Process for producing an amino acid-containing aqueous solution from a fish-soluble aqueous solution and associated fertilizers

Description

Field of invention

[0001] The present invention relates to a method for producing an aqueous solution containing amino acids from the soluble fraction of a heterogeneous mixture of fish by-products. The present invention also relates to an organic liquid fertilizer containing the aqueous solution of the invention. Prior art

[0002] Bio-sourced amino acids are products recognized as plant biostimulants, particularly for their positive effects on crop performance (improved plant growth and production, improved harvest quality, improved soil quality) and particularly under abiotic stress conditions.

[0003] Organic fertilizers are sources of macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium), micronutrients (boron, copper, iron, chloride, manganese, molybdenum, zinc) and organic matter which promote soil biodiversity unlike mineral fertilizers which can acidify the soil and therefore disrupt its biological fertility.

[0004] It is known from the prior art to use the soluble fraction of fish by-products to produce fish-based fertilizers, these fish-derived products significantly increasing the quantity and quality of harvests of different plant species as well as photosynthetic activity and improving soil properties.

[0005] US 5,393,318 describes a process for manufacturing a liquid fertilizer from fish heads. Bonito heads are boiled. The resulting liquid is defatted and enzymes are added. The temperature of the enzymatic reaction is 60°C; it is maintained for 3 hours. It is then heated to 95°C to stop the reaction. After filtration, an amino acid-rich liquid is obtained, which contains 7.9g / 100g of alanine protein, 6.2g / 100g of arginine protein, 5.5g / 100g of aspartic acid protein, 9.4g / 100g of glutamic acid protein, 15.5g / 100g of glycine protein, 3.6g / 100g of leucine, 4.6g / 100g of lysine protein, 1.5g / 100g of phenylalanine protein, 5.6g / 100g of proline protein, and 2.5g / 100g of valine protein. This document does not address the possible bacterial growth in liquid fertilizer.It is based on the assumption that, due to heating, for a period not defined in this document, all microorganisms have been eliminated. The liquid is stabilized either by partial dehydration to 40% dry extract without pH adjustment, or by total dehydration (drying). The case of heat-resistant forms (spore-forming forms) is not considered.

[0006] Document CN 105152690A describes a process for manufacturing an organic fertilizer from an aqueous fish suspension. The fish lysate is sterilized with chlorine, which deactivates the endogenous enzymes. A deodorization treatment is carried out at 60-80°C for 30 to 40 minutes. Enzymes are added to the disinfected and deodorized solution. These enzymes come from the fish viscera; they are added in an amount of 5 to 10% by mass. Hydrolysis is carried out in a sterile environment at 30-40°C and at a pH of 5-7 for 5 to 10 hours. It is then heated to 90°C-100°C to inactivate the enzymes. The resulting composition is sterile, due to the disinfection step and the hydrolysis carried out in a sterile environment, and is stabilized by total dehydration (freeze-drying). This process is nevertheless restrictive because the enzymatic reaction must take place in a sterile environment. It is also not very environmentally friendly due to the use of chlorine.Furthermore, again, it is not certain that the spores or sporulating forms were treated in such a way as to prevent their development and proliferation in the finished product.

[0007] WO 2021 / 092342 A1 describes a method for producing an organic fertilizer from marine organisms. This method is efficient and produces a fertilizer enriched with nutrients and compounds useful for growing crops and other plants.

[0008] However, it is important, under the conditions of use in question, taking into account the great diversity of pathogenic agents (vegetative forms and spores) likely to be present in organic matter of animal origin, to guarantee the microbiological safety of the product with regard to humans, animals and their environment, and in particular to reduce the content of pathogenic bacteria in the product, or even to make it zero, and in particular to reduce the content of bacteria of the genus Clostridium, more particularly C. perfringens, or even to render it null and void. Indeed, a product containing pathogenic bacteria at an unacceptable level can have a potential harmful effect on human and animal health when this product comes into contact with vegetable crops, market garden crops and / or with any plant production intended to be consumed as is.

[0009] Indeed, the genre Clostridium and in particular C. perfringens, is a ubiquitous pathogen, one of the main reservoirs of which is the intestinal tract of animals (poultry, cattle, pigs, fish). C. perfringensmultiplies rapidly in a meat or starch-based medium in a temperature range between 30°C and 50°C; keeping a product for several hours in this temperature range makes it possible for this bacterium to proliferate beyond 10 5< / g. Cooking destroys most of the vegetative forms, but not or only slightly the spores. Indeed, the spores of Clostridium perfringens show a certain thermoresistance to temperatures above 80°C. Only a temperature of 100°C allows a significant reduction of spores of Clostridium perfringens. Technical issues to be resolved

[0010] The present invention aims to remedy the drawbacks described above.

[0011] A first aim of the present invention is to propose a method for manufacturing an aqueous solution containing amino acids which is economical and which makes it possible to obtain an aqueous solution containing a limited quantity of colonies of pathogenic microorganisms (vegetative forms and spores), in particular bacteria of the genus Clostridium and in particular of C. perfringens.

[0012] Another object of the present invention is to provide a method for manufacturing an aqueous solution containing amino acids which does not require pH adjustment during the enzymatic step.

[0013] Another aim of the present invention is to propose a process which makes it possible, from a raw material having a great diversity in its composition, to obtain an aqueous solution which is reproducible on an industrial scale.

[0014] An object of the present invention is to provide an aqueous solution according to claim 8.

[0015] Another aim of the present invention is therefore to provide an aqueous solution which can be sprayed and contains at least 80% by mass of a mixture of peptides with a mass of less than 3 kDa.

[0016] Another object of the present invention is to provide an aqueous solution containing amino acids and which can be stored for 6 to 12 months without excessive proliferation of bacteria, in particular of at least one bacterium chosen from: Enterobacteriaceae (especially, Escherichia coli) , Enterococci, Clostridium notably C. perfringens, And Salmonella.

[0017] Another object of the invention is to provide an aqueous solution which contains little or no associated toxins produced by said bacteria, and in particular by C. perfringens, these toxins being recognized as pathogens.

[0018] Another aim of the present invention is to provide a method which requires a heat treatment for the inactivation of the enzymatic reaction and the destruction of microorganisms, the duration of which is less than or equal to 1 hour and which is effective at a heating temperature of less than 100°C.

[0019] Another aim of the present invention is to provide a fertilizer which can be applied to plants intended to be consumed as is without any harmful effect on human health, animal health or the environment.

[0020] Another aim of the present invention is to propose a plant biostimulant which, by root and / or foliar application at specific stages of development (flowering, fruit production) of the treated plants, makes it possible to improve the efficiency of use of nutrients, and / or the tolerance to abiotic stress, and / or the qualitative characteristics of the cultivated plants, in particular to stimulate vegetative growth, in particular in conditions of nitrogen deficiency, and / or to increase the chlorophyll content, in particular in conditions of nitrogen deficiency and / or to increase the nutritional quality (in particular to increase the vitamin C content). Description of the invention

[0021] The present invention relates to a method for producing an aqueous solution containing amino acids from a fish soluble(s) according to which: said fish soluble being at a given temperature, at least one protease having proteolytic activity at said given temperature is added to it without modification of pH; the pH is lowered to a value lower than 4.5 by adding at least one acid; and then heating to a temperature greater than or equal to 75°C and less than 100°C for a duration greater than or equal to 5 minutes; and filtering is carried out to obtain said solution.

