystalline polyester and / or semi-crystalline polyester, and amorphous polyester, which are targeted by the degradation method.

[0120] In one embodiment, the plastic article may be pretreated prior to the main depolymerization step (or, if present, prior to a preliminary depolymerization step) to physically alter its structure, thereby increasing the surface area for contact between the polyester and the enzyme and / or reducing microbial contamination from waste. Examples of pretreatment are described in patent application WO 2015 / 173265.

[0121] According to the present invention, it is possible to amorphize the polyester of a plastic product prior to the main depolymerization step (or, if present, prior to a preliminary depolymerization step) by any method known to those skilled in the art. Examples of amorphization processes are described in patent application WO 2017 / 198786. In a particular embodiment, the polyester is amorphized prior to any depolymerization step, followed by granulation and / or micronization.

[0122] Alternatively, it is possible to perform a foaming step on the plastic article prior to the main depolymerization step (or, if present, a preliminary depolymerization step) by any method known to those skilled in the art. An example of a foaming pretreatment process is described in patent application PCT / EP2020 / 087209.

[0123] In a preferred embodiment, the plastic product is pretreated prior to the main depolymerization step (or prior to a preliminary depolymerization step, if present), and the polyester of interest in the plastic product exhibits less than 30% crystallinity, preferably less than 25%, and more preferably less than 20%, prior to being provided to the main depolymerization step (or to the preliminary depolymerization step).

[0124] reactor [, According to the present invention, the method can be carried out in any reactor with a volume greater than 500 mL, greater than 1 L, preferably greater than 2 L, 5 L, or 10 L. In a particular embodiment, the method is carried out on a semi-industrial or industrial scale. Therefore, the method can be carried out in reactors with volumes greater than 100 L, 150 L, 1,000 L, 10,000 L, 100,000 L, or 400,000 L.

[0125] In the context of this invention, the total volume of the reactor is advantageously at least 10% larger than the volume of the reaction medium or reactor contents.

[0126] According to the invention, the reactor contents are maintained under stirring during the method. The stirring speed is adjusted by a person skilled in the art to allow the plastic product to remain suspended in the reactor, to allow for temperature uniformity, and to allow for precise pH adjustment if necessary.

[0127] In one embodiment, the concentration of the polyester introduced prior to the main depolymerization step (or prior to any preliminary depolymerization step) is greater than 150 g / kg, preferably greater than 200 g / kg, more preferably greater than 300 g / kg, and even more preferably greater than 400 g / kg relative to the total weight of the reaction medium (or the starting reaction medium).

[0128] In one particular embodiment, the polyester concentration is between 200 g / kg and 400 g / kg, preferably between 300 g / kg and 400 g / kg, introduced prior to the main depolymerization step (or prior to any preliminary depolymerization step). Alternatively, the polyester concentration is between 400 g / kg and 600 g / kg, introduced prior to the main depolymerization step (or prior to any preliminary depolymerization step).

[0129] In a preferred embodiment, the reaction medium comprises a liquid aqueous solvent, such as a buffer solution and / or water, preferably water. In a preferred embodiment, the liquid in the reaction medium does not contain non-aqueous solvents, especially inorganic solvents. In a particular embodiment, the liquid in the reaction medium comprises only water.

[0130] In one embodiment, during the main depolymerization step, additional amounts of polyester and / or enzymes (such as PET enzymes and / or MHET enzymes) may be added to the reaction medium continuously or sequentially. Specifically, during the main depolymerization step, additional amounts of polyester and / or enzymes may be added once or several times.

[0131] Specifically, polyester may be added to achieve a final concentration of introduced polyester in the reaction medium between 300 g / kg and 600 g / kg polyester, preferably between 400 g / kg and 600 g / kg, and more preferably between 500 g / kg and 600 g / kg. The final concentration of polyester corresponds to the total amount of polyester introduced into the reaction medium throughout the degradation process, which is based on the total weight of the reaction medium before the main depolymerization step, or on the total weight of the initial reaction medium (i.e., before any preliminary depolymerization step).

[0132] In one embodiment, the concentration of polyester introduced prior to the main depolymerization step is less than 300 g / kg, preferably between 200 g / kg and 300 g / kg, relative to the total weight of the reaction medium, and additional polyester is added during the main depolymerization step so that the final concentration of polyester introduced into the reaction medium reaches greater than 400 g / kg, more preferably greater than 500 g / kg, and even more preferably between 500 g / kg and 600 g / kg. In such embodiments, the main depolymerization step is preferably carried out in the reaction medium at a pH between 5 and 5.5, and the equivalent TA concentration in the liquid phase of the reaction medium, based on the total weight of the liquid phase, comprises between 30 g / kg and 70 g / kg, and at least 90% of the equivalent TA in the liquid phase of the reaction medium is in salt form. Depending on the circumstances, additional enzymes may also be added during the main depolymerization step.

