METHOD OF INJECTING CO2 AND ELIMINATING O2 IN A PLATE REACTOR

Abstract

The present invention relates to a method for culturing microorganisms in a biological reactor whose culture medium comprises carbon dioxide (CO2) as a carbon source. The supply of CO2 to the biological reactor is regulated by means of a membrane contactor.

Description

Title of the invention: METHOD FOR INJECTING CO2 AND ELIMINATING O2 IN A PLATE REACTOR FIELD OF THE INVENTION

[0001] The present invention relates to a method for culturing microorganisms in a biological reactor whose culture medium comprises carbon dioxide (CO2) as a carbon source. The supply of CO2 to the biological reactor is regulated by means of a membrane contactor. BACKGROUND OF THE INVENTION

[0002] Methods for culturing microorganisms are well known to those skilled in the art. Cultivation can be carried out on a laboratory scale in Petri dishes or on an industrial scale in biological reactors. Cultivating microorganisms requires reproducing the conditions of the original environment for optimal growth. Thus, the presence of organic substrates is essential. Other parameters must also be reproduced, such as brightness, temperature, pressure, humidity, pH, or gas concentrations.

[0003] Many microorganisms use carbon dioxide as a carbon source. In particular, autotrophic cultures do not include any other carbon source than the CO2 contained in the air. CO2 is transformed into oxygen (O2) and eliminated into the atmosphere. However, it has been shown that too high a concentration of CO2 leads to acidification of the culture medium and a decrease in pH. At the same time, too high a quantity of O2 in the culture medium leads to a decrease in the growth of microorganisms, and promotes the development of bacteria. Regulation of the concentration of CO2 and O2 in the culture media of microorganisms is therefore essential for the proper development of the latter.

[0004] In order to regulate the CO2 and O2 flows, many devices exist such as membrane bubblers or bubble columns, ceramic bubblers, or even bubble diffuser stones, etc. Although these methods have a good transfer rate, material losses are observed. On the other hand, these devices often lead to coalescence phenomena on the walls of the bioreactor, the blades and the bubblers, leading in particular to the obstruction of the latter and the disruption of the strains. Finally, the supply of light is also altered. There is therefore a need to develop a culture process for microorganisms in which the CO2 and O2 flows are optimally regulated and in which the problems linked to the use of existing devices are minimal, or even harmed.

[0005] In view of the environmental issues linked to the production of CO2 released into the atmosphere, in particular linked to the production of gases rich in CO2, such as industrial gaseous effluents, it has been envisaged to use these gases to feed biological reactors for the growth of microorganisms capable of growing with CO2 as the sole source of carbon. This decontamination of gases, also called decarbonization, is notably described in patent applications WO2018 / 060197, WO 2019 / 101899 or WO2021165621. If these processes have shown good efficiency in consuming the CO2 provided by the gases to be decarbonized, they still need to be improved so as to prevent part of the unconsumed CO2 from being released into the atmosphere.

[0006] The inventors have thus developed a method for culturing microorganisms comprising CO2 as a carbon source and comprising a step of culturing said microorganism in a biological reactor making it possible to improve the CO2 supply, in particular for the decarbonization of industrial gases. BRIEF DESCRIPTION OF THE INVENTION

[0007] The present invention relates to a method for culturing microorganisms comprising CO2 as a carbon source and comprising a step of culturing said microorganism in a biological reactor comprising CO2 supply means and characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and O2 flows in the culture medium, the CO2 flow being directed towards the culture medium, and the O2 flow being directed towards the outside of the culture medium.

[0008] In the context of the present invention, the microorganisms are essentially bacteria, yeasts and protists.

[0009] The cultivation method advantageously comprises the steps: a. Cultivation of the microorganisms, and b. Recovery of the biomass produced by said microorganisms.

[0010] The invention also relates to the use of a membrane contactor for regulating the flows of CO2 and O2 in a method of culturing microorganisms in which CO2 is a source of carbon in the culture medium.

[0011] The cultivation method according to the invention is particularly suitable for the decarbonation of a gas rich in CO2.

[0012] The invention also relates to a method for decarbonizing a CO2-rich gas which comprises injecting said gas into a biological reactor, said biological reactor comprising a culture medium and microorganisms capable of growing in said culture medium with CO2 as the sole carbon source and CO2 supply means, characterized in that the CO2 supply means include a membrane contactor for regulating the CO2 and O2 flows in the culture medium, the CO2 flow being directed towards the culture medium, and the O2 flow being directed out of the culture medium.

[0013] Finally, the invention relates to a microalgae fermentation device comprising a fermentation reactor, CO2 supply means, and where appropriate lighting means, characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and O2 flows in which the CO2 flow is directed towards the culture medium and the O2 flow is directed towards the outside of the culture medium. Brief description of the drawings

[0014] [Fig.l]: Method of culturing microorganisms in the presence of a membrane contactor.

[0015] [Fig.2]: Membrane contactor according to the invention and a sectional view of a membrane of the membrane contactor.

[0016] [Fig.3A] and [Fig.3B]: Representations of the phenomena occurring at the level of the membrane of the membrane contactor according to the invention, in particular diffusion phenomena ([Fig.3A]) and flows of carbon dioxide (CO2), dioxygen (O2) and the culture medium ([Fig.3B]).

[0017] [Fig.4]: Velocity of the medium in the membrane contactor as a function of the biomass productivity determined at 0.2 kg / m3 / J.

[0018] [Fig.5]: Velocity of the medium in the membrane contactor as a function of the biomass productivity determined at 0.79 kg / m3 / J.

[0019] [Fig.6]: Variation of the CO2 pressure in the membrane of the membrane contactor as a function of the quantity of CO2 in the culture medium.

[0020] [Fig.7]: Quantity of CO2 to be injected into the culture medium as a function of the temperature of the medium and the pressure in the membrane of the membrane contactor. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a method for culturing microorganisms in a culture medium comprising carbon dioxide (CO2) as a carbon source and comprising a step of culturing the microorganism in a biological reactor comprising CO2 supply means, characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and oxygen (O2) flows in the culture medium and in which the CO2 flow is directed towards the culture medium and the O2 flow is directed towards the outside of the culture medium.

[0022] The methods for culturing microorganisms are well known to those skilled in the art, whether in heterotrophic, autotrophic or mixotrophic mode.

[0023] The cultivation of microorganisms involves numerous parameters such as the nature and composition of the culture medium itself but also external factors which must be controlled and regulated throughout the process such as brightness, temperature, pressure, humidity level, pH, gas concentrations in the reactor, etc.

[0024] Culture media, essential for the development of microorganisms, are well known to those skilled in the art, who will be able to determine and adapt the quantity and nature of the substrates for their culture, such as for example sources of carbon, nitrogen, oxygen, phosphorus, etc.; minerals, such as calcium, iron, magnesium, potassium, sodium, sulfur, etc.; trace elements (boron, zinc, copper, cobalt, etc.); depending on the microorganism(s) cultivated, the size of the reactor, the quantity of biomass desired, etc.

[0025] The invention is particularly suitable for culture processes in a biological reactor. In the context of the present invention, the term "biological reactor" means a reactor within which biological phenomena develop, such as growth of pure cultures or microorganisms or of a consortium of microorganisms, in very varied fields such as the treatment of effluents or the production of biomass containing molecules of interest.

[0026] Biological reactors are well known to those skilled in the art, and generally consist of a closed tank in which a stirring or agitation element is mounted intended to promote homogenization of the contents of the tank. The stirring or agitation of the contents of the tank can also be carried out via a liquid pump which induces a circulation flow of the culture medium inside the tank.