[0022] The Applicant has in fact found that acidifying the solution obtained before its heat treatment (which allows both the stopping of the enzymatic reaction and the destruction of a large number of pathogenic germs in the solution) improves the effectiveness of the heat treatment in terms of the number of decimal reductions in the bacterial load. For the same given number of decimal reductions in the bacterial load, a reduction in the duration and / or temperature of the heat treatment is observed when the acidification is carried out before the heat treatment. Since the heat treatment is carried out at a temperature below 100°C, the solubilized amino acids, peptides and proteins are not degraded.

[0023] Without the Applicant being bound by this explanation, it appears that the number of bacterial spores is significantly reduced when acidification is carried out before heating (heat treatment). Indeed, a limited content of spore colonies of pathogenic microorganisms is observed in the solution of the invention, whereas the activity of the water and the humidity of the solution of the invention increases the thermoresistance of the spores and could allow survival of said spores, and their germination and proliferation if the conditions become favorable again.

[0024] Filtration is not limited according to the invention. It may be, for example, filtration with a cut-off threshold equal to or greater than 80 mesh and equal to or less than 120 mesh.

[0025] Advantageously, the heating (or heat treatment) duration may be less than or equal to 15 minutes, less than or equal to 35 minutes or less than or equal to 60 minutes.

[0026] The fish soluble and / or aqueous solution obtained can also be concentrated, in particular by evaporation under vacuum. Thus, the fish soluble(s) can, for example, be concentrated before the addition of the enzyme. The aqueous solution can be concentrated before or after filtration.

[0027] Acidification can be carried out by adding an organic or inorganic acid alone or in a mixture. Advantageously, an acid chosen from organic acids, in particular propionic acid, acetic acid, lactic acid, butyric acid, lignosulfonic acid, humic acid, citric acid and inorganic acids, in particular phosphoric acid, and mixtures of at least two of these acids, is used. Phosphoric acid has the advantage of providing inorganic phosphorus in the aqueous solution of the invention.

[0028] Advantageously, after addition of the acid(s), the pH is lowered to a value less than or equal to 4.5, preferably between 4 and 4.5 and in particular equal to 4.3 and / or by heating after addition of said acid to a temperature equal to or greater than 75°C, in particular equal to 80°C, 85°C or 90°C.

[0029] According to an advantageous implementation method, heating is carried out at 85°C for a period equal to or greater than 5 minutes after acidification by the acid(s).

[0030] The above-mentioned temperatures are easily reached without too much energy expenditure; the method of the invention therefore remains economical. Advantageously, the pH is lowered to a value as mentioned above and heating is carried out to a temperature as mentioned above. Such pH and temperature values make it possible to obtain a decimal reduction number of Clostridium perfringens equal to at least 5.

[0031] According to a particular implementation method and combinable with each of the aforementioned implementation methods, one or more endoproteases and / or one or more exoproteases are added. The enzymes are not limited according to the invention. Metalloprotease type enzymes should nevertheless be avoided because they are not very effective probably due to poisoning of the metal catalysts (cofactors) by the chelating agents present in the soluble material (sulfate, phosphate, proteins, etc.).

[0032] For example, the following enzymes can be used: Bacillus licheniformis endopeptidase in liquid form, alkaline serine protease, subtilisin type: Alcalase 4 L, Alcalase 2.4 L FG, Alcalase 2.5 L PF (Supplier: Novozymes) Bacillus licheniformis endopeptidase in liquid form, alkaline serine protease, subtilisin type: Corolase APC (Supplier: ABEnzyme) Trichoderma reesei endopeptidase in liquid form, alkaline serine protease, thermomycolin type: Corolase 8000 (Supplier: ABEnzyme) Bacillus licheniformis endopeptidase in liquid form, alkaline serine protease, subtilisin type: FoodPro Alkaline Protease (Supplier: Dupont / IFF) Bacillus licheniform endopeptidase in liquid form, alkaline serine protease, subtilisin type: Prolyve 1000 (Supplier: Lyven / Soufflet Biotechnologie) Aspergillus oryzae exopeptidase: Flavourzyme 1000 L (Supplier: Novozymes) Trichoderma reesei exopeptidase: TS-E 2206 (Supplier: Dupont / IFF)

[0033] Advantageously, according to a particular embodiment, the enzyme is an alkaline serine protease of the subtilisin type having an optimum pH for proteolytic activity between 8-9; and an optimum temperature for proteolytic activity between 60 - 70°C. It is advantageously added at a ratio of 0.1 to 2.0% mass of enzyme / mass of dry raw material.

[0034] According to a particular embodiment, said endoprotease(s) and / or said exoprotease(s) are added at an enzyme / dry substrate ratio equal to or greater than 0.1% and equal to or less than 2%, at a pH between 5 and 7, at a temperature between 50°C and 70°C, preferably between 55°C and 65°C, preferentially at 60°C, the temperature and the pH being maintained for a period of 1 to 24 hours, preferably 1 to 4 hours.

[0035] Advantageously, whatever the method of implementation, said fish soluble is previously obtained by: cooking said fish by-product(s) and pressing; removing the solid fraction by pressing and at least part of the fat; and possibly concentrating.

[0036] Such a soluble solution allows, from raw materials of disparate composition in terms of proteins, to obtain an aqueous solution whose amino acid composition is reproducible.

[0037] Advantageously, the product is concentrated under vacuum until a fish soluble having a mass content of dry matter equal to or greater than 25% and less than or equal to 45% and preferably equal to 35% is obtained.

[0038] The cooking of the fish and / or fish by-products is advantageously carried out at a temperature equal to 100°C. The pH of the fish soluble is advantageously equal to or greater than 5 and less than or equal to 7.

[0039] The soluble is obtained from fish by-products that may or may not be of the same species. Its production cost is thus limited. Furthermore, fish by-products, in particular the entrails (viscera) of fish, are a significant source of bacterial contamination. The method of the invention therefore makes sense when the fish soluble is obtained from whole fish and / or fish by-products containing fish entrails.

[0040] Advantageously, the soluble material contains a mass percentage of dry matter equal to or greater than 25% and less than or equal to 45% and / or a mass percentage of proteins of said dry matter equal to or greater than 80% and / or a mass percentage of minerals of said dry matter less than or equal to 20% and / or a mass percentage of fats of said dry matter less than or equal to 10%. Such a soluble material makes it possible to obtain an aqueous composition according to the invention which is particularly balanced in amino acids for its use as a biostimulant and / or fertilizer.

