EP3724234A1

EP3724234A1 - Chitin and process for producing chitin and/or chitosan by the enzymatic and chemical pathway

Info

Publication number: EP3724234A1
Application number: EP18839829.1A
Authority: EP
Inventors: Lorena SANCHEZ; Cecilia SOCOLSKY; Valérie ALEZRA; Corentin LE BERRE; Bénédicte LORETTE; Sophie Laurent; Nathalie BEREZINA
Original assignee: Ynsect SAS
Current assignee: Ynsect SAS
Priority date: 2017-12-15
Filing date: 2018-12-13
Publication date: 2020-10-21
Also published as: FR3075205A1; TW201927826A; US11958918B2; US20210070889A1; US20240150498A1; WO2019115970A1; FR3075205B1

Abstract

The present invention relates to chitin with a differential purity of more than 97.75% and to a process for producing chitin and/or chitosan by the enzymatic and chemical pathway.

Description

CHITINE AND PROCESS FOR OBTAINING CHITIN AND / OR CHITOSAN BY WAY

Enzyme-CHEMICAL

The present invention relates to a chitin, a chitosan and a process for preparing chitin and / or chitosan from insects.

According to the invention, "chitin" means a polymer composed mainly of glucosamine and N-acetyl-glucosamine units, said units possibly being optionally substituted with amino acids and / or peptides.

By "predominantly compound" is meant that said polymer comprises between 55% and 98% by weight, preferably between 75 and 90% by weight of glucosamine and N-acetyl-glucosamine units.

Chitin is the second most synthesized polymer in the world after cellulose. Indeed, chitin is synthesized by many species of the living world: it is partly the exoskeleton of crustaceans and insects and the side wall that surrounds and protects mushrooms. More particularly, in insects, chitin thus constitutes 3 to 60% of their exoskeleton.

By "chitosan" is meant according to the present invention the deacetylation products of chitin. The usual limit between chitosan and chitin is determined by the degree of acetylation: a compound with a degree of acetylation of less than 50% is called chitosan, beyond that, a compound with a degree of acetylation greater than 50% is named chitin.

The applications of chitin and / or chitosan are numerous: cosmetic (cosmetic composition), medical and pharmaceutical (pharmaceutical composition, treatment of burns, biomaterials, corneal dressings, surgical threads), dietary and food (human food including oenology and food animal, more specifically in aquaculture and poultry farming), technique (filtering agent, texturizer, flocculant or adsorbent especially for the filtration and depollution of water), etc. Indeed, chitin and / or chitosan are biocompatible, biodegradable and non-toxic materials.

Usually, chitin and chitosan are obtained from the different species synthesizing chitin, such as those mentioned above, and especially from crustaceans or insects.

It is particularly advantageous to obtain chitin and chitosan from insects, the latter being an abundant and renewable raw material. Obtaining high purity chitin and / or chitosan is sought in many applications, such as, for example, in cosmetics and pharmaceuticals. High purity limits especially the risk of allergy, local or generalized fever, relating to the application of cosmetic or pharmaceutical products containing chitin and / or chitosan. Such reactions may indeed be caused by impurities such as residual amino acids, ashes or lipids.

The invention therefore relates to a chitin whose purity by difference is greater than 97.75%.

In the context of the present application, for measuring purity, the known impurity contents, namely amino acids, lipids and ashes, are subtracted from the value of absolute purity (100%) in order to obtain the value of the purity estimated by difference. Thus, for example, a sample which contains 30% of amino acids, 10% of lipids and 1% of ash, is then assigned a purity by difference of 100-30-1-1 = 59%.

The chitin according to the invention, which has a high difference purity, thus has low levels of amino acids, lipids and ashes.

The chitin according to the invention advantageously has a purity with a difference greater than or equal to 98%, preferably greater than or equal to 98.1%.

The amino acid content of the chitin according to the invention is preferably determined according to the method NF EN ISO 13904 for tryptophan and NF EN ISO 13903 for the other amino acids.

The relative abundance, expressed as a percentage, can be calculated by relating the content of each amino acid to the total amino acid content.

Throughout the application, where no date is specified for a regulation, standard or directive, it is the regulation, standard or directive in effect on the filing date.

Methods for determining the fat content (lipids) are well known to those skilled in the art. By way of example and preferably, the determination of this content will be carried out by adapting the method of the EC regulation 152/2009.

The method of determining the ash content is well known to those skilled in the art. Preferably, this content is determined according to the NF V18-101 standard.

Advantageously, the chitin according to the invention comprises less than 1, 2% by weight of amino acids on the total dry weight of chitin.

Preferably, the chitin according to the invention comprises less than 1% by weight, more preferably less than 0.9% by weight, even more preferably less than 0.8% by weight, and even more preferably less than 0.75% by weight. by weight of amino acids on the total dry weight of chitin.

Advantageously, the residual amino acids present in the chitin according to the invention are: Threonine, Serine, Glycine, Glutamic acid, Alanine, Cysteine, Valine, Isoleucine, Aspartic acid, Leucine, Tyrosine, Phenylalanine, Histidine, Lysine, Tryptophan or a combination two or more of these. Preferably the residual amino acids present in the chitin according to the invention consist of: Cysteine, Valine, Histidine, Lysine, Tryptophan or a combination of two or more thereof, preferably in a combination of all these amino acids.

Advantageously, the chitin according to the invention comprises less than 2% by weight of ash on the total dry weight of chitin.

The chitin according to the invention preferably comprises less than 1, 6% by weight, more preferably less than 1, 4% by weight, still more preferably less than 1, 2% by weight of ash on the total dry weight of chitin.

Advantageously, the chitin according to the invention comprises less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.2% by weight of lipids on the total dry weight of chitin.

Even more preferentially, the chitin according to the invention does not comprise lipids.

Advantageously, the chitin according to the invention has a molecular mass of greater than or equal to 450 kg.MuM, preferably greater than or equal to 500 kg. mol ¹ , more preferably greater than or equal to 600 kg. mol ¹ , even more preferably greater than or equal to 650 kg. mol ¹ .

The molecular weight is determined by measuring the viscosity by falling ball.

Preferably, the molecular weight is determined according to a method of measuring the falling ball viscosity based on that described in the following publication: "Pacheco et al. ; Structural characterization of chitin and chitosan obtained by biological and chemical methods; Biomacromolecules; 12, 3285-3290, 201 1.

This method is used in particular in Example 1.

Preferably, the chitin according to the invention is an isolated chitin.

By "isolated" chitin, we mean a chitin that has been isolated or extracted from its natural environment.

More particularly, in the context of the present application, chitin is isolated or extracted from insects, more specifically cuticles of insects.