[0027] Biological reactors may also comprise illumination means, the supply of light of which may be continuous or cyclical (WO2019 / 034792, WO2021 / 160776). It is understood within the framework of the present invention that a person skilled in the art will be able to adapt the stirring speed and the quantity of light to obtain optimal culture conditions.

[0028] Biological reactors also generally include an air inlet and outlet allowing gas exchange between the exterior and interior of the reactor.

[0029] The air inlet can thus be coupled with a device, such as a pump, in order to inject a gas into the culture medium. The injected gas is chosen from the gases necessary for the development of the microorganisms in culture in said biological reactor. These include carbon dioxide (CO2), carbon monoxide (CO), oxygen (O2), or nitrogen (N2), or a mixture thereof. In a preferred embodiment, the gas injected into the culture medium is carbon dioxide.

[0030] The carbon dioxide injected into the reactor is supplied via an ambient air flow or via an external source such as industrial gases, fermentation processes or gas cylinders.

[0031] CO2 is thus dissolved in the culture medium and consumed by the microorganisms while O2 is produced. The latter is eliminated at the air outlet of the biological reactor.

[0032] It should be noted that the reactors may be equipped with other devices or apparatus used for the control and regulation of the reactor and the growth of the microorganisms. In particular, mention may be made of the use of probes or sensors for the measurement of the various culture parameters such as, for example: temperature, pH, pressure at the inlet and outlet of the reactor, etc.

[0033] According to the invention, in order to regulate the gas flows, and in particular the CO2 flow inside the biological reactor, one or more contactors are used.

[0034] With reference to [Fig. 1], the membrane contactor (2) is coupled to the biological reactor (1). In one embodiment, the membrane contactor is placed outside the biological reactor. In another embodiment, the membrane contactor is placed inside the biological reactor. Advantageously, the membrane contactor is placed inside the tank of the biological reactor. If necessary, the membrane contactor can be placed in a housing, the latter being able to be inside or outside the biological reactor. The circulation flow of the culture medium within the membrane contactor is ensured by the movement of the blades inside the biological reactor or by a pump. In one embodiment, the circulation flow of the culture medium is due to the stirring movement of the blades of the biological reactor.In another embodiment, the circulation flow of the culture medium in the membrane contactor is obtained thanks to the presence of a pump. The latter is preferably a liquid pump. In parallel, the circulation of the gas molecules in the membrane contactor is carried out thanks to a second pump, preferably a vacuum pump.

[0035] In one embodiment, the CO2 flow and the culture medium flow are parallel. In another embodiment, the CO2 flow and the culture medium flow are perpendicular. In another embodiment, the CO2 flow and the culture medium flow are crossed. Preferably, the flows are crossed, that is to say that the CO2 molecules circulate in a direction opposite to the culture medium flow.

[0036] Membrane contactors allow an efficient and homogeneous supply of CO2 to all microorganisms in culture processes thanks to the phenomenon of diffusion through the membranes. The latter create a physical separation between the gas phase and the culture medium, allowing only certain molecules to pass through the membrane. Thus, in the context of the present application, the membrane of the membrane contactor is a semi-permeable membrane.

[0037] Membrane contactors are thus characterized by the membranes which compose them, more particularly by the geometric configuration and the structure of the membrane.

[0038] The membranes, and more generally the membrane contactors, may be of a flat, spiral, tubular or hollow fiber geometric configuration. In the context of the present application, the membrane contactor is preferably a hollow fiber membrane. The membranes are thus made up of several fibers dispersed in bundles of tubes. The external diameter of the membranes is greater than 50 qm, preferably greater than 60 qm, even more preferably greater than 70 qm. In another embodiment, the hollow fiber membranes have an external diameter of at least 100 qm. In another embodiment, the external diameter of the membranes is less than 2 mm, preferably less than 1.5 mm, more preferably less than 1 mm. Advantageously, the external diameter of the hollow fiber membranes is between 100 qm and 1 mm.The internal diameter of the membranes according to the invention is preferably less than 900 qm, or even less than 850 qm. In a preferred embodiment, the external diameter of the hollow fiber membranes is between 100 and 800 qm.

[0039] As for the internal diameter of the hollow fiber membranes, this is, in the context of the invention, generally less than 1 mm, preferably less than 900 qm, less than 800 qm, less than 700 qm, less than 600 qm, less than 500 qm, less than 400 qm, less than 300 qm, less than 200 qm, or even less than 100 qm. In one embodiment, the internal diameter of the hollow fiber membranes according to the invention is between 1 and 100 qm. In another embodiment, the internal diameter is between 5 and 100 qm, preferably between 7 and 100 qm, even more preferably between 10 and 100 qm. Advantageously, the internal diameter of the hollow fiber membranes according to the invention is between 20 and 90 qm.

[0040] From a structural point of view, the membranes in the context of the invention are advantageously membranes with a homogeneous structure over the entire surface. Among these, a distinction is made between porous membranes and non-porous or dense membranes. In the context of the present application, the hollow fiber membranes are microporous membranes or non-porous membranes.

[0041] In one embodiment, the membrane of the membrane contactor is a porous membrane, and comprises pores whose diameter is less than 10 qm. Advantageously, the porous membrane is microporous, and has pores with a diameter less than 8 qm, preferably less than 5 qm, or even less than 3 pm, more preferably less than 2 pm. In another embodiment, the microporous membrane comprises pores whose diameter is greater than 0.001 pm, 0.002 pm, 0.003 pm, 0.004 pm, or even greater than 0.005 pm. Advantageously, the diameter of the pores of the membrane is thus between 0.005 and 2 pm. In one embodiment, the diameter of the pores is less than 1 pm, or even less than 0.5 pm and preferably less than 0.2 pm or even less than 0.1 pm. In another embodiment, the diameter of the pores of the membrane is between 0.005 and 0.1 pm. Yet, in another embodiment, the pore diameter is between 0.008 and 0.09 μm, preferably between 0.009 and 0.07 μm, or even preferably between 0.01 and 0.06 μm, and more preferably between 0.01 and 0.05 μm. Advantageously, the pore diameter of the membrane is approximately 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm or 0.05 μm.

[0042] In another embodiment, the membrane of the membrane contactor is a dense or non-porous membrane. The diffusion of the molecules is then characterized by a diffusion phenomenon through the membrane via the adsorption of molecules having a strong affinity with the membrane.

[0043] An example of a membrane contactor according to the invention is shown in [Fig.2].

[0044] The materials used for the production of the membranes are generally polymers, such as polyethylene (PE), polypropylene (PP), polysulfone (PSu), polyether sulfone (PES), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), polycarbonate (PC), polyacrylonitrile (PAN), and cellulose acetate (CA). Membranes can also be made from silicone or silicone derivatives. In the context of the present application, the term silicone includes inorganic compounds formed from a chain of silicon and oxygen atoms and whose silicon atoms may carry groups. Mention will be made in particular of polymers belonging to the siloxane family, and more particularly polydimethylsiloxane (PDMS) or compositions comprising polydimethylsiloxane (PDMS), in particular a ternary system composed of PDMS, water and tetrahydrofuran (THF). Advantageously, the membranes of the present application are made from silicone.

[0045] Such membrane contactors and their operating principles are known to those skilled in the art. They are commercially available, in particular under the references pervélys and 3M™ liqui-Cel.

[0046] The membrane contactor, and more precisely the membrane of the membrane contactor, creates a physical separation between the gas phase and the culture medium.

