Composition of amino acid chelates derived from a keratin hydrolysate with high levels of free amino acids, containing at least one mineral nutrient, and their use in agriculture

Abstract

Composition of at least one amino acid chelate of a particular keratin hydrolysate with at least one mineral nutrient, wherein the particular hydrolysate comprises at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate and the mineral nutrient is selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, process of preparation of this composition and uses in particular in agriculture as plant biostimulants.

Description

Title of the invention: Composition of amino acid chelates derived from a keratin hydrolysate with high levels of free amino acids with at least one mineral nutrient and their use in agriculture. Field of the invention

[0001] The invention relates to a composition of amino acid chelates derived from a keratin hydrolysate with a high content of free amino acids and at least one mineral nutrient. The invention relates more particularly to the use of this chelate composition in agriculture, especially as plant biostimulants. State of the art

[0002] To grow, develop, and bear fruit, a plant needs water, light, and nutrients. Plants draw from the soil the elements essential for their growth, such as macro- and micro-elements. However, each plant species has specific needs; therefore, to avoid the consequences of deficiencies, it is necessary to find a good balance among all the nutrients.

[0003] It is also known that sensitivity to deficiencies varies considerably depending on the plant in question: in a state of deficiency, some plants will nevertheless develop and produce products while other plants will not develop at all.

[0004] When nutrients available in the soil are insufficient, they can be supplied in the form of inputs, however it has been observed that, even in the presence of appropriate nutrients, the absorption by the plant of said nutrient(s) is not always efficient.

[0005] Moreover, depending on their composition, some commercial products have the disadvantage of being aggressive towards the seedling, or even the environment.

[0006] Consequently, there remains a continued need for new, effective products that allow for better nutrient absorption by the plant, a reduction in the quantity of mineral inputs or plant protection products, and in particular a reduction in overdosed products. Furthermore, there remains a continued need for products that are environmentally friendly and derived from the circular economy.

[0007] It is also advantageous to have products that stimulate plant development, protect them against abiotic stresses, and increase their performance, particularly in terms of improving harvest quality and yield, and that they are effective on several types of crops.

[0008] This need has been met by the present invention which relates in particular to a composition of amino acid chelates derived from a particular keratin hydrolysate and at least one mineral nutrient.

[0009] The Applicant's patent application WO2019 / 043128 A1 describes a keratin hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remaining amino acids in the hydrolysate being in the form of peptides having a molecular mass of 800 Daltons or less. This hydrolysate comprises L-cystine in a content of 4 to 6% by weight, cysteine ​​in a content of 0.1% or less by weight, and tyrosine in a content of 0.6% or less. This patent application does not describe the preparation of chelates with mineral nutrients obtained from this hydrolysate. Summary of the invention

[0010] The present invention relates to a composition of at least one amino acid chelate of a hydrolysate with at least one mineral nutrient, wherein the hydrolysate is a keratin hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remainder of the amino acids in the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Daltons, said hydrolysate having the following composition in total amino acids: an aspartic acid content of 5 to 8% by weight; a threonine content of 3 to 6% by weight; a serine content of 9 to 14% by weight; a glutamic acid content of 8 to 13% by weight; a glycine content of 6 to 9% by weight; an alanine content of 4 to 6% by weight; a valine content ranging from 6 to 10% by weight; a methionine content ranging from 0.1 to 0.6% by weight;an isoleucine content of 4 to 6% by weight; a leucine content of 6 to 9% by weight; a phenylalanine content of 2 to 5% by weight; a lysine content of 1 to 3% by weight; a histidine content of 0.4 to 1% by weight; an arginine content of 5.5 to 6.5% by weight; a proline content of 8.5 to 11% by weight; a tryptophan content of less than 0.1%, relative to the total weight of total amino acids in the hydrolysate; and the mineral nutrient being selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt, and copper. Advantageously, the hydrolysate comprises 2 to 12% by weight of peptides of 2, 3, 4 amino acids having a molecular mass less than or equal to 800 Daltons by weight relative to the total weight of the hydrolysate.

[0011] The present invention also relates to a method of preparing the composition according to the invention, said method comprising at least one step of mixing the particular hydrolysate, defined in the paragraph above, with at least one mineral nutrient is chosen from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably in the form of hydrated sulfate(s), said mixing step being carried out under agitation for a period of 1 hour to 3 hours.

[0012] Preferably in said process of preparing the composition according to the invention, the hydrolysate is prepared from an animal keratinous material, preferably poultry, according to a preparation process comprising at least the following steps, in this order: - subject the keratinous material to at least one acid hydrolysis, carried out in two stages: -a first hydrolysis carried out at a temperature ranging from 60 to 80°C for a period of 4 to 5 hours then -a second hydrolysis carried out at a temperature ranging from 100 to 115°C for a period of 5 to 7 hours, Both hydrolyses can be carried out without an intermediate pause or by performing an intermediate pause of between 1 hour and 7 days - extract the tyrosine and cystine from said hydrolysate preferably by means of a base; - desalinate the liquid phase obtained after the extraction of the cystine and tyrosine; - concentrate the desalinated liquid phase to obtain an aqueous composition comprising 45 to 55% by weight of keratin hydrolysate in solid form relative to the total weight of said composition.

[0013] The present invention further aims at the use of this composition in agriculture, preferably as a plant biostimulant.

[0014] In particular, the present invention aims at the use of the composition according to the invention as a biostimulant for plants selected from among field crops, vines, arboriculture, market gardening, medicinal and aromatic plants (PPMA), ornamental crops.

[0015] More particularly, the invention relates to the use of the composition according to the invention to improve the absorption of mineral nutrients and amino acids by the plant and to reduce the amount of mineral inputs.

[0016] Indeed, it has been shown that the composition of chelates according to the invention makes it possible to improve the absorption of mineral nutrients supplied by these chelates and also the absorption of mineral nutrients present in the soil.

[0017] More particularly, the invention relates to the use of the chelate composition according to the invention to stimulate plant development, to increase root biomass as well as leaf biomass, to improve plant size.

[0018] The composition of chelates according to the invention also makes it possible to improve crop yields.

[0019] The hydrolysate used in the composition according to the present invention is distinguished by its high content of free amino acids and also by the presence of 2 to 12% by weight of peptides of 2, 3, 4 amino acids having a molecular mass less than or equal to 800 Daltons by weight relative to the total weight of the hydrolysate.

[0020] The use of the chelate composition according to the invention is part of the search for more sustainable and resilient agriculture: chelates can be used in quantities much lower than the quantities used for fertilizers.

[0021] Indeed, without wishing to be linked to any theory, the composition of chelates according to the invention is not intended to provide nutrients such as carbon, nitrogen, phosphorus for plants but rather to enable the young plant to increase its capacity to assimilate both amino acids, and macro- and micro-elements.

[0022] The use of the chelate composition according to the invention therefore makes it possible to reduce soil fertilization. The use according to the invention thus indirectly produces effects on the soil since it allows for a reduction in inputs, plant protection products, and conventional chemical fertilizers.

