EP4103676A1

EP4103676A1 - Reactor having an optimized lighting device

Info

Publication number: EP4103676A1
Application number: EP21703939.5A
Authority: EP
Inventors: Philippe BOUDIER; François GODART
Original assignee: Fermentalg SA
Current assignee: Fermentalg SA
Priority date: 2020-02-14
Filing date: 2021-02-12
Publication date: 2022-12-21
Also published as: IL295397A; WO2021160776A1; MX2022009959A; US20230113048A1; FR3107281A1; CN115087724A; CA3167982A1; JP2023514244A; BR112022016113A2

Abstract

The present invention relates to a reactor comprising a vessel (1) for containing: • a mass to be treated, and • at least one lighting device (2a, 2b) intended to promote the treatment of said mass, characterized in that each lighting device (2a, 2b) comprises a light diffuser including at least one micro-etched plate (211) which is transparent to light radiation.

Description

REACTOR WITH OPTIMIZED LIGHTING DEVICE

FIELD OF THE INVENTION

The present invention relates to the general technical field of reactors with integrated lighting, in particular for the culture of photosensitive microorganisms.

It can be a bioreactor but also a chemical or physicochemical reactor.

BACKGROUND OF THE INVENTION

The concept of bioreactor, or biological reactor, here designates a reactor within which biological phenomena develop, such as the growth of cultures of pure microorganisms or of a consortium of microorganisms (in particular microalgae), in very varied fields such as the treatment of effluents, the production of biomass containing biomolecules of interest (that is to say biomolecules which we know how to use). This concept therefore includes in particular reactors called fermenters.

A bioreactor typically comprises a tank (cylindrical or parallelepiped) containing a culture medium of biological species (yeasts, bacteria, microscopic fungi, algae, animal and plant cells) for: the production of biomass, or for the production of a metabolite , or for the bioconversion of a molecule of interest.

Various types of operating conditions may be necessary for the growth of biological species within such a bioreactor; Thus, in particular, autotrophic (or photoautotrophic) growth regimes are known with a contribution of light (one also speaks of photosynthesis) or of mixotrophic growth (with a combined contribution of carbon source and light). It should also be noted that light can act on the metabolism of cells by inducing or repressing the production of certain compounds, independently of growth and photosynthesis. A contribution of light during the culture can therefore be useful even when the microorganisms are heterotrophic.

In the following, we will focus more specifically on photo-bioreactors, that is to say bioreactors in which a supply of light (continuously, cyclically, or in the form of pulses) is implemented.

Photo-bioreactors have already been proposed in which the light is supplied from the inside of the tank. Document US Pat. No. 3,986,297 proposes in particular a photo-bioreactor in which the supply of light is carried out by immersion, in the culture medium, of means illumination (such as xenon lamps). A drawback of this solution is that the efficiency of the photo-bioreactor is inversely proportional to the dimensions of the latter. Thus, the more the dimensions of the photo-bioreactor increase, the more its efficiency decreases.

Photo-bioreactors have also been proposed in which the light is supplied from the outside of the vessel. In particular, a well-controlled configuration consists in providing the tank with windows allowing the penetration of a light generated from outside the tank (natural or artificial light). A drawback of such a configuration is that the windows limit the illumination surface and absorb or reflect a significant part of the photons emitted by the illumination source.

Whether the light is supplied from inside or outside the tank, the productivity of a photo-bioreactor (production of biomass per unit of volume) is directly linked to its specific surface ( ratio of illuminated surface to culture volume). It is therefore necessary for the photo-bioreactor to have a large illuminated specific surface.

Whether flat or cylindrical, a drawback of current photo-bioreactors is that they must occupy a large floor area for their productivity to be acceptable.

Moreover, regardless of the light source chosen to illuminate the culture medium (neons, LEDs, natural light), its supply of photon energy is carried out in a very localized manner, so that: most of the photons emitted by the light source cannot be consumed biologically by the microorganism due to an overload of energy, the dissipation of the heat generated by the light source is poorly controlled, it is complex and expensive to produce photo-bioreactors of large dimensions.

An object of the present invention is to provide an economical photo-bioreactor, both in terms of investments and operating costs, and of which the land footprint is reduced.

Another aim of the invention is to provide a high capacity photo-bioreactor (tank of 1000 liters or more) in which the yield in quantity of photons (pmol-ph-s ¹ ) supplied by a luminous surface per unit of power (Watt) is optimized.