According to a preferred embodiment, chitin has a difference purity greater than or equal to 98.0% and advantageously a molar mass of greater than or equal to 800 kg. mol ¹ , a purity with a difference greater than or equal to 98.5% and advantageously a molar mass greater than or equal to 850 kg. mol ¹ .

According to this preferred embodiment, chitin advantageously comprises less than 0.35% by weight of amino acids on the total dry weight of chitin, and / or less than 0.9% by weight of ash on the total dry weight of chitin, and / or less than 0.3% by weight of lipids on the total dry weight of chitin.

The invention also relates to a chitosan whose purity by difference is greater than 97.75%.

Preferably, the difference purity of the chitosan according to the invention is greater than or equal to 98%, more preferably greater than or equal to 98.1%.

The difference purity, amino acid content, ash content, and lipid content of chitosan according to the invention are measured in the same manner as indicated above for chitin.

Advantageously, the chitosan according to the invention comprises less than 0.8% by weight of amino acids on the total dry weight of chitosan.

Preferably, the chitosan according to the invention comprises less than 0.6% by weight, and more preferably less than 0.4% by weight of amino acids on the total dry weight of chitosan.

Advantageously, the residual amino acids present in the chitosan according to the invention are: Threonine, Tyrosine, Lysine and / or Tryptophan.

Advantageously, the chitosan according to the invention comprises less than 2% by weight of ash on the total dry weight of chitosan.

The chitosan according to the invention preferably comprises less than 1.8% by weight, more preferably less than 1.5% by weight, and even more preferably less than 1.0% by weight of ash on the total dry weight of chitosan.

Advantageously, the chitosan according to the invention comprises less than 1% by weight, preferably less than 0.7% by weight, more preferably less than 0.5% by weight of lipids on the total dry weight of chitosan.

Advantageously, the chitosan according to the invention has a molecular mass greater than or equal to 250 kg. mol ^-1 , preferably greater than or equal to 300 kg. mol ^-1 , more preferably greater than or equal to 350 kg. mol ^-1 , even more preferably greater than or equal to 400 kg. mol ^-1 .

Preferably, the chitosan according to the invention is an isolated chitosan.

By "isolated" chitosan, we mean a chitosan that has been obtained from a chitin isolated or extracted from its natural environment.

More particularly, in the context of the present application, chitosan is obtained from a chitin isolated or extracted from insects, more specifically cuticles of insects.

According to a preferred embodiment, the chitosan has a difference purity greater than or equal to 97.9% and a molar mass greater than or equal to 480 kg. mol ¹ , more particularly, a difference purity of greater than or equal to 98.8% and a molar mass greater than or equal to 540 kg. mol ¹ .

According to this preferred embodiment, the chitosan advantageously comprises less than 0.4% by weight of amino acids on the total dry weight of chitosan, and / or less than 0.6% by weight of ash on the total dry weight of chitosan, and / or less than 0.2% by weight of lipids on the total dry weight of chitosan.

The invention also relates to a process for obtaining chitin and / or chitosan, from insects, comprising the following steps:

- separation of cuticles from the soft part of insects,

enzymatic hydrolysis of the cuticles with a protease, to obtain a solid residue, and

the basic treatment of the solid residue.

The process for obtaining chitin and / or chitosan according to the invention makes it possible to obtain a chitin and / or a chitosan of high purity.

In addition, the process according to the invention, and more particularly the enzymatic hydrolysis step, makes it possible to reduce certain disadvantages inherent in the subsequent basic treatment step, such as, for example, reducing the amount of base used during this step. This step also allows the recovery of a hydrolyzate.

Advantageously, the process according to the invention does not comprise an oxidation step, such as, for example, a treatment with hydrogen peroxide.

"Insects" means insects at any stage of development, such as adult, larval, or nymph stage (intermediate stage). Advantageously, the insects used in the method according to the invention are at a larval stage when the insects are holometabolous, at a nymphal stage (intermediate stage) when the insects are heterometabolic, or if necessary at an adult stage.

The insects used in the process according to the invention can be edible.

Advantageously, the preferred insects for carrying out the method according to the invention are, for example, Coleoptera, Diptera, Lepidoptera (such as, for example, Galleria mellonella), Isoptera, Orthoptera, Hymenoptera, Bats, Hemiptera. , Heteroptera, Ephemeroptera and Mecoptera, preferably Coleoptera, Diptera, Orthoptera, Lepidoptera or mixtures thereof, more preferably Coleoptera.

The beetles preferably used in the process according to the invention belong to the families Tenebrionidae, Melolonthidae, Dermestidae, Coccinellidae, Cerambycidae, Carabidae, Buprestidae, Cetoniidae, Dryophthoridae, or mixtures thereof.

More preferably, these are the following beetles: Tenebrio molitor, Alphitobius diaperinus, Zophobas morio, Tenebrio obscurus, Tribolium castaneum, Pachnoda marginata and Rhynchophorus ferrugineus, or mixtures thereof. Even more preferentially, it is Tenebrio molitor.

The process for obtaining chitin and / or chitosan according to the invention comprises a step of separating the cuticles from the soft part of the insects.

The cuticle is the outer layer (or exoskeleton) secreted by the epidermis of insects. It usually consists of three layers: the epicuticle, the exocuticle and the endocuticle.

The term "soft part" refers to the flesh (including muscles and viscera) and the juice (including body fluids, water and haemolymph) of the insects. In particular, the soft part does not consist in the juice of insects.

The separation of the cuticles from the soft part of insects can be carried out using any type of suitable separator.

According to a first embodiment, the separation of cuticles from the soft part is carried out using a band separator.

According to a second embodiment, the separation of cuticles from the soft part is carried out using a filter press.

This step of separating cuticles from the soft part of insects is more fully described in step 2 of the detailed process for obtaining chitin and / or chitosan according to the invention below. This separation of the cuticles from the soft part of the insect makes it possible in particular to separate the chitin from the soft part. Indeed, the cuticles obtained at the end of this separation step have a high chitin content of the order of 10 to 30% by weight on the total weight of cuticles, as indicated below.

In particular, the step of separating cuticles from the soft part is carried out without any prior step of grinding insects, particularly in the form of particles, has been performed.

The process for obtaining chitin and / or chitosan according to the invention advantageously comprises a slaughtering step prior to the step of separating the cuticles from the soft part.

This slaughtering step is more fully described in step 1 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Advantageously, following step 1 of slaughtering, the insects are directly used for the implementation of step 2 of cuticle separation of the soft part of the insects, that is to say that the insects are not subjected to no treatment, such as grinding, freezing or dehydration between step 1 and step 2.

The process for obtaining chitin and / or chitosan according to the invention comprises a step of enzymatic hydrolysis of cuticles by a protease, to obtain a solid residue, following the step of separating the cuticles from the soft part of the insects.

Advantageously, the enzymatic hydrolysis is carried out for a period of between 3 and 10 hours, preferably between 4 and 8 hours, such as for example of the order of 6 hours.