[0133] In one particular embodiment, the method of the present invention carried out in a reaction medium includes: a. A preliminary depolymerization step, carried out at a given pH adjusted to between 6.5 and 10, preferably between 7.5 and 8.5; and b. The main depolymerization step, which is carried out at a pH between 5 and 5.5. Both of the depolymerization steps involve contacting the plastic product with at least one enzyme capable of degrading the polyester. The concentration of polyester introduced before the preliminary depolymerization step is less than 300 g / kg relative to the total weight of the initial reaction medium, preferably between 200 g / kg and 300 g / kg. Additional polyester is added during the main depolymerization step so that the final concentration of polyester introduced into the reaction medium reaches greater than 400 g / kg, more preferably greater than 500 g / kg, and even more preferably between 500 g / kg and 600 g / kg, based on the total weight of the initial reaction medium. The pH of step (a) is adjusted until the equivalent TA concentration in the liquid phase of the reaction medium is at least 25 g / kg, preferably between 50 g / kg and 95 g / kg, based on the total weight of the liquid phase of the reaction medium.

[0134] Depending on the circumstances, additional enzymes may also be added during the main depolymerization step.

[0135] Another object of the present invention is to provide a reaction medium suitable for the main depolymerization step of the degradation method of the present invention, wherein the reaction medium contains, in the liquid phase, at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg of equivalent TA based on the total weight of the liquid phase of the reaction medium, and at least 90%, preferably at least 95%, 96%, 97%, 98%, or 99% of the equivalent TA is in salt form. Preferably, the reaction medium contains, in the liquid phase, at most 80 g / kg of equivalent TA based on the total weight of the liquid phase of the reaction medium.

[0136] In a particular embodiment, the method for degrading materials containing polymers, such as plastic products, further includes a step of recovering and, where appropriate, purifying monomers and / or oligomers and / or degradation products, preferably terephthalic acid, generated in the depolymerization step. The monomers and / or oligomers and / or degradation products generated from the depolymerization can be recovered sequentially or continuously.

[0137] A single type of monomer and / or oligomer or several different types of monomers and / or oligomers can be recovered. The recovered monomers and / or oligomers and / or degradation products can be purified using all suitable purification methods and, where appropriate, adapted to a repolymerizable form. Examples of purification are described in patent application WO 1999 / 023055. In a particular embodiment, the recovery of TA in the solid state involves separating the solid phase from the liquid phase of the reaction medium by filtration.

[0138] The recovered solid phase is soluble and / or dispersed in a solvent selected from water, DMF, NMP, DMSO, DMAC, or any solvent known to dissolve TA, and is filtered to remove impurities. The dissolved TA can then be recrystallized by any method known to those skilled in the art.

[0139] The TA salt contained in the liquid phase of the reaction medium can be recovered and reused in another degradation process according to the invention, so as to achieve a defined equivalent TA concentration in the liquid phase of the reaction medium of the other degradation process.

[0140] In one embodiment, MHET enzyme is added to the reaction medium after the main depolymerization step and before the purification process to hydrolyze the MHET generated during the depolymerization step to produce TA.

[0141] In a preferred embodiment, the repolymerizable monomers and / or oligomers can then be reused to synthesize polymers. Those skilled in the art can easily adapt the process parameters to the synthesis of monomers / oligomers and polymers.

[0142] Therefore, another object of the present invention is to provide a method for recycling materials containing polyester, such as plastic articles, the plastic articles comprising at least one polyester containing at least one TA monomer, the polyester preferably being PET, and / or to provide a method for generating monomers and / or oligomers and / or degradation products, preferably TA, from plastic articles containing at least one polyester having at least one TA monomer, comprising a main enzymatic hydropolymerization step of the plastic article at a pH between 4 and 6, and recovery and, if applicable, purification of the monomers and / or oligomers, wherein the enzymatic hydropolymerization step is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg, preferably at least 20 g / kg, more preferably at least 30 g / kg based on the total weight of the liquid phase of the reaction medium, and wherein at least 90%, preferably at least 95%, more preferably at least 96%, 97%, 98%, and 99% of the equivalent TA in the liquid phase of the reaction medium is in salt form.

[0143] All the specific embodiments described above regarding the methods for degrading materials containing polyester, such as plastic products, are also applicable to methods for producing monomers and / or oligomers and recycling methods.

[0144] Example [Example] [1] [-] [Degradation includes] [PET] [Methods for producing plastic products] [,] [Includes the main acidic depolymerization steps and preliminary enzymatic depolymerization steps] [, , ] The foaming process was carried out in a Leistritz ZSE 18 MAXX twin-screw extruder at a temperature above 250°C. The foam consisted of washed and colored PET flakes (98.5% by weight of the total mixture fed into the extruder), 1% by weight of citric acid (Orgather exp 141 / 183 from Adeka), and 0.5% by weight of water, all based on the total weight of the mixture fed into the extruder. The resulting extrudate was granulated into 2-3 mm solid pellets with a crystallinity of 7% (i.e., foamed PET).

