ENZYMATIC DEGRADATION PROCEDURE OF POLYETHYLENE TEREPHTHALATE

Abstract

The present invention relates to a process for the enzymatic depolymerization of polyethylene terephthalate (PET) by contacting said PET with an enzyme capable of depolymerizing said PET, characterized in that the PET has an initial degree of crystallinity of up to 25%;The depolymerization step is carried out at a temperature T equal to the Tg + / - 10°C of said PET. The enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than the crystallization time (tR) of said PET, where tD represents the time required for said enzyme to depolymerize at least 80% of said PET at said temperature T, and tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T. The selected enzyme has an amino acid sequence that is at least 90% identical to SEQ ID NO: 1 and comprises at least one combination of mutations selected from F2081 + D203C + S248C + Y92G, F208W + D203C + S248C + V170I + Y92G with respect to SEQ ID NO: 1.;

Description

ENZYMATIC DEGRADATION PROCEDURE OF POLYETHYLENE TEREPHTHALATE TECHNICAL FIELD OF THE INVENTION The present invention relates to an enzymatic depolymerization process for polyethylene terephthalate (PET), especially as contained in a plastic material. The process according to the invention can be implemented, particularly on an industrial or semi-industrial scale. BACKGROUND OF THE TECHNIQUE Plastic products are durable and inexpensive materials that can be used to manufacture a wide variety of products for diverse applications (food packaging, textiles for clothing, etc.). Consequently, plastic production has increased dramatically in recent decades. Most of these products are used for short-term applications, resulting in the accumulation of plastic waste and the need for its treatment. Among the various polymers that make up these plastics, polyethylene terephthalate (PET) stands out. This aromatic polyester, produced from terephthalic acid and ethylene glycol, is used in numerous applications such as food packaging (bottles, jars, cans, trays, bags), as well as in the production of textiles for clothing, home decor (carpets), linens, and more. To address the environmental and economic problems of waste accumulation, recycling and energy recovery technologies have been developed. Mechanical recycling remains the most widely used process today, but it presents numerous drawbacks. Its implementation requires sophisticated and costly sorting and leads to the production of lower-quality recycled plastics destined for lower-value applications (due to reduced molecular weight and uncontrolled additives). Furthermore, these recycled plastics are not competitive with virgin, petroleum-based plastics. Recently, innovative enzymatic recycling processes for plastic products have been developed, and are described in particular in patent applications WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265 and WO LLCRbn / Lzzza / YiAi 2017 / 198786. Unlike traditional mechanical recycling processes, these enzymatic processes, through enzymatic depolymerization of the polymer contained in the plastic, allow the polymer to be broken down into its main constituents (monomers). The resulting monomers can then be purified and used to repolymerize new polymers. Thanks to the specificity of the enzymes, these enzymatic processes eliminate the need for costly plastic sorting and offer infinite recycling, yielding recycled polymers of equivalent quality to petroleum-derived polymers. These processes, in particular, allow the production of terephthalic acid and ethylene glycol from PET. BRIEF SUMMARY OF THE INVENTION By studying the enzymatic depolymerization processes of PET, the applicant has managed to develop an optimized procedure that allows the enzymatic depolymerization of plastics containing PET at a temperature close to the Tg of said PET, so that the chains of said polymer are more easily accessible to the depolymerization enzyme and thus increase the rate of depolymerization. To achieve such a procedure, the inventor had to overcome paradoxical problems. Indeed, the enzymes suitable for depolymerizing polymers are predominantly more active on amorphous polymers than on semicrystalline polymers. However, although a depolymerization procedure at a temperature close to the Tg of a polymer might theoretically improve the enzyme's accessibility to the polymer chains to be depolymerized by increasing their mobility, when a polymer is subjected to a temperature near or above its Tg, it tends to recrystallize more rapidly, thus hindering depolymerization by the enzyme. The inventor has therefore demonstrated that it is possible to carry out a PET depolymerization process at a temperature close to or above the Tg of said PET, ensuring, on the one hand, that the degree of crystallinity of the PET is sufficiently low before the depolymerization step and, on the other hand, selecting a suitable enzyme to depolymerize said PET with a depolymerization time shorter than the time required for said PET to reach a degree of crystallinity incompatible with enzymatic depolymerization. The process developed by the inventor allows for maintaining depolymerization rates within a reactor that are compatible with its implementation on an industrial scale. As an example, the inventor achieved the depolymerization of more than 90% of a PET in less than 10 h at a temperature of 72 °C.Advantageously, the procedure of the invention can be applied to the depolymerization and / or recycling of plastics containing PET. Therefore, the invention relates to an enzymatic depolymerization process of polyethylene terephthalate (PET) by contacting said PET with an enzyme suitable for depolymerizing said PET, characterized in that the PET has an initial degree of crystallinity of at most 25%, the depolymerization step is carried out at a temperature T equal to the Tg + / - 10 °C of said PET, and the enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than the crystallization time (tR) of said PET, wherein the time tD represents the time required for said enzyme to depolymerize at least 80% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T. The depolymerization step is preferably carried out at a temperature T between 66 °C and 80 °C, preferably between 68 °C and 73 °C, with a time tD less than or equal to 20 h, preferably less than 16 h. FIGURE DESCRIPTION Figure 1: Recrystallization kinetics of PET contained in a plastic material during incubation of said material at different temperatures. DETAILED DESCRIPTION OF THE INVENTION Definitions In the context of the invention, the term "plastic material" refers to plastic products (such as sheets, trays, films, tubes, blocks, fibers, fabrics, etc.) and the plastic compositions used to make the plastic products. Preferably, the plastic material is composed of amorphous and / or semicrystalline polymers. The plastic material may also contain additional polymer(s), substances, or additives, such as LLCRbn / Lznza / YiAi plasticizers, mineral or organic fillers, colorants, etc. Thus, in the context of the invention, the plastic material refers to any plastic product and / or plastic composition comprising at least one polymer in semicrystalline and / or amorphous form and more especially at least one PET. Plastic products refer particularly to manufactured plastic products, such as rigid or flexible packaging (films, bottles, trays), agricultural films, bags, disposable items, textiles, fabrics, non-wovens, floor coverings, plastic waste or waste fibers, etc. The term polymer refers to a chemical compound whose structure consists of multiple repeating units (i.e., monomers) joined by covalent chemical bonds. In the context of the invention, the term polymer refers more specifically to such chemical compounds that form part of the composition of plastic materials. The term polyester refers to a polymer that contains an ester functional group in the backbone of its structure. The ester functional group is characterized by a bond between a carbon atom and three other atoms: a single bond to another carbon atom, a double bond to an oxygen atom, and a single bond to another oxygen atom. The oxygen atom bonded to the carbon atom by a single bond is, in turn, bonded to another carbon atom by a single bond. Polyesters can be composed of a single type of monomer (i.e., a homopolymer) or of at least two different monomers (i.e., a copolymer). Polyesters can be aromatic, aliphatic, or semiaromatic. For example, polyethylene terephthalate is a