It should be noted that in the context of the present application, and unless otherwise stated, the ranges of values indicated are inclusive.

Preferably, the enzymatic hydrolysis is carried out at a temperature of between 40 and 80 °, preferably between 50 and 70 °, such as for example about 60 ° C.

Advantageously, the enzymatic hydrolysis is carried out at a pH of between 6 and 8, preferably between 6.5 and 7.5.

The enzymatic hydrolysis can be carried out with a single protease or alternatively with a mixture of enzymes containing at least one protease, more preferably a mixture of enzymes containing several proteases, such as a mixture containing an endoprotease and an exoprotease, or a protease and a polysaccharase.

The enzyme or enzyme mixture is introduced in an amount of 0.2 at 10% by weight, preferably from 1 to 8% by weight, more preferably from 3 to 7% by weight relative to the weight of (wet) cuticles subjected to enzymatic hydrolysis.

In terms of enzymatic activity, the amount of enzyme or mixture of enzymes introduced is equivalent to an activity of between 2000 and 5000 SAPU ("Spectrophotometric Acid Protease Unit"), preferably between 3000 and 4000 SAPU, per 100 g wet weight, with a moisture of 30 to 70%, substrate to be processed, that is to say cuticles of insects.

This step of enzymatic hydrolysis of cuticles is more fully described in step 3 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

The process for obtaining chitin and / or chitosan according to the invention comprises a step of basic treatment of the solid residue, following the step of enzymatic hydrolysis of the cuticles.

Advantageously, the basic treatment is carried out using a strong base.

Advantageously, the strong base is chosen from sodium hydroxide or sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Preferably, the strong base is sodium or potassium hydroxide, more preferably sodium hydroxide.

Preferably, the base used for the basic treatment is in the form of an aqueous basic solution.

In this case, the molar concentration of the base in aqueous solution is advantageously between 0.1 and 5 mol.l ^-1 , preferably between 0.5 and 2 mol.l ^-1 , even more preferably equal to 1 mol. .L ^-1 (for example molar soda).

Preferably, the concentration of the base is adjusted so as to obtain a base ratio by dry weight in g: solid residue by dry weight in g: water by weight in g between 0.1: 0.45: 2 and 0, 8: 0.45: 15, more preferably between 0.3: 0.45: 8 and 0.7: 0.45: 12, such as for example about 0.36: 0.45: 9.23 .

This step of basic treatment of the solid residue is more fully described in step 4 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Advantageously, the basic treatment step of the solid residue is followed by a step of recovering chitin.

This step of recovering chitin is more fully described in step 5 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Optionally, the process for obtaining chitin and / or chitosan according to the invention further comprises a step of washing the chitin.

This optional step of washing the chitin is more fully described in step 6 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Optionally, the process for obtaining chitin and / or chitosan according to the invention further comprises a step of drying the chitin.

This optional step of drying the chitin is more fully described in step 7 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Since chitin may be marketed in the form of a powder, the process for obtaining chitin and / or chitosan according to the invention may optionally comprise a step of grinding chitin.

This optional step of grinding chitin is more fully described in step 8 of the detailed process for obtaining chitin and / or chitosan according to the invention hereinafter.

The grinding step can also be carried out in order to promote the deacetylation reaction, which makes it possible to prepare chitosan from chitin.

The deacetylation step, which aims to convert chitin into chitosan, is therefore implemented only when the desired product is chitosan.

This step of deacetylation of chitin is more fully described in step

9 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Advantageously, the deacetylation step of chitin is followed by a step of recovering chitosan.

This step of recovering chitosan is more fully described in step

10 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Optionally, the process for obtaining chitin and / or chitosan according to the invention further comprises a step of washing the chitosan.

This optional step of washing chitosan is more fully described in step 1 1 of the detailed process for obtaining chitin and / or chitosan according to the invention below.

Optionally, the process for obtaining chitin and / or chitosan according to the invention further comprises a step of drying the chitosan.

This optional drying step of chitosan is more fully described in step 12 of the detailed process for obtaining chitin and / or chitosan according to the invention below. Note that steps 6 to 8, 11 and 12 mentioned above, and described more fully in the detailed process for obtaining chitin and / or chitosan according to the invention below, are optional. However, the process for obtaining chitin and / or chitosan according to the invention advantageously comprises one or more of these steps, preferably all these steps.

Note also that the characteristics of steps 1 to 12 of the detailed process for obtaining chitin and / or chitosan according to the invention, which are described below, are not limited to an implementation in said detailed process, but apply to all embodiments of the process for obtaining chitin and / or chitosan according to the invention described in the present application, regardless of the number of steps provided in these embodiments.

These characteristics also apply to a particular process for obtaining chitin and to a particular process for obtaining chitosan according to the invention, described below.

The invention therefore relates more particularly to a particular method for obtaining chitin, from insects, comprising the following steps:

the slaughter of insects,

- separation of cuticles from the soft part of insects,

enzymatic hydrolysis of cuticles by a protease, to obtain a solid residue,

the basic treatment of the solid residue, and

- the recovery of chitin.

This process therefore comprises steps 1 to 5 of the detailed process for obtaining chitin and / or chitosan below and advantageously one or more of the optional steps 6 to 8 of this detailed method.

The invention also relates to chitin obtainable by the process for obtaining chitin and / or chitosan according to the invention, or by the particular method for obtaining chitin according to the invention.

The invention therefore also relates to a particular method for obtaining chitosan, from insects, comprising the following steps:

the slaughter of insects,

- separation of cuticles from the soft part of insects,

enzymatic hydrolysis of cuticles by a protease, to obtain a solid residue,

the basic treatment of the solid residue, - the recovery of chitin,

deacetylation of chitin, and

- the recovery of chitosan.

This process therefore comprises steps 1 to 5, 9 and 10 of the detailed process for obtaining chitin and / or chitosan below and advantageously one or more optional steps 6 to 8, 11 and 12 of this detailed process.

The invention also relates to the chitosan obtainable by the process for obtaining chitin and / or chitosan according to the invention, or by the particular method for obtaining chitosan according to the invention.

Chitin and / or chitosan according to the invention as well as chitin and / or chitosan capable of being obtained by a process according to the invention may advantageously be used in various applications:

in cosmetic, pharmaceutical, nutraceutical or dietary compositions,

as biomaterials for treating burns as second skin, for producing corneal dressings or surgical threads,

as a filtering, texturing, flocculating and / or adsorbent agent, in particular for filtering and depolluting water.

Detailed method for obtaining chitin and / or chitosan according to the invention • Step 1: Slaughtering insects

This slaughtering stage 1 may advantageously be carried out by thermal shock, such as boiling or bleaching. This step 1 makes it possible to kill the insects while lowering the microbial load (reduction of the risk of deterioration and health) and by inactivating the internal enzymes of the insects that can trigger an autolysis, and thus a rapid browning of these.