[0041] Advantageously, the fish soluble(s) contains a mass percentage of molecules whose molecular weight is greater than 10 kDa greater than or equal to 20% and less than or equal to 60% and / or it contains a quantity of free taurine greater than or equal to 1.2 g / 100g of protein and less than or equal to 2.0 g / 100g of protein and / or a total quantity of glycine greater than or equal to 10.0 g / 100g of protein and less than or equal to 18.1 g / 100g of protein and / or a quantity of proline greater than or equal to 4.4 g / 100g of protein and less than or equal to 8.0 g / 100g of protein.

[0042] The present invention also relates to an aqueous solution containing amino acids and obtainable according to the process of the invention.

[0043] According to the invention, the aqueous solution contains a mass percentage of dry matter equal to or greater than 30% and less than or equal to 40%, and / or a mass percentage of organic nitrogen of said dry matter equal to or greater than 10.5% and equal to or less than 12.5% and / or a mass percentage of total amino acids measured relative to its protein content equal to or greater than 65% and / or a mass percentage of said dry matter in total phosphorus equal to or greater than 2% and / or a mass percentage of said dry matter in total potassium equal to or greater than 2.5% and equal to or less than 3.0% and / or a pH equal to or less than 4.5, more particularly between 4 and 4.5 and / or a water activity equal to or less than 0.91.

[0044] According to the invention, the aqueous solution contains a mass percentage of dry matter equal to or greater than 33% and less than or equal to 36%, and / or a mass percentage of organic nitrogen of said dry matter equal to or greater than 10.5% and equal to or less than 12.5% and / or a mass percentage of total amino acids measured relative to its protein content equal to or greater than 65% and / or a mass percentage of said dry matter in total phosphorus equal to or greater than 2% and / or a mass percentage of said dry matter in total potassium equal to or greater than 2.5% and equal to or less than 3.0% and / or a pH equal to or less than 4.5, more particularly between 4 and 4.5 and / or a water activity equal to or less than 0.91.

[0045] Such an aqueous solution is suitable for use pure or diluted in water as a plant biostimulant.

[0046] Advantageously, the aqueous solution comprises at least 98% by mass of peptides with a molecular weight less than or equal to 10 kDa and at least 80%, in particular at least 90% by mass of peptides with a molecular weight less than or equal to 3 kDa. These small peptides, although not being free amino acids, nevertheless prove to be easily assimilated by plants. According to a particular embodiment which can be combined with any of the aforementioned embodiments, in particular with the content of peptides of less than 3 kDa, the aqueous solution of the invention contains less than 15 g of free amino acids per 100 g of proteins and more particularly a mass of free amino acids greater than or equal to 3.0 g per 100 g of proteins and less than or equal to 9.0 g per 100 g of proteins.

[0047] Advantageously, whatever the embodiment of the aqueous solution of the invention, it contains less than 10g / 100g of free amino acid proteins.

[0048] According to a particular embodiment, the aqueous solution of the invention contains a mass percentage of alanine measured relative to its protein content equal to or greater than 5.6 and equal to or less than 7.6 and / or a mass percentage of arginine measured relative to its protein content equal to or greater than 4.3 and equal to or less than 5.9 and / or a mass percentage of aspartic acid measured relative to its protein content equal to or greater than 4.8 and equal to or less than 5.6 and / or a mass percentage of glutamic acid measured relative to its protein content equal to or greater than 8.5 and equal to or less than 10.1 and / or a mass percentage of glycine measured relative to its protein content equal to or greater than 10.1 and equal to or less than 18.1 and / or a mass percentage of hydroxyproline measured relative to its protein content equal to or greater than 2.6 and equal to or less than 5.0 and / or a mass percentage of leucine,measured in relation to its protein content equal to or greater than 2.4 and equal to or less than 3.6 and / or a mass percentage of lysine measured in relation to its protein content equal to or greater than 3.2 and equal to or less than 4.4 and / or a mass percentage of phenylalanine, measured in relation to its protein content equal to or greater than 1.7 and equal to or less than 2.1 and / or a mass percentage of proline, measured in relation to its protein content equal to or greater than 4.4 and equal to or less than 8.0 and / or a mass percentage of valine measured in relation to its total protein content equal to or greater than 1.7 and equal to or less than 2.5. The above values can also be expressed in g of amino acid per 100g of protein contained in the solution of the invention.,

[0049] According to a particular embodiment, the aqueous solution of the invention contains a mass percentage of alanine measured relative to its protein content equal to or greater than 6.1 and equal to or less than 7.1 and / or a mass percentage of arginine measured relative to its protein content equal to or greater than 4.7 and equal to or less than 5.5 and / or a mass percentage of aspartic acid measured relative to its protein content equal to or greater than 4.8 and equal to or less than 5.6 and / or a mass percentage of glutamic acid measured relative to its protein content equal to or greater than 8.5 and equal to or less than 10.1 and / or a mass percentage of glycine measured relative to its protein content equal to or greater than 12.1 and equal to or less than 16.1 and / or a mass percentage of hydroxyproline measured relative to its protein content equal to or greater than 3.2 and equal to or less than 4.4 and / or a mass percentage of leucine,measured in relation to its protein content equal to or greater than 2.4 and equal to or less than 3.6 and / or a mass percentage of lysine measured in relation to its protein content equal to or greater than 3.2 and equal to or less than 4.4 and / or a mass percentage of phenylalanine, measured in relation to its protein content equal to or greater than 1.8 and equal to or less than 2.0 and / or a mass percentage of proline, measured in relation to its protein content equal to or greater than 5.3 and equal to or less than 7.1 and / or a mass percentage of valine measured in relation to its total protein content equal to or greater than 1.7 and equal to or less than 2.5. The above values can also be expressed in g of amino acid per 100g of protein contained in the solution of the invention.,

[0050] According to a particular embodiment which can possibly be combined with the aforementioned embodiments, the aqueous solution of the invention contains a mass percentage of taurine in free form measured relative to its protein content equal to or greater than 1.0 and equal to or less than 2.2, and preferably equal to or greater than 1.3 and equal to or less than 1.9. The above values can also be expressed in g of amino acid per 100g of protein contained in the solution of the invention.

[0051] According to a particular embodiment, possibly combinable with the aforementioned embodiments, it contains, by mass, at least 10.5% of organic nitrogen per 100g of dry matter and at least 1.0% of free taurine / 100g of protein.

[0052] The addition of glutamine to the aqueous solution of the invention makes it possible to reduce the activity of glutamine synthase when the solution of the invention is used as a fertilizer or in the composition of a fertilizer. This results in energy savings for the plant and the plant grows more. Glutamic acid (glutamine) is provided in the form of a free amino acid or linked to other amino acids by peptide bonding.

[0053] According to a particular embodiment, combinable with each of the other aforementioned embodiments, the solution of the invention contains a percentage of amino acids (free and non-free) measured per 100g of proteins, equal to or greater than 65 and less than or equal to 80 and / or it has a pH less than or equal to 4.5, more particularly equal to or less than 4.4 and a water activity less than or equal to 0.91, in particular equal to 0.906.