semiaromatic copolymer composed of two monomers, terephthalic acid and ethylene glycol. In the context of the invention, the term semicrystalline polymers refers to partially crystalline polymers in which crystalline and amorphous regions coexist. The degree of crystallinity of a semicrystalline polymer can be estimated by various analytical methods and is generally between 10% and 90%. A polymer with a degree of crystallinity below 10% can be considered amorphous. A depolymerization process relating to a polymer or plastic material refers to a process by which a polymer, or at least one polymer of a plastic material, is degraded into smaller molecules, such as monomers and / or oligomers. In the case of the present invention, a LLCRbn / Lznza / YiAi The depolymerization process of PET or a plastic material containing PET refers to a process in which PET is degraded into monomers such as terephthalic acid and / or ethylene glycol, and / or into oligomers such as dimethyl terephthalate (DMT), methyl-2-hydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET). PET Selection The depolymerization process according to the invention is based on the enzymatic depolymerization of PET by contacting the PET with at least one suitable enzyme. More particularly, the inventor has developed an enzymatic depolymerization process for PET comprising a depolymerization step carried out at a temperature T between the Tg - 10 °C and the Tg + 10 °C of the PET, starting from PET having an initial degree of crystallinity of no more than 25%. Also, according to a particular embodiment of the invention, the PET is selected to have an initial degree of crystallinity of no more than 25%. According to the invention, the PET subjected to the depolymerization stage is an amorphous and / or semicrystalline PET at the beginning of the depolymerization stage, with an initial degree of crystallinity of 25% or less. The initial degree of crystallinity refers to the degree of crystallinity of the PET at the start of the depolymerization stage, that is, before the PET is brought into contact with a depolymerization enzyme. Thus, if the PET is subjected to one or more pretreatment stages (amortization, micronization), the initial degree of crystallinity corresponds to the degree of crystallinity after these pretreatment stages. The degree of crystallinity of a semicrystalline polymer can be estimated by various analytical methods and is generally between 10% and 90%. For example, differential scanning calorimetry (DSC) or X-ray diffraction can be used to determine the degree of crystallinity of polymers. Other techniques are also suitable for determining the crystallinity of polymers, but with less reliability, such as small-angle X-ray scattering (SAXS) or large-angle X-ray scattering (WAXS) and infrared spectroscopy. In this application, crystallinity is measured by differential calorimetric analysis (DSC). More specifically, the LLCRbn / Lznza / YiAi DSC experiments were performed using the following protocol: a small amount of plastic material (several mg) is heated at a rate of LLCRbn / Lznza / YiAi constant heating, from room temperature or from a temperature below room temperature to a temperature above the melting temperature (Tf) of the polymer. Heat flow data are collected and plotted as a function of temperature. The degree of crystallinity (Xc) expressed as a percentage (%) is calculated according to the following formula: Xc(%) (AHf - hHcc) weight * Δ fif 100 %X 100 % Understanding that: - AHf corresponds to the enthalpy of fusion, which can be determined by integrating the endothermic fusion peak, - AHcc corresponds to the cold crystallization enthalpy, which is determined by integrating the exothermic cold crystallization peak, - weight represents the weight fraction of polyester in the plastic, and - AHf100% corresponds to the enthalpy of fusion of a completely crystalline polymer, and can be found in the literature. For example, an AHf100% of PET corresponds, according to the literature, to 125.5 J / g (Polymer Data Handbook, second edition, edited by James E. Mark, OXFORD, 2009). The margin of error in measuring the degree of crystallinity is approximately 10%. Thus, a crystallinity rating of 25% corresponds to a degree of crystallinity between 22.5% and 27.5%. According to one embodiment of the process, a PET is selected that has a degree of crystallinity of less than 25%, + / - 10%. In a preferred embodiment, the PET has an initial degree of crystallinity of less than 20%, + / - 10%. In another preferred embodiment, the PET subjected to the depolymerization step is an amorphous PET, i.e., it has a degree of crystallinity of less than 10%, + / - 10%. According to the invention, it is possible to implement a PET buffering step before the depolymerization step, by any means known to the skilled worker, to achieve an initial degree of crystallinity of 25% or less. This buffering step is described in particular in application WO 2017 / 198786. In one particular embodiment, the depolymerization process according to the invention is implemented with a plastic material comprising at least PET. In a preferred embodiment, the PET represents at least 80% by weight of said plastic material, preferably at least 85%, 90%, or 95%. In a particular context of the invention, the term "plastic material" designates any plastic product in the form of fibers, such as textiles, fabrics, non-wovens, yarns, etc. Thus, in a particular embodiment, the plastic material is selected from fibers and / or waste fibers and / or textile waste, and PET represents at least 60% by weight of the total weight of said plastic material, preferably at least 65%, 70%, 75%, 80%, 85%, 90%, or 95%. In one particular embodiment, the plastic material comprises a mixture of PET and polylactic acid (PLA), a mixture of PET and polyethylene (PE), a mixture of PET and polytrimethylene terephthalate (PTT), a mixture of PET and polyamide (PA), or a mixture of PET and cotton. Advantageously, the plastic materials introduced into the reactor are plastic waste or waste fibers. This waste may originate from the collection sector destined for recycling, but it may also be waste from the production or recycling industries and, therefore, may contain compounds other than plastic waste. This implies that PET can be introduced into the reactor along with other elements present in these streams (such as paper, cardboard, aluminum, glue, etc.).In a particular embodiment, the reactor in which the depolymerization stage is implemented is loaded with various plastic materials containing at least PET, preferably containing at least 80% PET, with respect to the total weight of plastic materials, preferably at least 85%, 90%, 95%. According to the invention, PET is characterized by its initial glass transition temperature (Tg), i.e., before contact with a depolymerizing enzyme. If the PET undergoes a pretreatment step (cure, micronization), it is characterized by its Tg after these pretreatment steps. This temperature can be estimated using various analytical methodologies. For example, differential scanning calorimetry (DSC) or differential thermal analysis (DTA) can be used to determine the crystallinity Tg of a polymer. In the present description, Tg corresponds to the glass transition temperature measured by DSC during the first temperature scan, as shown in the examples. Generally, the margin of error in the Tg measurement is approximately 2 °C. In one particular embodiment of the invention, the initial glass transition temperature (Tg) of the PET is between 60 °C and 90 °C, preferably between 60 °C and 85 °C. In another particular embodiment, the initial Tg of the PET is between 65 °C ± 1 °C and 80 °C ± 1 °C. In another particular embodiment, the initial Tg of the PET is between 65 °C ± 2 °C and 80 °C ± 2 °C. In yet another particular embodiment, the initial Tg of the PET is between 60 °C ± 2 °C and 70 °C ± 2 °C. According to the invention, it is possible to perform a pretreatment step of the PET polyester before the depolymerization step and, in particular, a grinding step of the PET or the PET-containing plastic material before the polyester depolymerization step. In a preferred embodiment, the PET or the PET-containing plastic material is reduced to powder form by any suitable means known to the person skilled in the art. In this particular case, the PET, or the PET-containing plastic material, is advantageously micronized so as to be transformed into a powder form. In one particular embodiment, the