For scalding, the insects, preferably the larvae, are thus scalded with water for 2 to 20 minutes, preferably 5 to 15 minutes. Preferably the water is at a temperature between 87 to I OO 'Ό, preferably 92-95 C. ^q

The quantity of water introduced during scalding is determined as follows: the ratio of the volume of water in ml to the weight in g of insect is preferably between 0.3 and 10, more preferably between 0 and 10. , 5 and 5, still more preferably between 0.7 and 3, even more preferably of the order of 1.

For bleaching, insects, preferably larvae, are bleached with water or by steam (nozzles or steam bed) at a temperature of between 80 and 10 ° C, preferably between 87 and 105 ° C, more preferably between 95 and 100 ° C, still more preferably 98 ° C or at the water at a temperature between 90 and 100 ° C, preferably between 92 and 95 ° C (by spray nozzles) or in mixed mode (water + steam) at a temperature between 80 and 130 ° C, preferably between 90 and 120 'Ό, more preferably between 95 and 105 ° C, even more preferably 98 ^q C. When the insects are bleached only with steam, bleaching is advantageously carried out in forced-circulation steam whiteners ("forced steaming"). "). The residence time in the bleaching chamber is between 5 seconds and 15 minutes, preferably between 1 and 7 minutes.

According to a preferred embodiment, the insects are beetles and in particular Tenebrio molitor.

• Step 2: Separation of cuticles from the soft part of insects

Step 2 aims to separate the cuticles from the soft part of insects.

By "band separator" is meant a device for separating the solid portion of the soft portion of a product, and which comprises a clamping band (or pressing belt) and a perforated drum.

By way of example, a belt separator may comprise a clamping band and a perforated drum, the clamping band surrounding at least a portion of the perforated drum.

The clamping band allows the application and application of the insects against the perforated drum so as to press the soft part of the insects through the perforations of the drum while the solid part of the insects (cuticles) remains. outside the drum.

The cuticles can then be recovered using a scraper knife.

By way of example, mention may be made of band separators from the Baader company, such as the band separators 601 to 607 ("soft separator 601 to 607"), or BFD Corporation SEPAmatic® Band Separators (410-4000V range).

Advantageously, the diameter of the perforations of the drum is between 0.5 and 3 mm, preferably between 1 and 2 mm.

Regarding the pressure, the skilled person is able to determine the pressure to be exerted for the separation of cuticles from the soft part of the insects.

A filter press is composed of filter cloths, and allows separation according to the pressure filtration principle.

Advantageously, the filter press used in the process for obtaining chitin and / or chitosan according to the invention is a band-press filter.

A band press filter has two perforated clamping bands (also called "filter cloths"). The insects are placed between the two perforated clamping bands so as to press the soft part of the insects through the perforations of the clamping bands, while the solid part of the insects remain between the two perforated clamping bands.

Those skilled in the art are able to determine the diameter of the perforations of the clamping bands and the pressure to be exerted, allowing the cuticles to be separated from the soft part of the insects.

By way of example, mention may be made of the belt press filter (or "belt press") from the Flottweg company, or the band press filters from the company ATR Créations.

This insect separation step differs from a conventional pressing that can be achieved for example with a single-screw or twin-screw press in that it allows a separation (net) of the soft part and cuticles of insects and not a separation of a juice from a solid fraction.

Advantageously, the separation of cuticles from the soft part of the insects is carried out using a band separator.

The cuticles obtained in step 2 comprise between 10 and 30%, preferably between 15 and 25% by weight of chitin, on the total dry weight of cuticles.

The determination of the chitin content is carried out by extraction thereof. For example, a method for determining chitin that can be used is AOAC 991 .43.

According to a preferred embodiment, the separation of cuticles from the part soft beetles and especially Tenebrio molitor is performed using a band separator.

Step 3: enzymatic hydrolysis of cuticles by a protease

The enzymatic hydrolysis is carried out by a protease or peptidase. In the present application, the names or suffixes "peptidase" and "protease" are used interchangeably to designate an enzyme lysing a peptide bond of proteins.

Preferably, the enzymatic hydrolysis is carried out at a temperature between 40 and 80 ° C, preferably between 50 and 70 ° C, such as for example about 60 ° C.

Preferably, the protease is selected from the group consisting of aminopepidases, metallocarboxypeptidases, serine endopeptidases, cysteine endopeptidases, aspartic endopeptidases, metalloendopeptidases, more preferably the protease is selected from serine endopeptidases, such that, for example, Alcalase 2.5L PF or Prolyve NP.

Advantageously, the enzymes can be chosen from the following:

^* na: not applicable

The enzyme or the enzyme mixture is introduced in an amount ranging from 0.2 to 15% by weight, preferably from 0.2 to 10% by weight, more preferably from 1 to 8% by weight. more preferably from 3 to 7% by weight relative to the weight of (wet) cuticles subjected to enzymatic hydrolysis.

It is usual to express the enzymatic activity of a protease in SAPU.

This enzymatic activity is measured on the basis of the principle of the measurement of tyrosine liberation at 275 nm during the hydrolysis of casein by a proteolytic enzyme (Valley research SAPU Assay method, by Karen PRATT).

SAPU (AA - i) X 11

- = - - - - g x 30 x C x 1

SAPU / g = a spectrophotometric unit of protease

DA = correlated absorbance

i = intercept

1 1 = final reaction volume

M = coefficient of the calibration curve 30 = reaction time (in minutes)

C = concentration of the enzyme (g / ml) in the enzyme solution added

1 = 1 mL volume of enzyme solution added

The enzymatic activity can also be expressed using the specific activity of an enzyme.

The specific activity of an enzyme is the catalytic activity expressed in International Unit (LU) per unit mass of enzyme (eg I.U./g enzyme).

Advantageously, the concentration of the enzyme or enzyme mixture used is between 100 and 250 LU. per gram of cuticle dry matter, preferably between 120 and 180 I.U. per gram of cuticle dry matter, more preferably between 120 and 150 I.U. per gram of cuticle dry matter.

Advantageously, the enzymatic hydrolysis step is carried out in the presence of water, such as fresh water.

The quantity of water used during the enzymatic hydrolysis is determined as follows: the ratio of the volume of water in L to the weight in g of wet cuticles is preferably between 0.005 and 5, more preferentially between 0.01 and 5, such as for example about 0.01, or alternatively between 0.05 and 2, or between 0.1 and 1.

The enzymatic hydrolysis step is advantageously carried out with stirring.

