Composition for growing media and / or growing solutions and / or plants

Abstract

Composition for soils and / or plants. The present invention relates to a composition for growing media and / or growing solutions and / or plants comprising the combination of: - a carboxylic acid, - a polysaccharide, - calcium, and - a microalga. It further relates to the use of the composition according to the invention to promote the formation of bacterial biofilms and / or their maturation on the growing medium, in the rhizosphere, and / or on the roots of a plant.

Description

Title of the invention: Composition for growing media and / or growing solutions and / or plants technical field

[0001] The present invention relates to the field of compositions intended for plants and / or soil having a beneficial effect on them. It relates in particular to a composition based on microalgae, an organic fraction and a mineral fraction to promote the formation of bacterial biofilms. Previous technique

[0002] Soil is an active, living, and dynamic ecosystem with a wide range of biodiversity on Earth. It harbors several thousand prokaryotic and eukaryotic life forms. The responses of the microbial community are influenced by the surrounding soil environment. As a natural resource, soil plays a vital role in biodiversity and participates in numerous other ecosystem services. Soil is said to be prolific due to the activity of microorganisms at a rate adequate for optimal plant development and growth. Even though they are abundant, soil nutrients and other essential elements are not readily available to plants. Through various processes (physical, chemical, and biological), root-associated microorganisms play a major role in soil formation and fertility.

[0003] Thus, a wide variety of microorganisms and macroorganisms exist in symbiosis in the rhizosphere. Bacteria are the most predominant.

[0004] Traditionally, bacterial cells have been identified and characterized as individual cells evolving independently among other cells. However, in nature, >90% of bacterial biomass develops in the form of biofilms.

[0005] A biofilm is defined as an aggregate of microorganisms whose cells are enclosed in a matrix of extracellular polymeric substance (EPS) adhering to each other and / or to a surface (IUPAC).

[0006] Biofilm formation is a complex process involving several steps: i. Attachment of planktonic bacteria to the biotic or abiotic surface by chemotaxis processes, ii. Cell adhesion and loss of mobility, iii. Production of exopolymers (EPS), iv. Biofilm maturation phases where the biofilm architecture and primary micro-colonies develop through the Quorum Sensing (QS) process, v. Dispersion phase: planktonic cells disperse from microcolonies by the Quorum Quenching (QQ) process.

[0007] Biofilms represent a form of bacterial resistance compared to a planktonic form (i.e., free-floating and isolated). In the medical field, strategies for controlling pathogens target biofilms. Conversely, and somewhat surprisingly, biofilms are of major importance in agriculture and in plant growth and nutrition. Therefore, efforts should be made to stimulate their formation, particularly in the soil and on root surfaces.

[0008] Biofilms offer advantages for both the plant and the soil. For the plant, they promote the benefits of PGPR1 (Plant Growth Promoting Rhizobacteria) organisms. Biofilms located near root systems increase tolerance to stress (biotic and abiotic). Extracellular polymeric substances play a central role in nutrient availability (nitrogen, phosphorus, etc.). For example, the establishment of a symbiosis between nitrogen-fixing rhizobia and plants.

[0009] In soil, biofilm stabilizes the environment for the development of microorganisms, acting as a carbon and nutrient reservoir. It provides protection against desiccation and promotes aggregation and adhesion. Within biofilms, microbial activity is increased tenfold.

[0010] The inventors have surprisingly discovered that the association of microalgae with a carboxylic acid, a polysaccharide and calcium makes it possible to promote the formation of bacterial biofilms and / or their maturation at the level of the soil, the rhizosphere and / or the roots of a plant. Description of the invention

[0011] The present invention relates to a composition for growing media and / or growing solutions and / or plants comprising the following combination: - of a carboxylic acid, advantageously in a content of between 1% and 5% by weight relative to the total weight of the mixture, - of a polysaccharide, advantageously in a content of between 15% and 27% by weight relative to the total weight of the combination, - of calcium, advantageously at a content between 43% and 69% by weight relative to the total weight of the mixture, and - of a microalga, advantageously in extract form, more advantageously in a content of between 15% and 25% by weight relative to the total weight of the association.

[0012] For the purposes of the present invention, "composition for growing media and / or growing solutions and / or plants" means a composition intended to be administered to growing media and / or growing solutions and / or plants, particularly cultivated plants, to provide them with a benefit. Advantageously, this composition is phytosanitarily acceptable.