[0054] Advantageously, it has a pH as mentioned above and a water activity as mentioned above. These values are compatible with storage of the aqueous solution of the invention for 6 to 12 months without risk of excessive proliferation of bacteria.

[0055] The Applicant has found that an aqueous solution such as the aforementioned, when used as a plant biostimulant or in the composition of such a product, makes it possible to obtain more productive plants, more resilient to abiotic stress caused by a change in environment such as a nitrogen deficiency and whose elemental composition is richer than that of an untreated plant. The vegetative growth, the chlorophyll content, the foliar nitrogen content of the plant is significantly greater after use of a liquid organic fertilizer such as the aforementioned.

[0056] The achievement of more productive, more resilient plants can be explained by a modification of the activity of nitrate reductase and glutamate synthase. Nitrate reductase is an enzyme catalyzing the mineralization and use of nitrate into nitrite and then ammonium or dinitrogen. This enzyme is an indicator of the functioning of the nitrogen cycle. The measurements highlight that the activity of nitrate reductase increases with the content of the solution of the invention applied. Thus, the nitrogen cycle is stimulated in the presence of the solution of the invention. Glutamine synthase is an enzyme catalyzing the condensation of glutamate and ammonia into glutamine, i.e. the degradation of an amino acid.The decrease in activity can be explained by the fact that the solution of the invention is rich in glutamine, thus the assimilation of the amino acids present in the solution of the invention allows the plant to save energy to operate the foliar glutamine synthase.

[0057] Achieving more productive, more resilient plants can also be explained by stimulating soil life. Applying a liquid organic fertilizer such as the one mentioned above stimulates root colonization and does not negatively impact the biogeochemical cycles of carbon and phosphorus.

[0058] The Applicant also found that amino acids are more quickly available to the plant. This is reflected by the reduction in the activity of leucine amino-reductase, responsible for the transformation of proteins into amino acids. This result can be explained by an absorption of nitrogen by the plant in the form of peptides directly at the level of the liquid organic fertilizer of the invention.

[0059] According to the invention, the aqueous solution of the invention contains less than 10 CFU / g of bacteria Clostridium, in particular of C perfringens and less than 10 CFU / g of spores of Clostridium, including spores of C. perfringens, less than 100 CFU / g of fecal streptococci (enterococci) and less than 10 CFU / g of Salmonella. Such a solution can be stored for 6 to 12 months without risk of excessive bacterial proliferation.

[0060] The present invention also relates to a biostimulant comprising or consisting of the aqueous solution of the invention and a fertilizer comprising or consisting of the aqueous solution according to the invention. Definitions

[0061] “endoprotease” (or endopeptidase) within the meaning of the patent means an enzyme which breaks peptide bonds within the peptide chain.

[0062] “exoprotease” (or exopeptidase) within the meaning of the patent means an enzyme which breaks the peptide bond between the first amino acid and the second amino acid of the peptide chain, and therefore releases the N-terminal amino acid.

[0063] The terms "fish by-products" within the meaning of the invention designate whole fish and parts not intended for human consumption chosen from: skin, bones, head and viscera. A fish by-product(s) within the meaning of the invention advantageously contains fish viscera.

[0064] A whole fish, within the meaning of the invention, contains its viscera.

[0065] The terms "plants" or "vegetables" designate, within the meaning of the invention, any plant or part of a plant, such as the root system, the stem, the leaf or the fruit, at any stage of development, from the seed to the mature plant.

[0066] “Biostimulant” or “growth activator”, within the meaning of the invention, means any product which stimulates the nutrition processes of plants independently of the nutrients it contains for the sole purpose of improving one or more of the following characteristics of plants or their rhizosphere: nutrient use efficiency, tolerance to abiotic stress, qualitative characteristics and the availability of nutrients confined in the soil or rhizosphere.

[0067] “Fertilizer” as used herein means any substance, mixture, microorganism or other material applied or intended to be applied to plants, alone or mixed with another material, for the purpose of providing plants with nutrients or improving their nutritional efficiency. Plant biostimulants are included.

[0068] The terms "number of decimal reductions" or "decimal reduction rate" noted "n" designate the number of divisions by ten of the bacterial load and are calculated as follows: n = log (N 0 / N) where N 0 corresponds to a population at time 0 and N to a population at time t.

[0069] The term "fish soluble" refers to an aqueous solution containing proteins, peptides and / or amino acids from fish by-products.

[0070] The term "preservation" means, within the meaning of the present invention, the possibility of preserving the product in a closed and unopened container, at an ambient temperature ideally below 25°C and in a dry place, without bacterial proliferation and / or without denaturation of the chemical composition of the product, in particular peptides and / or proteins, due, for example, to enzymatic reactions. EXAMPLES Example 1 has) preparation of fish soluble

[0071] The starting product is the soluble fraction of protein-rich fish by-products, also called "fish solubles". This fraction is recovered after cooking the fish by-products, removing the solid fraction by pressing, removing part of the oil by centrifugation and removing the water by vacuum concentration. The operating conditions of evaporation-concentration (vacuum concentration) are favorable to the sporulation of heat-resistant germs of the ASR type such as C. perfringens.

[0072] Table 1 below gives an example of fish soluble that can be used for the manufacture of the aqueous solution of the invention. Table 1 Nutritional Values Review Setting Unit Value Analysis method Humidity g / 100 g of raw product 66.7+ / - 0.8 Thermogravimetry. Adapted from EC regulation 152 / 09 and standard NF V 04-401. The sample is dispersed on sand and dried at 103°C + / - 2°C Dry Matter g / 100 g of raw product 33,3+ / - 0.8 Dry matter = 100-Humidity Fats g / 100 g of dry product 1.8+ / - 1.5 Gravimetry, Adapted from EC Regulation 152 / 09 The sample is hydrolyzed with hydrochloric acid and filtered. The residue is dried and extracted with petroleum ether. The solvent is distilled and the residue dried and weighed. Total nitrogen g / 100 g of dry product 13,6+ / - 0.4 Kjeldahl (Titrimetry). Adapted from EC Regulation 152 / 2009, Order of 08 / 09 / 1977 (OJ of 03 / 11 / 1977) The sample is digested with sulfuric acid (with copper as a catalyst). The proteins are converted into ammonium sulfate. The sample is made alkaline and the ammonia is distilled and titrated. The protein content is calculated with the factor 6.25 Kjeldahl for protein determination Kjeldhal Proteins g / 100 g of dry product 85,0+ / - 2.7 Mineral Matters g / 100 g of dry product 13,2+ / - 0.9 Gravimetry Adapted from EC Regulation 152 / 2009. Incineration in a furnace at 550°C b) preparation of the aqueous solution of the invention

[0073] The fish soluble obtained in step a) is introduced into a reactor. The resulting mixture is subjected to enzymatic hydrolysis, with stirring, with a serine endoprotease (Savinase ®< from Novozyme) added at a ratio of 0.5% enzyme / dry weight of raw material. The enzymatic hydrolysis is carried out at a temperature of 65°C. The pH of the mixture is not modified, it is equal to 6.1. The enzymatic hydrolysis is carried out for a duration of 4 hours.