[0023] Other aspects, advantages, properties of the invention will become clear from the description, in particular from the examples that follow, which are indicative and in no way limiting. Detailed description

[0024] Composition of chelates

[0025] The present invention relates to a composition of amino acid chelates of a particular keratin hydrolysate with at least one mineral nutrient.

[0026] For the purposes of this text, "chelation" means the formation of a complex between one or two amino acid(s) (the ligand) and a mineral nutrient (the metal cation) in which the mineral nutrient is attached to the amino acid by at least two coordination bonds.

[0027] In the present invention, the chelation of mineral ions takes place with amino acids in free form, but also with small peptides (of 2, 3 or 4 amino acids). The degree of chelation of the mineral ion, that is to say the ratio between chelated ions and total ions (chelated + unchelated), depends on the amino acid and the metal ion present.

[0028] Keratin hydrolysate

[0029] The keratin hydrolysate used according to the present invention, also referred to as the "particular hydrolysate" in this text, is distinguished by its high level of amino acids in free form: at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remainder also being in highly hydrolyzed form since the remainder of the amino acids in the hydrolysate is in the form of small peptides having a molecular mass less than or equal to 800 Daltons.

[0030] Without wishing to be linked to a theory, it appears that the presence of small peptides in this particular hydrolysate, in particular dipeptides and tripeptides, also allows for additional chelation with mineral nutrients.

[0031] This composition was established using an HPLC analysis method on a gel permeation chromatography column, which allows for the determination of the molecular weight distribution of products containing proteins and / or peptides and / or free amino acids. The sample is dissolved: the molecular weight distribution is performed on the soluble portion of the products to be analyzed. The hydrolysate used in the present invention is completely soluble in water at the concentrations required for the analysis. The sample is then injected into an HPLC system, followed by UV detection. The separation of the different compounds is based on their molecular size.

[0032] Advantageously, the hydrolysate used according to the present invention is obtained from natural keratinous materials of animal origin, particularly poultry, advantageously from poultry feathers. Examples of poultry include hens, especially laying hens, chickens, turkeys, ducks, geese, etc. The natural keratinous materials may also be selected from animal hair, particularly pig bristles, animal hooves, and animal nails.

[0033] In particular, advantageously the hydrolysate used according to the present invention is not obtained from human keratin such as hair.

[0034] The hydrolysate used in the composition according to the invention is a keratin hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remaining amino acids in the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Daltons, said hydrolysate having the following composition in total amino acids: an aspartic acid content ranging from 5 to 8% by weight, preferably ranging from 6 to 7% by weight; a threonine content ranging from 3 to 6% by weight, preferably from 4 to 5% by weight; a serine content ranging from 9 to 14% by weight, preferably ranging from 10 to 12% by weight; a glutamic acid content ranging from 9 to 11% by weight; a glycine content of 6 to 9% by weight, preferably 6.5 to 8% by weight; an alanine content of 4 to 6% by weight, preferably 4 to 5% by weight weight; a valine content of 6 to 10% by weight, preferably 6.5 to 8% by weight; a methionine content of 0.1 to 0.6% by weight; an isoleucine content of 4 to 6% by weight, preferably 4 to 5% by weight; a leucine content of 6 to 9% by weight, preferably 7 to 8% by weight; a phenylalanine content of 2 to 5% by weight; a lysine content of 1 to 3% by weight; a histidine content of 0.4 to 1% by weight; an arginine content of 5.5 to 6.5% by weight; a proline content ranging from 8.5 to 11% by weight, a tryptophan content of less than 0.1%, preferably 0% by weight relative to the total weight of total amino acids in the hydrolysate.

[0035] Amino acids are determined according to a method adapted from EC Regulation 152 / 2009.

[0036] According to this method, for the determination of the quantities of total amino acids, hydrolysis using an acid is carried out beforehand.

[0037] For the determination of the quantities of free and total amino acids, the amino acids are separated by chromatography (“HPLC” or “HPLC” in English) preferably with an ion exchange column and quantified by reaction with ninhydrin and photometric detection generally at 570 nm.

[0038] According to a preferred embodiment, the hydrolysate comprises the following free amino acids: at least 95% free aspartic acid by weight relative to the total weight of aspartic acid in the hydrolysate; at least 95% free threonine by weight relative to the total weight of threonine in the hydrolysate; at least 95% free serine by weight relative to the total weight of serine in the hydrolysate; at least 93% free glutamic acid by weight relative to the total weight of glutamic acid in the hydrolysate; at least 93% free glycine by weight relative to the total weight of glycine in the hydrolysate; at least 93% free alanine by weight relative to the total weight of alanine in the hydrolysate; at least 95% of methionine in free form by weight relative to the total weight of methionine in the hydrolysate;at least 93% of phenylalanine in free form by weight relative to the total weight of phenylalanine in the hydrolysate; at least 95% of proline in free form by weight relative to the total weight of proline in the hydrolysate.

[0039] As shown in Table 1, many amino acids are at least 95% in free form relative to the total weight of said amino acid in the hydrolysate.

[0040] The free amino acids are in their natural, undenatured L (levorotatory) configuration, thus readily available to soil microorganisms and plants. Furthermore, the hydrolysate used according to the invention has high levels of free branched-chain amino acids: valine, leucine, and isoleucine. These branched-chain amino acids are known to be more difficult to release under identical processing conditions.

[0041] Advantageously, the total amino acid content (free and bound) of the hydrolysate used according to the invention, i.e., the active substance of the hydrolysate, ranges from 40% to 95%, preferably 45% to 94% by weight relative to the total weight of the hydrolysate, the hydrolysate further comprising mineral matter and water. As already mentioned, the amino acids of the hydrolysate used in the invention are essentially free amino acids.

[0042] The hydrolysate used to form the chelate composition according to the invention also comprises small peptides, the percentage of small peptides—having a molecular mass less than or equal to 800 Daltons—in the hydrolysate ranging from 2 to 12% by weight relative to the total weight of the hydrolysate. Within this fraction, the most abundant peptides are those with the lowest mass.

[0043] As mentioned above, small peptides, particularly those of 2 to 3 amino acids, have a very good chelating capacity with respect to mineral ions. Thus, their presence in a hydrolysate increases the capacity of that hydrolysate to chelate these ions, compared to a hydrolysate that does not contain them.

[0044] Preferably, the mineral content of said hydrolysate, preferably sodium or potassium chloride, phosphate or sulfate, is less than or equal to 9% by weight, preferably less than 8% by weight relative to the total weight of the hydrolysate. This mineral content is determined after calcination of the hydrolysate at 550°C for 4 hours.

[0045] The hydrolysate used according to the invention is also soluble in water; indeed, 1 g of hydrolysate is soluble in 5 ml of water. This is because the hydrolysate contains a very high proportion of water-soluble amino acids, both by number and weight. Furthermore, the low levels of cystine and tyrosine in the preferred hydrolysate also contribute to its high water solubility. This instant solubility is an advantage for farmers using the hydrolysate in liquid form, as it avoids all the practical problems encountered during spraying, particularly clogging of the sprayer nozzles.