[0013] For the purposes of the present invention, "phytosanitarily acceptable" means acceptable for use on plants or growing media and / or growing solutions, i.e. non-polluting to the environment and non-toxic to humans (users).

[0014] For the purposes of the present invention, "growing medium" means any soil or support on which a crop can grow, such as artificial soil, cultivated agricultural soil, uncultivated agricultural soil, peat, potting soil, rock wool or coconut fiber.

[0015] For the purposes of the present invention, "culture solution" means any solution which enables the cultivation of a plant such as, for example, irrigation water, liquid solution intended for fertigation by sprinkling or drip irrigation, hydroponic bath or aeroponic solution.

[0016] The term "plant" in this application means the plant considered as a whole, including its root system, vegetative system, seeds and fruits.

[0017] The plants according to the invention can be chosen from among major crops such as cereals (wheat, maize, barley), protein crops (peas), oilseeds (soybeans, sunflowers), Solanaceae crops (potatoes), Amaranthaceae crops (sugar beets), specialty crops such as, in particular, market garden crops (lettuce, spinach, onions, shallots, tomatoes, melons), grapevines, fruit trees (pears, apples, nectarines), or horticultural crops. In particular, the plant may belong to the order Monocotyledons, preferably to the Poaceae family. Poaceae, commonly called grasses, include most of the species commonly referred to as "grasses" and "cereals." Examples of Poaceae include wheat, rice, barley, oats, rye, sugarcane, meadow grass, and maize.

[0018] Legume plants belong to the Fabaceae family. Legume plants play an important role in the food sector due to their high protein and essential amino acid content. Non-limiting examples of legume plants include soybeans, peanuts, beans, peas (particularly of the species P. sativum), lentils, chickpeas, broad beans, field beans, vetches, grass peas, alfalfa, clover, lupins, mung beans (sprouted soybeans), licorice, rosewood, bird's-foot trefoil, sainfoin, rooibos, and fenugreek.

[0019] The composition according to the invention therefore comprises the association of a carboxylic acid, a polysaccharide, calcium, and a microalga.

[0020] The term “carboxylic acid” should be understood in its common meaning, that is, an acid of the formula R-COOH, where R is a hydrogen atom or an organic group, advantageously an organic group comprising between 1 and 10 carbon atoms. The carboxylic acid usable in the combination according to the invention may be a monocarboxylic acid or a polycarboxylic acid, advantageously a tricarboxylic acid. Advantageously, it is a weak acid, in particular an organic acid. Within the scope of the present invention, the carboxylic acid may be selected from methanoic acid, ethanoic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, benzoic acid, 2-hydroxybenzoic acid, and 2-mercaptopropanoic acid.In a preferred embodiment, the carboxylic acid is selected from formic acid, acetic acid, lactic acid, citric acid, oxalic acid, propionic acid, malic acid, tartaric acid, fumaric acid, gluconic acid, sorbic acid, and butyric acid; preferably, the carboxylic acid is selected from formic acid, citric acid, acetic acid, and lactic acid. In a particularly preferred embodiment, the carboxylic acid is citric acid.

[0021] Advantageously, the carboxylic acid is present in the association in a content of between 1% and 5% by weight, advantageously between 2% and 4% by weight, more advantageously between 3% and 4% by weight, in particular between 3% and 3.5% by weight, more particularly in a content of 3.3% by weight, relative to the total weight of the association.

[0022] In the context of the present invention, the carboxylic acid promotes the formation of EPS in synergy with the calcium of the association according to the invention.

[0023] In the context of the present invention, the terms "between ... and ..." and "from ... to ..." mean that the limits of the range are included.

[0024] For the purposes of the present invention, "polysaccharide" means any polymer of the carbohydrate family composed of several monosaccharides linked together by glycosidic bonds. It may be a homopolysaccharide (composed of the same monosaccharide) or a heteropolysaccharide (formed of different monosaccharides). Advantageously, it is a heteropolysaccharide, more advantageously of plant origin, and even more advantageously with a linear chain. The polysaccharide usable within the scope of the present invention may be chosen from starch, inulin, cellulose, and pectin. It is advantageously a pectin, more advantageously having a degree of methylation between 5% and 80%, even more advantageously between 50% and 80%, more particularly between 60% and 80%, and even more particularly between 70% and 80%, for example, 71%.

[0025] Advantageously, the polysaccharide is present in the association in a content between 15% and 27% by weight, advantageously between 20% and 25% by weight, more particularly at a content of 22% by weight, relative to the total weight of the association.