PET or PET-containing plastic material introduced into the reactor is in powder form with an average particle size (d50) of less than 2 mm, preferably less than 1 mm. In another embodiment, the PET or PET-containing plastic material introduced into the reactor is in powder form with an average particle size (d50) of less than 500 µm. In a particular embodiment, the depolymerization process comprises a PET buffering step, followed by a crushing and / or micronization step of the PET or the plastic material containing the PET before the PET depolymerization step. In one particular embodiment, the depolymerization process comprises a PET buffering step prior to the PET depolymerization step, and the PET or PET-containing plastic material is introduced into the reactor in the form of granules from the extruder used for buffering. In this way, the PET or PET-containing plastic material is introduced in the form of granules smaller than 2 mm. LLCRbn / Lzzza / YiAi preferably with a size less than 1 mm. Enzyme selection According to the invention, the depolymerization process is implemented using an enzyme capable of depolymerizing PET. More specifically, the depolymerization step is carried out using an enzyme selected such that the depolymerization time (tD) of PET using said enzyme is strictly less than the crystallization time (tR) of said PET. According to the invention, the crystallization time (tR) of PET is defined as the time required for PET with an initial crystallinity Xc to reach a crystallinity rate, or degree, of 35% or less at a temperature T. This time depends on the material's age and / or polymer age (i.e., the presence of additives and comonomers), its molecular weight, its glass transition temperature (Tg), and its thermal history (previous treatments involving cooling and / or heating, such as abatement or micronization). This time is measured under temperature-controlled conditions and is unaffected by agitation and / or pH during measurement. According to the invention, the crystallization time (tR) of PET can be measured at a temperature T by incubating the PET-containing plastic material at that temperature T and regularly measuring the degree of crystallinity (using DSC) of samples taken at different time intervals. According to the invention, the depolymerization time (tD) represents the time required for the polymer-degrading enzyme to depolymerize at least 80% of the polymer at a temperature T. In one particular embodiment, this time is determined at the enzyme's optimum pH and enzyme saturation concentration, i.e., a concentration above which the reaction rate is not enhanced by the addition of enzyme. Thus, the tD time corresponds to the time required for the enzyme to release 80% of the monomers present in the polymer. In a particular case of the invention, the tD time corresponds to the time required to obtain, after contact of the enzyme with the PET, 80% of the terephthalic acid (TA) equivalents present in the PET, the TA equivalent corresponding to the free TA and the TA present in the BHET and MHET oligomers. In another particular embodiment of the invention, the tD time corresponds to the time required to CRbn i znz -i / YiAi obtain, after contact of the enzyme with the PET, 80% of monoethylene glycol (MEG) equivalents in the PET, the MEG equivalent corresponding to the free MEG and the MEG present in the oligomers of BHET and MHET. It is specified that the measurement of times tD and tR is performed at the same temperature T. According to the invention, the enzyme is advantageously selected from enzymes that have a melting temperature (Tf) strictly higher than the temperature T at which the depolymerization step is carried out. In the context of the invention, the melting point (Tf) corresponds more specifically to the temperature at which half of the enzyme in question is unfolded or misfolded, such that it has lost all or part of its activity relative to the activity of the correctly folded enzyme. Tf allows, in particular, the estimation of the thermostability of the enzyme in question. Tf can be measured by any means known to a person skilled in the art, especially differential fluorometric analysis (DFA). Alternatively, Tf can be evaluated by analyzing the protein folding using the circular dichroism method. Preferably, Tf is measured by DFA, as described in the experimental section. In a preferred mode, the enzyme is selected from enzymes having a Tf greater than or equal to temperature T+10°C, preferably greater than or equal to temperature T+15°C, more preferably greater than or equal to temperature T+20°C. The depolymerization activity of an enzyme on a polymer can be evaluated by any means known to the skilled worker. For example, it can be evaluated by measuring the polymer mass loss or the polymer depolymerization rate, i.e., the amount of monomers and / or oligomers produced over a period of time. Thus, in the context of the invention, the depolymerization activity of a PET-degrading enzyme can be evaluated by measuring the amounts of oligomers (BHET and / or MHET) and / or monomers (terephthalic acid and / or ethylene glycol and / or DMT) released under specific temperature and pH conditions by contacting the PET or PET-containing plastic material with the enzyme. The depolymerization activity of LLCRbn / Lznza / YiAi can also be assessed by monitoring the addition of base during the depolymerization reaction. Base is effectively added to neutralize the terephthalic acid produced during depolymerization, thereby regulating the pH. Similarly, the amount of base added during the reaction allows for the measurement of the amount of terephthalic acid produced. Preferably, a basic solution is added to maintain the reaction medium at the enzyme's optimum pH. Advantageously, this enzyme is selected from among cutinases, lipases, and esterases that degrade PET. In particular, this enzyme is selected from among the esterases that degrade PET. For example, the enzyme can be selected from cutinases obtained from Thermobifida cellulosityca, Thermobifida halotolerans, Thermobifida fusca, Thermobifida alba, Bacillus subtilis, Fusarium solani pisi, Humicola insolens (such as referenced A0A075B5G4 in the Uniprot repository), Sirococcus conigenus, Pseudomonas mendocina, and Thielavia terrestris or a variant thereof. In other cases, the cutinase is selected from metagenomic banks of cutinases, such as the LC-Cutinase described in Sulaiman et al, 2012, or variants of the latter. In other cases, the enzyme is a lipase, preferably from Ideonella sakaiensis. Alternatively, the enzyme can be selected from commercial enzymes, such as Novozym 51032 or variants thereof. Of course, it is possible to load the reactor with several enzymes, and in particular with at least two of the enzymes mentioned above. In a particular case, the enzyme (or enzymes) is selected from among those enzymes that have an amino acid sequence exhibiting at least 75% identity with SEQ ID No. 1 and / or SEQ ID No. 2 and / or SEQ ID No. 3 and / or SEQ ID No. 4 and / or SEQ ID No. 5, and that have PET depolymerization activity. LLCRbn / Lzzza / YiAi In one particular mode, the enzyme is capable of depolymerizing the polymer into oligomers. In this case, it advantageously associates with an enzyme capable of depolymerizing these oligomers into monomers. In a specific example, the two enzymes are then selected from among those that have an amino acid sequence exhibiting at least 75% identity with SEQ ID No. 4 and / or SEQ ID No. 5. The inventor has identified that the process of the invention was particularly suitable in the particular case in which the selected enzyme has an amino acid sequence that exhibits at least 90% identity with SEQ ID No. 1 and comprises at least one combination of mutations selected from F208I + D203C + S248C + Y92G, F208W + D203C + S248C + Y92G or F208I + D203C + S248C + V170I + Y92G with respect to SEQ ID No. 1. Advantageously, the time tD is less than or equal to 20 h, preferably less than or equal to 18 h, 16 h, 14 h, 12 h, or 10 h. In one embodiment, the time tD is between 1 h and 16 h, preferably between 1 h and 10 h. Conversely, the crystallization time tR is preferably greater than or equal to 20 h, preferably greater than or equal to 18 h, 16 h, 14 h, 12 h, or 10 h. In a particular embodiment, the time tR corresponds to the time required for said PET, which has an initial crystallinity less than or equal to 25%, to reach a crystallinity of 30%, or less than 30%, at said temperature