BRIEF DESCRIPTION OF THE INVENTION

To this end, the invention provides a reactor including a vessel intended to contain: o a mass to be treated, and o at least one lighting device intended to promote the treatment of this mass, remarkable in that each lighting device understand : a light diffuser, the diffuser including at least one micro-etched plate transparent to light radiation, said plate having opposite back and front faces and at least two slices between the back and front faces, the area of each face being greater at the area of each wafer, the rear face including a plurality of micropatterns, a light source for generating the light radiation, the light source being disposed on at least one wafer of the plate and being oriented such that the radiation light that it generates propagates in the plate.

This solution makes it possible to obtain a photo-bioreactor with better yields (energy on the one hand, and in biomass production on the other hand) than existing photo-bioreactors.

Indeed, the use of one (or more) micro-etched plate (s) allows the homogeneous conduction of the light radiation generated by the light source. Photon energy is guided through the entire micro-etched pack and emerges from it over the entire surface of its front face, which improves the ratio of illuminated area / illuminated volume directly in contact with the culture medium.

Thus, the invention makes it possible to increase the pmol-photons ratio s ^-1 W ¹ per unit of volume, which ensures a reduction in the environmental footprint of the photo-bioreactor and reduces the costs associated with its operation.

Preferred but non-limiting aspects of the assembly according to the invention are as follows: each plate can be substantially planar and comprise four slices, each light source including a plurality of light emitting diodes arranged on at least one of the more slices. small dimensions; each plate may be cylindrical and include two wafers, each light source including a plurality of light emitting diodes disposed on at least one of the two wafers; the diodes of the plurality of light-emitting diodes can be placed on the edge of the plate furthest from the bottom of the tank; each light diffuser can comprise a pair of micro-etched plates arranged so that their rear faces extend facing each other; each light diffuser may further comprise at least one layer of material reflecting light radiation, each layer of reflecting material extending over the rear face of a respective plate; each light diffuser may further comprise at least one transmission layer, each layer of transmission material extending over the front face of a respective plate; the reactor may include a plurality of light diffusers, two adjacent light diffusers being spaced apart by a distance of between 2 and 10 centimeters, preferably between 4 and 8 centimeters, and even more preferably substantially equal to 6 centimeters; the light source of each lighting device can be adapted to generate continuous light radiation; the reactor can comprise a plurality of light diffusers, two adjacent light diffusers being spaced apart by a distance of between 8 and 150 centimeters, preferably between 10 and 50 centimeters, and even more preferably substantially equal to 11 centimeters; the light source of each lighting device can be adapted to generate a discontinuous light radiation in the form of flashes composed of an alternation of dark phases and of illuminated phases, for example at a frequency between 10 and 50 kHz; the tank may have a capacity of 100m ³ , the area covered by the plates of the light diffusers being between 2000 and 3000m ² , preferably between 2250 and 2750m ² , preferably substantially equal to 2500m ² ; the lighting devices may be composed of: o a first group of lighting devices of a first height, and o a second group of lighting devices of a second height less than the first height, a lighting device of the second group being arranged between two successive lighting devices of the first group; the reactor can further comprise an injection system including a plurality of diffusion units, each diffusion unit: extending between two adjacent light diffusers, and o being separated from the other diffusion units by at least two diffusers successive light; each lighting device can be independently connected to an electrical power supply module so that each lighting device can be individually removed from the reactor during operation thereof. BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics of the reactor according to the invention will emerge better from the following description of several variant embodiments, given by way of non-limiting examples, from the appended drawings in which:

Figure 1 is a schematic perspective representation of a first variant of the photo-bioreactor according to the invention;

Figure 2 is a schematic perspective representation of a lighting device; Figure 3 is a schematic cross-sectional representation of a first embodiment of the lighting device;

Figure 4 is a schematic cross-sectional representation of a second embodiment of the lighting device;

Figure 5 is a schematic representation of an experimental variant of a photo bioreactor;

FIG. 6 is a curve illustrating the yield in biomass production (as a function of various parameters) obtained from the experimental variant of a photo bioreactor illustrated in FIG. 5;

FIG. 7 is a partial cross-sectional view of a second variant of a photo bioreactor;

Figure 8 is a curve illustrating the maximum concentration of microalgae as a function of the distance between two adjacent lighting devices;

Fig. 9 is a block diagram illustrating the difference between continuous lighting and discontinuous lighting;

Figure 10 shows curves of microalgae concentration as a function of the distance between two adjacent lighting devices in the case of continuous lighting on the one hand and in the case of discontinuous lighting on the other hand.