[0074] Hydrolysis is stopped by adding a 50% citric acid solution until a pH of 4 is reached within the same reactor. The resulting mixture is then heated to 85°C for 15 minutes.

[0075] The mixture is filtered to 0.8 mm and packaged in an IBC type container. The water activity Aw is 0.910.

[0076] Throughout this application the measurement of water activity is measured by the Novasina Labswift-aw aw-meter (internal method INRD28). The sample is placed in a closed compartment equipped with a cell, after equilibration, the relative humidity of the air trapped with it is measured. The "NOVASINA" Aw-meter measures the equilibrium humidity (HRE) in % RH, directly linked to the water activity according to the following formula: Aw = HRE / 100.

[0077] The resulting composition is an aqueous solution that can be used as a liquid organic fertilizer. It contains free and non-free amino acids (i.e., forming peptides and / or proteins). Its composition is shown in Table 2 below: Table 2 Setting Unit Value Analysis method Dry Matter g / 100 g of raw product 39,6 NF U44 171 Drying at 105°C Kjeldhal Proteins g / 100 g of dry product 81,10+ / -2.6 Kjeldahl (Titrimetry). Adapted from EC Regulation 152 / 2009, from the decree of 08 / 09 / 1977 (OJ of 03 / 11 / 1977) The sample is digested with sulfuric acid (with copper as a catalyst). The proteins are converted into ammonium sulfate. The sample is made alkaline and the ammonia is distilled and titrated. The protein content calculated with the factor 6.25 Total Kjeldahl nitrogen for agronomic value g / 100 g of dry product 12,10 Kjeldahl, NF EN 15604 Total phosphorus g / 100 g of dry product 2,00 NF ISO 11885 Aqua Regia-ICP Total potassium g / 100 g of dry product 2,50 NF ISO 11885 Aqua Regia-ICP pH - 4,30 Direct measurement by pHmetry aw - 0,910 Novasina Awmeter Internal Method

[0078] Table 3 below lists the molecular weights of the peptides contained in the aqueous solution of the invention of Example 1. The distribution of molecular weights, made on the soluble part of the products to be analyzed, is obtained by HPLC liquid chromatographic analysis. This method makes it possible to determine the distribution of molecular weights of different products, containing proteins, peptides and free amino acids, by HPLC on a gel permeation chromatographic column separating the compounds according to their molecular size. This detection is done in Ultraviolet. HPLC-UV SEC column. Table 3 Molecular weight balance % PM > 10KDa 0,62 % PM ≤ 10KDa 99,38 % PM ≤ 3KDa 84,73 Mw (Da) 1572 Mn (Da) 570 Polydispersity index Mw / Mn 2,76

[0079] It is observed that the vast majority of peptides have a molar mass less than or equal to 3 kDa. Such peptides are easily assimilated by plants due to their size.

[0080] Table 4 below indicates the different amino acids contained in the solution of the invention of Example 1. Table 4 Assessment of total and free amino acid profile (g / 100g protein) Amino acids Free Totals To the 0,72 6,89 Arg 0,00 5,34 Asp 0,06 4,85 Cys 0,10 0,20 Glue 0,48 8,74 Gly 0,24 16,05 His 0,08 1,03 HyPro NC 4,24 Island 0,10 1,21 Leu 0,21 2,50 Lily 0,27 3,30 Met 0,11 1,41 Orn 0,04 0,25 Phe 0,10 1,83 Pro 0,09 7,09 Ser 0,06 3,40 Tau 1,33 NC Thr 0,11 2,06 Trp 0,00 0,09 Tyr 0,08 0,45 Valley 0,27 1,79 Total 4,44 72,73

[0081] Amino acids are detected by acid hydrolysis by ion chromatography - UV) according to ISO 13903:2005; EU 152 / 2009. Cystine and methionine are measured after oxidative hydrolysis by ion chromatography - UV according to ISO 13903:2005; EU 152 / 2009. Free amino acids (except tryptophan) are measured by ion chromatography - UV according to ISO 13903:2005). Free tryptophan is measured by (HPLC) (LC / FLUO) according to EN-ISO 130904:2016

[0082] The aqueous solution of the invention contains 13% more protein than that described in US 5,393,318. It also contains a greater quantity of the following amino acids: alanine, arginine, asparagine, glutamine, glycine, hydroxyproline, leucine, lysine, phenylalanine, proline, and valine.

[0083] Increasing glycine content is interesting because it is known to increase resistance to environmental stresses, including frost. It is also known to improve the taste and sweetness of fruits and leaves; glycine is also a chelating agent and a precursor of chlorophyll. Similarly, increasing proline content is interesting because the latter is known to improve the quality of crops at the organoleptic level (increased sugar content), improve fruit firmness. Proline is also known as an osmoprotectant: it increases the resistance of proteins, enzymes and membranes to the denaturing effects of high salt levels and unphysiological temperatures. It is an anti-stress agent; it increases pollen production and fertility and allows the regulation of water balance.

[0084] Similarly, taurine is known to increase root and aerial growth and improve crop quality. Example 2: Study of the health indicators of fish soluble and the solution of the invention

[0085] Table 5 below lists the different types of flora and bacteria present in the fish soluble from example 1. Table 5 Fish soluble Setting Unit Value Analysis method Mesophilic aerobic flora 30°C CFU / g < 2000 NF EN ISO 4833-1 or XP V 08-034 ASR bacteria 46°C CFU / g 3400* NF V 08-061 (boxes) ASR spores (including Clostridium) 46°C CFU / g 7400 NF V 08-061 (boxes) Enterobacteriaceae 30°C CFU / g < 10 NF V 08-054 Enterococci (fecal streptococci) CFU / g < 100 Internal method on Slanetz medium 48h at 37°C - Confirmation on BEA Yeasts CFU / g < 10 NF V 08-059 Molds CFU / g < 10 NF V 08-059 * number calculated from the last inoculated dilution

[0086] Table 6 below lists the different types of flora and bacteria present in the aqueous solution of the invention obtained in Example 1. Table 6 Aqueous solution of the invention Setting Unit Value Analysis method Mesophilic aerobic flora 30°C CFU / g < 200 NF EN ISO 4833-1 or XP V 08-034 ASR bacteria (including Clostridium ) 46°C CFU / g < 10 NF V 08-061 (boxes) ASR spores 46°C CFU / g 50* NF V 08-061 (boxes) Enterobacteriaceae 30°C CFU / g < 10 NF V 08-054 Enterococci (fecal streptococci) CFU / g < 100 Internal method on Slanetz medium 48h at 37°C - Confirmation on BEA Yeasts CFU / g < 10 NF V 08-059 Molds CFU / g < 10 NF V 08-059 Salmonella (excluding typhi And paratyphi ) CFU / 25g 0 NF EN ISO 6579-1 Bacteria Clostridium perfringens CFU / g < 10 NF EN ISO 7937 Spores Clostridium perfringens CFU / g < 10 NF EN ISO 7937 and NF V 08-250 AND. Coli β-glucuronidase + CFU / g < 10 NF ISO 16649-2 * Estimated Number takes into account the estimation of small numbers