[0145] The degradation method of this invention (including a preliminary depolymerization step and a major depolymerization step) was performed in a 500 mL reactor using a variant of LC-keratinase (Sulaiman et al., Appl Environ Microbiol. March 2012). This variant (hereinafter referred to as "LCC-ICCIG") corresponds to the enzyme of SEQ ID NO: 1, which has the following mutations compared to SEQ ID NO: 1: F208I + D203C + S248C + V170I + Y92G, and is expressed as a recombinant protein by Trichoderma reesei.

[0146] At the start of the method, 200 g / kg of foamed PET was added to the reactor based on the total weight of the initial reaction medium, along with LCC-ICCIG in 100 mM phosphate buffer at pH 8 and 4 mg / g PET (the difference being that in Ref-2, PET and enzyme were added to water). During the initial depolymerization step, the temperature was maintained at 60°C, and the pH of the reaction medium was adjusted to pH 8 ± 0.05 by adding 25% NaOH solution (Ref-1, Ref-4, Ref-5) or 5% NaOH solution (Ref-2, Ref-3).

[0147] The pH and conditions during the initial depolymerization step are maintained until the equivalent TA concentration in the liquid phase of the reaction medium reaches a specific value between 33 and 90 g / kg, as mentioned in Table 1 below (the "equivalent TA concentration" is related to the "depolymerization rate"). Then, the addition of alkali is stopped (the "amount of NaOH added" is also mentioned in Table 1) and the temperature is lowered to 56°C. Therefore, the pH of the reaction medium is decreased until it reaches the target pH for the main depolymerization step, as also mentioned in Table 1 below.

[0148] During the initial depolymerization step, the equivalent TA concentration in the liquid phase was measured by routine sampling. The amount of equivalent terephthalic acid generated was measured by analyzing the sample from the reaction medium using ultra-high performance liquid chromatography (UHPLC).

[0149] Dilute the sample in 100 mM potassium phosphate buffer, pH 8. Mix 1 mL of the sample or diluted sample with 1 mL of methanol and 100 μL of 6 N HCl. After homogenization and filtration through a 0.45 μm syringe filter, inject 20 μL of the sample into an Ultimate 3000 UHPLC system (Thermo Fisher Scientific, Waltham, MA), including a pump assembly, automated sampler, column temperature control at 25 °C, and a UV detector at 240 nm. Separate terephthalic acid and oligomers (MHET and BHET) molecules using a gradient of methanol (30% to 90%) in 1 mM H₂SO₄ at 1 m / min through an HPLC Discovery HS C18 column (150 mm × 4.6 mm, 5 μm) equipped with a pre-column (Supelco, Bellefonte, PA). Only TA, MHET, and BHET were measured based on a standard curve prepared from commercially available TA and BHET, and internally synthesized MHET (via partial alkaline-catalyzed hydrolysis of BHET). The TA equivalent is the sum of the measured TA, MHET, and BHET.

[0150] During the main depolymerization step, the PET depolymerization rate is determined by measuring the total equivalent TA generated (both soluble and precipitated TA). This generation is determined by quantifying the total TA in the slurry fraction (including the liquid phase and further containing TA precipitated in the suspension within this liquid phase) using a method described for the preliminary depolymerization step, which allows for the dissolution of the precipitated TA.

[0151] The depolymerization rate after 140 h of reaction and the pH of the reaction medium during the main depolymerization steps are shown in Table 1 below. Table 1 also mentions the equivalent TA concentration when pH adjustment was stopped during the preliminary depolymerization step, and the equivalent TA concentration (and the concentration of alkali added to the reaction medium) in the reaction medium before the main depolymerization step.

[0152] Two comparisons were also conducted: ● "Control 1" corresponds to the method performed at 56°C in 100mM phosphate buffer, wherein the pH was adjusted to 8 by adding 25% NaOH solution. ● "Control 2" corresponds to the method performed at 56°C in 100mM phosphate buffer, wherein the pH was adjusted to 5.2 by adding 5% NaOH solution.