DETAILED DESCRIPTION OF THE INVENTION

Various examples of photo-bioreactors according to the invention will now be described with reference to the figures. In these various figures, the equivalent elements are designated by the same reference numeral.

7. General

With reference to Figure 1, the bioreactor comprises:

A tank 1 intended to receive a mass to be treated, A plurality of lighting devices 2a, 2b, and

An injection system including a plurality of diffusion units 3 of carbon dioxide (C0 ₂ ) in the form of gas bubbles or in the form of a fluid consisting of C0 ₂ dissolved in an aqueous medium.

Each lighting device is intended to be integrated into the tank for the treatment of the medium contained in the tank. These lighting devices are intended to be completely immersed in the culture medium. In the following, the bioreactor will be described with reference to the treatment of a biomass formed from microorganisms, for example microalgae. It will be understood, however, that the following description also applies to other types of reactors, chemical or physicochemical.

As illustrated in Figure 1, the lighting devices 2a, 2b are arranged at a non-zero distance from the bottom of the tank. The lighting devices 2a, 2b can be of different heights. In particular, the bioreactor can comprise: a first group 2a of lighting devices having a first height h _a , and a second group 2b of lighting devices having a second height h _b less than the first height h _a , a device lighting of the second group 2b being arranged between two successive lighting devices of the first group 2a. This makes it possible to promote mixing and homogenization of the mass to be treated.

To further increase the mixing and homogenization of the mass to be treated, the diffusion units 3 of the injection system can be placed periodically downstream of each lighting device of the first group 2a (the reactor being devoid of a control unit. diffusion 3 downstream of the lighting device of the second group 2b). Thus, after having circulated under the lighting device of the first group 2a, the mass to be treated is entrained vertically towards the top of the tank 1 (ie direction opposite the bottom) by the bubbles of C0 ₂ (or the fluid containing the C0 ₂ dissolved) emitted (or emitted) by the diffusion units 3. The mass to be treated passes above the lighting device of the second group 2b and falls to the bottom of the tank by gravity. This creates a circulation of the mass to be treated through the tank, which improves the mixing and homogenization of the mass to be treated.

As a variant, the lighting devices 2a, 2b of the bioreactor can all be of identical height. This makes it possible to simplify the installation of the lighting devices by an operator. In this case, the diffusion units 3 are arranged every two lighting devices so that two successive diffusion units 3 are separated by two adjacent lighting devices 2a, 2b. 1.1. Tank

The tank 1 is intended to contain the mass to be treated. It comprises a bottom and at least one side wall.

In the embodiment illustrated in FIG. 1, the tank 1 is substantially parallelepiped. It consists of a bottom, four side walls and a ceiling (or cover) at least partially removable.

In other embodiments, the tank 1 may be cylindrical and include a lower base forming a bottom, an upper base forming a cover, and a side wall between the lower and upper bases.

The material constituting the walls of the tank 1 can be stainless steel or equivalent. Of course, other materials can be chosen depending on the intended application (Plexiglass®, Polypropylene, Concrete, etc.). In all cases, the tank is preferably made of a material resistant to cleaning products (bleach, peroxide, etc.).

7.2. Lighting device

Referring to Figure 2, each lighting device 2a, 2b comprises: one (or more) light diffuser (s) 21, and one (or more) light source (s) 22.

The light source 22 allows the generation of a luminous flux. The light diffuser 21 makes it possible to: guide the light flux generated by the light source, and redisperse it homogeneously towards the mass to be treated.

Advantageously, each light source 22 can be independently connected to an electric power supply module. The module makes it possible to supply the electrical energy necessary for the generation of the luminous flux. The fact that each light source is independently connected to an electrical power supply module allows each lighting device 2a, 2b to be individually removed from the bioreactor during operation.

1.2.1. Light diffuser

The light diffuser 21 comprises one (or more) textured plate (s) 211. Each plate 211 can be substantially flat and rectangular (suitable in the case of a parallelepipedal tank) or tubular (suitable in the case of a cylindrical tank).