[0046] The mineral nutrients used

[0047] The composition according to the present invention comprises at least one mineral nutrient selected from the group consisting of iron (Fe), zinc (Zn), manganese (Mn), magnesium (Mg), calcium (Ca), molybdenum (Mo), cobalt (Co), and copper (Cu). More particularly, iron (Fe), magnesium (Mg), and calcium (Ca) are classified as macroelements, and zinc (Zn), manganese (Mn), molybdenum (Mo), and copper (Cu) are classified as microelements.

[0048] According to a first variant of the composition of the invention, the chelate(s) comprises a single mineral nutrient selected from the group consisting of iron, the zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably consisting of zinc, magnesium, calcium and copper.

[0049] According to a second variant of the composition of the invention, the chelate(s) comprises / comprise several mineral nutrients selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably the chelate(s) comprises / comprise 2, 3, 4 or 5 mineral nutrients selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably iron, zinc, manganese and molybdenum.

[0050] Preferably, the chelate(s) comprises / include iron, zinc, manganese and / or molybdenum.

[0051] According to another embodiment of the invention, the chelate(s) further comprise at least one anion selected from borate, silicate, phosphate, nitrate.

[0052] According to a first variant of this mode, the chelate(s) comprises molybdenum and a borate.

[0053] According to a second variant of this mode, the chelate(s) comprises / include iron, zinc, manganese, molybdenum and a borate.

[0054] Advantageously, the quantity of total amino acids in the composition of chelates according to the invention ranges from 10% to 60%, preferably from 15% to 35%, and preferably from 20% to 30%, by weight relative to the total weight of the composition.

[0055] By "total amino acids of the chelate composition" means free amino acids and bound amino acids, these free and bound amino acids being in chelated or non-chelated form.

[0056] Advantageously, the total amount of mineral nutrients in the composition of chelates according to the invention ranges from 0.1% to 15%, preferably from 0.2% to 10%, and preferably from 0.5% to 5% by weight relative to the total weight of the composition.

[0057] It has been observed that the composition of chelates according to the present invention allows very good absorption of amino acids on the one hand and mineral nutrients on the other hand, thus allowing a reduction of inputs to improve plant growth and productivity.

[0058] According to a first particular embodiment, the chelate composition according to the present invention comprises the particular hydrolysate and zinc.

[0059] According to a second particular embodiment, the chelate composition according to the present invention comprises the particular hydrolysate and calcium.

[0060] According to a third particular embodiment, the chelate composition according to the present invention comprises the particular hydrolysate and magnesium.

[0061] According to a fourth particular embodiment, the chelate composition according to the present invention comprises the particular hydrolysate and copper.

[0062] The chelate composition according to the invention can be used with other plant protection products and / or fertilizers applied in solution to the soil and plants; in fact, they allow the end user to avoid adding additional passes of agricultural machinery on the fields.

[0063] Process for preparing the hydrolysate

[0064] The hydrolysate used according to the invention is a chemical hydrolysate, since it is obtained by carrying out at least one acidic chemical hydrolysis step. Thus, the keratin hydrolysate used according to the invention is prepared from animal keratin material, preferably poultry, according to a preparation process comprising at least one acid hydrolysis step using a strong acid selected from hydrochloric, phosphoric, and sulfuric acids, preferably hydrochloric acid.

[0065] Advantageously, the hydrolysate used according to the invention is obtained by a preparation process in which the keratin material is preferably poultry keratin material, comprising at least the following steps, in this order: - subjecting the keratin material to at least one acid hydrolysis under conditions suitable for obtaining a hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remainder of the amino acids in the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Daltons.

[0066] Preferably, tyrosine and cystine are extracted from said hydrolysate, preferably this extraction is carried out by precipitation using a mineral base.

[0067] The hydrolysate used according to the invention is obtained from natural keratinous materials, advantageously from poultry feathers. Examples of poultry include hens, chickens, turkeys, ducks, geese...

[0068] In particular, the hydrolysate used according to the invention is not obtained from human keratin such as hair.

[0069] The process for preparing the keratin hydrolysate used according to the invention implements at least one hydrolysis using an acid under conditions suitable for obtaining a hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remainder of the amino acids in the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Daltons.

[0070] The hydrolysis of keratin is carried out using an acid, preferably a strong acid chosen from hydrochloric, phosphoric and sulfuric acids, preferably Hydrochloric acid. Preferably, the strong acid is used in a concentration ranging from 10 to 30%, preferably from 15 to 25%.

[0071] The hydrolysis is generally carried out over a period of 1 to 8 hours, preferably 6 to 7 hours, at a temperature of 100 to 115°C, preferably 105 to 115°C. The hydrolysis can be carried out in several steps, for example 2, 3 or 4 steps.

[0072] According to a particular variant, the hydrolysis is carried out in two steps: - a first hydrolysis carried out at a temperature ranging from 60 to 80°C for a period of 4 to 5 hours then - a second hydrolysis carried out at a temperature ranging from 100 to 115°C for a period of 5 to 7 hours, the two hydrolyses being able to be carried out without an intermediate pause stage or by carrying out an intermediate pause stage of between 1 hour and 7 days.

[0073] More specifically the first hydrolysis is carried out at 72°C for 4.5 hours and the second hydrolysis is carried out at 107°C for 6 hours, with an intermediate break of 24 to 80 hours being carried out between the two hydrolyses.

[0074] The hydrolysis, carried out in one or more steps, is advantageously followed by at least one step of extraction of cystine and tyrosine.

[0075] The extraction step of cystine and tyrosine is carried out using a base, preferably sodium hydroxide, potassium hydroxide, or more preferably sodium hydroxide. The addition of a base to the hydrolysate causes the less soluble amino acids (mainly cystine and tyrosine) to precipitate, thus making them separable from the liquid phase by suitable techniques, such as filtration or dewatering.

[0076] The hydrolysis and extraction steps of cystine and tyrosine may be followed by optional purification steps of the hydrolysate obtained.

[0077] The invention further relates to a method of preparing the hydrolysate in which tyrosine and cystine are extracted from said hydrolysate and the liquid phase obtained after the extraction of cystine and tyrosine is desalted.

[0078] In particular, the liquid phase obtained after the extraction of cystine and tyrosine can be desalinated to extract the salts formed by the action of the base on the acid, and thus obtain a desalinated liquid phase.

[0079] The hydrolysis, cystine and tyrosine extraction, and desalination steps can be followed by optional concentration and drying steps, for example by spray drying.

[0080] The desalination, concentration and drying stages are classic stages whose implementation falls within the skills of a person skilled in the art.

[0081] The step of extracting cystine and tyrosine can be followed by an optional step of recovering certain amino acids from the precipitate by re-dissolving the latter in acid, then re-precipitating with a base, the amino acids to be recovered then being in the liquid phase, which can be added to the liquid phase from the first dewatering.

[0082] Preferably, the hydrolysate used according to the present invention comprises less than 1% by weight of tyrosine relative to the total weight of the hydrolysate, preferably less than 0.5%, even more preferably, the hydrolysate contains no tyrosine, the only traces of tyrosine being due to the limitations of the operating conditions and the equipment used during the extraction step.

[0083] Preferably, the hydrolysate according to the present invention comprises less than 2.5%, preferably less than 1.5% and preferably less than 1% by weight of cystine relative to the total weight of the hydrolysate, even more preferably, the hydrolysate does not contain cystine.