[0153] After 140 hours of reaction, the theoretical base consumption (Y base) was determined, corresponding to the amount of base added to the final reaction medium to dissolve the precipitated TA (or the amount of base that should have been introduced if the entire method were carried out at pH 8 with the same enzyme). The base consumption savings during the method (in percentage) were then determined using the following formula: Equivalent TA concentration (g / kg) in the shift liquid phase Addition of NaOH (g / kg) to the reaction medium Transformation of depolymerization rate (%) Total depolymerization rate (%) at T=140 h pH during the main acidic depolymerization step Alkali consumption savings (%) Ref-1 38 16 twenty one % 39% 5.26 47% Ref-2 33 12 twenty one % 35% 5.27 44% Ref-3 36 13 twenty one % 35% 5.35 43% Ref-4 58 twenty four 33% 62% 5.42 47% Ref-5 90 38 56% 92% 5.42 39% Control 1 (adjusted pH 8) - - - 95% 8 0 Control 2 (pH adjusted to 5.2) - - - 38% 5.2 25% Table 1: Parameters and Results of the Method of the Invention

[0154] The results showed that the method of the present invention allowed for alkali savings of between 39% and 47% compared to the adjusted method at pH 8 (Control 1, no alkali consumption savings) or the adjusted method at pH 5.2 (Control 2, 25% alkali savings).

[0155] [Example] [2] [-] [PET] Degradation methods for plastic products [,] [Includes preliminary enzymatic hydrolysis and polymerization steps] [,] [Subsequent feed batch acid depolymerization step] [, , ] The method of the present invention is implemented using the conditions used in Ref-5 of Example 1.

[0156] When the previously introduced PET has reached 90% hydrolysis (= 136 h), additional PET and enzyme are added to achieve a total added PET amount of 400 g / kg (based on the total weight of the initial reaction medium), while maintaining the enzyme concentration at 4 mg / g PET, as described in Table 2 below. The total equivalent concentration of polyester relative to the total weight of the initial reaction medium is given. Time (hours) 0 136 Total concentration of polyester in the reaction medium (g of polyester introduced during the method / kg of initial reaction medium) 200 400 The amount of enzyme in the initial reaction medium, expressed in mg / g polyester. 4 4 Table 2: Parameters of the Method of the Invention

[0157] After 350 hours, the depolymerization rate and alkali consumption savings were 70% and 60%, respectively.

[0158] [Example] [3] [-] [degradation] [PET] [Methods for producing plastic products] [,] [Included] [PET] [Enzymes and] [MHET] [Preliminary enzymatic depolymerization steps and main depolymerization steps] [, , ] The method of the present invention is carried out as described in Example 1 (i.e., the slices used, the enzymes used, and the quantity thereof).

[0159] During the initial depolymerization step, the temperature was maintained at 60°C and the pH of the reaction medium was adjusted to pH 8 ± 0.05 by adding 25% NaOH solution.

[0160] The pH and conditions were maintained during the initial depolymerization step until the equivalent TA concentration in the liquid phase of the reaction medium reached 49.3 g / kg (i.e., after 9.1 h of reaction). Subsequently, the addition of alkali was stopped, and the temperature was lowered to 56 °C.

[0161] After 23.4 h of reaction, 9.5 mg of purified MHET enzyme from *Escherichia coli* SEQ ID N°2 (Saka Sakai) was added to the reaction medium.

[0162] The equivalent TA concentration at which pH adjustment was stopped during the initial depolymerization step, the equivalent TA concentration in the reaction medium before the main depolymerization step (and the concentration of alkali added to the reaction medium), the depolymerization rate after 70 h of reaction, and the pH of the reaction medium during the main depolymerization step are shown in Table 3 below.

[0163] Example 1, Ref-4, can be considered a control, in which no MHET enzyme was added (Control-3). Equivalent TA concentration (g / kg) in the shift liquid phase Addition of NaOH (g / kg) to the reaction medium Transformation of depolymerization rate (%) Total depolymerization rate (%) at T=70 h pH during the main depolymerization step Alkali consumption savings (%) Ref-6 49.3 20 30% 69% 5.4 59% Ref-4 (= Reference 3) 58 twenty four 33% 58% 5.42 43% Table 3: Parameters and Results of the Method of the Invention

[0164] After 70 hours, the depolymerization rate and alkali consumption savings of Ref-6 were 69% and 59% respectively compared to the pH 8 adjusted method.

[0165] These results further demonstrate that the addition of MHET enzyme improves the depolymerization rate and reduces alkali consumption compared to the method of the present invention without MHET enzyme.

[0166] [Example] [4] [-] [degradation] [PET] [Methods for producing plastic products] [,] [Included] [PET] [Preliminary enzymatic depolymerization steps and main depolymerization steps] [, , ] The degradation method of the present invention (including a preliminary depolymerization step and a major depolymerization step) is carried out in a 500 mL reactor using a purified variant of the enzyme of SEQ ID N°3, which contains the following mutation L210T + V172I + N213M and is expressed as a recombinant protein by Escherichia coli.

[0167] The conditions for the introduced thin film and the initial depolymerization step (i.e., pH adjustment, temperature, enzyme quantity) are the same as those described in Example 3.