T. Thus, in a particular embodiment, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - PET has an initial crystallinity level of up to 25%; - the depolymerization stage is carried out at a temperature T equal to the Tg + / -10 °C of said PET, and - the enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the tD time represents the time required for the selected enzyme to depolymerize at least 80% of said PET at said temperature T, and the tR time represents the time required for said PET to achieve a degree of crystallinity of 30% or less than 30%, at said temperature T. LLCRbn / Lzzza / YiAi Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. Thus, in a particular embodiment, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - a PET is selected that has an initial degree of crystallinity of no more than 25%; - an enzyme is selected that can degrade PET, such that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (tR) of said PET, wherein the time tD represents the time required for the selected enzyme to depolymerize at least 80% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of 30% or less at said temperature T; and - an enzymatic depolymerization step of said PET is carried out by bringing said PET into contact with said enzyme at a temperature T equal to the Tg + / - 10 °C of said PET. Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. In a preferred embodiment, the time tD corresponds to the time required by said enzyme to depolymerize at least 85% of said PET at said temperature T, preferably at least 90%. Thus, in a particular embodiment, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - PET has an initial crystallinity level of up to 25%; - the depolymerization stage is carried out at a temperature T equal to the Tg + / -10 °C of said PET, and - the enzyme is selected so that the depolymerization time (tD) of PET using that enzyme is strictly less than a crystallization time LLCRbn / Lznza / YiAi (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 85% of said PET at said temperature T, preferably at least 90%, and the time tR represents the time required for said PET to achieve a degree of crystallinity of at most 35%, preferably at most 30% at said temperature T. Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. In a particular embodiment, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - a PET is selected that has an initial degree of crystallinity of no more than 25%; - an enzyme is selected that can depolymerize PET, such that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 85% of said PET at said temperature T, preferably at least 90%, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35%, preferably a degree of crystallinity of at most 30% at said temperature T; and - a depolymerization step of said PET is carried out by bringing said enzyme into contact with said PET at a temperature T equal to the Tg + / - 10 °C of said PET. Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. More generally, the enzymatic depolymerization process of PET according to the invention comprises the steps in which: - a PET is selected that has an initial degree of crystallinity such as LLCRbn / Lzzza / YiAi maximum of 25%; - An enzyme is selected that can degrade PET, such that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required for said enzyme to depolymerize at least 80% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of 35% or less at said temperature T - A depolymerization step is carried out by bringing the enzyme into contact with the PET, at a temperature T equal to the Tg + / - 10 °C of said PET. Depolymerization stage The depolymerization step according to the invention is advantageously implemented in a reactor with a volume greater than 500 milliliters (mL), greater than 1 liter (L), preferably greater than 2 L, 5 L, or 10 L. In one particular embodiment, the process of the invention can be implemented on an industrial and semi-industrial scale. Therefore, it is possible to use a reactor with a volume greater than 100 L, 150 L, 1000 L, 10000 L, 100000 L, or 400000 L. According to the invention, it is possible to load the reactor intended for the polymerization stage directly with PET, or with plastic materials that contain at least PET. According to the invention, the amount of enzyme introduced during the depolymerization step is advantageously sufficient to allow total or almost total depolymerization of said PET (i.e., a quantity degradation of at least 80% by weight with respect to the weight of said PET introduced) in reaction times compatible with an industrial-scale implementation. In one embodiment, the weight ratio of the amount of enzyme introduced to the amount of PET introduced is between 0.01 / 1000 and 3 / 1000. Preferably, the ratio of the amount of enzyme introduced to the amount of PET introduced is between 0.5 / 1000 and 2.5 / 1000, more preferably between 1 / 1000 and 2 / 1000. In one particular case, the amount of enzyme introduced is greater than or equal to the amount of enzyme required to achieve a saturating enzyme concentration. In one particular case, the The enzyme LLCRbn / Lznza / YiAi may be introduced in the form of a composition comprising, in addition to the enzyme, excipients, which may be selected from buffers commonly used in biochemistry, preservatives, and / or stabilizing agents. The amount of enzyme then advantageously refers to the amount of enzyme free of any excipients. According to the invention, the PET depolymerization step is carried out at a temperature T equal to the Tg + / - 10 °C of said PET, where Tg is the temperature of said PET before the depolymerization step. Advantageously, the temperature is kept below the enzyme inactivation temperature. In one particular embodiment, the PET depolymerization step is carried out at a temperature T between Tg - 10 °C and Tg + 5 °C of PET. In another particular embodiment, the depolymerization step is carried out at a temperature T between Tg - 8 °C and Tg + 2 °C of PET. In yet another particular embodiment, the depolymerization step is carried out at a temperature T between Tg - 10 °C and Tg - 5 °C of PET. In one particular embodiment, the PET has a glass transition temperature (Tg) of 78 °C ± 2 °C and the depolymerization step is carried out at a temperature T of 70 °C ± 2 °C. In another particular embodiment, the PET has a Tg of 78 °C ± 2 °C and the depolymerization step is carried out at a temperature T of 72 °C ± 2 °C. In another particular embodiment, the PET has a Tg of 75 °C ± 2 °C and the depolymerization step is carried out at a temperature T of 68 °C ± 2 °C. In yet another particular embodiment, the PET has a Tg of 75 °C ± 2 °C and the depolymerization step is carried out at a temperature T of 70 °C ± 2 °C. In another particular embodiment, the PET has a Tg between 70 °C+ / -2 °C and 75 °C + / -2 °C and the depolymerization step is carried out at a temperature T between 65 °C + / -2 °C and 72 °C + / -2 °C. In one particular embodiment, the PET is derived from a plastic material selected from fibers and / or waste fibers and / or textiles, and has a glass transition temperature (Tg) between 60°C ± 1°C and 75°C ± 1°C, and the depolymerization step is carried out at a temperature T of 65°C ± 2°C. In another particular embodiment, the PET is derived from a plastic material selected from fibers and / or waste fibers and / or textiles, and has a glass transition temperature (Tg) between 60°C ± 1°C and 70°C ± 1°C, and the depolymerization step is carried out at a temperature T of 60°C ± 2°C. LLCRbn / Lzzza / YiAi In one particular embodiment, the depolymerization step is carried out at a temperature T between 66 °C and 80 °C, preferably between 68 °C and 73 °C. In another particular embodiment, the depolymerization step is carried out at a temperature T of 72 °C ± 1 °C. In yet another particular embodiment, the depolymerization step is carried out at a temperature T of 70 °C ± 1 °C. Thus, in a particular embodiment, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - PET has an initial crystallinity level of up to 25% and a Tg between 65 °C+ / -1 °C and 80 °C+ / -1 °C; - the depolymerization step is carried out at a temperature T between 66 °C and 80 °C, preferably between 68 °C and 73 °C, and - the enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the tD time represents the time required for the selected enzyme to depolymerize at least 80% of said PET at said temperature T, and the tR time represents the time required for said PET to achieve a degree of crystallinity of 35% or less than 35%, at said temperature T. Advantageously, a PET is selected that has an initial crystallinity rate of no more than 25%, preferably no more than 20%. In a particular embodiment, a PET is selected that has an initial degree of crystallinity of no more than 25% and a Tg between 65 °C ± 1 °C and 80 °C ± 1 °C. In another particular mode of implementation, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - PET has an initial crystallinity level of up to 25% and a Tg between 65 °C+ / -1 °C and 80 °C+ / -1 °C; - the depolymerization stage is carried out at a temperature T of 72 °C+ / - 1 °C, and - the enzyme is selected so that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time csbn i znz -i / YiAi (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to achieve a degree of crystallinity of at most 35% at said temperature T. Preferably, tR represents the time required for said PET to reach a degree of crystallinity of at most 30% at said temperature T. Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. In another particular mode of implementation, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - a PET is selected that has an initial crystallinity degree of at most 25% and a Tg between 75 °C+ / -1 °C and 80 °C+ / -1 °C; - the depolymerization stage is carried out at a temperature T of 72 °C+ / - 1 °C, and - the enzyme is selected so that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T. Preferably, tR represents the time required for said PET to reach a degree of crystallinity of at most 30% at said temperature T. Advantageously, the enzyme is selected from enzymes that have a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. In another particular mode of implementation, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that LLCRbn / Lzzza / YiAi - PET has an initial crystallinity level of up to 25% and a Tg between 65 °C+ / -1 °C and 80 °C+ / -1 °C; - the depolymerization stage is carried out at a temperature T of 70 °C+ / - 1 °C, and The enzyme is selected so that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T. Preferably, tR represents the time required for said PET to reach a degree of crystallinity of at most 30% at said temperature T. Advantageously, the enzyme is selected from enzymes having a Tf greater than or equal to temperature T+10°C, preferably greater than or equal to temperature T+15°C, more preferably greater than or equal to temperature T+20°C. Thus, advantageously, in this embodiment, a PET is selected that has an initial degree of crystallinity of at most 25% and a Tg between 65 °C+ / -1 °C and 80 °C+ / -1 °C and the depolymerization step is carried out at a temperature T of 70 °C+ / - 1 °C. In another particular mode of implementation, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - a plastic material is selected from fibers and / or fiber waste and / or textiles comprising PET that has an initial crystallinity degree of at most 25% and a Tg between 60 °C+ / -1 °C and 75 °C+ / -1 °C; - An enzyme is selected that can degrade PET, such that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity such as LLCRbn / Lzzza / YiAi maximum of 35% at said temperature T, and - A PET depolymerization step is carried out by bringing said enzyme into contact with said plastic material at a temperature T of 65 °C+ / - 1 °C. Preferably, tR represents the time required for said PET to reach a degree of crystallinity of 30% at said temperature T. Advantageously, the enzyme is selected from enzymes having a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. In another particular mode of implementation, the enzymatic depolymerization process of polyethylene terephthalate (PET) according to the invention is characterized in that - a plastic material is selected from fibers and / or fiber waste and / or textiles comprising PET that has an initial crystallinity degree of at most 25% and a Tg between 60 °C+ / -1 °C and 70 °C+ / -1 °C; - an enzyme is selected that can degrade PET, such that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T, and - A PET depolymerization step is carried out by bringing said enzyme into contact with said plastic material at a temperature T of 60 °C+ / - 1 °C. Preferably, tR represents the time required for said PET to reach a degree of crystallinity of at most 30% at said temperature T. Advantageously, the enzyme is selected from enzymes having a Tf greater than or equal to temperature T+10 °C, preferably greater than or equal to temperature T+15 °C, more preferably greater than or equal to temperature T+20 °C. LLCRbn / Lzzza / YiAi In a particular embodiment, the crystallization time (tR) of PET is measured before the depolymerization step, in a sample of said PET. According to the invention, the enzyme is selected such that the depolymerization time (tD) of the PET by said enzyme is strictly less than the crystallization time (tR) of said PET. Preferably, the enzyme is selected such that the tD corresponds to the time required for said enzyme to depolymerize at least 90% of said PET at said temperature T, and such that the tR corresponds to the time required for said PET to reach a degree of crystallinity of at most 30% at said temperature T. In one particular embodiment, the tD is less than 20 h, preferably less than 18 h, 16 h, 14 h, 12 h, or 10 h. In another particular embodiment, the tD is between 1 and 16 h, preferably between 1 and 10 h. According to the invention, the PET depolymerization step is carried out by bringing said PET into contact with said selected enzyme at a temperature T. Advantageously, the pH is regulated to optimize the performance of the depolymerization procedure depending on the solubility of the monomers / oligomers. In one particular embodiment, the pH is regulated to be maintained at the optimum pH of the enzyme + / - 1. Specifically, the pH is regulated to be maintained between 6.5 and 9. In another particular embodiment, the pH is regulated between 6.5 and 8.5 during the depolymerization step, preferably between 7 and 8. In yet another particular embodiment, the pH is regulated between 7.5 and 8.5. According to the invention, the reactor contents are kept in agitation during the depolymerization stage. The person skilled in the art controls the agitation speed to ensure it is sufficient to suspend the plastic / polyester material introduced into the reactor, maintain temperature homogeneity, and precisely regulate the pH. For example, the agitation speed is maintained between 50 rpm and 500 rpm, specifically at 80 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm. EXAMPLES Example 1: Measurement of the crystallization time (tR) of PET 1.1 Amortization of PET in plastic material The depolymerization process is carried out using colored and washed plastic flakes from the recycling industry. LLCRbn / Lznza / YiAi PET plastic waste. These plastic materials, composed of 98% PET (w / w) with an average crystallinity of 34%, were subjected to an extrusion stage, followed by rapid cooling to allow for the absorption of the PET contained in the waste. The extruder used for absorption was a KMB ZE 60A twin-screw extruder equipped with a gear pump, a filter changer, a die, and a cutting system with an underwater die head. The regulated temperature was 265 °C in the extruder areas, 280 °C in the gear pump areas, 280 °C in the filter changer areas, and 360 °C in the die. The water used in the granulation system was regulated to a temperature of 80 °C. A gravimetric dosing system marketed by Brabender was used to introduce the flakes. A flow rate of 150 kg / h was used.For granulation, a nozzle with 120 holes, each 0.8 mm in diameter, was used. The cutting speed was 4500 rpm. The deburring process yielded granules smaller than 1 mm with a measured degree of crystallinity of 16% (by DSC). The granules were then subjected to a pulverizing stage using a disc pulverizer. The powder was sieved through a 400 µm sieve to recover only the smaller particles. The degree of crystallinity of this powder was determined to be 16%, as described in Example 1.2 below. 