[0084] Furthermore, insofar as the hydrolysate according to the invention is not obtained under reducing conditions, it does not include cysteine.

[0085] Method for preparing the chelate composition

[0086] Preferably, the hydrolysate in liquid form obtained after the extraction of cystine and tyrosine, and after desalination and concentration, is mixed with salts of the chosen mineral elements, preferably sulfates in hydrated form, under stirring, in the desired proportions.

[0087] The mixing is carried out at room temperature for a period of 1 to 3 hours.

[0088] It is possible to use the chelate composition as such for the intended applications.

[0089] It is also possible to dilute the product with water to promote the dissolution of mineral salts in the mixture and ensure good homogeneity, or to facilitate its use in agriculture.

[0090] In the case of a suspension, homogeneity can be obtained by grinding in the liquid phase. The stability of the suspension (absence of settling over time) can be obtained by the possible addition of additives known to those skilled in the art (bentonite, attapulgite, for example).

[0091] It is also possible to dry the chelate composition in solution form by spray drying, so as to obtain the product in powder form.

[0092] Uses

[0093] The composition according to the present invention is advantageously used in agriculture, preferably on plants selected from among major crops, vineyards, arboriculture, market gardening, medicinal and aromatic plants, ornamental crops.

[0094] Preferably, the chelating composition according to the invention is used in the form of an aqueous solution comprising 45 to 55% by weight of keratin hydrolysate in solid form relative to the total weight of said composition. The aqueous composition may serve as a carrier for other active ingredients and be diluted accordingly.

[0095] The composition according to the present invention can also be used with at least one agent chosen from plant protection products, biocontrol agents, plant biostimulants, microorganism-based products, in particular as a coating.

[0096] The following examples are intended to illustrate the invention without limiting its scope. Examples

[0097] Example 1- Keratin hydrolysate

[0098] Preparation of the hydrolysate

[0099] Hydrolysis

[0100] In a 55,000-litre reactor / hydrolyzer, 9,000 kg of poultry feathers containing 50% dry matter are introduced. Chemical hydrolysis is carried out by adding 18,000 litres of hydrochloric acid (23%); the hydrolysis is performed at 72°C for 4.5 hours.

[0101] The resulting product is stored for 48 hours, allowing its temperature to naturally reach room temperature. Then, a second chemical hydrolysis is carried out by heating at 107°C for 6 hours without the addition of acid.

[0102] The hydrolysate obtained comprises 88% by weight of free amino acids, the remainder of the amino acids in the hydrolysate being in the form of small peptides having a molecular mass less than or equal to 800 Daltons.

[0103] Purification

[0104] The hydrolysate is then allowed to settle in order to remove the grease from the keratinous material that floats on the surface of the aqueous phase. The excess hydrochloric acid introduced during the hydrolysis step is removed by distillation. 8000 kg of concentrate are recovered. Then 4500 kg of water are added to obtain 12500 kg of diluted concentrate.

[0105] pH adjustment

[0106] 30.5% sodium hydroxide is added to the hydrolysate to raise the pH to a value between 4 and 5. Upon addition of sodium hydroxide, the less soluble amino acids, particularly cystine, tyrosine, leucine, and isoleucine, precipitate at least partially. The other amino acids remain completely in solution in the liquid phase.

[0107] Spin drying

[0108] The suspension is then placed in a centrifuge, to separate the precipitate (2000 kg), and recover the liquid phase (17000 kg) in a tank.

[0109] Recovery of certain amino acids from the precipitate

[0110] The precipitate (2000 kg) is redissolved in approximately 4% hydrochloric acid (7000 kg), decolorized by passing over carbon, and then the solution is neutralized by adding 30% sodium hydroxide (1250 kg). A new precipitate forms, which is separated by dewatering: 650 kg of precipitate and 8750 kg of liquid phase are obtained.

[0111] Combination of liquid phases and desalination

[0112] The liquid phases from the first spin-drying (17000 kg) and the second spin-drying (8750 kg) are combined and desalinated jointly by electrodialysis to give approximately 17500 kg of desalinated liquid phase.

[0113] Concentration and / or drying

[0114] The liquid phase is concentrated by evaporation of water to reach 55% dry matter (hydrolysate in liquid form);

[0115] Table 1 shows the contents and weight fractions of each of the amino acids in the hydrolysate in powder form.

[0116] [Tables 1] % weight relative to the total weight of total amino acids in the hydrolysate. Weight fraction of free amino acids / total amino acids: Aspartic acid 6.44 98%, Threonine 4.32 99%, Serine 10.72 100%, Glutamic acid 9.78 95%, Glycine 7.30 97%, Alanine 4.38 97%, Valine 7.30 70%, Cystine 1.93 63%, Methionine 0.48 100%, Isoleucine 4.37 77%, Leucine 7.23 92%, Tyrosine 0.77 81%, Phenylalanine 4.44 96%, Lysine 1.71 91% Histidine 0.60 93% Arginine 5.84 92% Proline 9.89 99% total 87.44%

[0117] The free amino acid content is 93.1% by weight relative to the weight of total amino acids (free and bound).

[0118] In the following examples, the hydrolysate used is the hydrolysate according to example 1, in liquid form, it corresponds to a dry matter content of 55% and a nitrogen content of 7.1%.

[0119] In the following examples, the statistical differences between the values ​​were determined by the ANOVA method.

[0120] Application doses have sometimes been expressed per hectare (ha), i.e. per 10000 m2.

[0121] Example 2 - Preparation of chelate compositions

[0122] Example 2.1 Preparation of the chelate composition “keratin-Zn hydrolysate”

[0123] In a 5-liter reactor, 1734 grams of hydrolysate according to Example 1 in concentrated liquid form, 660 g of zinc sulfate heptahydrate, and 600 grams of water are introduced. The mixture is stirred for one hour at room temperature. The reaction medium is a viscous, opaque brown solution.

[0124] The formulation, i.e., the resulting chelate composition, comprises 29.8% total amino acids, of which 27.1% are free amino acids, and 5.00% zinc. The density of this formulation is 1.305.

[0125] Example 2.2 Preparation of the chelate composition “keratin hydrolysate-nutrients”

[0126] In a 5-liter reactor, 1783 g of hydrolysate according to Example 1 in concentrated liquid form, 283 g of iron(II) sulfate heptahydrate, 125 g of zinc sulfate heptahydrate, 87 g of manganese(II) sulfate monohydrate, 96 g of magnesium sulfate heptahydrate, 282 g of monoethanolamine borate solution—comprising, by weight, 20% monoethanolamine, 57.5% boric acid, and 22.5% water—2.6 g of anhydrous sodium molybdate(III), and 341 g of water are loaded. The mixture is stirred for one hour at room temperature. The medium is a very viscous, brownish-blue liquid.

[0127] The formulation, i.e., the resulting chelate composition, comprises 24.8% total amino acids, of which 22.5% are free amino acids, and the following trace elements: 1.89% iron, 0.94% zinc, 0.94% manganese, 1.03% boron, and 0.04% molybdenum. The density of this formulation is 1.350.