[0168] The pH and conditions were maintained during the initial depolymerization step until the equivalent TA concentration in the liquid phase of the reaction medium reached 42 g / kg. Subsequently, the addition of alkali was stopped, and the temperature was lowered to 56°C.

[0169] The equivalent TA concentration at which pH adjustment was stopped during the initial depolymerization step, the equivalent TA concentration in the reaction medium before the main depolymerization step (and the concentration of alkali added to the reaction medium), the depolymerization rate after 30 h of reaction, and the pH of the reaction medium during the main depolymerization step are shown in Table 4 below. Equivalent TA concentration (g / kg) in the shift liquid phase Addition of NaOH (g / kg) to the reaction medium Transformation of depolymerization rate (%) Total depolymerization rate (%) at T=30 h pH during the main depolymerization step Alkali consumption savings (%) Ref-7 42 twenty one 27% 35% 5.1 twenty three% Table 4: Parameters and Results of the Method of the Invention

[0170] After 30 hours, the depolymerization rate and alkali consumption savings were 35% and 23% respectively compared to the adjusted method at pH 8.

[0171] <![CDATA[ <110> CARBIOS, a French company <![CDATA[ <120> Method for degrading plastic products containing at least one polyester]]> <![CDATA[ <130> B3539PC00]]> <![CDATA[ <160> 3 ]]> <![CDATA[ <170> PatentIn version 3.5]]> <![CDATA[ <210> 1]]> <![CDATA[ <211> 258]]> <![CDATA[ <212> PRT]]> <![CDATA[ <213> Artificial sequence <![CDATA[ <220> ]]> <![CDATA[ <223> Keratinase <![CDATA[ <400> 1]]> Ser Asn Pro Tyr Gln Arg Gly Pro Asn Pro Thr Arg Ser Ala Leu Thr 1 5 10 15 Ala Asp Gly Pro Phe Ser Val Ala Thr Tyr Thr Val Ser Arg Leu Ser 20 25 30 Val Ser Gly Phe Gly Gly Gly Val Ile Tyr Tyr Pro Thr Gly Thr Ser 35 40 45 Leu Thr Phe Gly Gly Ile Ala Met Ser Pro Gly Tyr Thr Ala Asp Ala 50 55 60 Ser Ser Leu Ala Trp Leu Gly Arg Arg Leu Ala Ser His Gly Phe Val 65 70 75 80 Val Leu Val Ile Asn Thr Asn Ser Arg Phe Asp Tyr Pro Asp Ser Arg 85 90 95 Ala Ser Gln Leu Ser Ala Ala Leu Asn Tyr Leu Arg Thr Ser Ser Pro 100 105 110 Ser Ala Val Arg Ala Arg Leu Asp Ala Asn Arg Leu Ala Val Ala Gly 115 120 125 His Ser Met Gly Gly Gly Gly Thr Leu Arg Ile Ala Glu Gln Asn Pro 130 135 140 Ser Leu Lys Ala Ala Val Pro Leu Thr Pro Trp His Thr Asp Lys Thr 145 150 155 160 Phe Asn Thr Ser Val Pro Val Leu Ile Val Gly Ala Glu Ala Asp Thr 165 170 175 Val Ala Pro Val Ser Gln His Ala Ile Pro Phe Tyr Gln Asn Leu Pro 180 185 190 Ser Thr Thr Pro Lys Val Tyr Val Glu Leu Asp Asn Ala Ser His Phe 195 200 205 Ala Pro Asn Ser Asn Asn Ala Ala Ile Ser Val Tyr Thr Ile Ser Trp 210 215 220 Met Lys Leu Trp Val Asp Asn Asp Thr Arg Tyr Arg Gln Phe Leu Cys 225 230 235 240 Asn Val Asn Asp Pro Ala Leu Ser Asp Phe Arg Thr Asn Asn Arg His 245 250 255 Cys Gln <![CDATA[ <210> 2]]> <![CDATA[ <211> 594]]> <![CDATA[ <212> PRT]]> <![CDATA[ <213> Artificial sequence <![CDATA[ <220> ]]> <![CDATA[ <223> MHET enzyme E. edione <![CDATA[ <400> 2]]> Cys Ala Gly Gly Gly Ser Thr Pro Leu Pro Leu Pro Gln Gln Gln Pro 1 5 10 15 Pro Gln Gln Glu Pro Pro Pro Pro Pro Val Pro Leu Ala Ser Arg Ala 20 25 30 Ala Cys Glu Ala Leu Lys Asp Gly Asn Gly Asp Met Val Trp Pro Asn 35 40 45 Ala Ala Thr Val Val Glu Val Ala Ala Trp Arg Asp Ala Ala Pro Ala 50 55 60 Thr Ala Ser Ala Ala Ala Leu Pro Glu His Cys Glu Val Ser Gly Ala 65 70 75 80 Ile Ala Lys Arg Thr Gly Ile Asp Gly Tyr Pro Tyr Glu Ile Lys Phe 85 90 95 Arg Leu Arg Met Pro Ala Glu Trp Asn Gly Arg Phe Phe Met Glu Gly 100 105 110 Gly Ser Gly Thr Asn Gly Ser Leu Ser Ala Ala Thr Gly Ser Ile Gly 115 120 125 Gly Gly Gln Ile Ala Ser Ala