1.2 Measurement of Tg and degree of crystallinity of PET For the DSC analysis, a Mettler Toledo DSC 3 instrument with a dry airflow was used. Only the first temperature sweep was performed to determine the thermal characteristics of the PET powder, using a sample of the powder obtained in Example 1.1, specifically the glass transition temperature (Tg) and the initial crystallinity level. The temperature increase was carried out from 25 °C to 280 °C at a heating rate of 10 °C / min with approximately 10 mg of sample, using a 40 µL aluminum crucible. The Tg was determined using the STARe Mettler Toledo program, at the center of the glass transition represented graphically on the thermogram of the sample and the initial degree of crystallinity, according to the equation detailed in the description. The Tg of the PET powder produced in Example 1.1 was evaluated at 78.4 °C. 1.3 Measurement of the crystallization kinetics of the PET plastic material Five grams of the powder obtained in Example 1.1 (plastic materials containing PET) and 20 ml of water were mixed in a 40 ml flask. The sealed flask was then immersed in a heated water bath at the desired incubation temperature T. Samples were taken at different time intervals. The resulting powder was placed on absorbent paper and air-dried for at least 12 hours. A DSC analysis was then performed on approximately 10 mg of the sample to assess the degree of crystallinity, as described in Example 1.2. Figure 1 shows the evolution of PET crystallinity over time, at different temperatures: 65 °C, 70 °C, 72 °C, 75 °C. At 65 °C, the crystallinity of PET in the powder of Example 1.1 varies very little, and after 72 to 65 °C, the crystallinity remains below 20% (data not shown). This is also the case for temperatures below 65 °C. At 70 °C, 72 °C, and 75 °C, PET reaches 35% crystallinity after 17.5 h, 11.5 h, and 5 h, respectively. At 70 °C, 72 °C, and 75 °C, PET reaches 30% crystallinity after 16 h, 10 h, and 4.3 h, respectively. Example 2: Evaluation of the melting temperatures (Tf) of enzymes 2.1 Enzyme production The genes were expressed in competent E. coli BL21 (DE3) cells (New England Biolabs, Ipswich, MA) by culturing them on ZYM self-inducible medium (Studier et al., 2005 - Prot. Exp. Pur. 41, 207-234) for 23 hours at 21 °C. E. coli cells were collected by centrifugation (6,000 x g, 10 min at 4 °C) and resuspended in lysis buffer (20 mM Tris-HCl, pH 8, 300 mM NaCl). The cells were disrupted by sonication on ice, and the lysate was clarified by centrifugation (10,000 x g, 30 min at 4 °C). The soluble fraction was treated with TALON metal affinity resin (Clontech, CA). After washing the unbound proteins with lysis buffer containing 10 mM midazole, the bound proteins were eluted with an elution buffer (20 mM Tris-HCl, pH 8, 300 mM NaCl, 100 mM midazole). The buffer was then changed to a storage buffer (20 mM Tris-HCl, pH 8, 300 mM NaCl) by dialysis.The concentration of purified proteins was determined based on the molar extinction coefficient calculated for 280 nm. 2.2 Evaluation of the Tf LLCRbn / Lzzza / YiAi DSF was used to evaluate the melting temperatures (Tf) of the enzymes used. Protein samples were prepared at a concentration of 14 µm (0.4 mg / ml) and stored in a buffer composed of 20 mM Tris HCl, pH 8.0, and 300 mM NaCl. SYPRO Orange Dye 5000x DMSO stock solution was first diluted 250-fold in water. Protein samples were loaded into a 96-well PCR plate (Lifescience Bio-Rad, France, catalog no. HSP9601), with each well containing a final volume of 25 µL. The final protein and SYPRO Orange dye concentrations in each well were 5 µm (0.14 mg / ml) and 10x, respectively. The volumes loaded into each well were as follows: 15 µL of buffer, 9 µL of the 0.4 mg / ml protein solution, and 1 µL of the 250x diluted SYPRO Orange solution. The PCR plates were then sealed with optical-grade adhesive tape and centrifuged at 2000 rpm for 1 min at room temperature.DSF experiments were then performed using a Bio-Rad CFX96 real-time PCR system configured with the FRET channel to utilize excitation filters 450 / 490 and emission filters 560 / 580. Samples were heated from 25 to 100 °C at a rate of 1 °C / min. Fluorescence measurements were taken every 0.3 °C. The melting temperature was determined from one or more peaks of the first derivatives of the melting curve using the Bio-Rad CFX Manager software. Tf values ​​are the average of three measurements. Table 1: Melting temperature as a function of enzymes LLCRbn / Lzzza / YiAi Enzymes that degrade PET Tf E1: SEQ ID N°1 84.7 °C E2: SEQ ID N°1 + F208I + D203C + S248C + Y92G 94.0 °C E3: SEQ ID N°1 + F208W + D203C + S248C + Y92G 98.0 °C E4: SEQ ID N°1 + F208I + D203C + S248C + V170I + Y92G 94.6°C Example 3: Depolymerization procedure in a reactor The procedure was carried out in a 500 mL Minibio bioreactor (Applikon Biotechnology, Delft, The Netherlands). From 0.69 pmol to 1.10 μmol of purified protein (produced according to Example 2.1) prepared in 80 mL of 100 mM potassium phosphate buffer, pH 8, was combined with 20 g of the PET-containing powder prepared according to Example 1 (Xc = 16%, Tg = 78.4 °C). Temperature control was achieved by immersion in a water bath, and a propeller stirrer was used to maintain a constant stirring speed of 250 rpm. The pH was adjusted to 8 with 6 N NaOH and ensured using the my-Control bio control system (Applikon Biotechnology, Delft, The Netherlands), and base consumption was recorded throughout the procedure. The characterization of the PET depolymerization rate was carried out by regularly sampling samples subjected to ultra-high-performance liquid chromatography (UHPLC) analysis, measuring the amount of terephthalic acid equivalents produced according to the method described above. The amount of terephthalic acid produced can also be estimated from the amount of base added to the medium during the reaction. The concentration of AT equivalents was determined by ultra-high-performance liquid chromatography (UHPLC). If necessary (in the presence of insoluble AT), samples were diluted in 100 mM potassium phosphate buffer, pH 8. 150 µL of methanol and 6.5 µL of 6 N HCl were added to 150 µL of sample or dilution. After homogenization and filtration through a 0.45 µm syringe filter, 20 µL of sample were injected into the Ultimate 3000 UHPLC system (Thermo Fisher Scientific, Waltham, MA), which comprised a pump module, an autosampler, a column oven thermostated at 25 °C, and a UV detector at 240 nm. Terephthalic acid (AT) and the produced molecules (MHET and BHET) were separated using a methanol gradient (30% to 90%) in 1 mM H2SO4 at 1 m / min through a Discovery HS C18 HPLC column (150 mm x 4.6 mm, 5 μm) fitted with a pre-column (Supelco, Bellefonte, PA).AT, MHET, and BHET were determined from their standard curves prepared from AT and commercial BHET, and from MHET synthesized in the laboratory. The AT equivalents correspond to the sum of the measured AT and the AT contained in the measured MHET and BHET. The enzymes of Example 2 were analyzed at different temperatures (70 °C ± 1 °C and 72 °C ± 1 °C) to evaluate which ones could be selected to implement the procedure of the invention at these different temperatures. In this way, the enzymes were tested at a saturation concentration. Tests were also carried out at a temperature of 60 °C, the temperature of 60 °C corresponding to the temperature usually... LLCRbn / Lznza / YiAi used in the depolymerization procedures of the previous technique (negative control). As a reminder, the crystallization times tR of the PET obtained in example 1.1 to achieve 30% and 35% crystallinity are, respectively, 16 h and 17.5 h at 70 °C, and 10 h and 11.5 h at 72 °C. LLCRbn / Lzzza / YiAi Tables 2, 3, 4 and 5 below indicate, respectively, the measurement of the tD times of the enzymes E1, E2, E3 and E4 at different temperatures. 60 °C 72 °C Enzymes Tf tD (80%) tD (90%) tD (80%) tD (90%) E1 84.7 °C 28 h 36 h Never reached Never reached Table 2: Measurement of tD times of E1 at 60°C (control) and 72°. For E1, tD is therefore greater than tR at 72 °C. Thus, the enzyme cannot be selected for implementation of the invention's process. One reason for this is that it is not sufficiently stable and / or active to achieve 80% conversion before the PET has reached a degree of crystallinity greater than 30%. 