[0128] Example 2.3 Preparation of the chelate composition “keratin-B-Mo hydrolysate”

[0129] In a 5-liter reactor, 1203 g of hydrolysate according to Example 1 in concentrated liquid form, 1781 g of monoethanolamine borate solution—comprising, by weight, 20% monoethanolamine, 57.5% boric acid, and 22.5% water—and 16.1 g of anhydrous sodium molybdate are loaded. The mixture is stirred for one hour at room temperature. The medium is a viscous, brown liquid with blue reflections.

[0130] The formulation, i.e. the composition of chelates obtained, comprises 19.8% total amino acids, of which 18.0% are free amino acids, and the following trace elements: 5.00% boron and 0.20% molybdenum. The density of this formulation is 1.243.

[0131] Example 2.4 Preparation of the chelate composition “keratin-Mg hydrolysate”

[0132] In a 5 L reactor, 1225 g of hydrolysate according to Example 1 in concentrated liquid form, 300 g of water, and 830 g of magnesium sulfate heptahydrate are loaded. The mixture is stirred for one hour at room temperature. The medium is a thick brown solution with a slight precipitate.

[0133] The formulation, i.e. the composition of chelates obtained, comprises 25.3% total amino acids, of which 23.0% are free amino acids, and 3.5% magnesium. The density of this formulation is 1.31.

[0134] Example 2.5 Preparation of the "keratin-Cu hydrolysate" chelate composition

[0135] In a 5 L reactor, 3300 g of the hydrolysate according to Example 1 in concentrated liquid form, 1500 g of water, and 688 g of copper(II) sulfate pentahydrate are loaded. The mixture is stirred for one hour at room temperature. The medium is a fairly fluid, brown solution with bluish reflections.

[0136] The formulation, i.e., the resulting chelate composition, comprises 29.8% total amino acids, of which 27.1% are free amino acids, and 3.20% copper. The density of this formulation is 1.305.

[0137] Example 3 - Application to plants

[0138] Example 3.1 Application of the composition “keratin-Zn hydrolysate”

[0139] Example 3.1.1 On flax

[0140] Flax seeds of Variety Ideo were placed in seed furrows using a seed drill - in order to ensure homogeneous sowing - at a density of 2320 g of flax seeds per 1 m2.

[0141] Then the chelate composition prepared in Example 2.1 was applied as a foliar spray at BBCH stage 15. The growth stage of the flax plants was determined using the BBCH scale for fiber flax. According to this scale, codes 10 to 19 correspond to the development of the leaves, in particular the codes 15 corresponds to the presence of 5 spread leaves.

[0142] The chelate composition was applied at a dose corresponding to 5.5 litres of the chelate composition in liquid form (in a slurry of 200L of water) for 10000 m2 of planted area.

[0143] As a control, flax seeds of the same variety were planted at the same density of 2320 g flax seeds per 1 m2.

[0144] Another control was used, keratin hydrolysate according to Example 1 at a dose corresponding to 3 litres of hydrolysate in liquid form (in a slurry of 200 L of water) per 10000 m2 of planted area and sprayed on the leaves at BBCH15 stage 1. This dose corresponds to the same quantity of keratin hydrolysate as that present in 5.5 L of keratin-Zn hydrolysate (composition of Example 2.1).

[0145] Table 2 shows the macro-element (NH4+ and Ca) concentrations in ppm measured in flax sap at BBCH stage 51. The growth stage of the flax plants was determined using the BBCH scale for fiber flax. According to this scale, codes 50 to 59 correspond to the development of flower buds, specifically code 51, which corresponds to the presence of 10% of visible flower buds.

[0146] [Tables2] Macronutrient content in flax sap - BBC H51 in ppm nH4+ Ca Untreated control 216 1285 Treatment with hydrolysis from example 1 246 1417 Treatment with composition from example 2.1 312 1561

[0147] Table 3 shows the micronutrient (B and Zn) content in ppm measured in flax sap at BBCH stage 51. The growth stage of the flax plants was determined using the BBCH scale for fiber flax. According to this scale, codes 50 to 59 correspond to the development of flower buds, specifically code 51, which corresponds to the presence of 10% of visible flower buds.

[0148] [Tables3] Micronutrient content in flax sap - BBC H51 in ppm B Zn Untreated control 2.09 3.18 Treatment with the hydrolysis of example 1 2.19 3.50 Treatment with the composition of example 2.1 2.7 3.5

[0149] The use of the chelate composition according to the invention made it possible to increase the content of ammonium, calcium, boron and zinc in the sap at BBCH stage 51.

[0150] This increase in the micro- and macro-element content at this stage reflects better assimilation of nutrients by the plant when the chelate composition according to the invention is used, in particular better assimilation of nutrients not present in the composition (according to example 2.1) applied.

[0151] Example 3.1.2 On maize

[0152] Futurixx variety maize seeds were placed in pots at a rate of 3 seeds per pot. The pots have a capacity of 4 litres and the growing medium used consists of 50% perlite and 50% vermiculite.

[0153] The different modalities, applied by foliar spraying at BBCH stage 16, are detailed in Table 4 below. The growth stage of the maize plants was determined using the BBCH maize growth chart. According to this chart, codes 10 to 19 correspond to leaf development, in particular code 16 corresponds to the presence of 6 fully unfurled leaves.

[0154] [Tables4] Treatment Method Application Rate Rate / Plants 1 Control Water - - 2 Hydrolysate from Example 1 3 L / hectare 0.03 x 10³ L / plant 3 ZnSO4, 7H2O 3 L / ha i.e. 440 g of Zn per hectare 0.03 x 10³ L / plant 4 Composition according to Example 2.1 5.5 L / ha (i.e., 360 g of Zn / hectare) 0.06 x 10³ L / plant 5 Zinc EDTA Solution 3 L / ha i.e. 440 g of Zn per hectare 4.9 x 10³ g / plant

[0155] The chelate composition according to example 2.1 was applied at a dose corresponding to 5.5 litres of said composition in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area (modality 4).

[0156] As a control, maize seeds of the same variety were planted at the same density of 3 seeds per pot and watered only with water (modality 1).

[0157] Another control was used, keratin hydrolysate alone at a dose corresponding to 3 liters of hydrolysate in liquid form (in a slurry of 200 L of water) per 10,000 m² of planted area, sprayed on the leaves at BBCH stage 16 (treatment 2). This dose corresponds to the same quantity of keratin hydrolysate as that present in 5.5 L of keratin-Zn hydrolysate (composition of example 2.1).

[0158] Another control was used: zinc alone at a dose corresponding to 440 g of solid zinc (in a slurry of 200 L of water) per 10,000 m² of planted area, sprayed onto the leaves at BBCH stage 16 (treatment 3). This dose corresponds to 50% of the amount of zinc present in 5.5 L of keratin-zinc hydrolysate. This dose is 22% higher by weight than the amount of zinc present in 5.5 L of the keratin-zinc hydrolysate composition (composition of Example 2.1).

[0159] Another control was used: zinc-EDTA at a dose corresponding to 440 g of zinc in solid form (in a slurry of 200 L of water) per 10,000 m² of planted area, sprayed onto the leaves at BBCH stage 16 (treatment 5). This treatment allows for comparison of the effectiveness of a chemical chelate composition with the chelate composition according to the invention. This dose corresponds to 22% more by weight than the amount of zinc present in 5.5 L of keratin-Zn hydrolysate (composition of Example 2.1).