Leu Ser Arg Asn Phe Ala Thr Ile Ala 130 135 140 Thr Asp Gly Gly His Asp Asn Ala Val Asn Asp Asn Pro Asp Ala Leu 145 150 155 160 Gly Thr Val Ala Phe Gly Leu Asp Pro Gln Ala Arg Leu Asp Met Gly 165 170 175 Tyr Asn Ser Tyr Asp Gln Val Thr Gln Ala Gly Lys Ala Ala Val Ala 180 185 190 Arg Phe Tyr Gly Arg Ala Ala Asp Lys Ser Tyr Phe Ile Gly Cys Ser 195 200 205 Glu Gly Gly Arg Glu Gly Met Met Leu Ser Gln Arg Phe Pro Ser His 210 215 220 Tyr Asp Gly Ile Val Ala Gly Ala Pro Gly Tyr Gln Leu Pro Lys Ala 225 230 235 240 Gly Ile Ser Gly Ala Trp Thr Thr Gln Ser Leu Ala Pro Ala Ala Val 245 250 255 Gly Leu Asp Ala Gln Gly Val Pro Leu Ile Asn Lys Ser Phe Ser Asp 260 265 270 Ala Asp Leu His Leu Leu Ser Gln Ala Ile Leu Gly Thr Cys Asp Ala 275 280 285 Leu Asp Gly Leu Ala Asp Gly Ile Val Asp Asn Tyr Arg Ala Cys Gln 290 295 300 Ala Ala Phe Asp Pro Ala Thr Ala Ala Asn Pro Ala Asn Gly Gln Ala 305 310 315 320 Leu Gln Cys Val Gly Ala Lys Thr Ala Asp Cys Leu Ser Pro Val Gln 325 330 335 Val Thr Ala Ile Lys Arg Ala Met Ala Gly Pro Val Asn Ser Ala Gly 340 345 350 Thr Pro Leu Tyr Asn Arg Trp Ala Trp Asp Ala Gly Met Ser Gly Leu 355 360 365 Ser Gly Thr Thr Tyr Asn Gln Gly Trp Arg Ser Trp Trp Leu Gly Ser 370 375 380 Phe Asn Ser Ser Ala Asn Asn Ala Gln Arg Val Ser Gly Phe Ser Ala 385 390 395 400 Arg Ser Trp Leu Val Asp Phe Ala Thr Pro Pro Glu Pro Met Pro Met 405 410 415 Thr Gln Val Ala Ala Arg Met Met Lys Phe Asp Phe Asp Ile Asp Pro 420 425 430 Leu Lys Ile Trp Ala Thr Ser Gly Gln Phe Thr Gln Ser Ser Met Asp 435 440 445 Trp His Gly Ala Thr Ser Thr Asp Leu Ala Ala Phe Arg Asp Arg Gly 450 455 460 Gly Lys Met Ile Leu Tyr His Gly Met Ser Asp Ala Ala Phe Ser Ala 465 470 475 480 Leu Asp Thr Ala Asp Tyr Tyr Glu Arg Leu Gly Ala Ala Met Pro Gly 485 490 495 Ala Ala Gly Phe Ala Arg Leu Phe Leu Val Pro Gly Met Asn His Cys 500 505 510 Ser Gly Gly Pro Gly Thr Asp Arg Phe Asp Met Leu Thr Pro Leu Val 515 520 525 Ala Trp Val Glu Arg Gly Glu Ala Pro Asp Gln Ile Ser Ala Trp Ser 530 535 540 Gly Thr Pro Gly Tyr Phe Gly Val Ala Ala Arg Thr Arg Pro Leu Cys 545 550 555 560 Pro Tyr Pro Gln Ile Ala Arg Tyr Lys Gly Ser Gly Asp Ile Asn Thr 565 570 575 Glu Ala Asn Phe Ala Cys Ala Ala Pro Pro Leu Glu His His His 580 585 590 His His <![CDATA[ <210> 3]]> <![CDATA[ <211> 267]]> <![CDATA[ <212> PRT]]> <![CDATA[ <213> Artificial sequence <![CDATA[ <220> ]]> <![CDATA[ <223> Polyester degrading enzymes <![CDATA[ <400> 3]]> Met Ala Asn Pro Tyr Glu Arg Gly Pro Asp Pro Thr Glu Ser Ser Ile 1 5 10 15 Glu Ala Val Arg Gly Pro Phe Ala Val Ala Gln Thr Thr Val Ser Arg 20 25 30 Leu Gln Ala Asp Gly Phe Gly Gly Gly Thr Ile Tyr Tyr Pro Thr Asp 35 40 45 Thr Ser Gln Gly Thr Phe Gly Ala Val Ala Ile Ser Pro Gly Phe Thr 50 55 60 Ala Gly Gln Glu Ser Ile Ala Trp Leu Gly Pro Arg Ile Ala Ser Gln 65 70 75 80 Gly Phe Val Val Ile Thr Ile Asp Thr Ile Thr Arg Leu Asp Gln Pro 85 90 95 Asp Ser Arg Gly Arg Gln Leu Gln Ala Ala Leu Asp His Leu Arg Thr 100 105 110 Asn Ser Val Val Arg Asn Arg Ile Asp Pro Asn Arg Met Ala Val Met 115 120 125 Gly His Ser Met Gly Gly Gly Gly Ala Leu Ser Ala Ala Ala Asn Asn 130 135 140 Thr Ser Leu Glu Ala Ala Ile Pro Leu Gln Gly Trp His Thr Arg Lys 145 150 155 160 Asn Trp Ser Ser Val Arg Thr Pro Thr Leu Val Val Gly Ala Gln Leu 165 170 175 Asp Thr Ile Ala Pro Val Ser Ser His Ser Glu Ala Phe Tyr Asn Ser 180 185 190 Leu Pro Ser Asp Leu Asp Lys Ala Tyr Met Glu Leu Arg Gly Ala Ser 195 200 205 His Leu Val Ser Asn Thr Pro Asp Thr Thr Thr Ala Lys Tyr Ser Ile 210 215 220 Ala Trp Leu Lys Arg Phe Val Asp Asp Asp Leu Arg Tyr Glu Gln Phe 225 230 235 240 Leu Cys Pro Ala Pro Asp Asp Phe Ala Ile Ser Glu Tyr Arg Ser Thr 245 250 255 Cys Pro Phe Leu Glu His His His His His His 260 265