According to a preferred embodiment, the enzymatic hydrolysis step is carried out for 5 to 7 hours, such as, for example, approximately 6 hours, at a temperature of 50 to 70 ° C., such as for example of approximately 60 ° C. , and the enzyme is a serine endopeptidase, such as for example Alcalase 2.5L PF. Preferably, the enzyme is introduced at a concentration of between 120 and 150 I.U., for example of the order of 120 I.U. per gram of cuticle dry matter. Preferably, the amount of water used during this enzymatic hydrolysis step is of the order of 0.01 L of water per g of wet cuticles.

At the end of the enzymatic hydrolysis reaction of the cuticles, the reaction medium is then separated in order to recover a solid residue comprising chitin and a hydrolyzate.

The separation step can be carried out by any suitable separation method. These methods are known to those skilled in the art.

For example, it is possible to use a juice extractor, such as those marketed by the company Angel®.

The recovered solid residue is advantageously homogenized, for example by mixing. • Step 4: Basic treatment of the solid residue

In step 4, the solid residue recovered at the end of step 3 is subjected to a basic treatment, that is to say that it is brought into contact with a base (or basic agent).

Advantageously, the basic treatment is carried out using a strong base.

The basic treatment is advantageously carried out for a period of between 5 and 60 hours, preferably for a period of between 5 and 50 hours, such as for example 48 hours.

The duration of the basic treatment may advantageously be adapted according to the properties of the chitin that one wishes to obtain, such as its whiteness (white color).

The duration of the basic treatment may be less than 40 hours, or even less than 30 hours, such as for example 24 hours.

Advantageously, the basic treatment is carried out at a temperature of between 60 and 100%, preferably between 80 and 100%, more preferably about 90 ° C.

For this, the reaction medium may, for example, be heated using an oil bath, a heat exchanger or a jacket heating system, so as to achieve the desired temperature.

The basic treatment step is advantageously carried out with stirring.

According to a first preferred embodiment, the basic treatment step is carried out using sodium hydroxide in the form of an aqueous basic solution. Preferably, the concentration of sodium hydroxide in aqueous solution is equal to 1 mol.L ¹ . Preferably, the ratio of sodium hydroxide in dry weight to g: solid residue in dry weight in g: water in weight in g is of the order of 1: 1: 25. Preferably, the duration of this basic treatment is about 48 hours. Preferably, this basic treatment is carried out at a temperature of about 90 ° C.

According to a second preferred embodiment, the basic treatment step is carried out using potassium hydroxide in the form of an aqueous basic solution. Preferably, the concentration of potassium hydroxide in aqueous solution is equal to 1 mol.L ^-1 . Preferably, the ratio of potassium hydroxide to dry weight in g: solid residue in dry weight in g: water in weight in g is of the order of 1, 4: 1: 25. Preferably, the duration of this basic treatment is about 48 hours. Preferably, this basic treatment is carried out at a temperature of about 90 ° C.

• Step 5: Recovery of chitin

Step 5 of recovering chitin, from the reaction medium obtained at the end of step 4, can be carried out by any appropriate recovery method. These methods are known to those skilled in the art.

By way of example, mention may be made of filtration, centrifugation and decantation.

Advantageously, the recovery of chitin is carried out by filtration.

• Step (optional) 6: Wash the chitin

The chitin recovered at the end of step 5 is then optionally washed.

Step 6 of washing the chitin is advantageously carried out using tap water, preferably warm, that is to say whose temperature is between 15 and 60 ° C.

Preferably, the washing is carried out until the pH is neutralized.

• Step (optional) 7: Drying of chitin

The chitin is then optionally dried.

Preferably, the drying step is carried out at a temperature between 40 and 105 ° C, preferably at about 60 ° C.

The drying step is carried out for a period of between 10 and 80 hours, preferably for about 24 hours.

Advantageously, the drying is carried out using a drying oven, such as model FED 1 15 or FP53 from Binder®.

In order to prepare chitosan from chitin, the following steps may further be performed:

• Step (optional) 8: Crushing chitin

The chitin obtained at the end of step 5, 6 or 7 is then optionally ground, for example in an ultracentrifuge sieve mill.

The production of chitosan from chitin, by the deacetylation reaction, depends largely on the size of the chitin particles. Thus, a very fine grinding of the chitin before deacetylation makes it possible to significantly increase the yields and the speed of the deacetylation reaction, as illustrated in Table 1 below:

^* Measure DA Degree of Acetylation

Table 1: Efficacy of the deacetylation according to the prior grinding of chitin

The conditions of the deacetylation carried out in the test reported in Table 1 are as follows: 4 hours of reaction, 100 ° C., NaOH in aqueous solution at 30% by volume, in an estimated chitin ratio: NaOH solution equal to 1 20.

Therefore, chitin is preferentially milled to a particle size of less than 300 μm, such as less than 260 μm, less than 200 μm, or less than 160 μm.

· Step 9: Deacetylation of chitin

This step is implemented only in the case where obtaining chitosan is desired.

The chitin is then placed in a reactor where a base is added.

Advantageously, the deacetylation of chitin is carried out using a strong base.

Preferably, the base used for the basic treatment is in the form of an aqueous basic solution, preferably a concentrated aqueous basic solution.

In this case, the molar concentration of the base in aqueous solution is advantageously between 4 and 25 mol.L ¹ , preferably between 6 and 22 mol.L ¹ , more preferably between 8 and 19 mol.L ¹ , still more preferably between 10 and 19 mol. Even more preferably between 12.5 and 19 mol.L ¹ .

Preferably, the concentration of the base is adjusted so as to obtain a base ratio by dry weight in g: chitin dry weight in g: water by weight in g between 18: 1: 35 and 55: 1: 55, such for example between 18: 1: 35 and 30: 1: 55, or about 24: 1: 45, more preferably about 38: 1: 50. The most preferred values are especially those to be used when of the use of sodium hydroxide.

Preferably, the deacetylation is carried out for 1 to 24 hours and preferably 2 to 18 hours.

Advantageously, this deacetylation is carried out twice, with an intermediate step of neutralizing the pH. For example, the deacetylation can be carried out in two times two hours, that is to say for 4 hours, with an intermediate intermediate pH neutralization step.

The deacetylation temperature is advantageously between 80 and 150.degree. C., preferably between 90 and 120.degree. C. and more preferably at 100.degree.

• Step 10: Recovery of chitosan

The step 10 of recovering chitosan from the reaction medium obtained at the end of step 9 can be carried out by any appropriate recovery method. These methods are known to those skilled in the art.

Advantageously, the recovery of chitosan is carried out by filtration.

In the case where step 8 of chitin grinding is carried out, the recovered chitosan is in powder form.

Chitosan can then undergo any operation known to those skilled in the art to functionalize it, including the addition of radicals (carboxylation, hydroxylation ...).

• Step (optional) 11: Wash

The chitosan recovered at the end of step 10 is then optionally washed.