[0047] With reference to Figure 3, the transfer of material takes place according to a pressure or concentration gradient across the membrane of the membrane contactor.

[0048] In one embodiment, the pressure gradient or concentration of gas molecules results from an overpressure of the CO2 concentration. A person skilled in the art will be able to determine the CO2 flow rate at the inlet of the membrane contactor to be applied in order to create this overpressure, in particular as a function of the biological reactor and the quantity of biomass desired, without this affecting the culture of the microorganisms.

[0049] In another embodiment, the CO2 is injected at a regular flow rate depending on the CO2 consumption necessary for the growth of the microorganisms. The CO2 consumed is thus transformed into O2 molecules which diffuse through the membrane and lead to an increase in pressure in the gas phase. A threshold value of the O2 concentration can optionally be determined by the operator in order to program the release of the O2 molecules to the outside of the membrane contactor and / or the biological reactor via the air outlet.

[0050] In another embodiment, the concentration gradient results from a deficit of O2 molecules in the gas phase. The absence or low concentration of O2 molecules can be implemented in particular using a pump, preferably a vacuum pump, which removes the O2 molecules from the membrane contactor and / or the biological reactor.

[0051] Within the framework of the present application, it is understood that the membrane contactor and / or the biological reactor may / may comprise other devices and apparatus ensuring the safety of the culture of the microorganisms and of the operators.

[0052] The CO2 concentration is thus regulated by at least one of the preceding devices, i.e. via a pressure or concentration gradient resulting from an overpressure of CO2 or O2 in the membrane contactor, or even from a low concentration of O2 in the membrane contactor.

[0053] In one embodiment, the concentration of dissolved CO2 in the culture medium is thus between 0 and 3500 mg / L. In another embodiment, the concentration of dissolved CO2 is at least 100 mg / L, or even at least 200 mg / L, preferably at least 400 mg / L, more preferably at least 600 mg / L. In another embodiment, the concentration of dissolved CO2 in the culture medium is less than 3400 mg / L, or even less than 3200 mg / L, preferably less than 3000 mg / L. In another embodiment, the concentration of dissolved CO2 in the culture medium is between 600 and 3000 mg / L, preferably between 600 and 2500 mg / L, more preferably between 600 and 2000 mg / L. Advantageously, the concentration of CO2 dissolved in the medium of culture is between 600 and 1500 mg / L, or even between 800 and 1500 mg / L. In a preferred embodiment, the dissolved CO2 concentration is at least 1000 mg / L, or even at least 1200 mg / L.

[0054] In parallel, the amount of O2 dissolved in the culture medium is maintained at a concentration of less than 35 g / m3. In one embodiment, the concentration of O2 dissolved in the culture medium is less than 34 g / m3, or even 33 g / m3, preferably less than 32 g / m3, even more preferably less than 31 g / m3. In another embodiment, the amount of O2 dissolved in the culture medium is at least 8 g / m3. In a preferred embodiment, the concentration of O2 dissolved in the culture medium is between 8 and 30 g / m3.

[0055] Advantageously, the CO2 concentration in the culture medium is regulated so as to provide the necessary and sufficient quantity for the culture of the microorganisms, so that all of the CO2 is consumed without loss into the atmosphere. In particular, the only gas exchanges between the reactor and the external environment are carried out via the membrane contactor.

[0056] According to a particular embodiment of the invention, the injected CO2 comes from a CO2-rich gas which is to be treated so as to eliminate the CO2, without releasing it into the atmosphere. In particular, the CO2 is an industrial gaseous effluent rich in CO2. In particular, the industrial gaseous effluent rich in CO2 has been pretreated so as to eliminate microparticles and / or toxic components likely to affect the culture of the microorganisms.

[0057] Figures 2 and 3 represent a membrane contactor as well as the CO2 and O2 flows which exist at the level of the membrane.

[0058] With reference to [Fig.2], the membrane contactor (2) comprises the culture medium (13) which moves in the membrane contactor. At the inlet (4), the culture medium is low in CO2 and high in O2. During its propagation in the membrane contactor, it becomes enriched in CO2 and its O2 concentration decreases according to the exchange phenomenon which occurs at the membrane (14). Thus, at the outlet of the membrane contactor (3), the culture medium is rich in CO2 and low in O2. In parallel, a flow of CO2 is applied to the membrane contactor. The latter is therefore characterized by the presence of a gas inlet (6) and outlet (7) on either side of the membrane contactor.

[0059] With reference to Figures 2 and 3, at the level of the membrane (14), exchange phenomena between the CO2 and O2 molecules occur. While the CO2 diffuses from the inside to the outside of the membranes, the O2 molecules cross the membrane from the culture medium and are eliminated at the same time as the excess CO2 molecules.

[0060] Microorganisms and cultured microorganisms are well known to those skilled in the art. These include bacteria, yeasts, or even protists, and more particularly algae and microalgae. According to a preferred embodiment, the cultured microorganisms are protists.

[0061] By protist is meant all eukaryotic unicellular microorganisms. Microalgae (Chlorophytes such as Chlorella, Senedesmus, Tetraselmis, Haematococcus; Charophytes, chrysophytes including diatoms; Nannochloropsis; Euglenophytes such as Euglena, Phacus; Rodophytes including Galdieria, etc.), unicellular fungi (Thrautochytrids such as Schizochytrium, Aurantiochytrium, etc.), cyanobacteria (Anabaena, Nostoc, Microcistis, Arthrospira, Spirulina, etc.) or heterotrophic flagellates (Crypthecodinium etc.) are part of the protist group.

[0062] In one embodiment, the microorganisms according to the invention are algae and microalgae preferably belonging to the classes of Chlorophytes, Rodophytes, Thraustochytrids and Diatoms.

[0063] Lorsque les microalgues sont du genre Chlorella, elles poignant être choisies parmi les species C. acuminata, C. angustoellipsoidea, C. anitrata, C. antarctica, C. aureoviridis, C. autotrophica, C. botryoides, C. caldaria, C. candida, C. capsulata, C. chlorelloides, C. cladoniae, C. coelastroides, C. colonialis, C. commuais, C. conductrix, C. conglomerata, C. desiccata, C. ellipsoidea, C. elongata, C. emersonii, C. faginea, C. fusca, C. glucotropha, C. homosphaera, C. infusionum, C. kessleri, C. koettlitzii, C. lacustris, C. lewinii, C. lichina, C. lobophora, C. luteo-viridis, C. marina, C. miniata, C. minor, C. minutissima, C. mirabilis, C. mucosa, C. mutabilis, C. noctuma, C. nordstedtii, C. oblonga, C. oocystoides, C. ovalis, C. paramecii, C. parasitica, C. parva, C. peruviana, C. photophila, C. pituita, C. pringsheimii, C. protothecoides, C. pulchelloides, C. pyrenoidosa, C. regularis, C. reisiglii, C. reniformis, C. rotunda, C. rubescens, C. rugosa, C. saccharophila, C.salina, C. simplex, C. singularis, C. sorokiniana, C. spaerckii, C. sphaerica, C. stigmatophora, C. subsphaerica, C. terricola, C. trebouxioides, C. vannielii, C. variabilis, C. viscosa, C. volutis, C. vulgaris, C. zopfingiensis. Advantageously according to the invention the algae of the genus Chlorella may be selected algae among the species C. sorokiniana or C. vulgaris. .

[0064] When the microalgae are of the genus Euglena, they may be selected from among others the species E. viridis, E. gracilis, E. limosa, E. globosa, E. prowsei, E. polomorpha.