60 °C 72 °C Enzymes Tf tD (80%) tD (90%) tD (80%) tD (90%) E2 94.0 °C 18h 21h 6h 9h Table 3: Measurement of tD times of E2 at 60 °C (control) and 72 °C. The enzyme E2 can be selected to implement the process of the invention at 72 °C, which allows for a significant improvement in performance compared to a process at 60 °C (a 2.3-fold decrease in the time to reach 90% depolymerization). E2 simultaneously has a sufficiently high Tf (> ​​T + 20 °C) and a sufficiently low tD to achieve 80% depolymerization before the PET reaches excessively high crystallinity (tR to reach 30% crystallinity = 10 h) at 72 °C. 72 °C Enzymes Tf tD (80%) tD (90%) E3 98.0 °C 7 h 10 h Table 4: Measurement of tD times from E3 at 72 °C. Analogously to E2, E3 can be selected to implement the procedure of the invention at 72 °C. 60 °C 70 °C 72 °C Enzymes Tf tD (80%) tD (90%) tD (80%) tD (80%) tD (90%) E4 94.6 °C 17h 20h 12h 7h 10h Table 5: Measurement of tD times of E4 at 60 °C (control), 70 °C and 72 °C. LLCRbn / Lzzza / YiAi Analogously to E2 and E3, E4 can also be selected to implement the procedure of the invention at 70 °C and 72 °C, allowing a significant improvement in performance compared to a procedure at 60 °C. Example 4: Degradation procedure for a plastic material derived from textile waste comprising PET 4.1 Measurement of the crystallization time (tR) of PET from textile waste 4.1.1 PET amortization of PET from the plastic material derived from textile waste and measurement of the degree of crystallinity of PET The depolymerization process was carried out using production waste from a waterjet weaving process. The material in question is in the form of skeins of continuous strands and contains approximately 100% PET. This textile material underwent a drying stage at 60 °C for 16 h, followed by an extrusion stage and rapid cooling to allow the PET in the waste to deamorphize. The extruder used for deamorphization was a Leistritz ZSE 18 MAXX twin-screw extruder. The heating zone temperatures were set according to the following profile: 265°C-265°C-265°C-255°C-255°C-250°C-250°C-245°C-245°C245°C The spindle speed was set at 150 rpm. The material was fed into the extruder manually. The ring reaching the extruder head was immediately immersed in a water bath at 10°C. The resulting ring was granulated and then reduced to a fine powder using a micronizer (1 mm mesh). The powder was then sieved through a 500 µm sieve to recover only particles smaller than this size. The crystallinity of the powder was determined according to Example 1.2, with a value of less than 10%. 4. 1.2 Measurement of the crystallization kinetics of PET plastic material The crystallization time (tR) of PET from textile waste was measured using the same protocol as in Example 1.3. At 68 °C, the crystallinity of the PET in the powder obtained in Example 4.1 varies very little, and after 29 h at 68 °C, the crystallinity remains below 20%. The same occurs at 60 °C. 4.1.3 Measurement of Tg of PET The Tg measurement of PET was carried out using the same protocol as in Example 1.2. The Tg of the PET powder produced in Example 4.1.1 was evaluated at 75.7 °C. 4.2 Selection of the enzyme for a reactor depolymerization procedure of PET plastic material from textile waste. For the depolymerization tests, a 5 L³ domed-bottom reactor (Global Process Concept) was used. The reactor was equipped with a temperature probe and a pH probe (Hamilton, EasyFerm HB BioArc 325). The regulation of these two parameters to reference values ​​was ensured by internal PID controllers of the C-bio software (Global Process Concept). A 5.5 cm diameter propeller stirrer attached to the central shaft, rotating at 300 rpm, was used to agitate the reaction medium. In all tests, the pH was adjusted to 8.0 by adding 20% ​​sodium hydroxide. Enzyme E4 was added at a weight ratio of 1 / 1000 per amount of PET introduced. It was produced by fermentation of a recombinant microorganism in liquid medium. Table 6 below indicates, respectively, the measurement of the tD times of the E4 enzyme on the plastic material defined in point 4.1.1 at different temperatures. LLCRbn / Lzzza / YiAi 60 °C 68 °C Enzymes Tf tD (80%) tD (90%) tD (80%) tD (90%) E4 94.0 °C 18h 29h 9h 13h Table 6: Measurement of tD times of E4 at 60 °C and 68 °C. Since tD remains lower than tR at 68 °C, E4 can therefore be selected to implement the procedure of the invention at 68 °C on the plastic material defined in point 4.1.1, while allowing a significant improvement in performance compared to a procedure at 60 °C. Example 5: Degradation procedure for a plastic material, derived from plastic waste. Selection and scaling. 5.1 Measurement of the crystallization time (tR) of PET from plastic waste 5.1.1 PET amortization of PET from plastic material derived from plastic waste and measurement of the degree of crystallinity of PET The extruder used for the granulation process was a KMB ZE 60A twin-screw extruder equipped with a gear pump, a filter changer, a die, and a cutting system with an underwater head. The temperature was set at 265 °C in the extruder areas, 275 °C in the gear pump areas, 275 °C in the filter changer areas, and 350 °C in the die. The screw rotation speed was 160 rpm. The water used in the granulation system was regulated to a temperature of 80 °C. Two gravimetric dosing systems, marketed by Brabender, were used to feed the flakes. A flow rate of 300 kg / h was used. For granulation, a die with 240 holes of 0.75 mm diameter was used. The cutting speed was 3800 rpm. The amortization allowed obtaining granules of less than 1 mm in size whose degree of crystallinity measured was 12% (by DSC).The granules were then subjected to a pulverizing stage using a disc pulverizer. The powder was sieved through a 500 µm sieve to recover only the smaller particles. The crystallinity of the powder was determined according to Example 1.2, as equal to 16.5% (DSC). 5.1.2 Measurement of Tg of PET The Tg measurement of PET was carried out using the same protocol as in Example 1.2. The Tg of the PET powder produced in Example 5.1.1 was evaluated at 75.2 °C. 5.1.3 Measurement of the crystallization kinetics of PET plastic material The crystallization time (tR) of PET from plastic material was measured using the same protocol as in Example 1.3. At 60 °C and 66 °C, the crystallinity of the PET in the powder obtained in Example 5.1 varies very little, and after 30 h at 60 °C or 66 °C, the crystallinity remains below 22%. At 72 °C, it reaches 30% in 18 h (tR). 5.2 Enzyme selection for a depolymerization procedure in LLCRbn / Lznza / YiAi reactor of PET plastic material from plastic waste. For experiment A, a 500 ml flat-bottom stirred reactor (MiniBioréacteurs, Global Process Concept) was used. It was equipped with a temperature probe and a pH probe (Hamilton, EAsyFerm HB BioArc 120). The regulation of these two parameters at the specified values ​​was ensured by internal PID controllers of the C-bio software (Global Process Concept). A 3 cm diameter propeller stirrer attached to the central shaft, rotating at 300 rpm, was used to stir the reaction medium. For tests B and C, a domed bottom reactor with a total volume of 5 L (Global Process Concept) was used as described in Example 4.2. In all tests, the pH was adjusted to 8.0 by adding 20% ​​sodium hydroxide. Enzyme E4 was added at a weight ratio of 1 / 1000 per amount of PET introduced. It was produced by fermentation of a recombinant microorganism in liquid medium. LLCRbn / Lzzza / YiAi Table 7 below indicates, respectively, the measurement of the tD times of the E4 enzyme at different temperatures. ABC Reactor volume 500 mi 5 1 5 1 T (°C) 60 66 72 tD (80%) 28 h 24.4 h 17.2 h Table 7: Measurement of the tD times of E4 at different temperatures, with tD being less than tR, E4 can therefore be selected to implement the procedure of the invention at these two temperatures on the plastic material defined in point 5.1.1. It is observed that the use of E4 at 66 °C and 72 °C should allow a significant improvement in performance compared to a procedure at 60 °C. 5.3 Scaling Validation Since the previous steps allowed validation that the E4 enzyme can be selected, the procedure can be implemented according to the invention. For this assay (D), a flat-bottom reactor with a total volume of 1000 L was used. The reactor was equipped with a temperature probe and a pH probe (In Pro3100 / SG / 325, Mettler Toledo). A variable-diameter propeller stirrer was used to agitate the reaction medium. The pH was adjusted to 8.0 by adding 20% ​​sodium hydroxide (w / w). Enzyme E4 was added at a weight ratio of 2 / 1000 per unit of PET introduced. It was produced by fermentation of a recombinant microorganism in liquid medium. The degradation performed at a temperature of 66 °C was continued using the same methods described above. In this way, degradation rates of 10, 80% and 90% were obtained respectively after 14h and 24h. The results obtained for semi-industrial volumes are therefore consistent with those obtained during enzyme selection. It is observed that, advantageously, the use of larger volumes allows for better agitation and, therefore, improved yields.