Step 1 1 of washing the chitosan is advantageously carried out using tap water. Preferably, this water has a temperature between 15 and 60 ° C.

Preferably, the washing is carried out until the pH is neutralized.

• Step (optional) 12: Drying

The chitosan, which may be in the form of a powder, is then optionally dried between 30 and 60%, advantageously between 50 and 70.degree. 60'Ό, to obtain chitosan or a chitosan powder having a dry matter content greater than 85%, more particularly greater than 90%.

The invention will be better understood from the following examples, which are given for illustrative purposes. EXAMPLE 1 Process for Obtaining Chitin According to the Invention

I. Materials and methods

Tenebrio molitor larvae were used. On receipt of the larvae, they can be stored at 4 ° C for 0 to 15 days in their breeding tanks before slaughter without major degradation. The weight of the larvae (age) used is variable and therefore their composition may vary, as illustrated in Table 2 below:

^* % Is expressed as dry weight on wet weight of larvae.

Table 2: Biochemical composition of larvae of Tenebrio molitor according to their weight.

· Step 1: Slaughtering insects

Live larvae (+ 4 ° C to + 25 ° C) are conveyed in a thickness of between 2 and 10 cm, on a perforated belt (1 mm) to a bleaching chamber. The insects are thus bleached with steam (nozzles or steam bed) at 98 ° C under forced ventilation or with water at 92-95 'Ό (spray nozzles) or in mixed mode (water + steam). The residence time in the bleaching chamber is between 5 seconds and 15 minutes, ideally 5 minutes.

The temperature of the larvae at the bleaching outlet is between 75 'Ό and

98 ° C.

• Step 2: Separation of the soft part of cuticles from insects The larvae, once blanched, are conveyed to the feed hopper of a band separator to separate cuticles from the soft part of the larvae.

Advantageously, the separation takes place immediately after slaughtering so that the larvae do not have time to cool to room temperature.

The band separator used is a 601 band separator from Baader.

The diameter of the perforations of the drum is 1, 3 mm.

The soft part of the insects is recovered in a tank.

The cuticles are recovered using a scraper knife.

The dry matter percentage of the cuticles is about 35-45%.

Step 3: enzymatic hydrolysis of cuticles by a protease

In 2 liters of 3 liters with a condenser and a stirrer (Heidolph® RZR1), 160.015 ± 0.007 g of wet cuticles obtained in step 2 (dry matter = 38 ± 5%), 8 g of Prolyve® NP (5% of the mass of wet cuticles) and 1, 6 L ± 0.02 L of hot water. The medium is heated with a water bath at a temperature of 60 ± 2 ° C for 6 hours. Then the temperature is raised to 80 ° for 15 minutes. The reaction medium is then separated by juice extractor (Angelia 7500). Throughout the reaction, the reaction medium is stirred at 280 rpm. The pH is between 6 and 8, preferably between 6.5 and 7.5. The specific activity of Prolyve® NP is 1132.1 I.U./g enzyme. 8 g of Prolyve® NP is used, ie 9056.8 IU for 160.015 ± 0.007 g of wet cuticles (dry matter = 38 ± 5%). The concentration of the enzyme is therefore about 149 I.U./g dry matter of cuticles.

58 ± 2 g of solid residue and a hydrolyzate are obtained. The solid residue is mixed to be homogeneous, weighed and then refrigerated for the night. The hydrolyzate is lyophilized.

• Step 4: Basic treatment of the solid residue

In a 2 L three-neck flask fitted with a condenser and a mechanical stirrer (Heidolph® RZR1), the solid residue obtained in step 3 (dry matter = 44 ± 16%) and 512.05 ± 0 is placed. 02 mL of aqueous solution of sodium hydroxide of concentration equal to 1 mol.L ¹ . The medium is heated with an oil bath at a temperature of 90 ± 2 ° for 24 hours.

About 0.02 L of aqueous sodium hydroxide solution is therefore used per gram of solids solids.

The basic ratio by dry weight in g: solid residue by dry weight in g: water by weight in g is approximately equal to 0.36: 0.45: 9.23. • Step 5: Recovery of chitin

The reaction medium obtained at the end of step 4 is then filtered (SEFAR Filter MEDIFAB® 03-60 / 42) so as to recover the chitin.

• Step (optional) 6: Wash the chitin

The chitin recovered at the end of step 5 is then rinsed with warm tap water until the pH is neutralized.

• Step (optional) 7: Drying of chitin

The chitin is then dried for 24 hours, at 60 ° C, in a drying oven (Binder®, model FP53).

9.6 ± 0.2 g of chitin are thus obtained.

II. Analytical methods

Measurement of dry matter and moisture content

The percentage of dry matter and the moisture content are calculated as follows.

2 g of chitin are weighed into cups, introduced into a drying oven (Binder®, model FED 1 15) and dried at 105 ° for 24 h (or until complete drying).

The percentage of dry matter is obtained by making the ratio of the dry mass of chitin after drying on the mass of chitin before drying.

The moisture content is obtained by removing the percentage of dry matter to the value of 100%.

This measurement method can also be used to measure the percentage of dry matter and the moisture content of the cuticles.

Ash content measurement

The ash content was determined according to the NF V18-101 standard method.

Measurement of crude protein content

The protein content is obtained by the Dumas method, with the conversion coefficient of 6.25, adapted from the NF EN ISO 16634-1 standard.

Measurement of fat or fat content

The lipid content is obtained by a method adapted from EC regulation 152/2009 - process B - SN.

Relative content and abundance of amino acids

The amino acid content of the chitin according to the invention is preferably determined according to the method NF EN ISO 13904 or an adapted method of the EC regulation 152/2009 of 27 January -2009 - SN (these two methods being equivalent) for the tryptophan, and according to the method NF EN ISO 13903 or a method resulting from the regulation CE 152/2009 of 27-01 -2009 - SN for the other amino acids (these two methods being equivalent).

Relative abundance was calculated by relating the content of each amino acid to the total amino acid content.

Total amino acid content

The total amino acid content was determined by summing the individual values obtained for each amino acid, including tryptophan.

Purity by difference

In the case of this measurement, the known impurity contents (amino acids, lipids and ash) were subtracted from the value of absolute purity (100%) to obtain the value of the purity estimated by difference. For example, a sample that contains 30% amino acids, 10% lipids and 1% ash, is then assigned a purity by difference of 100-30-10-1 = 59%

Molecular weight of chitin

The molecular weight was determined according to a method of measuring the falling ball viscosity based on that described in the following publication: "Pacheco et al. ; Structural characterization of chitin and chitosan obtained by biological and chemical methods; Biomacromolecules; 12, 3285-3290, 2011 ".