[0087] In view of the comparison of Tables 5 and 6, there is a clear decrease in the mesophilic aerobic flora at 30°C and also a clear decrease in the quantity of bacteria and sulfite-reducing anaerobic spores (ASR of which the genus Clostridium is part) in the aqueous solution of the invention compared to the starting fish soluble. These sulfite-reducing anaerobic spores and in particular Clostridium and more particularly C. perfringens, when activated and placed in favorable conditions, are capable of transforming into new cells capable of reproducing and generating bacterial colonization in the finished product, over time. It is therefore noted that the aqueous solution of the invention has less risk of giving rise to a significant proliferation of bacteria and in particular of bacteria of the genus Clostridium and more particularly of C. perfringens. Example 3 : Study of the effect of reversing the acidification step with heat treatment in terms of the number of decimal reductions in bacterial load

[0088] Sym'Previus simulation software is a modeling software that allows you to evaluate the effectiveness of a heat treatment to eliminate a microorganism. It calculates the reduction rate at the end of treatment and the probability of survival of any microorganisms. It takes into account the heat resistance of each strain of bacteria, the heating temperature, its duration, the pH of the treated product and its water activity.

[0089] The values of D - that is, the time required to divide the population by 10, of spores of Clostridium perfringens - vary depending on the strain. At a heating temperature of 100°C, it takes, depending on the strain, between 0.2 and 43 minutes to divide the spore population by 10. Clostridium perfringens. At a heating temperature of 95°C, it takes between 1.3 and 63 minutes. The spores of Clostridium perfringens are more heat resistant than bacteria Escherichia coli And Salmonella spp.In fact, at a heating temperature of 60°C, it takes between 0.5 and 3 minutes to divide the bacterial population by 10. Escherichia coli and, between 2 and 6 minutes to divide the bacteria population by 10 Salmonella spp. The temperature and duration of the hydrolysis step, and the temperature rise to 85°C achieved in ten minutes for the heat treatment, eliminate the risk of development of Escherichia coli And Salmonella spp. in the aqueous solution of the invention. To evaluate the effectiveness of the heat treatment of the invention, the decimal reduction number of sporulating bacteria of Clostridium perfringens is therefore monitored and calculated using the Sym'previus software. A reduction in pathogenic bacteria is considered significant from 5 decimal reductions (Regulation (EU) No. 142 / 2011). The number of decimal reductions in sporulating bacteria of Clostridium perfringenstargeted to ensure the effectiveness of the heat treatment is therefore 5 decimal reductions.

[0090] Table 7 below indicates, depending on the heating temperature and heating duration, the average and minimum decimal reduction number at the 95% confidence threshold of sporulating bacteria. Clostridium perfringens obtained for the product without prior acidification with a water activity (aw) of 0.927 + / - 0.009 and a pH of 5.9 (without acidification). Table 7 Decimal reduction number Set temperature time (in minutes) 0 5 15 35 50 75°C on average 0,1 0,2 0,4 0,7 1 at the minimum confidence threshold of 95% 0,1 0,2 0,3 0,4 80°C on average 0,1 0,5 0,9 1,6 2,3 at the minimum confidence threshold of 95% 0,2 0,4 0,6 0,9 85°C on average 0,3 1 2,3 4,2 5 at the minimum confidence threshold of 95% 0,4 0,9 1,5 2,3 90°C on average 0,9 2,6 5,6 9,6 14,4 at the minimum confidence threshold of 95% 1 2,3 3,8 5,7

[0091] Table 8 below indicates, depending on the heating temperature and heating duration, the average and minimum decimal reduction number at the 95% confidence threshold of sporulating bacteria. Clostridium perfringensobtained for the product having undergone the acidification step before the heat treatment step (product of the invention); the addition of acid makes it possible to obtain a pH of 4.3; the water activity (aw) is 0.919 + / - 0.006.

[0092] It is noted that despite a water activity greater than 0.91, the method of the invention is effective in terms of reducing the bacterial load and the load of spores and / or sporulating species. Table 8 Decimal reduction number Set temperature time (in min) from reaching the set temperature 0 5 15 35 50 75°C on average 1,2 2,5 4,7 7,5 10,9 at the minimum confidence threshold of 95% 1,1 2 3,2 4,5 80°C on average 1,9 5,5 10,8 at the minimum confidence threshold of 95% 0 2,4 4,7 85°C on average 3,7 12 26 at the minimum confidence threshold of 95% 1,6 5 11,5 90°C on average 6,5 29 63 at the minimum confidence threshold of 95% 2,6 8,5 22

[0093] Comparing Tables 7 and 8, we see that for bacteria Clostridium perfringens,Heat treatment before acidification (85°C for 15 min) provides a decimal reduction of 2.3 log with a 5% chance of being at a minimum of 0.9 log. This reduction is insufficient if the initial contamination is significant. On the contrary, when this same heat treatment is carried out after acidification (85°C for 15 min), a decimal reduction of 26 log is obtained with a 5% chance of being at a minimum of 11 log, i.e. 10 times greater than when the heat treatment is carried out before acidification.

[0094] Referring to Tables 7 and 8, it can be seen that to achieve the target decimal reduction number of 5, when the heat treatment is carried out before acidification, it is necessary to heat for more than 50 min at 85°C or 15 min at 90°C with 95% confidence levels lower than the target decimal reduction. For the same target decimal reduction number of 5, heating for 5 minutes at 85°C is sufficient when the heat treatment is carried out after acidification. Example 4: Aging test

[0095] The aqueous solution of Example 1 was stored at 15°C for 12 months.

[0096] The bacterial flora assay was carried out at various intervals.

[0097] The bacterial load of the solution is less than 3000 CFU / g after its manufacture.

[0098] An aging test of this solution at room temperature for 12 months was carried out. After 12 months, the bacterial load of the solution is less than 10 CFU / g, the product is therefore stable over time.