[0026] In the context of the present invention, the polysaccharide helps and promotes the formation of EPS in the biofilm.

[0027] The calcium usable within the framework of the present invention may be a calcium salt (carbonate, citrate, malate, lactate, gluconate, etc.) or marine calcium. Advantageously, it is marine calcium.

[0028] For the purposes of this invention, "marine calcium" means calcium derived from marine shells of the Maerl type. Maerl is an accumulation of coralline algae rich in limestone.

[0029] Advantageously, calcium is present in the association in a content of between 43% and 69% by weight, advantageously between 45% and 65% by weight, more advantageously between 50% and 60% by weight, in particular between 52% and 56% by weight, more particularly in a content of 54.8% by weight, relative to the total weight of the association.

[0030] In the context of the present invention, calcium plays a role in the structuring of EPS. It acts as a binder to promote the cohesion of the biofilm.

[0031] The microalgae usable within the framework of the present invention are advantageously eukaryotic microalgae, more advantageously chosen from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Nannochloropsis sp, Ske-letonema sp, Phaeodactylum sp, Dunaliella sp, Haematococcus pluvialis, Isochrysis sp and their mixtures, even more advantageously chosen from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Isochrysis sp and their mixtures.

[0032] In particular, the microalga usable within the framework of the present invention is in the form of biomass or extract, more advantageously in the form of extract.

[0033] In the context of the present invention, the microalga is an inducer of biofilm formation (quorum sensing).

[0034] The term "extract" refers to the product resulting from an extraction from a source. For example, the source may be a biological source, such as cells. When cells are involved, the term "extract" therefore refers to the product resulting from the extraction of the cell contents. Thus, for example, the term "microalgae extract" refers to the product resulting from the extraction of the cell contents of a microalga. The extraction may be carried out with an aqueous solvent or an organic solvent, advantageously with an aqueous solvent, more advantageously with water as the sole solvent. In particular, the extract may be water-soluble. The extraction may be carried out by any extraction method well known to those skilled in the art, such as hot decoction, maceration, extrusion, or extraction under sub-aquatic conditions. Critically acclaimed methods include ultrasound-assisted extraction, with or without grinding such as ultrasonic grinding or grinding with a blender, advantageously by maceration. Extraction can be carried out at temperatures ranging from 4°C to 300°C, including ambient temperature, i.e., approximately 20°C.

[0035] Thus advantageously the microalga extract is an extract of a eukaryotic microalga, advantageously chosen from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Nannochloropsis sp, Skeletonema sp, Phaeodactylum sp, Du-naliella sp, Haematococcus pluvialis, Isochrysis sp and their mixtures, more advantageously chosen from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Isochrysis sp and their mixtures.

[0036] Advantageously, the microalga, in particular the microalga extract, is present in the association in a content of between 15% and 25% by weight, advantageously between 17% and 23% by weight, more advantageously between 18% and 22% by weight, more particularly in a content of 20% by weight, relative to the total weight of the association.

[0037] Advantageously the association according to the invention is present in the composition for soils and / or plants according to the invention in a content of between 0.1% and 20% in particular between 0.15% and 10%, more particularly between 0.2% and 1%, even more particularly in a content of 0.25%, by weight in relation to the total weight of the composition.