Each plate 211 comprises a rear face 2113, a front face 2114 and: four side edges (or edges) 2111 in the case of a rectangular plate 211, or two side edges (or edges) 2111 in the case of a plate 211 tubular. Each side edge 2111 can be polished, and at least one of the side edges 2111 is intended to come into contact with the light source 22 to allow the transmission of the light flux through the plate 211.

The material constituting each plate 211 can be poly-methyl methacrylate (PMMA) or another transparent material known to those skilled in the art which allows the plate 211 to conduct - by total internal reflection on its front and rear faces - the luminous flux emitted by the light source 22, such as for example: another transparent methacrylate resin such as methyl methacrylate, ethyl ethacrylate, butyl methacrylate, propyl or isopropyl methacrylate, or a transparent resin polystyrene, polycarbonate, polyacrylate, or glass / fused silica type.

1.2. 1.1. Micro-patterns

With reference to FIG. 3, each plate 211 comprises a plurality of micro-patterns 2112 on its rear face 2113. The micro-patterns 2112 make it possible to intercept the rays 23 of the luminous flux circulating through the plate 211 and to direct them towards the front face 2114 so as to facilitate their transmission out of the plate 211. More precisely, the radiations 23 which strike each micro-pattern 2112 are redispersed. Each radiation 23 is re-emitted at an angle such that it can exit the plate 211 via the front face 2114 opposite to the rear face 2113 comprising the micro-patterns 2112.

Each micro-pattern 2112 can consist of a cavity - point or groove - having a shape chosen from a conical shape, a (poly) pyramidal shape, a quadrangular shape, or any other shape known to those skilled in the art and allowing each micro-pattern 2112 to deflect the radiations 23 of the luminous flux. Particularly in the example illustrated in Figure 3, the micro-patterns 2112 consist of fine grooves parallel to the side edge 2111 in contact with the light source 22.

Of course, the micro-patterns 2112 can consist of deflection elements other than cavities, such as: light scattering particles arranged in the material constituting the plate 211, or surface texturing components arranged on the rear face 2113, such as for example emergent hemispherical structures, bumps extending outwardly from the rear face 2113, emerged pyramidal structures or combinations comprising at least one of the preceding structures. The height (ie dimension along an axis perpendicular to the rear face) of each micro-pattern 2112 can be between 0.15 and 0.5 µm, and the pitch between two adjacent micro-patterns can be between 20 and 900 µm , and in particular greater than or equal to 100 μm.

Advantageously, the micro-patterns 2112 can be arranged on the rear face 2113 at a consecutive spacing inversely proportional to the distance of said micro-patterns 2112 from the side edge 2111 in contact with the light source 22. Such an arrangement makes it possible to obtain a constant luminous intensity over the entire surface of the rear face 2113. In fact, the intensity of the luminous flux which penetrates into the plate 211 decreases as a function of its distance relative to the light source 22. By varying the density of the microphone - patterns 2112 on the rear face 2113, it is possible to compensate for the loss of intensity by an increasing density of micro-patterns 2112.

1.2.1.2. Reflective layer

The light diffuser 21 may also include a layer of material 212 reflecting the light flux.

This layer of reflective material 212 preferably extends over the entire rear face 2113 of the plate 211 including the plurality of micro-patterns 2112.

The reflective material layer 212 may consist of a film of reflective material such as a metallized aluminum film. Alternatively, the layer of reflective material 212 may consist of a paint having a lower refractive index than that of the material 211 constituting each plate 21.

1.2.1.3. Transmission layer

The light diffuser 21 can also include a transmission layer 213 on the front face 2114 of the plate 211.

This transmission layer 213 helps to promote the transmission of radiation 23 of the light flux to the outside of the plate 211.

This transmission layer 213 also makes it possible to smooth the illumination effect obtained with the light diffuser 21.

The transmission layer 213 finally makes it possible to protect the plate 21 against possible mechanical attacks (scratches due to friction, etc.).

The transmission layer 213 may for example consist of a protective varnish with a refractive index close to the refractive index of the material constituting the plate 211.

7.2.2. Light source

Each light source 22 may include one (or more) light emitting diode (s) (LED) 221. Preferably, each diode 221 is a high power light emitting diode. (HPLED), that is to say an LED with a power greater than 1 Watt. For example, each diode 221 can be a light emitting diode with direct chip mounting (also known under the name of “COB” LED, acronym of the English expression “Chip On Board”). In this case, the light source 22 may include a COB LED module composed of several LED chips attached to a substrate (for example) of ceramic. This makes it possible to generate a more powerful and dense luminous flux.