[0065] When microalgae are of the genus Scenedesmus, they may be selected from the species S. abundans, S. aciculatus, S. aculeolatus, S. aculeotatus, S. acuminatus, S. acutiformis, S. acutus, S. aldavei, S. alternos, S. ambunoehli, S. ambunoehli. anhuiensis, S. anomalus, S. antennatus, S. antillarum, S. apicaudatus, S. apiculatus, S. arcuatus, S. aristatus, S. armatus, S. arthrodesmiformis, S. arvemensis, S. asymmetricus, S. bacillaris, S. baculiformis, S. bajacalifomicus, S. balatonicus, S. basiliensis, S. bemardii, S. bicaudatus, S. bicellularis, S. bidentatus, S. bijuga, S. bijugatus, S. bijugus, S. brasiliensis, S. breviaculeatus, S. brevispina, S. caribeanus, S. carinatus, S. caudato-aculeolatus, S. caudatus, S. chlorelloides, S. circumfusus, S. coalitus, S. costatogranulatus, S. crassidentatus, S. curvatus, S. decorus, S. denticulatus, S. deserticola, S. diagonalis, S. dileticus, S. dimorphus, S. disciformis, S. dispar, S. distentus, S. ecomis, S. ellipsoideus, S. ellipticus, S. falcatus, S. fenestratus, S. flavescens, S. flexuosus, S. furcosus, S. fuscus, S. fusiformis, S. gracilis, S. graevenitzii, S. grahneisii, S. granulatus, S. gujaratensis, S. gutwinskii, S. hanleyi, S. helveticus, S. heteracanthus, S. hindakii, S.hirsutus, S. hortobagyi, S. houlensis, S. huangshanensis, S. hystrix, S. incrassatulus, S. indianensis, S. indiens, S. inermis, S. insignis, S. intermedius, S. javanensis, S. jovais, S. jugalis, S. kerguelensis, S. kissii, S. komarekii, S. lefevrei, S. linearis, S. littoralis, S. longispina, S. longus, S. luna, S. lunatus, S. magnus, S. maximus, S. microspina, S. minutus, S. mirus, S. morzinensis, S. multicauda, S. multiformis, S. multispina, S. multistriatus, S. naegelii, S. nanus, S. notatus, S. nygaardii, S. oahuensis, S. obliquus, S. obtusiusculus, S. obtusus, S. olvaltemus, S. oocystiformis, S. opoliensis, S. omatus, S. ovaltemus, S. pannonicus, S. papillosum, S. parisiensis, S. parvus, S. pecsensis, S. pectinatus, S. perforatus, S. planctonicus, S. plarydiscus, S. platydiscus, S. pleiomorphus, S. polessicus, S. poly denticulatus, S. polyglobulus, S. polyspinosus, S. praetervisus, S. prismaticus, S. producto-capitatus, S. protuberans, S. pseudoarmatus, S. pseudobemardii, S.pseudodenticulatus, S. pseudogranulatus, S. pseudohystrix, S. pyrus, S. quadrialatus, S. quadricauda, S. quadricaudata, S. quadricaudus, S. quadrispina, S. raciborskii, S. ralfsii, S. reginae, S. regularis, S. reniformis, S. rostrato-spinosus, S. rotundus, S. rubescens, S. scenedesmoides, S. schnepfii, S. schroeteri, S. securiformis, S. semicristatus, S. semipulcher, S. sempervirens, S. senilis, S. serrato-perforatus, S. serratus, S. serrulatus, S. setiferus, S. sihensis, S. smithii, S. soli, S. sooi, S. spicatus, S. spinoso-aculeolatus, S. spinosus, S. spinulatus, S. striatus., S. subspicatus, S. tenuispina, S. terrestris, S. tetradesmiformis, S. transilvanicus, S. tricostatus, S. tropicus, S. tschudyi, S. vacuolatus, S. variabilis, S. velitaris, S. verrucosus, S. vesiculosus, S. westii, S. weberi, S. wisconsinensis, S. wuhanensis, S. wuhuensis. . Advantageously, according to the invention, the algae of the genus Scenedesmus may be algae chosen from the species S. obliquus or S. abundans.

[0066] When the microalgae are diatoms, they may be chosen from the following genera: Nitzschia, Navicula, Gyrosigma, Phaeodactylum, Thalassiosira, etc.