[0160] Table 5 below represents the zinc content at 106 g / plant measured in maize leaves 24 h after application of the products.

[0161] [Tables5] Treatment Method Zinc content (pg / plant) in maize leaves - 24 h after treatment application 1 Control (water) 41.4 2 Hydrolysate from example 1 38.07 3 ZnSO4, 7H2O 42.76 4 Composition according to example 2.1 73.09 5 Zinc EDTA solution 47.85

[0162] The use of the chelate composition according to the invention (modality 4) makes it possible to increase the zinc content in the leaves at BBCH stage 16.

[0163] This increase in Zn content at this stage reflects better nutrient assimilation by the plant when zinc is chelated with keratin hydrolysate.

[0164] The chelate composition according to the invention is more efficient than a chemical chelate, (+35% compared to modality 5) and than zinc alone (+41% compared to modality 3).

[0165] This result is statistically significant (p<0.10).

[0166] Example 3.2 Application of the "keratin hydrolysate-nutrients" composition

[0167] Example 3.2.1 On maize

[0168] Futurixx variety maize seeds were placed in pots at a rate of 3 seeds per pot. The pots have a capacity of 4 litres and the growing medium used consists of 50% perlite and 50% vermiculite.

[0169] The different modalities, applied by foliar spraying at BBCH stage 16, are detailed in Table 6 below. The growth stage of the maize plants was determined using the BBCH maize growth chart. According to this chart, codes 10 to 19 correspond to leaf development, in particular code 16 corresponds to the presence of 6 fully unfurled leaves.

[0170] [Tableauxô] Treatment Method Application Rate Rate / Plants 1 Control Water - 2 Hydrolysate from Example 1 3 L / ha 0.03 x 10³ L / plant 3 Nutrient Solution 1.5 L / ha 0.015 x 10³ L / plant 4 Composition according to Example 2.2 1.5 L / ha 0.015 x 10³ L / plant 5 EDTA-Nutrient Solution 1.5 L / ha 0.015 x 10³ L / plant

[0171] The chelate composition according to example 2.2 was applied at a dose corresponding to 1.5 liters of the composition in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area (modality 4).

[0172] As a control, maize seeds of the same variety were planted at the same density of 3 seeds per pot and watered only with water (modality 1).

[0173] Another control was used, keratin hydrolysate alone at a dose corresponding to 3 litres of hydrolysate in liquid form (in a slurry of 200 L of water) per 10,000 m2 of planted area and sprayed on the leaves at BBCH16 stage 1 (modality 2). This dose corresponds to the same quantity of keratin hydrolysate as that present in 1.5 L of keratin-Zn hydrolysate (composition of example 2.2).

[0174] Another control was used, the nutrients alone at a dose corresponding to 1.5 L / ha in liquid form (in a slurry of 200 L of water) per 10,000 m² of planted area and sprayed onto the leaves at BBCH stage 16 (treatment 3). This dose corresponds to the same quantity of nutrients as that present in 1.5 L of keratin-nutrient hydrolysate (composition of Example 2.2).

[0175] Another control was used, the nutrient-EDTA at a dose corresponding to 1.5 L / ha in liquid form (in a slurry of 200 L of water) for 10,000 m² of planted area and sprayed on the leaves at BBCH stage 16 (treatment 5). This treatment allows comparison of the effectiveness of a chemical chelate composition with the chelate composition according to the invention.

[0176] Table 7 represents the zinc and manganese (micronutrient) content in pg / plant measured in maize leaves 24 h after application of the products.

[0177] [Tables7] Treatment Modality Zn content (pg / plant) in corn leaves - 24 h after treatment application Mg content (pg / plant) in corn leaves - 24 h after treatment application 1 Control (water) 196.8 533.7 2 Hydrolysate from example 1 310.2 768 3 Nutrients 319.7 736.6 4 Composition according to example 2.2 337 933 5 Nutrients EDTA solution 240.9 573.1

[0178] The use of the chelate composition according to the invention (modality 4) makes it possible to increase the zinc and manganese content in maize leaves at BBCH stage 16.

[0179] This increase in micronutrient content at this stage reflects better nutrient assimilation by the plant when zinc is chelated with keratin hydrolysate.

[0180] With the same quantity of nutrients, the composition of chelates is more efficient than a chemical chelate (+21% for Zn and +39% for Mn, cf. modality 5) and that the nutrients alone (+5% for Zn and +28% for Mn; cf. modality 3).

[0181] This result is statistically significant (p<0.10).

[0182] Example 3.2.2 On the carrots

[0183] Carrot seeds of the Nérac variety were placed in seed furrows using a seed drill - in order to ensure homogeneous sowing - at a density of 71.4 g carrot seeds per 1 m2.

[0184] The chelate composition according to Example 2.2 was then applied as a foliar spray at BBCH stage 16, 10 days after the first application, and then again at BBCH stage 42. The growth stage of the carrots was determined using the BBCH scale for root and tuber species. According to this scale, codes 10 to 19 correspond to leaf development; in particular, code 16 corresponds to the presence of 6 fully unfurled leaves. According to this scale, codes 40 to 49 correspond to the development of the harvestable vegetative organs; in particular, code 42 corresponds to 20% of the final size of the carrot root.

[0185] The chelate composition according to example 2.2 was applied at a dose corresponding to 1 litre of said composition in liquid form (in a slurry of 400 L of water) for 10000 m2 of planted area (modality 3).

[0186] As a control, carrot seeds of the same variety were planted at the same density of 71.4 g carrot seeds per 1 m2 and watered only with water (modality 1).

[0187] Another control was used, keratin hydrolysate alone at a dose corresponding to 1 liter of hydrolysate in liquid form (in a slurry of 400 L of water) per 10,000 m² of planted area, sprayed onto the leaves (treatment 2). This dose corresponds to twice the amount of keratin hydrolysate present in 1 L of the keratin-nutrient composition (composition of example 2.2).

[0188] Another control was used, the nutrients alone at a dose corresponding to 1 L / ha in liquid form (in a slurry of 400 L of water) per 10,000 m² of planted area and sprayed on the leaves (treatment 4). This dose corresponds to the same quantity of nutrients present in 1 L of the composition according to example 2.2.

[0189] Table 8 represents the root and leaf biomass 3 months after carrot sowing.

[0190] [Tables8] Treatment Method Measurement in g of root biomass Measurement in g of leaf biomass 1 Control (water) 92.84 32.11 2 Hydrolysate of example 1 94.43 34.42 3 Composition according to example 2.2 104.06 35.58 4 nutrients 97.25 35.2

[0191] The use of the composition according to example 2.2 of the invention makes it possible to increase root and leaf biomass 3 months after sowing.

[0192] The chelate composition according to the invention is more effective than keratin hydrolysate alone and nutrients alone.