The diodes 221 of the light source 22 can be individual, or be arranged “in a strip” or “in a ribbon” (see patent application FR1050015). The use of diodes arranged in a ribbon makes it possible to facilitate the manufacture of the lighting device, each light source 22 being intended to come into contact with a lateral edge of the to be placed on a lateral edge 2111 of the plate 211 of the diffuser. light 21. The diodes 221 can be supplied with electrical energy via one (or more) connection cable (s) electrically connected to a source of electrical energy.

Whatever arrangement is chosen, the diodes 221 of the light source 22 can all be identical with the same excitation regime, or be different. In particular, the diodes 221 of a light source 22 can have: distinct excitation regimes (for example continuous regime for some, and flash regime at a frequency between 1 and 150 kHz for others), and / or distinct emission spectra (for example in white light for some and in blue light for others), etc.

Each light source 22 can also include one (or more) reflector (s) (not shown) for reflecting, orienting and focusing the light produced by the diodes 221.

Each light source is intended to come into contact with a lateral edge of the plate 211 so that the radiation 23 of the luminous flux generated by the light source propagates inside the plate 211. Advantageously, the diodes 221 and the connection cable (s) can be embedded / molded in resin to seal each light source.

In the embodiment illustrated in FIG. 3, the lighting device comprises a light source 22 intended to come into contact with a lateral edge 2111 of the plate 211. As a variant, each lighting device can comprise two sources of light. light 22 intended to come into contact with a respective opposite side edge 2111 of the plate 211. Still another variant, each lighting device may comprise four light sources 22 intended to come into contact with a respective side edge 2111 of the plate 211 .

1.3. Injection system The injection system makes it possible to supply the bioreactor with nutrients, in particular with C0 ₂ . In particular, the injection system makes it possible: to supply the carbon dioxide necessary for the development of the biomass and to suspend the carrier particles of microorganisms contained in the biomass culture medium.

The supply of carbon dioxide can be continuous or discontinuous in response to certain criteria such as time or pH As indicated above, carbon dioxide can be introduced: in the form of gas bubbles, or in the form of a solution aqueous pumped or pushed into the bioreactor. The introduction of carbon dioxide in the form of gas bubbles allows a better distribution of C0 ₂ in the tank.

The injection system can include: a C0 ₂ supply unit - such as a booster (in the case of _{gaseous C0 2} ) or a pump (of the turbine type in the case of _{fluid C0 2} ) - preferably fitted a non-return valve to prevent sludge or effluent from rising to the level of the C0 ₂ supply unit, a plurality of diffusion units 3 forming: o in the case of gaseous _{C0 2} , micro-bubbling heads for the diffusion of bubbles of different diameters, o in the case of C0 ₂ dissolved in an aqueous medium, fluid ejection nozzles for the diffusion of the fluid containing dissolved _{C0 2.}

Diffusion units can be of different types known to those skilled in the art, for example diffusers made of microporous composite materials, membrane (EPDM, silicone, etc., preferably EPDM), ceramic or slot, etc.

Each diffusion unit is preferably placed in the immediate vicinity of the bottom of the tank. Furthermore, each diffusion unit 3 is arranged between two adjacent lighting devices 2a, 2b, the different diffusion units 3 being arranged so that each diffusion unit 3 is surrounded by lighting devices separate from the lighting devices. 2a, 2b surrounding the other diffusion units 3 In other words, each diffusion unit 3 is separated from the nearest diffusion unit 3 (or the closest units) by two lighting devices 2a, 2b .

1 4. Biomass treatment The biomass cultivated in the reactor according to the invention can be harvested by any technique known to those skilled in the art such as sedimentation, filtration, flotation or centrifugation techniques.

The biomass harvest can be carried out continuously or semi-continuously, in particular in the case where the bioreactor is located on an industrial site. For this purpose, the bioreactor can be associated with a separation unit - decanter and / or centrifuge and / or filter etc. - allowing to take a portion of the contents of the tank to separate the biomass from the culture medium

The biomass thus extracted can then be packaged (vacuum freezing, etc.) for later use. The culture medium, once separated from the biomass, can be reintroduced into the tank of the bioreactor.