[0067] Like the microalgues sont du genre Nitzschia, elles pourront être choisies parmi les spèces N. abbreviata, N. aboaueasis, N. abridia, N. accessas, N. accommodata, N. aciculariformis, N. acicularioides, N. acicularis (comprenant all ces variétés), N. acidoclinata, N. actiaastroides, N. actydrophila, N. acula, N. acumiaata (comprenant all ces variétés), N. acuta, N. adamata, N. adamatoides, N. adapta, N. adducta, N. adductoides, N. admissa, N. admissoides, N. aequalis, N. aequatorialis, N. aequora, N. aequorea, N. aerophila, N. aerophiloides, N. aestuari, N. affinis, N. Africana, N. agaewii, N. agnita, N. alba, N. albicostalis, N. alexaadriaa, N. alicae, N. allaassoaii, N. alpiaa, N. alpiaobacillum, N. amabilis, N. ambigua, N. Americana, N. amisaeasis, N. amphibia, N. amphibia (including all varieties), N. amphibioides, N. amphicephala, N. amphilepta, N. amphioxoides, N. amphioxys (including all varieties), N. amphiplectaas, N. amphiprora, N. amplectens, N.amundonii, N. anassae, N. aadicola, N. angularis (including all varieties), N. angulata, N. angustata (including all varieties), N. angustatula, N. angustiforaminata, N. aniae, N. antarctica, N. aatillarum, N. apiceconica, N. apiculata, N. archibaldii, N. arcuata, N. arcula, N. arcus, N. ardua, N. aremoaica, N. arenosa, N. areolata, N. armoricana, N. asperula, N. astridiae, N. atomus, N. attenuata, N. aurantiaca, N. aurariae, N. aurica, N. auricula, N. australis, N. austriaca, N. bacata (comprenant all ces variétés), N. bacillariaeformis, N. bacilliformis, N. bacillum, N. balatoais, N. balcanica, N. baltica, N. barbie ri (comprenant all ces variétés), N. barkleyi, N. barroaii, N. barrowiana, N. bartholomei, N. bathursteasis, N. bavarica, N. behrei, N. bergii, N. beyeri, N. biacrula, N. bicapitata (including all varieties),. bicuneata, N. bifurcata, N. bilobata (comprenant all ces variétés), N. birostrata, N. bisculpta, N. bita, N. bizerteasis, N.blaakaarteasis, N. bombiformis, N. borealis, N. bosumtwieasis, N. braarudii, N. brebissoaii (including all varieties), N. bremensis (including all varieties), N. brevior, N. brevirostris, N. brevissima (including all varieties), N. brevistriata, N. brightwellii, N. brittonii, N. brunoi, N. bryophila, N. buceros, N. bukensis, N. bulnheimiana, N. buschbeckii, N. calcicola, N. caledoaeasis, N. calida (comprenant all ces variétés), N. califomica, N. campechiana, N. capensis, N. capitata, N. capitellata (comprenant all varieties), N. capuluspalae, N. carnicobarica, N. carnico-barica, N. challengeri, N. chalonii, N. chandolensis, N. chardezii, N. chasei, N. chauhanii, N. chungara, N. chutteri, N. circumsuta, N. clarissima, N. clausii, N. clemeatei, N. clemeatia, N. clevei, N. closterium (including all varieties), N. coarctata, N. coccoaeiformis, N. commuais (including all varieties), N. commutata, N. commutatoides, N. compacta, N.compressa (including all these varieties), N. concordia, N. confiais, N. coaformata, N. coafusa, N. coagoleasis, N. costastricta (including all these varieties), N. coasummata, N. corpuleata, N. costei, N. coutei, N. creticola, N. cucumis, N. cursoria, N. curta, N. . curvata, N. curvilineata, N. curvipunctata, N. curvirostris (including all these varieties), N. curvula (including all these varieties), N. cuspidata, N. cylindiformis, N. cylindrus, N. dakariensis, N. davidsonii, N. dealpina, N. debilis, N. decipiens, N. delauneyi, N. delicatissima, N. delicatula, N. delognei, N. denticula (including all these varieties), N. denticuloides, N. desertorum, N. dianae, N. diaphana, N. diducta, N. didyma, N. dietrichii, N. dilatata, N. diluviana, N. dippelii, N. directa, N. diserta, N. disputata, N. dissipata (including all these varieties), N. dissipatoides, N. distans (including all these varieties), N. distantoides, N. divaricata, N. divergens, N. diversa, N. diversostata, N. doljensis, N. draveillensis, N. droebakensis, N. dubia (including all these varieties), N. dubiformis, N. dubioides, N. ebroicensis, N. eglei, N. elegans, N. elegantula, N. elegens, N. elliptica, N. elongata, N. entomon, N. epiphytica, N. epiphyticoides, N. epithemiformis, N. epithemioides, N. epithemoides (including all these varieties), N. epsilon, N. erlandssonii, N. erosa, N. etoshensis, N. examinanda, N. eximia, N. famelica, N. fasciculata, N. febigeri, N. ferox, N. ferrazae, N. fibula-fissa, N. filiformis (including all these varieties), N. flexa, N. flexoides, N. fluminensis, N. fluorescens, N. fluvialis, N. fogedii, N. fonticola (including all these varieties), N. fonticoloides, N. fontifica, N. fontifica, N. fontifuga, N. N. formosa, N. fossalis, N. fossilis, N. fragilariiformis, N. franconica, N. fraudulenta, N. frauenfeldii, N. frequens, N. frickei, N. frigida (including all these varieties), N. frustuloides, N. frustulum (including all varieties), N. fruticos, N. fruticos N. fusiformis, N. gaarderi, N. gaertnerae, N. gandersheimiensis, N. garrensis, N. gazellae, N. geitleri, N. geitlerii, N. gelida (comprenant toutes ces variétés), N. geniculata, N. gessneri, N. gieskesii, N. gigantea, N. glasela, N. glaciala, N. glaciala. (including all these varieties), N. glandiformis, N. goetzeana (including all these varieties), N. gotlandica, N. graciliformis, N. gracilis (including all these varieties), N. gracillima, N. graciloides, N.gradifera, N. graeffii, N. grana, N. grandis, N. granii (including all these varieties), N. granulata (including all these varieties), N. granulosa, N. groenlandica, N. grossestriata, N. grovei, N. gruendleri, N. grunowii, N. guadalupensis, N. guineensis, N. guttula, N. gyrosigma, N. habirshawii, N. habishawii, N. hadriatica, N. halteriformis, N. hamburgiensis, N. hantzschiana (including all these varieties), N. harderi, N. harrissonii, N. hassiaca, N. heidenii, N. heimii, N. hemistriata, N. heteropolica, N. heuflerania, N. heufleriana (including all these varieties), N. hiemalis, N. hiengheneana, N. hierosolymitana, N. hoehnkii, N. holastica, N. hollerupensis, N. holsatica, N. hamburgiensis, N. hudsonii, N. hummii, N. hungarica (including all these varieties), N. hustedti, N. hustedtiana, N. hyalina, N. hybrida (including all these varieties), N. hybridaeformis, N. ignorata (including all these varieties), N. iltisii, N. impressa, N. improvisa, N. incerta, N. incognito, N.inconspicua, N. incrustans, N. incurva (including all these varieties), N. indica, . N. indistincta, N. inducta, N. inflatula, N. ingenua, N. inimasta, N. innominata, N. insecta, N. insignis (comprising all these varieties), N. intermedia (comprising all these varieties), N. intermissa, N. interrupta, N. interruptestriata, N. invicta (comprising all these varieties). varieties), N. invisa, N. invisitata, N. iranica, N. irregularis, N. irremissa, N. irrepta, N. irresoluta, N. irritans, N. italica, N. janischii, N. jelineckii, N. johnmartinii, N. juba, N. jucunda, N. jugata (including all these varieties), N. jugiformis, N. kahlii, N. kanakarum, N. kanayae, N. kavirondoensis, N. kerguelensis, N. kimberliensis, N. kittlii, N. kittonii, N. knysnensis, N. kolaczeckii, N. kotschyi, N. kowiensis, N. krachiensis, N. krenicola, N. kuetzingiana (comprenant). all these varieties), N. kuetzingii, N. kuetzingioides, N. kurzeana, N. kurzii, N. kützingiana (including all these varieties), N. labella, N. labuensis, N. lacrima, N. lacunarum, N. lacunicola, N. lacus-karluki, N. lacustris, N. lacustris.lacuum, N. laevis, N. laevissima, N. lagunae, N. lagunensis, N. lamprocampa (including all these varieties), N. lanceola (including all these varieties), N. lanceolata (including all these varieties), N. lancettula, N. lancetula, N. lancetulae, N. lancetal, N. langu. latens, N. latestriata, N. latiuscula, N. lauenbergiana, N. lauenburgiana, N. lecointei, N. leehyi, N. legleri, N. lehyi, N. leistikowii, N. lesbia, N. lesinensis, N. lesothensis, N. leucosigma, N. levinensis variants ( N. leucosigma), N. leucosigma ( liebetruthii (including all these varieties), N. ligowskii, N. limicola, N. limulus, N. linearis (including all these varieties), N. lineata, N. lineola, N. linkei, N. lionella, N. littoralis (including all these varieties), N. littore, N. longa, N. longa, N. longirostris, N. longissima (including all these varieties), N. lorenziana (including all these varieties), N. lucisensibilis, N. lunaris, N. lunata, N. lurida, N. luzonensis, N. macaronesica, N. macedonica, N.macéra, N. machardyae, N. macilenta (including all these varieties), N. magnacarina, N. mahihaensis, N. mahoodii, N. maillardii, N. major, N. majuscula (including all these varieties), N. makarovae, N. manca, N. mancoides, N. manguini, N. marginata, N. marginulata (including all these varieties), N. marina, N. martiana, N. maxima, N. media, N. medioconstricta, N. mediocris, N. mediterranea, N. metzeltinii, N. microcephala (including all these varieties), N. migrons, N. minuta, N. minutissima, N. minutula, N. miramarensis, N. miserabilis, N. mitchelliana, N. modesta, N. moissacensis (including all these varieties), N. mollis, N. monachorum, N. monoensis, N. montanestris, N. morosa, N. multistriata, N. nana, N. natalensis, N. natans, N. nathorsti, N. navicularis, N. navis-varingica, N. navrongensis, N. neglecta, N. nelsonii, N. neocaledonica, N. neoconstricta, N. neofrigida, N. neogena, N. neotropica, N. nereidis, N. nicobarica, N. nienhuisii, N. normannii, N. notabilis, N. nova, N.novae-guineaensis, N. novae-guineensis, N. novaehollandiae, N. nova-zealandia, N. nyassensis, N. oberheimiana, N. obesa, N. obliquecostata, N. obscura, N. obscurepunctata, N. obsidialis, N. obsoleta, N. . obsoletiformis, N. obtusa (including all these varieties), N. obtusangula, N. oceanica, N. ocellata, N. oliffi, N. omega, N. osmophila, N. ossiformis, N. ostenfeldii, N. ovalis, N. paaschei, N. pacifica, N. palace, N. palacecom (including all these varieties). these varieties), N. paleacea, N. paleaeformis, N. paleoides, N. palustris, N. pamirensis, N. panduriformis (including all these varieties), N. pantocsekii, N. paradoxa (including all these varieties), N. parallela, N. parallela, N. strarotavula, N. all these varieties), N. parvuloides, N. paxillifer, N. peisonis, N. pelagica, N. pellucida, N. permuta, N. peragallii, N. perindistincta, N. perminuta, N. perpusilla (including all these varieties), N. perspicua, N. persuad, N. persuadica, N. persaadica, N. petitiana, N. philippinarum, N. pilum, N. pinguescens, N. piscinarum, N. plana (including all these varieties), N. planctonica, N. plicatula, N. plioveterana, N. polaris, N. polymorpha, N. ponciensis, N. praecurta, N.praefossilis, N. praereinholdii, N. princeps, N. procera, N. prolongata (including all varieties), N. prolongatoides, N. promare, N. propinqua, N. pseudepiphytica, N. pseudoamphioxoides, N. pseudoamphioxys, N. pseudoamphyoxys, N. pseudoatomus, N. pseudobacata, N. pseudocapitata, N. pseudocarinata, N. pseudocommunis, N. pseudocylindrica, N. pseudodelicatissima, N. pseudofonticola, N. pseudohungarica, N. pseudohybrida, N. pseudonana, N. pseudoseriata, N. pseudosigma, N. pseudosinuata, N. pseudostagnorum, N. pubens, N. pulcherrima, N. pumila, N. punctata (include all varieties), N. pungens (include all varieties), N. pungiformis, N. pura, N. puriformis, N. pusilla (comprehent toutes ces variétés), N. putrida, N. quadrangula, N. quickiana, N. rabenhorstii, N. radicula (including all these varieties), N. rautenbachiae, N. recta (including all these varieties), N. rectiformis, N. rectilonga, N. rectirobusta, N. rectissima, N. régula, N. reimeri, N. reimerii, N.reimersenii, N. retusa, N. reversa, N. rhombica, N. rhombiformis, N. rhopalodioides, N. richterae, N. rigida (including all these varieties), N. ritscheri, N. robusta, N. rochensis, N. rolandii, N. romana, N. romanoides, N. romanowiana, N. rorida, N. rosenstockii, N. rostellata, N. rostrata, N. ruda, N. rugosa, N. rupestris, N. rusingae, N. ruttneri, N. salinarum, N. salinicola, N. salpaespinosae, N. salvadoriana, N. sansimoni, N. sarcophagum, N. scabra, N. scalaris, N. scaligera, N. scalpelliformis, N. schoenfeldii, N. schwabei, N. schweikertii, N. scutellum, N. sellingii, N. semicostata, N. semirobusta, N. separanda, N. seriata (including all these varieties), N. serpenticola, N. serpentiraphe, N. serrata, N. sibula (including all these varieties), N. sigma (including all these varieties), N. sigmaformis, N. sigmatella, N. sigmoidea (including all these varieties), N. silica, N. silicula (including all these varieties), N. siliqua, N. similis, N. simplex, N. simpliciformis, N.sinensis, N. sinuata (including all these varieties), N. smithii, N. sociabilis, N. socialis (including all these varieties), N. solgensis, N. solida, N. solda, N. soratensis, N. sp., N. spathulata. (including all these varieties), N. speciosa, N. spectabilis (including all these varieties), N. sphaerophora, N. spiculoides, N. spiculum, N. spinarum, N. spinifera, N. stagnorum, N. steenbergensis, N. stellata, N. steynii, N. stimulus, N. stoliczkiana, N. stompsii (including all these varieties), N. strelnikovae, N. stricta, N. strigillata, N. striolata, N. subaccommodata, N. subacicularis, N. subacuta, N. subamphioxioides, N. subapiculata, N. subbacata, N. subcapitata, N. subcapitellata, N. subcohaerens (including all these varieties), N. subcommunis, N. subconstricta, N. subcurvata, N. subdenticula, N. subfalcata, N. subfraudulenta, N. subfrequens, N. subfrustulum, N. subgraciloides, N. subinflata, N. subinvicta, N. sublaevis, N. sublanceolata, N. sublica, N. sublinearis, N. sublongirostris, N. submarina, N. submediocris, N. subodiosa, N. subpacifica, N. subpunctata, N. subromana, N. subrostrata, N. subrostratoides, N. subrostroides, N. subsalsa, N. subtilioides, N.subtilis (including all these varieties), N. subtubicola, N. subvitrea, N. suchlandtii, N. sulcata, N. sundaensis, N. supralitorea, N. tabellaria, N. taenia, N. taeniiformis, N. tantata, N. tarda, N. taylorii, N. temperei, N. tenella, N. tenerifa, N. tenuiarcuata, N. tenuirostris, N. tenuis (including all these varieties), N. tenuissima, N. tergestina, N. terrestris, N. terricola, N. thermalis (including all these varieties), N. thermaloides, N. tibetana, N. tirstrupensis, N. tonoensis, N. towutensis, N. translucida, N. tropica, N. tryblionella (including all these varieties), N. tsarenkoi, N. tubicola, N. tumida, N. turgidula, N. turgiduloides, N. umaoiensis, N. umbilicata, N. umbonata, N. vacillata, N. vacua, N. valdecostata, N. valdestriata, N. valens, N. valga, N. valida (including all these varieties), N. vanheurckii, N. vanoyei, N. vasta, N. ventricosa, N. vermicularioides, N. vermicularis (including all these varieties), N. vermicularoides, N. vexans, N. victoriae, N.vidovichii, N. vildaryana, N. villarealii, N. virgata, N. visurgis, N. vitrea (including all these varieties), N. vivax (including all these varieties), N. vixnegligenda, N. vonhauseniae, N. vulga, N. weaveri, N. weissflogii, N. westii, N. williamsiii, N. wipplingeri, N. witkowskii, N. wodensis, N. woltereckii, N. woltereckoides, N. wuellerstorfii, N. wunsamiae, N. yunchengensis, N. zebuana, N. zululandica. .