[0038] The composition according to the invention may further comprise a phytosanitarily acceptable excipient. It may also further comprise other ingredients besides the combination according to the invention. Thus, the composition may include natural or synthetic biostimulant compounds such as amino acids, growth regulators, humic substances, plant extracts, microbial extracts, minerals such as nitrogen, phosphorus, potassium, molybdenum, sulfur, magnesium, iron, chlorine, manganese, zinc, boron, boric acid, disodium octaborate tetrahydrate, calcium borate, magnesium borate, sodium borosilicate, sodium tetraborate decahydrate, sodium borate, sodium tetraborate, disodium tetraborate, lime, gypsum, superphosphate, iron sulfate, iron chelate, ferritin, zinc oxide, zinc sulfate, zinc chelate,potassium nitrate, calcium nitrate, magnesium nitrate, ammonium phosphate, ammonium sulfate, magnesium sulfate, monopotassium phosphate, calcium carbonate, ammonium nitrate sulfate, ammonium thiosulfate, ammonia liquor, calcium cyanamide, crotonylidene diurea, diacyandiamide, isobutylidene diurea, sodium nitrate, potassium carbonate, potassium chloride, potassium and magnesium sulfate, potassium metaphosphate, potassium sulfate, chloride, calcium, calcium oxide, calcitic limestone, dolomitic limestone, magnesium ammonium phosphate, magnesium oxide, copper chelates, cupric ammonium phosphate, copper sulfate, copper frits, copper polyflavonoid, malachite, azurite, cuprous oxide, cupric oxide, cupric acetate, boron fries, ferric sulfate, ferrous sulfate, ferrous ammonium sulfate, ferrous ammonium phosphate, ferrous oxalate, ferrous carbonate, iron lignosulfonate, iron polyflavonoid, iron frits, iron methoxyphenylpropane, ferrous oxide, ferric oxide, iron ammonium polyphosphate, manganese oxide, manganese methoxyphenylpropane, manganese frits, manganese chloride, the manganese carbonate, manganese sulfate, manganese chelate, manganese ammonium phosphate, manganese polyflavonoid, ammonium molybdate,sodium molybdate, molybdenum frits, molybdenum trioxide, molybdenum disulfide, zinc frits, zinc carbonate, zinc phosphate, zinc ammonium phosphate, zinc sulfide, zinc lignosulfonate, zinc polyflavonoid, or a combination thereof, and / or any excipient suitable for administration to a culture medium and / or culture solution and / or plant.

[0039] The composition according to the invention may be in solid form, in particular as a powder, granules or microgranules, as a liquid suspension or gel, or in water-soluble form. In particular, the composition is not lyophilized or dehydrated.

[0040] Advantageously, the composition according to the present invention can be a fertilizer, in particular a fertilizer or amendment, the fertilizer advantageously being a simple, binary or ternary solid fertilizer of the organo-mineral or organic fertilizer type, or a water-soluble fertilizer and the amendment advantageously being an organo-mineral or organic amendment.

[0041] The term “fertilizer” refers to a substance, or a mixture of substances, natural or synthetic, used in agriculture, horticulture and forestry to improve growing media, in particular their structure, and to fertilize cultivated plants. Fertilizers include fertilizers and soil amendments.

[0042] The term “fertilizer” refers to fertilizing materials whose main function is to provide plants with elements directly useful for their nutrition (major fertilizing elements, secondary fertilizing elements and trace elements).

[0043] The term "amendment" refers to a substance intended to improve the quality of growing media, and in particular to improve the pH of growing media. Advantageously, the amendment is chosen from basic mineral amendments of the limestone and / or limestone and magnesium type; humic amendments of the type compost or manure.

[0044] The present invention further relates to the use of the composition according to the invention, to promote the formation of bacterial biofilms and / or their maturation at the level of the culture medium, the rhizosphere and / or the roots of a plant.

[0045] Advantageously, the use according to the invention is to enhance plant growth and / or improve nutrient availability such as N-fixation or solubilization, and / or enhance plant stress tolerance, such as biotic and / or abiotic stress, and / or protect culture media against desiccation and / or enhance the formation and / or stability of culture media aggregates, and / or stabilize the growth environment of microorganisms in the culture media and / or increase the abundance and microbial activity of the culture media.

[0046] In an advantageous embodiment, the use according to the invention is by root application, either in open fields or in soilless systems. The composition according to the invention can be applied to the surface or mixed with the growing media and / or solutions. In particular, in the case of growing solutions, it is more a matter of mixing. In the case of growing media, the composition according to the invention can be applied to the surface or mixed with the medium, for example, with the first layers of the medium. The application can be carried out directly on the growing medium, over the entire surface of the growing medium, or in a localized manner in the root zone of the plants to be treated, by any suitable means of distribution, such as, for example, by spraying in the case of a liquid suspension.

[0047] Advantageously, the composition according to the invention is used by applying it at a concentration of 1 kilogram to 100 kilograms of the composition per hectare, in one or more applications. Those skilled in the art will be able to adjust the quantities to be used according to the chosen application method. In particular, relatively smaller quantities are used when the composition according to the invention is applied to the root zone, while relatively larger quantities are used when the composition is applied over the entire surface of the growing medium. The composition according to the invention can be used in a single application or in sequential applications.

[0048] The application can take place before and / or during the growth of cultivated plants, before and / or after plant germination, for example during transplanting in the case of plants requiring transplanting. Advantageously, it takes place after germination.