1 5 Other characteristics of the bioreactor

The reactor can also include a control module including one (or more) sensor (s) for checking the parameters of the bioreactor. In particular, the control module can include: one (or more) pH probe (s), one (or more) sensor (s) for measuring the level of C0 ₂ , one (or more) light sensor (s), one (or more) PO3 / ₄ , and / or NO3, and / or NHL sensor (s), one (or more) temperature sensor (s).

The various sensors and probes of the control module make it possible to maintain optimal values for the parameters of the bioreactor influencing the growth of the biomass. In particular, the control module can adapt the quantity of C0 ₂ injected into the culture medium according to the measurements carried out by the pH probe and / or by the sensor (s) for measuring the level of C0 ₂ , etc. . For example, if the _{measured C0 2} rate is less than a threshold, the control module can order the injection of a greater quantity of C0 ₂ into the tank (relative to a set quantity). Conversely, if the measured pH is below a predetermined threshold, the control module can order the injection of a lower quantity of C0 ₂ (relative to a set quantity).

Likewise, if the measured temperature is lower (respectively higher) than a threshold temperature, the control module can control the activation of a heat exchanger - such as a plate exchanger - integrated in the bioreactor tank to heat. (respectively cool) the culture medium.

Also, depending on the measurements made by the PO _3/4 , NO ₃ , NH ₄ sensor (s), the control module can adapt a quantity of nutrient (phosphorus, nitrogen, etc.) injected into the culture medium (by acting on the activation / deactivation of a pump connected to a source of nutrients, etc.).

Finally, the measurement of information representative of the light inside the culture medium allows an estimate of the biomass concentration inside the tank. Thus, it is possible to regulate the step of harvesting the biomass. In particular, if the light measurement inside the tank is representative of a too low biomass concentration, the control module can suspend the biomass harvest. Conversely, if the light measurement inside the tank the tank is representative of a too high biomass concentration, the control module can initiate the biomass harvest. 2. Characteristics of the photo-bioreactor

2.1. Case of continuous light radiation

We will now describe various aspects relating to a sizing of the bioreactor allowing optimal use of the light flux from the lighting devices. This sizing of the bioreactor is carried out by considering a continuous light supply, that is to say by considering that each light source 22 generates continuous light radiation of constant intensity over time.

2.1. 1. Photon capture model

To understand whether the flow of photons from the lighting devices is used optimally by the mass to be treated, it is proposed to use a model on the capture of photons by microalgae as a function of an emission surface and d 'a geometry of the reactor.

The following representation shows the adjustable parameters to deduce productivities in a photo-bioreactor. Here it will be preferable to reduce as much as possible the unlit fraction of the reactor and to increase the surface receiving the photon flux.

The global model of the surface efficiency of a photo-bioreactor is as follows:

Where: f _d is the volume fraction not illuminated by design of the reactor (f _d = 0 if the entire surface of the reactor is illuminated); p _M is the maximum energy efficiency of conversion of light energy into physicochemical energy; f is the molar quantum yield of photosynthesis; a is the linear diffusion modulus; ang _ht is the illuminated specific surface of the reactor over the volume;

K corresponds to a half-saturation constant of photosynthesis (depends on the microorganism); ή corresponds to the mean degree of collimation of the Incident radiation;

Q _n is the average flux density on the surface of the photo-bioreactor.

The maximum performance of a photo-bioreactor can be characterized by some simplifications of the constants in an ideal case. Therefore production will depend on the following:

The dark fraction "S _x ", which corresponds to the unlit volume ratio (fd = 0): in kg / m ^ //

Where q is expressed is the half-saturation constant of photosynthesis (30,000 pmol / kgx / s),

The surface production "P _x " due to the capture of the captured surface photon flux:

Px = Sx * aLight in kg / m // With corrective factor of 20%

The volume production as a function of the surface photon flux collected in relation to the total volume: _ _ Light

3Light - ~ Vr

Applying the previous calculation rules for: an acrylic sheet 0.2m wide and 0.4m long an incident light of 250pmol / m2 / s, - a total reactor volume of 0.008 m ³ , no shadow zone (fd = 0), then the maximum theoretical volumetric productivity is estimated at 100 mg / L / D, as illustrated by the table below.

This is confirmed in an experiment using the reactor shown in Figure 5, in which the lighting device comprises an acrylic plate disposed under the bottom of a vessel with transparent walls. An average production of 102 mg / L / D over 140 hours is obtained (minimum: 60 mg / L / D, maximum: 130 mg / L / D), as shown in Figure 6.