[0099] Table 9 below groups together the results obtained. Table 9 Aqueous solution of the invention Setting Unit T0 T+4 months T+6 months T+12 months Mesophilic aerobic flora 30°C CFU / g < 3000 150 < 100 < 10 ASR bacteria 46°C CFU / g < 10 80* 50* 40* ASR spores 46°C CFU / g 40* < 10 20** 40* Enterobacteriaceae 30°C CFU / g < 10 < 10 < 10 < 10 Enterococci (fecal streptococci) CFU / g < 100 < 100 < 100 < 100 Salmonella (excluding typhi And paratyphi ) CFU / 25g 0 0 0 0 Bacteria Clostridium perfringens CFU / g < 10 < 10 < 10 < 10 Spores Clostridium perfringens CFU / g < 10 < 10 < 10 < 10 AND. Coli β-glucuronidase + CFU / g < 10 < 10 < 10 < 10 Coaqualase-producing staphylococci + CFU / g < 10 < 10 < 10 < 10 Yeasts CFU / g < 10 < 10 < 10 < 100 Molds CFU / g < 10 < 10 < 10 < 100 * Estimated Number takes into account the estimation of small numbers ** present at a rate lower than the quantification threshold of 40 Example 5 : biostimulant effect of the invention on lettuce

[0100] The impact of treatment with the aqueous solution of the invention on the development and quality of lettuce as well as on soil life as a function of the nitrogen content of the soil at planting was studied.

[0101] The test is carried out in a growth chamber using a 12-modality design with 5 repetitions at a humidity of 70%, a photoperiod of 14 / 10 h and a temperature of 18 / 15°C. A Butter Lettuce crop of the Analota variety is planted in a 1L pot filled with a mixture of 33% sand, 33% vermiculite and 33% market garden soil. Table 10 describes the nitrogen contents of the soil at planting, the doses (dilution in water of the solution of the invention) and the quantities of the solution of the invention applied according to the tested modalities. Table 10 Nitrogen units Product Doses Number of applications Terms and Conditions NO STRESS Classic floor 60 units Witness - 0 1 Dose 1 0,75 ml.l -1< 3 2 Dose 2 1,50 ml.l -1< 3 3 Dose 3 3,00 ml.l -1< 3 4 STRESS Medium ground 20 units Witness - 0 6 Dose 1 1,50 ml.l -1< 3 7 Dose 2 2,25 ml.l -1< 3 8 Dose 3 3,00 ml.l -1< 3 9 Weak ground < 20 units Dose 1 1,50 ml.l -1< 3 10 Dose 2 2,25 ml.l -1< 3 11 Dose 3 3,00 ml.l -1< 3 12

[0102] The solution of the invention was applied by root route at a rate of 2 applications at 0 and 21 days added during fertilization at a rate of 100 ml, the third application was applied by foliar route, by spraying after 35 days at a rate of 100 ml.

[0103] Tables 11 and 12 show the average results obtained for the physiological and biological parameters measured. Table 11 NO STRESS Classic floor Unit T Dose 1 Dose 2 Dose 3 Fresh aerial biomass g 44,9 55,0 58,7 66,7 Dry aboveground biomass g 5,5 5,5 5,5 5,8 Fresh root biomass g 16,2 20,2 16,6 17,1 Dry root biomass g 1,6 1,7 1,5 1,6 Colonization frequency % 8,0 8,0 2,0 28,0 Colonization intensity % 0,6 0,6 0,2 7,0 Abundance of arbuscules % 6,0 6,0 2,0 10,0 Vitamin C mg / 100g MS nm nm nm nm B-glucosidase mU nm nm nm nm Leucine amino peptidase mU nm nm nm nm Phosphatase mU nm nm nm nm Chlorophyll µg / cm 2< 19,7 17,2 19,5 20,7 Flavonols - 0,6 0,6 0,6 0,6 Anthocyanins - 0,3 0,3 0,3 0,3 Nutrient Balance Index (NBI) - 31,6 30,1 32,4 33,7 Table 12 STRESS Medium ground Weak ground Unit T Dose 1 Dose 2 Dose 3 T Dose 1 Dose 2 Dose 3 Fresh aerial biomass g 18,5 20,7 22,5 26,0 26,6 31,3 39,6 41,7 Dry aboveground biomass g 3,6 3,6 3,6 3,7 19,7 19,9 24,2 26,6 Fresh root biomass g 11,7 16,6 21,0 19,0 18,0 20,7 28,1 28,9 Dry root biomass g 1,5 1,7 1,8 2,1 7,5 11,8 15,1 26,3 Colonization frequency % nm nm nm nm 93,3 86,7 90,7 86,7 Colonization intensity % nm nm nm nm 10,7 13,6 17,8 17,8 Abundance of arbuscules % nm nm nm nm 0,4 0,2 0,0 3,4 Vitamin C mg / 100 g DM nm nm nm nm 0,6 0,9 1,0 1,0 B-glucosidase mU nm nm nm nm 0,6 0,5 0,5 0,6 Leucine amino peptidase mU nm nm nm nm 11,4 10,8 11,3 9,6 Phosphatase mU nm nm nm nm 1,0 1,1 1,0 1,0 Chlorophyll µg / cm 2< 11,5 11,3 12,5 13,6 18,4 19,2 20,8 20,9 Flavonols - 1,1 1,0 1,0 0,9 0,8 0,8 0,7 0,6 Anthocyanins - 0,5 0,5 0,5 0,5 0,4 0,4 0,4 0,4 Nutrient Balance Index (NBI) - 10,4 11,3 12,6 15,1 23,1 24,2 31,8 34,0

[0104] From Tables 11 and 12, it can be seen that lettuce productivity in conventional soil is increased by more than 49% (44.9g of fresh aerial biomass without treatment / 66.7g with treatment with the solution of the invention). On medium soil, a 40% increase in productivity is observed (18.5g of fresh aerial biomass on medium soil compared to 26.0g with treatment with the solution of the invention). On poor soil, the fresh aerial biomass increases from 26.6g to 41.7g. The effect of the solution of the invention on the fresh aerial biomass is concentration and soil-dependent.

[0105] With reference to tables 11 and 12, it can be seen that the chlorophyll index (measured with a Dualex ®< FORCE A sensor) increases from 11.3 to 13.6 µg / cm 2< on medium soil and from 18.4 to 20.9 µg / cm 2< on poor soil after using the solution according to the invention.

[0106] Regarding root growth, fresh root biomass increases from 11.7 g without treatment to 19.0 g with treatment with the solution of the invention, on medium soil. On poor soil, it increases from 18.0 g without treatment to 28.9 g with treatment with the solution of the invention (see Table 11).

[0107] With reference to Table 11, it is noted that the vitamin C content in lettuce increases when the latter is treated with the solution of the invention (0.6g / 100g of dry leaf without treatment against 1.0g / 100g of dry leaf with treatment).

[0108] Referring to Table 11, we see that the flavonoid index (measured with a dualex ®< FORCE A sensor) increases from 1.1 without treatment to 0.9 with treatment on medium soil. It increases from 0.8 without treatment to 0.6 with treatment on poor soil (nitrogen deficient). The flavonoid content of a plant is significant for its reaction to abiotic stress. The more stressed the plant is, the more its flavonoid content increases.

[0109] In view of these results, a biostimulant activity of the solution of the invention is observed regardless of the type of soil. Treatment with the solution of the invention makes it possible to obtain more productive plants, more resilient to environmental conditions and whose elemental composition is richer than the modality not treated with the solution of the invention.