In particular, the method for determining the molecular weight of chitin relies on viscosity measurements of dilute solutions of chitin. The dilutions are carried out in dimethylacetamide containing 5% lithium chloride (DMAc-LiCl 5%). Indeed, the polymers in solution increase the viscosity of a solvent. The viscosity of the polymer in solution depends on its concentration and molecular weight. The relation is defined by the Mark-Houwink-Sakurada equation:

[h] = KM ^a

with [h]: the intrinsic viscosity, M: the molecular weight, K and has specific constants of a solvent / polymer system at a given temperature.

The values for chitin dissolved in 5% DMAc-LiCl 5 at 25 ° C. are: K = 0.24 mL · g ^-1 and a = 0.69 (Pacheco et al; 201 1).

The intrinsic viscosity corresponds to the specific viscosity when the concentration of the polymer tends to zero.

[h] = c li®m 0 (v ^ c) /

To measure the specific viscosity of chitin, five low concentration solutions are prepared in 5% DMAc-LiCl. The flow times of the Solvent alone (t ₀ ) and solutions (t) of the different concentrations are measured by a ball drop micro-viscometer to calculate the relative viscosity (h _G ). From the relative viscosity fa), it is necessary to calculate the specific viscosities (h _er), restricted (h _ίbά) and inherent (h _ih ^ of each concentration of chitin.

The intrinsic viscosity is then calculated by plotting the curves "concentration vs. reduced viscosity "(positive slope) and" concentration vs. inherent viscosity "(negative slope). Each of these curves is extrapolated to zero concentration. The ordinate at the origin corresponds to the intrinsic viscosity. Similar results are expected from both curves. Finally, to determine the molecular mass of chitin, the Mark-Houwink-Sakurada equation is applied.

III. Results

The properties of the chitin obtained are shown in Table 3 below.

^* MS: dry matter

TABLE 3 Properties of Chitin Obtained in Example 1

The relative amino acid abundance of the chitin obtained is shown in Table 4 below. It is expressed in%.

Table 4: Relative amino acid abundance of chitin obtained in Example 1

Three amino acids appear particularly resistant to the process, namely, valine, histidine and lysine. They represent in fact more than 93% of the residual amino acids.

EXAMPLE 2 Process for Obtaining Chitosan According to the Invention

To prepare chitosan, the chitin resulting from step 5, 6 or 7 of Example 1 is used.

· Step (optional) 8: Crushing chitin

The chitin was milled in an ultracentrifugal screen mill at a size of 250 μm.

• Step 9: Deacetylation of chitin

The chitin is then placed in a reactor where a concentrated sodium hydroxide solution is added. Sodium hydroxide in aqueous solution at a content of 50% (ie a concentration of sodium hydroxide in aqueous solution of 12.5 mol / L) is added according to a weight ratio in g of milled chitin / volume in mL of sodium hydroxide in aqueous solution equal to 1: 50. The tank is then heated to a temperature of 100 ° C. The deacetylation reaction is carried out for 2 times 2 hours, with an intermediate step of neutralizing the pH.

• Step 10: Recovery of chitosan

The reaction medium obtained at the end of step 9 is then filtered (SEFAR MEDIFAB® Filter 03-60 / 42) so as to recover chitosan.

• Step (optional) 11: Wash

The chitosan recovered at the end of step 10 is then rinsed with warm tap water until the pH is neutralized.

Chitosan powder is thus obtained.

The chitosan obtained has a purity by difference greater than 98%.

The molecular weight of the chitosan obtained is equal to 307 +/- 60 kg. mol ^-1 .

· Step (optional) 12: Drying

The chitosan powder is then dried at 60 ° C. in order to obtain a powder having a dry matter content greater than 85%.

EXAMPLE 3 Method for Obtaining Comparative Chitin I. Materials and Methods

• Step 1: Slaughtering insects

This step is identical to that of Example 1.

Step 2: Separation of cuticles from the soft part of insects This step is identical to that of Example 1.

• Step 3: Basic treatment of cuticles

In a 2 L three-neck equipped with a condenser and a mechanical stirrer (Heidolph® RZR1), 90.02 ± 0.02 g of wet cuticles obtained in step 2 (dry matter = 40.1 ± 0.1%) and 1.80 ± 0.02 L of aqueous sodium hydroxide solution of concentration equal to 1 mol.L ¹ . The medium is heated with an oil bath at a temperature of 90 ± 2 ° C for 48 hours. Throughout the reaction, the reaction medium is stirred at 280 rpm.

About 0.05 L of aqueous sodium hydroxide solution is therefore used per gram of cuticle solids.

The ratio by weight of dry weight to g: cuticles in dry weight in g: water in weight in g is approximately equal to 0.9: 0.45: 22.

• Step 4: Recovery of chitin

The reaction medium obtained at the end of step 3 is then filtered (SEFAR Filter MEDIFAB® 03-60 / 42) so as to recover the chitin.

• Step (optional) 5: Washing the chitin

The chitin recovered at the end of step 4 is then rinsed with warm tap water until the pH is neutralized.

• Step (optional) 6: Drying chitin

6.3 ± 0.2 g of chitin are thus obtained.

II. Results

The properties of the chitin obtained at the end of step 6 are presented in Table 5 below.

^* MS: dry matter

* ^* aa: amino acids

TABLE 5 Properties of Chitin Obtained in Example 3

The relative amino acid abundance of the chitin obtained is shown in Table 6 below. It is expressed in%.

TABLE 6 Relative Amino Acid Abundance of Chitin Obtained in Example 3

5 amino acids appear particularly resistant to the process, namely alanine, cysteine, valine, histidine and lysine. Histidine, lysine and alanine are the 3 most resistant amino acids. They represent in fact more than 85% of the residual amino acids.

EXAMPLE 4 Obtaining chitin according to the invention from different insects

Different insects were used in this example: Tenebrio molitor,

Pachnoda marginata, Zophobas morio and Galleria mellonella.

Cuticles were obtained from the larval stage of different insects according to steps 1 and 2 described in Example 1.

• Enzymatic hydrolysis of cuticles by a protease

The cuticles then undergo an enzymatic hydrolysis step under the following conditions:

In a 2 L three-neck equipped with a condenser and a stirrer (Heidolph® RZR1), ITH g of wet cuticles obtained in the preceding step (dry matter = ni%), a qi (g or mL quantity) are placed. ) of protease and 1.6 L ± 0.02 L of hot water, so that the protease concentration is about 140 IU / g of dry cuticles. The medium is heated with a water bath at a temperature of 60 ± 2 ° C for 6 hours. Then the temperature is raised to 80 ° C for 15 minutes. The reaction medium is then separated via a juice extractor (Angelia 7500). Throughout the reaction, the reaction medium is stirred at 300 rpm. The pH is between 6 and 8, preferably between 6.5 and 7.5.