Claims

1. A process for the enzymatic depolymerization of polyethylene terephthalate (PET) by contacting said PET with an enzyme suitable for depolymerizing said PET, characterized in that - the PET has an initial degree of crystallinity of at most 25%; - the depolymerization step is carried out at a temperature T equal to the Tg + / - 10 °C of said PET; and - the enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than a crystallization time (tR) of said PET, wherein the time tD represents the time required for said enzyme to depolymerize at least 80% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T.

2. Depolymerization process according to claim 1, characterized in that the temperature T is between the Tg-10 °C and the Tg +5 °C of PET.

3. Depolymerization process according to any one of the preceding claims, characterized in that the temperature T is between 66 °C and 80 °C, preferably between 68 °C and 73 °C.

4. Depolymerization process according to one of the preceding claims, characterized in that the crystallization time of the PET is measured before the depolymerization step, in a sample of said PET.

5. Depolymerization process according to one of the preceding claims, characterized in that the selected enzyme has a tD time less than or equal to 20 h.

6. Depolymerization process according to any one of the preceding claims, characterized in that the enzyme is selected from enzymes having a melting temperature (Tf) strictly higher than the temperature T.

7. Depolymerization process according to any one of the preceding claims, characterized in that the enzyme is selected from enzymes having a Tf greater than or equal to temperature T+10°C, preferably greater than or equal to temperature T+15°C, more preferably greater than or equal to T+20°C.

8. Depolymerization process according to any one of the preceding claims, characterized in that a PET having an initial degree of crystallinity of less than 25% is selected.

9. Depolymerization process according to any one of the preceding claims, characterized in that the initial degree of crystallinity of the PET is less than 20%.

10. Depolymerization process according to any one of the preceding claims, characterized in that the depolymerization time (tD) is between 1 and 16 h, preferably between 1 and 10 h.

11. Depolymerization process according to any one of the preceding claims, characterized in that the PET is subjected to an amortization stage prior to the depolymerization stage.

12. Depolymerization process according to any one of the preceding claims, characterized in that time tD represents the time required for said enzyme to depolymerize at least 90% of said PET at said temperature T, and time tR represents the time required for said PET to achieve a degree of crystallinity of at most 30% at said temperature T.

13. Depolymerization process according to any one of the preceding claims, characterized in that LLCRbn / Lznza / YiAi - the PET has an initial degree of crystallinity of at most 25% and a Tg between 65 °C+ / -1 °C and 80 °C+ / -1 °C; - the depolymerization step is carried out at a temperature T of 72 °C+ / - 1 °C; and - the enzyme is selected so that the depolymerization time (tD) of the PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to reach a degree of crystallinity of at most 35% at said temperature T.

14. Depolymerization process according to any one of the preceding claims characterized in that: - a plastic material is selected from fibers and / or fiber waste and / or textiles comprising PET having an initial degree of crystallinity of at most 25% and a Tg between 60 °C+ / -1 °C and 75 °C+ / -1 °C; - the depolymerization step is carried out at a temperature T of 65 °C+ / - 1 °C, and - an enzyme is selected that can degrade PET so that the depolymerization time (tD) of PET by said enzyme is strictly less than a crystallization time (TR) of said PET, wherein the time tD represents the time required by the selected enzyme to depolymerize at least 80%, preferably at least 85%, more preferably at least 90% of said PET at said temperature T, and the time tR represents the time required for said PET to achieve a degree of crystallinity of at most 35% at said temperature T.