[0172]

Claims

1. A method for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), wherein the method comprises performing a major enzymatic hydropolymerization step on the at least one polyester at a pH between 5.0 and 5.5 and at a temperature of 56°C + / - 1°C or 60°C + / - 1°C, wherein the enzymatic hydropolymerization step is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg based on the total weight of the liquid phase of the reaction medium, wherein at least 90% of the equivalent TA is in salt form, and wherein the major enzymatic hydropolymerization step is performed by contacting the plastic product in the reaction medium with an enzyme capable of degrading the at least one polyester, the enzyme being selected from the sequences SEQ ID n°1, SEQ ID n°2 and / or SEQ ID n°3.

2. The method of claim 1, wherein the main enzymatic hydropolymerization step is carried out in a reaction medium, wherein the liquid phase of the reaction medium contains an equivalent TA concentration between 20 g / kg and 80 g / kg, and wherein at least 95% of the equivalent TA in the liquid phase of the reaction medium is in salt form.

3. The method of claim 1 or 2, wherein the pH of the main enzymatic hydrolysis polymerization step is not adjusted.

4. The method of claim 1 or 2, wherein the equivalent TA concentration contained in the liquid phase of the reaction medium is between 5 g / kg and 110 g / kg.

5. The method of claim 1 or 2, wherein the reaction medium is obtained by performing a preliminary depolymerization step prior to the main enzymatic depolymerization step, the preliminary depolymerization step being performed by contacting the plastic product in the initial reaction medium with a depolymerizing agent selected from chemical and / or biological depolymerizing agents, the preliminary depolymerization step being performed at a given pH between 6.5 and 10.

6. The method of claim 5, wherein the initial depolymerization step is carried out by contacting the plastic product in an initial reaction medium with at least one enzyme of the polyester capable of degrading the plastic product, and wherein the pH is adjusted to a given pH between 7.00 and 9.50 by adding an alkali to the reaction medium, and / or includes a temperature between 50°C and 80°C.

7. The method of claim 5, wherein the pH of the preliminary depolymerization step is adjusted to the given pH until the equivalent TA concentration in the liquid phase of the reaction medium is between 5 g / kg and 110 g / kg, and wherein the main depolymerization step is carried out at a pH between 5 and 5.

5.

8. The method of claim 5, wherein both depolymerization steps are carried out by contacting the plastic product with at least one enzyme exhibiting polyester degradation activity at a pH between 4 and 9 and / or with at least two enzymes.

9. The method of claim 8, wherein the plastic product is simultaneously contacted with at least one PET enzyme and at least one MHET enzyme.