[0193] Table 9 shows the average weight in grams of marketable carrots at harvest

[0194] [Tables9] Method Treatment Measurement in g of marketable carrots at harvest 1 Control water 218.33 2 Hydrolysate from example 1 256.95 3 Composition according to example 2.2 281.29 4 Nutrients 232.68 The use of the chelate composition according to the invention significantly increases the average weight of marketable carrots at harvest by 29% compared to the water control. The chelate composition according to the invention is more effective than keratin hydrolysate alone and trace elements alone.

[0195] Example 3.2.3 On tomatoes

[0196] Microtom WT variety tomato seeds were sown in pots, one seed per pot, in a climate chamber. The pots had a capacity of 2 liters, and the growing medium used was a mixture of Hortifibre, clay, brown peat, and blonde peat.

[0197] Then the chelate composition according to example 2.2 was applied as a foliar spray 3, 5 and 10 weeks after sowing. The trial lasted 19 weeks.

[0198] The chelate composition was applied at a dose corresponding to 1.5 liters of said composition in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area.

[0199] As a control, tomato seeds of the same variety were planted at the same density of one seed per pot and watered only with water (modality 1).

[0200] Another control was used, keratin hydrolysate alone at a dose corresponding to 3 liters of hydrolysate in liquid form (in a slurry of 400 L of water) per 10,000 m² of planted area, sprayed onto the leaves. This dose corresponds to twice the amount of keratin hydrolysate present in 1 L of the composition according to Example 2.2

[0201] Table 10 represents the root and leaf biomass of tomatoes at the end of the trial.

[0202] Table 10] Treatment Method Measurement in g of root biomass Measurement in g of leaf biomass 1 Control (water) 2.038 14.9 2 Hydrolysate of Example 1 2.018 21.6 3 Composition according to Example 2.2 2.427 21.6

[0203] The use of the chelate composition according to the invention significantly increases the root and leaf biomass of tomato plants. The chelate composition according to the invention is more effective than keratin hydrolysate alone. It promotes good early development and vigor in tomato plants.

[0204] Example 3.3 Application of the composition “keratin-B-Mo hydrolysate”

[0205] Example 3. 3.1 On rapeseed

[0206] Helypse Variety rapeseed seeds were placed in seed furrows using a seed drill - in order to ensure homogeneous sowing - at a density of 40 g rapeseed per 1 m2.

[0207] Then the chelate composition according to example 2.3 was applied as a foliar spray at BBCH stage 59. The growth stage of the rapeseed plants was determined using the BBCH rapeseed growth chart. According to this chart, codes 50 to 59 correspond to the appearance of inflorescences; in particular, code 59 corresponds to the presence of the first petals, but the flowers are still closed.

[0208] The chelate composition was applied at a dose corresponding to 1.5 litres of said composition in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area (modality 3).

[0209] As a control, rapeseed seeds of the same variety were planted at the same density of 40 g rapeseed per 1 m2 and watered only with water (modality 1).

[0210] Another control was used, keratin hydrolysate alone at a dose corresponding to 1.5 litres of hydrolysate in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area and sprayed on the leaves at BBCH59 stage 1 (modality 2).

[0211] Another control was used, a mixture of boron and molybdenum alone at a dose corresponding to 1.5 L / ha in liquid form (in a slurry of 400 L of water) per 10,000 m² of planted area, sprayed onto the leaves (treatment 4). This dose corresponds to the quantity of trace element present in 1.5 L of the composition according to example 3.2. Table 11 shows the boron and molybdenum content in ppm measured in rapeseed leaves 48 h after application of the products.

[0212] [Tables 11] Treatment Method B content (ppm) in rapeseed leaves - 48 h after treatment application Mo content (ppm) in rapeseed leaves - 48 h after treatment application 1 Control (water) 26 0.86 2 Hydrolysate from example 1 27.12 1.05 3 Composition according to example 2.3 38.08 1.1 4 B-Mo 32.68 1.25

[0213] The use of the chelate composition according to the invention makes it possible to increase the boron and molybdenum content in rapeseed leaves 48 h after application of the products at BBCH stage 59.

[0214] This increase in micronutrient content at this stage reflects better nutrient uptake by the plant when boron and molybdenum are chelated with keratin hydrolysate. Applying boron and molybdenum at BBCH stage 59 ensures successful rapeseed flowering.

[0215] Example 3.4 Application of the composition “keratin-Mg hydrolysate”

[0216] Example 3.4.1 On rice

[0217] Rice seeds of Variety Samagrin were placed in seed furrows using a seed drill - in order to ensure homogeneous sowing.

[0218] Then the chelate composition according to example 2.4 was applied as a foliar spray twice: at BBCH stage 41 and BBCH stage 61. The rice growth stage was determined using the BBCH scale for cereals. According to this scale, codes 40 to 49 correspond to ear swelling, in particular code 41 This corresponds to the beginning of swelling, that is, the elongation of the leaf sheath of the last leaf. According to this scale, codes 60 to 69 correspond to flowering; in particular, code 61 corresponds to the beginning of flowering, when the first anthers are visible.

[0219] The chelate composition according to example 2.4 was applied at a dose corresponding to 4 litres of said composition in liquid form (in a slurry of 200 L of water) for 10000 m2 of planted area.

[0220] As a control, rice seeds of the same variety were planted at the same density.

[0221] Table 12 shows the number of grains per ear and the yield in kg / ha compared to the untreated control.

[0222] [Tables 12] Treatment Number of grains per ear Control water 80.87 Composition according to example 2.4 98.93

[0223] The use of the chelate according to the invention makes it possible to have an impact on the final yield of rice compared to an untreated control: the number of grains per ear is increased by 22%.

[0224] Example 3.5 Application of the composition “keratin-Cu hydrolysate”

[0225] Example 3.5.1 On the vine

[0226] The test was carried out on a Cabernet Franc vine.

[0227] The chelate composition according to Example 2.5 was applied as a foliar spray at growth stages BBCH11, BBCH19, BBCH53, BBCH57, BBCH60, BBCH69, BBCH71, BBCH75, BBCH77, and BBCH79. The growth stage of the grapevine plants was determined using the BBCH Grapevine Growth Chart. According to this chart, codes 10 to 19 correspond to the first unfurled leaves; in particular, code 11 corresponds to the presence of the first leaf, and code 19 corresponds to nine or more leaves. According to this chart, codes 50 to 59 correspond to the appearance of inflorescences; in particular, code 53 corresponds to the presence of the first cluster, and code 57 corresponds to the point at which the clusters are well-developed and the flowers are separating. According to this scale, codes 60 to 69 correspond to flowering; in particular, code 60 corresponds to the presence of the first flower caps that separate from the receptacle, and code 69 corresponds to the end of flowering.According to this scale, codes 70 to 79 correspond to fruit set, in particular code 71 corresponds to the beginning of fruit development, code 75 corresponds to the berries which. are the size of peas, code 77 corresponds to the cluster closure stage and code 79 corresponds to complete cluster closure, the fruits have finished enlarging.