[0049] The present invention will be better understood upon reading the description of the drawings and examples that follow, which are given by way of non-limiting illustration. Brief description of the drawings

[0050] [Fig-1] Fig. 1 represents the quantity of biofilm obtained in mg in the presence of the compositions tested under the conditions of the example.

[0051] [Fig.2] Fig.2 represents the quantity of wrinkles (textural nuance) in the presence (combination of the 4) and absence (control) of the association according to the invention under the conditions of the example.

[0052] [Fig.3] Fig.3 represents the enlarged photograph of the presence or absence of a wrinkle under the conditions of the example.

[0053] EXAMPLE

[0054] When cultured in liquid medium, the Bacillus subtilis strain is known to produce architecturally rich and complex surface pellicles. These structures are called wrinkles. They confer several advantages to biofilm development. They increase the surface area to volume ratio, improving oxygenation. This increased surface area allows for greater airborne dispersion. The wrinkles promote the formation of a complex network of liquid channels within the biofilm, which facilitates nutrient circulation. This very distinct morphotype is observed when the biofilm is mature.

[0055] Materials and methods

[0056] Biological material

[0057] For the experiments, the Bacillus subtilis strain was chosen. This model was selected because it is widely referenced as a plant-beneficial strain of the PGPR 7 (Plant Growth Promoting Rhizobacteria) type. This strain is referenced as a model for studying biofilm and its ability to produce a stable and quantifiable biofilm.

[0058] Growing environments and conditions

[0059] The strains are preserved from fresh culture diluted with 80% glycerol (40% final) and stored at -80°C. These cryotubes serve as the starting point for all experiments, in order to prevent genetic degeneration through repeated subculturing.

[0060] In summary: The cultivation is conducted according to the following chronology: i. Isolation from the cryotube; ii. Liquid preculture; iii. Culture and production of boxed biofilm; iv. Reading.

[0061] In detail: Cells from cryotubes are plated using the quadrant method on TSA agar (Tripton: 15 g / L; soy peptone: 5 g / L; NaCl: 5 g / L; Agar: 15 g / L). The isolated cells are incubated at 30°C for 24 hours. At least 10 colonies are suspended in TSB medium (Tripton: 15 g / L; soy peptone: 5 g / L; NaCl: 5 g / L). The preculture is incubated at 30°C, 150 rpm (agitation promotes planktonic growth of the cells), for 15 hours. (precisely). The preculture is calibrated (with TSB) to a D0600nm = 1 using a UV spectrophotometer (ClarioStar Plus, BMG Labtech). This inoculum is used to inoculate, at a 1 / 10 ratio (final D0000nm = 0.1), the Petri dishes, previously filled with TSB medium (with or without supplementation of the products to be tested). The dishes are incubated at 30°C, without shaking, for 48 hours.

[0062] Quantitative analysis of biofilm

[0063] In summary: The measurement of the biofilm mass is carried out according to the following chronology: i. biofilm production; ii. Harvest; iii. Freeze-drying; iv. Weigh.

[0064] In detail: After growth of the strain in Petri dishes, a biofilm forms on the surface and walls of the dishes. The submersible is carefully removed to avoid breaking or removing the biofilm. All of the biofilm is harvested using a rake and transferred to a 50 mL bottle. The samples are then lyophilized. The total dry biomass can thus be measured.

[0065] Qualitative analysis of the biofilm

[0066] In summary: The analysis of the quality (wrinkle production) of the biofilm is carried out according to the following chronology: i. production of plate biofilm; ii. Imaging; iii. Texture analysis.

[0067] In detail: The pre-culture steps for the strain are the same as for biofilm quantification. The culture step is carried out in a 24-well plate (in TSB supplemented with the products to be tested). The plate is incubated at 30°C, without agitation, for 48 hours. After biofilm production, imaging is performed. The camera used is the Exo GigE exol38CGE camera. The camera is coupled to a V1624-MPZ lens with a focal length of 16 mm, and the image is taken in the focal plane at a height of 34 cm. Subsequently, for each modality, an image extraction (representative of the sample) is performed. A texture analysis is then carried out. The processing of the results is carried out on the "autocorrelation" and "cluster shade" data according to the method described in Haralick RM, Shanmugam K and Dinstein I (1973 Textural features for image classification IEEE Transactions on Systems, Man, and Cybernetics 3 610-21).