[0068] Advantageously according to the invention, the algae of the genus Nitzschia may be algae selected from the species N. sp.

[0069] When the microalgae are of the genus Haematococcus, they may be chosen from the species: H. buetschlii, H. capensis, H. carocellus, H. droebakensis, H. grevilei, H. insignis, H. lacustris, H. murorum, H. pluvialis, H. salinus, H. sanguineis, H. thermalis, H. zimbabwiensis.

[0070] When the microalgae are of the genus Aurantiochytrium, they can be chosen from the species: A. limacinum, A. mangrovei.

[0071] When the microalgae are of the genus Schizochytrium, they may be chosen from the species: S. aggregatum, S. limacinum, S. mangrovei, S. minutum, S. octosporum.

[0072] When the microalgae are of the genus Crypthecodinium, they may be chosen from the species: C. cohnii, C. setense.

[0073] When the microalgae are of the Tetraselmis genus, they may be chosen from the species: T. alacris, T. apiculata, T. amoldii, T. ascus, T. astigmatica, T. bichlora, T. bilobata, T. bolosiana, T. chui, T. contracta, T. convolutae, T. cordiformis, T. desikacharyi, T. elliptica, T. fontiana, T. gracilis, T. hazenii, T. helgolandica, T. impellucida, T. incisa, T. inconspicua, T. indica, T. levis, T. maculata, T. marina, T. mediterranea, T. micropapillata, T. rubens, T. striata, T. subcordiformis, T. suecica, T. tetrabrachia, T. tetrathele, T. verrucosa, T. viridis, T. wettsteinii.

[0074] According to a particular embodiment of the invention, the protists are chosen from the genera Chlorella, Galdieria, Euglena, cyanobacteria and diatoms.

[0075] The cultivation of microorganisms can be carried out in the absence or presence of a carbon source, and / or in the absence or presence of light. The method according to the invention is thus suitable for the cultivation of microorganisms in heterotrophic, autotrophic or mixotrophic mode. In a preferred embodiment, the microorganisms are microalgae cultivated in an autotrophic or mixotrophic mode. Advantageously, the microorganisms cultivated according to the invention are autotrophic microalgae.

[0076] The method for culturing microorganisms comprises culturing said microorganisms in a biological reactor coupled to the membrane contactor according to the invention, and recovering the biomass produced by the microorganisms. The biomass produced may be used for the preparation of pharmaceutical, cosmetic, nutraceutical or food compositions.

[0077] The invention thus also relates to the use of a membrane contactor for regulating CO2 and O2 flows in a method for culturing microorganisms in which CO2 is a source of carbon in the culture medium. The membrane contactor can be placed inside or outside the biological reactor. It is understood that the membrane contactor can optionally be placed in a housing, the latter being inside or outside the biological reactor. Preferably, the membrane contactor is placed inside the biological reactor. The microorganisms and other culture means are described previously.

[0078] The invention also relates to a method for decarbonizing a CO2-rich gas which comprises injecting said gas into a biological reactor, said biological reactor comprising a culture medium and microorganisms capable of growing in said culture medium with CO2 as the sole source of carbon and means CO2 supply means, characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and O2 flows in the culture medium, the CO2 flow being directed towards the culture medium, and the O2 flow being directed towards the outside of the culture medium.

[0079] Advantageously, the CO2 concentration in the culture medium is regulated so as to provide the necessary and sufficient quantity for the culture of the microorganisms, so that all of the CO2 is consumed without loss into the atmosphere.

[0080] In particular, in the decarbonization process according to the invention the only gas exchanges between the reactor and the external environment are made by the membrane contactor. The reactor is advantageously closed.

[0081] Finally, the invention relates to a device for fermenting microorganisms, said microorganisms being microalgae according to the invention. The fermentation device comprises: a. a fermentation tank or biological reactor, and b. a CO2 supply means, comprising a membrane contactor according to the invention making it possible to regulate the flows of CO2 and O2, the flow of CO2 being directed towards the culture medium and the flow of O2 being directed towards the outside of the culture medium.

[0082] With reference to [Fig. 1], the device comprises a membrane contactor (2) coupled to the biological reactor (1). The flow of the culture medium contained in the biological reactor (3) and (4) is ensured by means of a pump arranged (5) between the biological reactor and the membrane contactor. Measuring probes or sensors (10) and (11) can be added to the device. These include CO2 and O2 measuring probes.

[0083] The membrane contactor is furthermore connected to a CO2 source which induces a flow of CO2 in the membrane contactor (6) and (7). The device according to the invention may also comprise a vacuum pump (8) in order to create a flow of CO2. The device may furthermore comprise a buffer tank (9) allowing the storage of CO2. Preferably the buffer tank is placed between the CO2 supply source and the membrane contactor.

[0084] According to the invention, the membrane contactor comprises a membrane, preferably a hollow fiber membrane. In one embodiment, the hollow fiber membrane is chosen from microporous membranes and non-porous or dense membranes.

[0085] In the fermentation device, the membrane contactor may be placed inside or outside the reactor. It is understood that the membrane contactor can be placed in a housing, itself placed inside or outside the biological reactor. In a preferred embodiment, the membrane contactor is placed inside the reactor.

[0086] According to a particular embodiment, the reactor is closed, isolated from the outside, the only gas exchanges with the outside being made via the membrane contactor with a supply of CO2 and an evacuation of O2. EXAMPLES

[0087] EXAMPLE 1: Variation in the quantity of dioxygen (O 2 )

[0088] Purpose: To eliminate dissolved O2 based on geometric and physical characteristics chemical reactions of the reactor by varying the flow rate of the medium in the contactor.

[0089] Experimental conditions: Photobioreactor in which the light emission surface remains constant (250 m2). The quantity of photons emitted by the light surfaces varies from 1050 to 0 pmol photons / m2 / s. There is no unlit area in the reactor (fd=O).

[0090] In this configuration it is possible to determine the speed of the flow of the medium in the membranes as a function of the quantity of O2 present in the medium and produced by the microalgae according to the configurations of the photobioreactor.

[0091] The quantity of O2 produced is modeled via the production of biomass with the following method: PQ2 = *PV °where Y02 / x is equal to 1.5 kgO2 / kg of biomass produced and PV is the volumetric productivity.

[0092] The dissolved oxygen concentration is between 8 g / m3 and 30 g / m3. Indeed, it has been found that a dissolved oxygen concentration lower than 8 g / m3 can have a negative effect on the growth of microalgae, while an O2 solubility higher than 30 g / m3 can induce a loss of biomass productivity on Chlorella vulgaris. Therefore, the flux of the medium in the membrane contactor depends on AO2 corresponding to the following formula:

[0093] AO2 (mg / L) = -0.79 - 0.66 * initial O2 concentration (mg / L) + 0.29 * medium flow velocity (L / min)

[0094] The most influential factors for changes in dissolved O2 concentration are therefore the initial O2 concentration of the liquid and the flow rate of the liquid in the contactor.

[0095] Case A: the system is sized to produce 0.2 kg / m3 / Jet and the O2 production will remain between the minimum and maximum limits shown in [Fig.2]. In order to reach the minimum limit, a flow rate of 15.72 L / min in O2 is necessary ([Fig.4]).

[0096] O2 production remains reasonable because it remains within the tolerable limits for good photosynthesis. It will still be possible to stay as close as possible to the minimum limit by adjusting the flow rate.

[0097] Case B: the system is defined to produce 0.79 kg / m3 / J, the O2 production will be beyond the maximum limit. It is therefore necessary to reduce the O2 concentration by 22.25 mg / L, thanks to a flow rate in the membranes of the order of 38.07 L / min ([Fig.5]).

[0098] In a second step, if productivity increases as in case B, the production of O2 will be harmful to the microalgae because it is above the limits. It will then be necessary to activate the flow in the membranes to reach the upper limit. It will be chemically and biologically difficult to reach the minimum limit due to the shear stresses of the microalgae and the exchange time between the culture medium and the membrane.

[0099] This process is preferred in the case of cultures where carbon dioxide (CO2) is not supplied in a gaseous form, such as through the use of sodium bicarbonate or potassium carbonate. In this case, the carbon is supplied by mineral means. Only the quantity of O2 produced by the microalgae will need to be eliminated from the culture medium.