[0110] Stimulation of soil life was also observed following application of the aqueous solution of the invention. This increase in fungal colonization can be demonstrated by staining with Trypan blue using a protocol published by Phillips and Hayman in 1970. The solution of the invention therefore also stimulates soil life, which results in an increase in soil-plant exchanges, which can be observed through the increase in fungal colonization of the roots.

[0111] Similar results were obtained with tomatoes - where an improvement in fruit productivity was also observed, wheat and radish.

[0112] Some of these results are presented in the journal Infos Ctifl (Charlotte Berthelot et al., December 2021: From co-product to biostimulant, the story of a protein hydrolyzate). This article presents the results of trials conducted over two years, validating the benefits of using the protein hydrolyzate according to the invention as a biostimulant in the cultivation of butter lettuce, round radish, and vine tomatoes. This study also shows that the protein hydrolyzate according to the invention facilitates plant development under stressful conditions. For example, lettuce development is maintained under conditions of water and heat stress, as well as during nitrogen deficiency. In the latter condition, the results highlight the possibility of substantial fertilizer savings (more rational fertilization).The use of an aqueous solution obtained by the process of the invention as a biostimulant is therefore particularly advantageous in the context of abiotic stress such as nitrogen deficiencies or variations in temperature or humidity.

Claims

1. A method for producing an aqueous solution containing amino acids from a fish soluble, characterised by: - said fish soluble being at a given temperature, adding at least one protease having proteolytic activity at said given temperature thereto, without modification of pH; - lowering the pH to a value less than 4.5 by adding at least one acid; and - then heating the acidified solution to a temperature greater than or equal to 75°C and less than 100°C for a duration greater than or equal to 5 minutes and - filtering to obtain said solution.

2. The production method according to claim 1, characterised in that by adding said acid, the pH is lowered to a value less than or equal to 4.5, in particular equal to 4.3 and / or after adding said acid, heating to a temperature equal to or greater than 75°C, in particular equal to 80°C, 85°C or 90°C.

3. The method according to claim 1 or 2, characterised by adding one or more endoproteases and / or one or more exoproteases.

4. The method according to claim 3, characterised by adding said endoprotease(s) and / or said exoprotease(s) at an enzyme / dry substrate ratio equal to or greater than 0.1% and equal to or less than 2%, at a temperature between 50°C and 70°C, preferably between 55°C and 65°C, preferably at 60°C, the temperature and pH being maintained for a period from 1 to 24 hours, preferably from 1 to 4 hours.

5. The method according to any one of the preceding claims, characterised in that fish soluble is obtained by: - cooking said fish by-product(s); - removing the solid fraction by pressing and at least part of the fat; and optionally - concentration.

6. The method according to claim 5, characterised in that said soluble contains a mass percentage of dry matter equal to or greater than 25% and less than or equal to 45% and / or a mass percentage of protein of said dry matter equal to or greater than 80% and / or a mass percentage of minerals of said dry matter equal to or less than 20% and / or a mass percentage of fat of said dry matter equal to or less than 10%.

7. The method according to claim 5 or 6, characterised in that said fish soluble contains a mass percentage of molecules whose molecular weight is greater than or equal to 10 kDa greater than or equal to 20% and less than or equal to 60% and / or in that it contains an amount of free taurine greater than or equal to 1.2g / 100g of protein and less than or equal to 2.0g / 100g of protein and / or a total amount of glycine greater than or equal to 10.0g / 100g of protein and less than or equal to 18.1g / 100g of protein and / or an amount of proline greater than or equal to 4.4g / 100g of protein and less than or equal to 8.0g / 100g of protein.

8. An aqueous solution containing amino acids and obtainable according to the method according to any one of the preceding claims, characterised in that it contains a mass percentage of dry matter equal to or greater than 30% and less than or equal to 40%, and less than 10 CFU / g of Clostridium bacteria and in particular C. perfringens, less than 10 CFU / g of Clostridium spores and in particular C. perfringens spores, less than 100 CFU / g of faecal streptococci and less than 10 CFU / g of Salmonella.

9. The aqueous solution according to claim 8, containing amino acids, characterised in that it has a pH between 4 and 4.5.

10. The aqueous solution according to claim 8 or 9, characterised in that it contains a mass percentage of organic nitrogen of said dry matter equal to or greater than 10.5% and equal to or less than 12.5% and / or a mass percentage of total amino acids measured relative to its protein content equal to or greater than 65% and / or a mass percentage of said dry matter in total phosphorus equal to or greater than 2% and / or a mass percentage of said dry matter in total potassium equal to or greater than 2.5% and equal to or less than 3.0% and / or a water activity of 0.91 or less.

11. The aqueous solution according to any one of claims 8 to 10, characterised in that it comprises at least 98% by mass of peptides with a molecular weight less than or equal to 10 kDa and at least 80%, in particular at least 90% by mass of peptides with a molecular weight less than or equal to 3 kDa.

12. The aqueous solution according to any one of claims 8 to 11, characterised in that it contains a mass percentage of alanine measured relative to its protein content equal to or greater than 5.6 and equal to or less than 7.6 and / or a mass percentage of arginine measured relative to its protein content equal to or greater than 4.3 and equal to or less than 5.9 and / or a mass percentage of aspartic acid measured relative to its protein content equal to or greater than 4.8 and equal to or less than 5.6 and / or a mass percentage of glutamic acid measured relative to its protein content equal to or greater than 8.5 and equal to or less than 10.1 and / or a mass percentage of glycine measured relative to its protein content equal to or greater than 10.1 and equal to or less than 18.1 and / or a mass percentage of hydroxyproline measured relative to its protein content equal to or greater than 2.6 and equal to or less than 5.0 and / or a mass percentage of leucine, measured with respect to its protein content equal to or greater than 2.4 and equal to or less than 3.6 and / or a mass percentage of lysine measured with respect to its protein content equal to or greater than 3.2 and equal to or less than 4.4 and / or a mass percentage of phenylalanine, measured with respect to its protein content equal to or greater than 1.7 and equal to or less than 2.1 and / or a mass percentage of proline, measured with respect to its protein content equal to or greater than 4.4 and equal to or less than 8.0 and / or a percentage by mass of valine measured with respect to its total protein content equal to or greater than 1.7 and equal to or less than 2.5.

13. The aqueous solution according to any one of claims 8 to 12, characterised in that it contains a percentage of amino acids measured relative to 100g of protein, equal to or greater than 65 and less than or equal to 80 and / or in that it has a pH less than or equal to 4.5, more particularly less than or equal to 4.4 and a water activity less than or equal to 0.91, in particular equal to 0.906.

14. The aqueous solution according to any one of claims 8 to 13, characterised in that it contains, by mass, at least 10.5% organic nitrogen relative to 100g of dry matter and at least 1.0% free taurine / 100g of protein.

15. A biostimulant or fertiliser comprising or consisting of the aqueous solution according to any one of claims 8 to 14.