M ₂ g of solid residue and a hydrolyzate are obtained. The various experimental conditions are summarized in Table 7. The solid residue is mixed to be homogeneous, weighed and then refrigerated for the night. The hydrolyzate is lyophilized.

Table 7: Experimental conditions of the different enzymatic hydrolyses as functions of the insects used

• Basic treatment of solid residue

In a 2 L tricolor equipped with a refrigerant and a mechanical stirrer

(Heidolph® RZR1), place m ₂ g of solid residue obtained in the preceding step (dry matter = n ₂ %), and a volume Vi (Vi = m ₂ ^* n ₂ ^* 25 mL) of aqueous solution of sodium hydroxide (or potassium hydroxide) of concentration equal to 1.0 mol.L ¹ . The medium is heated with an oil bath at a temperature of 90 ± 2 ° C for 48 hours. Throughout the reaction, the reaction medium is stirred at 300 rpm. • Recovery, washing and drying of chitin

Chitin is recovered at the end of the basic treatment step, washed and then dried under the conditions described in steps 5, 6 and 7 of Example 1 respectively.

Experimental conditions of basic treatment for different insects are presented in Table 8.

Table 8: Experimental conditions of basic treatment of different insects

A mass m ₃ of chitin is collected. The yield is calculated as follows: m ₃ / m ^* 100 and the results are shown in Table 9.

Table 9: Chitin extraction yields for different insects

The chitins are then analyzed according to the analysis methods indicated in point II of Example 1. The results of analyzes are shown in Table 10, in which the ash, lipid and amino acid contents correspond to levels of gram per 100 g of dry matter.

Table 10: Properties of chitins obtained from different insects and different proteases

The method according to the invention makes it possible to obtain a chitin having a high purity, and this, whatever the insect or the hydrolysis conditions (protease and base) used.

The relative amino acid abundance of the chitins obtained is shown in Table 1 1 below and is expressed in percentages.

different insects

The conditions of enzymatic hydrolysis (protease used), basic treatment (NaOH or KOH) as well as the insects used influence the amino acid composition of the resulting chitin.

EXAMPLE 5 Obtaining chitosan according to the invention from different insects

• Grinding of chitin

Each chitin obtained in Example 4 is finely ground in a centrifugal mill (Retsch® ZM200) with a 250 μm pore grid.

• Deacetylation of chitin

In a 2 L three-neck equipped with a condenser and a stirrer (Heidolph® RZR1), a mass of m ₄ g of the chitin obtained after the milling stage is placed, and a volume V ₂ (V ₂ = m ₄ ^* 50 mL) of aqueous solution of sodium hydroxide (or hydroxide potassium) of concentration equal to 19.0 mol.L ¹ . The medium is heated with an oil bath at a temperature of 100 ± 2 ° C for 2 hours. Throughout the reaction, the reaction medium is stirred at 300 rpm.

• Recovery of chitosan

The reaction medium obtained at the end of the deacetylation step is then filtered (SEFAR Filter MEDIFAB® 03-60 / 42) so as to recover the chitosan.

• Washing of chitosan

The recovered chitosan is then rinsed with warm tap water until the pH is neutralized.

It is then reacted in a tricolor containing the same amount of aqueous solution of sodium hydroxide (or potassium hydroxide) and the previous 3 steps (deacetylation, recovery and washing) are repeated identically.

• Drying of chitosan

The deacetylation, recovery and washing steps are therefore carried out twice in total. At the end of these steps, the chitosan is dried for 24 hours, at 60 ° C., in a drying oven (Binder®, model FP53). A mass m ₅ of chitosan is collected. The yield is calculated as follows: m ₅ / m ₄ ^* 100 and the results are summarized in Table 12. In particular, Table 12 refers to a base ratio: chitin: water which is a ratio by dry weight in g for base and chitin, and in weight in g for water.

Table 12: Chitin masses, volume base and yield of obtaining chitosan according to insects

The chitosans are then analyzed according to the analysis methods indicated in point II of Example 1. The results of analyzes are shown in Table 13, in which the ash, lipid and amino acid contents correspond to contents in grams per 100 g of dry matter. In this table, the measured lipid content is at the limit of detection.

Table 13 Ownership of chitosans obtained from different insects

Since the process according to the invention makes it possible to obtain a chitin of high purity, the resulting chitosan also has this characteristic, even under different deacetylation conditions.

Claims

1. Chitin whose purity by difference is greater than 97.75%, the purity by difference being obtained by subtracting the impurity content in amino acids, lipids and ashes, to the value of absolute purity, said value of absolute purity being equal 100%.

2. Chitin according to claim 1, comprising less than 1, 2% by weight of amino acids on the total dry weight of chitin.

3. Chitin according to claim 1 or 2, comprising less than 2% by weight of ash on the total dry weight of chitin.

4. Chitin according to any one of claims 1 to 3, whose purity by difference is greater than or equal to 98.0% and the molar mass is greater than or equal to 800 kg. mol ^-1 , the molar mass being determined by measuring the viscosity by falling ball.

5. Chitosan whose purity by difference is greater than 97.75%, the purity by difference being obtained by subtracting the impurity contents in amino acids, lipids and ashes, to the value of absolute purity, said value of absolute purity being equal. 100%.

6. Chitosan according to claim 5, whose purity by difference is greater than or equal to 97.9% and the molar mass greater than or equal to 480 kg. mol ^-1 , the molar mass being determined by measuring the viscosity by falling ball.

7. Process for obtaining chitin and / or chitosan, from insects, comprising the following steps:

- separation of cuticles from the soft part of insects,

the basic treatment of the solid residue.

The method of claim 7, wherein the separation of cuticles from the soft part of the insects is performed using a band separator.

The method of claim 7 or 8, wherein the protease is selected from the group consisting of aminopepidases, metallocarboxypeptidases, serine endopeptidases, cysteine endopeptidases, aspartic endopeptidases, metalloendopeptidases.

The method of claim 9, wherein the protease is selected from serine endopeptidases.

1 1. A process according to any one of claims 7 to 10, wherein the basic treatment is carried out with a strong base.

12. Process for obtaining chitin, from insects, comprising the following steps:

the slaughter of insects,

- separation of cuticles from the soft part of insects,

enzymatic hydrolysis of cuticles by a protease, to obtain a solid residue,

the basic treatment of the solid residue, and

- the recovery of chitin.

13. Chitin obtainable by the method according to any one of claims 7 to 12.

14. Process for obtaining chitosan, from insects, comprising the following steps:

the slaughter of insects,

- separation of cuticles from the soft part of insects,

enzymatic hydrolysis of cuticles by a protease, to obtain a solid residue,

the basic treatment of the solid residue,

- the recovery of chitin,

deacetylation of chitin, and

- the recovery of chitosan.

15. Chitosan obtainable by the process according to any one of claims 7 to 12, 14.

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