[0068] Results

[0069] 5 compositions were tested: - Citric acid (Sigma) at 0.08g / L in TSB medium; - Pectin with a degree of methylation of 71% (Cargill) at 0.55 g / L in the medium TSB; - Marine calcium at 1.37g / L in TSB medium; - Extract of the microalga Isochrysis, obtained by aqueous extraction (Necton) at 0.5g / L in TSB medium; - A combination of the four compounds according to the invention at 2.5 g / L in TSB medium, the combination comprising 3.3% citric acid, 22% pectin, 54.8% marine calcium, and 20% microalgae extract, by weight relative to the total weight of the combination

[0070] . The ability of the compounds to promote biofilm production was thus tested individually and in combination. Culture in the absence of compounds was chosen as the baseline level for biofilm production (under our culture conditions).

[0071] Biofilm production

[0072] The results are presented in [Fig.1].

[0073] In the absence of the compound (Control), biofilm production reaches 22.3 ± 3.8 mg. In the presence of the compounds alone, there is no significant difference compared to the control. In the presence of the object of the invention, there is an 80% increase in the amount of biofilm. These data demonstrate that each compound alone has no measurable effect on the biofilm, but that the combination of the four results in a significant increase in biofilm production.

[0074] Biofilm maturity

[0075] The object of this invention is to promote both biofilm production and biofilm maturity, with the aim of producing more and more mature biofilm.

[0076] Culture in the absence of compounds was chosen as the baseline level of biofilm production (under our culture conditions). Treatment with the combination of products was tested.

[0077] The results are presented in Figures 2 and 3.

[0078] Under normal growth conditions, the film formed on the surface of the culture It opacifies the medium but does not form wrinkles. This results in a surface that appears homogeneous. In the presence of the combination of compounds according to the invention, a 60% increase in texture nuance is observed. These results reflect an increased capacity of a biofilm to mature by forming wrinkles.

[0079] The results showed that the addition of the composition according to the invention stimulates the formation of bacterial biofilm. The morphology of the biofilm is also modified by the addition of said composition and is reflected in the presence of wrinkles on the surface of the biofilm. These wrinkles increase the surface area to volume ratio and allow for better oxygen regulation by the bacteria.

Claims

Demands

1. Composition for culture media and / or culture solutions and / or plants comprising the combination of: - a carboxylic acid in a content of between 1% and 5% by weight relative to the total weight of the combination, - a polysaccharide in a content of between 15% and 27% by weight relative to the total weight of the combination, - calcium in a content of between 43% and 69% by weight relative to the total weight of the combination, and - a microalga, advantageously in extract form, in a content of between 15% and 25% by weight relative to the total weight of the combination.

2. Composition according to claim 1, characterized in that the carboxylic acid is citric acid.

3. Composition according to any one of claims 1 or 2, characterized in that the polysaccharide is a pectin, advantageously having a degree of methylation between 5% and 80%.

4. Composition according to any one of claims 1 to 3, characterized in that the calcium is marine calcium.

5. Composition according to any one of claims 1 to 4, characterized in that the microalga is a eukaryotic microalga, advantageously selected from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Nannochloropsis sp, Skeletonema sp, Phaeo-dactylum sp, Dunaliella sp, Haematococcus pluvialis, Isochrysis sp and mixtures thereof, more advantageously selected from the group consisting of Chlorella vulgaris, Chlorella sorokiniana, Isochrysis sp and mixtures thereof.

6. A composition according to any one of claims 1 to 5, characterized in that it further comprises a phytosanitarily acceptable excipient

7. Composition according to any one of claims 1 to 6, characterized in that it is in solid form, in particular in the form of powder, granules or microgranules, in liquid form or in gel form.

8. A composition according to any one of claims 1 to 7, characterized in that it is a fertilizer, in particular a fertilizer or soil amendment, the fertilizer advantageously being a solid fertilizer simple, binary or ternary of organo-mineral or organic fertilizer type, or a water-soluble fertilizer and the amendment being advantageously an organo-mineral or organic amendment.

9. Use of the composition according to any one of claims 1 to 8, to promote the formation of bacterial biofilms and / or their maturation at the level of the culture medium, the rhizosphere and / or the roots of a plant.

10. Use according to claim 9 to enhance plant growth and / or enhance nutrient availability and / or enhance plant stress tolerance and / or protect growing media from desiccation and / or enhance the formation and / or stability of growing media aggregates, and / or stabilize the growing media microorganism development environment and / or increase the abundance and microbial activity of growing media.

11. Use according to any one of claims 9 or 10 by root application, open field or soilless.

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