[0100] Table 1 summarizes the different parameters for systems A and B. Productivity A Productivity B Productivity 0.20 0.79 Min O2 Terminal 8 8 Max O2 Terminal 27 27 Input m O2 mg / L / h 12 49 AO2 min -4 -41 AO2 max 15 -22 Q for min L / min 16 Q for max L / min 0 38

[0101] EXAMPLE 2: Variation in the quantity of carbon dioxide (CO 2 )

[0102] The most influential factors for the change of dissolved CO2 concentration in the liquid are the CO2 pressure in the membrane and the initial concentration of dissolved CO2 in the culture medium. However, the liquid temperature, gas flow rate, liquid flow rate and the initial O2 concentration of the liquid do not have a significant influence. It is therefore possible to increase or decrease the amount of dissolved CO2 depending on the amount initially present in the culture medium by varying the pressure conditions in the lumen. The variation in the amount of CO2 can thus be defined according to the following equation:

[0103] ACO2 (mg / L) = 664.96 - 0.46 * initial CO2 concentration (mg / L) + 888.30 * pressure (bar)

[0104] If the concentration of the culture medium includes a concentration of 100 mg / L of CO2 and we wish to have a constant concentration of dissolved CO2 of 1200 mg / L, it will be necessary to fill the CO2 delta of 1100 mg / L with a pressure inside the lumen of the order of 0.542 bar ([Fig.6]). This maintenance of CO2 will have to be corrected over time according to the quantity and emission surfaces of the photons sent into the tank.

[0105] This process will be preferred in a culture where the desorption of dioxygen will be carried out via periodic agitation (sequences of large bubbles, gentle mechanical agitation with banana-type blades). The CO2 injection process then becomes less aggressive for the microalgae compared to a case of air / CO2 injection with a bubbler. Indeed, in the latter case it is necessary to send a strong flow of air with little CO2 (98% air), thus accentuating the shear stresses.

[0106] The parameters of Example 2 are summarized in the table below. Reactor geometry case Light surface 25 25 Qn 800.00 200.00 K 30000.00 30000.00 Vr 1.00 1.00 A light 25.00 25.00 fd 0.00 0.00 Sx 0.03 0.01 Px continuous 0.66 0.17 Corrected efficiency 0.79 0.20 Assimilation kgCO2 / kgbiomass 2.059 2.059 KgCO2 / biomas se / J 1.62552958 0.41041054 Initial CO2 concentration mg / L 100 100 Target CO2 concentration mg / L 1200 1200 ACO2 mg / L 1100 1100 V (L) 1000 1000 Pressure required for target CO2 (bar) 0.542 0.542 Quantity of CO2 to be supplied for target + growth kgCO2 2.726 1.510

[0107] EXAMPLE 3: Quantity of CO2 to be injected into the culture medium as a function of temperature and pressure

[0108] This process is best suited to the needs of microalgae cultivation thanks to the adjustment of the pressure of the carrier gas, here CO2. The measurement is easily verifiable with the measurement of dissolved CO2 which allows the target CO2 concentration to be quickly adjusted.

[0109] The CO2 flow rate is adjusted to eliminate at least 85% of the initial O2 produced. The parameters are then checked via pressure gauges, gas and liquid flow meters, etc.

[0110] The following elements will be given priority: - The O2 gas pressure of the input gas is lower than the O2 gas pressure of the culture medium (PO2 input gas < PO2 culture medium) - The CO2 gas pressure of the input gas is higher than the CO2 gas pressure of the culture medium (PCO2 input gas > PCO2 culture medium)

[0111] Experimental conditions: Photobioreactor with 25 m2 of light surface and 1050 pmol photons / m2 / s of surface emission. Biomass production is estimated at 1.03 kg / m3 / J, i.e. a CO2 consumption of around 2.12 kgCO2 / kgBiomass / m3 / J.

[0112] Goal: Eliminate the O2 produced by the photosynthesis of microalgae via the injection of concentrated CO2 which will take the role of a vector gas.

[0113] The amount of CO2 injected depends on the initial concentration of the culture medium, the pressure admitted in the CO2 vector membrane and the CO2 delta between the target and initial CO2 concentration. These parameters are impacted by the temperature.

[0114] When the culture medium is saturated with CO2, an additional quantity of CO2 will be added in order to serve as a vector for O2 but also to anticipate CO2 consumption by the biomass. This method makes it possible to maintain maximum CO2 availability depending on the strain in correlation with its carbon consumption.

[0115] The table shows the different parameters allowing the calculation of ACO2 and the CO2 pressure necessary to reach a saturation in dissolved CO2 depending on the temperature of the culture medium. The results also allow the calculation of the quantity of CO2 to be added for the growth of microalgae and to eliminate O2. Determine ACO2 [mC02] [P] Temperature ° Celsius 20 ° Fahrenheit 68 CO2 density at kg / m3 1.82818281 Initial CO2 concentration mg / L 300 Target CO2 concentration mg / L 1200 aco2 mg 900 VL 1000 Quantity of CO2 to be supplied for the target kg 0.9 CO2 pressure required for the target Bar -0.263298 Set Q to adjust % O2 removed Quantity of CO2 to be supplied to reach the target and excess for microalgae growth kg / J 3.02485775

[0116] The parameters of Example 3 are summarized in the table below. Reactor geometry case Light surface 25 Qn 1050 K 30000 Vr 1.00 A light 25 fd 0 Sx 0.03 Px continuous 0.86 Corrected efficiency 1.03 Assimilation kgCO2 / kgbiomass 2.059 kgCO2 / biomass se / reactor / J 2.12485775

Claims

Claims

1. A method of culturing a microorganism in a culture medium comprising CO2 as a carbon source and comprising a step of culturing the microorganism in a biological reactor comprising CO2 supply means, characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and O2 flows in the culture medium, wherein the CO2 flow is directed towards the culture medium and the O2 flow is directed towards the outside of the culture medium, said membrane contactor comprising a circulation flow of the culture medium and a circulation flow of CO2, the two flows being separated by a membrane, and, in the biological reactor, the CO2 concentration is between 0 and 3500 mg / L and the O2 concentration is between 8 and 30 g / m3.

2. Method according to claim 1 characterized in that the membrane contactor is a hollow fiber membrane.

3. Method according to claim 2, characterized in that the external diameter of the hollow fiber membranes is between 100 and 800 μm.

4. Method according to one of claims 2 or 3, characterized in that the diameter of the pores of the membrane is between 0.01 and 0.05 μm.

5. Method according to one of claims 2 to 4, characterized in that the hollow fiber membrane is a microporous membrane or a non-porous membrane.

6. Method according to one of claims 1 to 5, characterized in that the concentration of CO2 in the culture medium is at least 1000 mg / L.

7. Method according to one of claims 1 to 6, characterized in that the CO2 concentration in the culture medium is regulated so as to provide the necessary and sufficient quantity for the culture of the microorganisms, all of the CO2 being consumed without loss into the atmosphere.

8. Method according to one of claims 1 to 7, characterized in that the only gas exchanges between the reactor and the external environment are carried out via the membrane contactor.

9. Method according to one of claims 1 to 8, characterized in that the microorganisms are bacteria, yeasts or protists, in particular microalgae.

10. Method according to one of claims 1 to 9, characterized in that the microorganisms are microalgae cultivated in autotrophic mode.

11. Microalgae fermentation device comprising a fermentation reactor, CO2 supply means, and where appropriate lighting means, characterized in that the CO2 supply means comprise a membrane contactor for regulating the CO2 and O2 flows in which the CO2 flow is directed towards the culture medium and the O2 flow is directed towards the outside of the culture medium, said membrane contactor comprising a circulation flow of the culture medium and a circulation flow of CO2, the two flows being separated by a membrane, and, in the fermentation reactor, the CO2 concentration is between 0 and 3500 mg / L and the O2 concentration is between 8 and 30 g / m3.

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