[0228] Table 13 below describes all the methods used in this experiment

[0229] [Tables 13] Treatment Copper dose applied to the entire crop Unit BBCH Stage Control Water (treatment 1) 0 Full dose copper (treatment 2) 4.2 kg / ha 11 19 53 57 60 69 71 75 77 79 Reduced dose copper (treatment 3) 1.26 kg / ha 11 19 53 57 60 69 71 75 77 79 Reduced dose copper + keratin hydrolysate (0.25 kg / ha) (treatment 4) 1.26 kg / ha 11 19 53 57 60 69 71 75 77 79 Composition according to example 1 1.884 kg / ha 11 ' 2.5 19 (modality 5) 53 57 60 69 71 75 77 79

[0230] The composition according to the invention (example 2.5) was applied at a dose corresponding to 1.5 liters of liquid copper chelate (in a slurry of 200 L of water) per 10,000 m² of planted area. The quantity of copper applied was reduced by 55% by weight compared to the crop's requirement when copper alone, in conventional form, is applied (method 5).

[0231] As a control, the vine stocks were watered only with water (modality 1).

[0232] Another control was used, full-dose copper (modality 2), i.e. in order to to allow the winegrower complete protection of his vines against mildew. According to this method, copper is applied in the classic form of "Bordeaux mixture RSR" ("Bordeaux mixture" in English): that is to say, containing 20% ​​by weight of copper sulfate.

[0233] Another control was used, copper in classical form in a reduced dose, i.e. -70% copper compared to the full dose (modality 3).

[0234] Another control was used, copper in reduced dose and was combined extemporaneously with keratin hydrolysate alone (modality 4).

[0235] Table 14 shows the percentage of downy mildew severity on grape bunches. Severity represents the percentage of berries showing symptoms of downy mildew on a bunch.

[0236] [Tables 14] Treatment: Severity of downy mildew on grape bunches (% of downy mildew on the bunch) Control: water (treatment 1) 77.31 Full dose copper (treatment 2) 34.30 Reduced dose copper (treatment 3) 54.65 Reduced dose copper + keratin hydrolysate (0.25 kg / ha) (treatment 4) 37.9 Composition according to example 2.5 (treatment 5) 29.3

[0237] The use of the composition according to the invention makes it possible to significantly reduce, by 55%, the doses of copper while maintaining the effectiveness of a full dose of copper in conventional form.

Claims

1.

2. Demands Composition of at least one amino acid chelate of a hydrolysate with at least one mineral nutrient, wherein the hydrolysate is a keratin hydrolysate comprising at least 88% by weight of free amino acids relative to the total weight of amino acids in the hydrolysate, the remainder of the amino acids in the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Daltons, said hydrolysate having the following composition in total amino acids: an aspartic acid content of 5 to 8% by weight; a threonine content of 3 to 6% by weight; a serine content of 9 to 14% by weight; a glutamic acid content of 8 to 13% by weight; a glycine content of 6 to 9% by weight; an alanine content of 4 to 6% by weight; a valine content ranging from 6 to 10% by weight; a methionine content ranging from 0.1 to 0.6% by weight; an isoleucine content ranging from 4 to 6% by weight;a leucine content ranging from 6 to 9% by weight; a phenylalanine content ranging from 2 to 5% by weight; a lysine content ranging from 1 to 3% by weight; a histidine content ranging from 0.4 to 1% by weight; an arginine content ranging from 5.5 to 6.5% by weight; a proline content ranging from 8.5 to 11% by weight; a tryptophan content of less than 0.1%, relative to the total weight of total amino acids in the hydrolysate; and the mineral nutrient being selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt, and copper. Composition according to claim 1 wherein the hydrolysate has the following composition in total amino acids: an aspartic acid content of 6 to 7% by weight; a threonine content of 4 to 5% by weight; a serine content of 10 to 12% by weight; a glutamic acid content of 9 to 11% by weight; a glycine content of 6.5 to 8% by weight; an alanine content of 4 to 5% by weight; a valine content of 6.5 to 8% by weight; an isoleucine content of 4 to 5% by weight; a leucine content of 7 to 8% by weight; a tryptophan content of 0% relative to the total weight of the total amino acids of the hydrolysate.

3. Composition according to claim 1 or 2 wherein the hydrolysate comprises from 2 to 12% by weight of peptides of 2, 3, 4 amino acids having a molecular mass less than or equal to 800 Daltons by weight relative to the total weight of the hydrolysate.

4. Composition according to any one of the preceding claims wherein the chelate(s) comprises / comprise a single mineral nutrient selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably consisting of zinc, magnesium, calcium and copper.

5. Composition according to any one of claims 1 to 3 wherein the chelate(s) comprises 2, 3, 4 or 5 mineral nutrients selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably the chelate comprises iron, zinc, manganese and molybdenum.

6. Composition according to any one of the preceding claims wherein the chelate(s) further comprises at least one anion selected from borate, silicate, phosphate, nitrate.

7. A composition according to any one of the preceding claims, wherein the hydrolysate comprises the following free amino acids: at least 95% free aspartic acid by weight relative to the total weight of aspartic acid in the hydrolysate; at least 95% free threonine by weight relative to the total weight of threonine in the hydrolysate; at least 95% free serine by weight relative to the total weight of serine in the hydrolysate; at least 93% free glutamic acid by weight relative to the total weight of glutamic acid in the hydrolysate; at least 93% free glycine by weight relative to the total weight of glycine in the hydrolysate; at least 93% free alanine by weight relative to the total weight of alanine in the hydrolysate; at least 95% of methionine in free form by weight relative to the total weight of methionine in the hydrolysate;at least 93% of phenylalanine in free form by weight relative to the total weight of phenylalanine in the hydrolysate; at least 95% of proline in free form by weight relative to the total weight of proline in the hydrolysate.

8. A method for preparing the composition according to any one of claims 1 to 7 comprising at least one step of mixing the hydrolysate defined in any one of claims 1 to 3 with at least one mineral nutrient is selected from the group consisting of iron, zinc, manganese, magnesium, calcium, molybdenum, cobalt and copper, preferably in the form of hydrated sulfate(s), said mixing step being carried out under stirring for a period of 1 hour to 3 hours.

9. A process for preparing the composition according to the preceding claim, wherein the hydrolysate is prepared from an animal keratin material, preferably poultry, according to a preparation process comprising at least the following steps, in this order: - subjecting the keratin material to at least one acid hydrolysis, carried out in two stages: - a first hydrolysis carried out at a temperature of 60 to 80°C for a period of 4 to 5 hours and then - a second hydrolysis carried out at a temperature of 100 to 115°C for a period of 5 to 7 hours, the two hydrolyses being able to be carried out without an intermediate resting step or by carrying out an intermediate resting step of between 1 hour and 7 days - extracting the tyrosine and cystine from said hydrolysate preferably by means of a base; - desalting the liquid phase obtained after the extraction of the cystine and tyrosine;- concentrate the desalinated liquid phase to obtain an aqueous composition comprising 45 to 55% by weight of keratin hydrolysate in solid form relative to the total weight of said composition.;

10. Use of the composition according to any one of claims 1 to 7 or obtained according to claim 8 or 9 in agriculture, preferably as a plant biostimulant.

11. Use of the composition according to the preceding claim as a biostimulant for plants selected from among field crops, vines, arboriculture, market gardening, medicinal and aromatic plants, ornamental crops.

12. Use of the composition according to claim 10 or 11 to improve the absorption of mineral nutrients and amino acids by the plant and to reduce the amount of mineral inputs.