10. The method of claim 9, wherein the PET enzyme and the MHET enzyme are included in a multi-enzyme system.

11. The method of claim 8, wherein the plastic product is first contacted with the PET enzyme, and the MHET enzyme is introduced into the reaction medium after the PET enzyme.

12. The method of claim 5 for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), comprising: a. performing a preliminary enzymatic depolymerization step at a given pH adjusted to between 7.5 and 8.5 and at a temperature between 60°C and 72°C; and b. performing a major depolymerization step at a pH between 5.0 and 5.5 and at a temperature of 56°C + / - 1°C or 60°C + / - 1°C, wherein the pH is not adjusted, wherein each depolymerization step comprises contacting the plastic product with at least one enzyme capable of degrading the at least one polyester, wherein the major enzymatic depolymerization step is performed by contacting the plastic product in the reaction medium with an enzyme selected from the sequences SEQ ID n°1, SEQ ID n°2 and / or SEQ ID n°3, and wherein, based on the total weight of the liquid phase of the reaction medium, the equivalent TA concentration contained in the liquid phase of the reaction medium is between 5 g / kg and 110 g / kg. Stop the pH adjustment in step (a) when the pH is between g / kg.

13. The method of claim 12 for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), comprising: a. performing a preliminary depolymerization step by contacting the plastic product with at least one PET enzyme at a given pH adjusted between 7.5 and 8.5 and at a temperature between 60°C and 72°C; and b. performing a major depolymerization step by contacting the plastic product with an enzyme selected from sequences SEQ ID n°1, SEQ ID n°2 and / or SEQ ID n°3 at a pH between 5.0 and 5.5 and at a temperature of 56°C + / - 1°C or 60°C + / - 1°C, wherein the pH is not adjusted, and wherein the pH adjustment in step (a) is stopped when the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 95 g / kg.

14. The method of claim 12 for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), comprising: a. performing a preliminary depolymerization step by contacting the plastic product simultaneously with at least one PET enzyme and at least one MHET enzyme at a given pH adjusted between 7.5 and 8.5 and at a temperature between 60°C and 72°C; and b. performing a primary depolymerization step at a pH between 5.0 and 5.5 and at a temperature of 56°C + / - 1°C or 60°C + / - 1°C, wherein the pH is not adjusted, wherein the pH adjustment in step (a) is stopped when the equivalent TA concentration in the liquid phase of the reaction medium is between 30 g / kg and 95 g / kg.

15. The method of claim 12 for degrading a plastic product comprising at least one polyester containing at least one terephthalic acid monomer (TA), wherein during the main depolymerization step (b), at least one additional amount of PET enzyme and / or MHET enzyme is added to the reaction medium once or several times.

16. The method of claim 1 or 2, wherein the equivalent TA concentration in the reaction medium is obtained by adding TA salt and / or oligomer salt and / or by adding TA in its acidic and basic forms to the reaction medium prior to the main depolymerization step, until the equivalent TA concentration in the liquid phase of the reaction medium reaches between 10 g / kg and 80 g / kg based on the total weight of the liquid phase of the reaction medium, wherein at least 90% of the equivalent TA in the liquid phase is in salt form, and wherein the main depolymerization step is carried out at a pH between 5 and 5.

5.

17. The method of claim 1 or 2, wherein the concentration of polyester introduced into the reaction medium before the main depolymerization step or before the preliminary depolymerization step is greater than 150 g / kg based on the total weight of the reaction medium.

18. The method of claim 1 or 2, wherein the polyester is selected from PET, PTT, PBT, PEIT, PBAT, PCT, PETG, PBST and PBSTIL.

19. The method of claim 1 or 2, wherein the polyester is subjected to an amorphization and / or foaming step prior to the main depolymerization step or prior to the preliminary depolymerization step, and / or wherein the method further comprises a step of recovering and, where appropriate, purifying the oligomers and / or monomers generated by the depolymerization of the polyester.

20. A method for generating TA from a plastic article containing at least one polyester having at least one TA monomer, comprising subjecting the plastic article to a primary enzymatic hydropolymerization step at a pH between 5.0 and 5.5 and at a temperature of 56°C + / - 1°C or 60°C + / - 1°C, and recovering and, if appropriate, purifying the monomer and / or oligomer, wherein the enzymatic hydropolymerization step is carried out in a reaction medium, wherein the equivalent TA concentration in the liquid phase of the reaction medium is at least 10 g / kg based on the total weight of the liquid phase of the reaction medium, and wherein at least 90% of the equivalent TA in the liquid phase of the reaction medium is in salt form, and wherein the primary enzymatic hydropolymerization step is carried out by contacting the plastic product in the reaction medium with an enzyme capable of degrading the at least one polyester, the enzyme being selected from the sequences SEQ ID n°1, SEQ ID n°2 and / or SEQ ID n°3.