The addition of air with 2% of C0 ₂ ensures the mixing and brings carbon to the mass to be treated. 2.7.2. Determination of an optimum surface area of plates for the reactor lighting devices

The objective is to determine the optimum light flux diffusion area for the reactor. Of course, the number and arrangement of lighting devices can vary depending on the amount of biomass you want to produce.

If one wishes to produce 1 kg of biomass per m ³ of culture in a volume of 100 m ³ by applying the formulas of the global modeling described in point 2.1., The lighting devices must include 2500 m ² of light plates (light diffusers) emitting 1000 pmol / m ² / s (light sources).

This number is directly related to the desired efficiency, volume, geometry and light intensity.

We obtain the following table:

2.1.3. Determination of a maximum quantity of biomass not to be exceeded

The objective is to determine the maximum concentration not to be exceeded so as not to have a dark zone in the medium (ie maintain an f _d = 0),

We assume a reactor as illustrated in Figure 7 and comprising: a vessel having the following dimensions: 17meters x 2meters x 3meters (Length x width x Height in meters), and a volume of 100 m ³ of lighting devices including plates having dimensions of 3 meters x 2 meters x 0.01 meters (Length x width x Thickness).

To have a luminous surface of 2500m ² , the number of plates must be 2500 / (3x2) = 417 plates, for a total thickness of 4.17 meters (the thickness of each plate being 1 centimeter).

In order to minimize the bulk relative to the introduction of the plates into the tank, each lighting device can include two plates joined by their rear faces so that their front faces are opposite to each other (the rear faces of the two plates extending opposite and being in contact). An example of such a lighting device is illustrated in FIG. 4. The spacing between the different lighting devices is then given by the following formula: d = (L - Etot) / (½ X Nbpiaques) d = (17-4.17) / (½ x 417).

Where: d is the free distance between the front faces of two successive lighting devices, L corresponds to the length of the tank,

Etot corresponds to the total thickness of the plates of the lighting devices (i.e. sum of the thicknesses of the plates),

Nbpi _acks is the number of plates required to have a bright surface 2500m ^2.

The following tables summarize the various results above.

In order not to have a dark zone in the medium (ie maintain an f _d = 0), it is necessary to have a sufficient flow of photons (F) up to the adjoining zone (B) between two lighting devices adjacent.

The luminous intensity as a function of the distance Z can be expressed from the following formula: l (z) = l ₀ -e ^{ka B z}

Where: lo corresponds to the incident light,

K _a is an absorption coefficient,

B corresponds to the biomass concentration,

Z corresponds to the length of the tank.

FIG. 8 illustrates the maximum concentration of microalgae as a function of a distance between two adjacent lighting devices. If we consider that from 50 pmol / m ² / s, the quantity of light is insufficient to have satisfactory yields, it is possible to determine the maximum concentration not to be exceeded. In the case of the device illustrated in figure 7 (and considering a free space "d" of 6 centimeters between the lighting devices), with an adjoining zone B located at 0.03 meters from each lighting device, the maximum concentration at not to cross is 1.5 g / L.

This concentration can be measured using suspended matter sensors such as: 6131 Blue-Green Algae Sensor or ALS-OD4.

2.1.4. Determination of a load in C0 ₂

The quantity of C0 ₂ must be obtained in such a way as to correspond to the proportion of photons provided (Bring as much C0 ₂ as there are photons provided by the reactor).

Therefore, the flow of the mix (Air / C0 ₂ ) must be adjusted to the selected light choice.

Here for 1 kg / m ³ / J 90% C0 _{2 is} needed with a flow rate of 4.77 m ³ / h.

2.1.5. Specificity of the plates

Those skilled in the art will know how to choose the right type of plate for each light diffuser. It will prioritize:

The type of etching (type V ...) which best transmits the photons over the entire plate,

The material with the best light propagation rate for the transmission panel that receives the engravings (acrylic, polycarbonate, etc.),

Optimal reflection material to obtain the strongest luminosity,

The most efficient material for homogenizing the flow of photons.

Those skilled in the art will choose the positioning of the LEDs on one, two, three or four sides of each plate, as well as the shape (rectangle, square, cylindrical) of each plate depending on the culture conditions. He will favor the most uniform LEDs in order to fill the entire edge of the engraved plate.

2.2. Case of discontinuous light radiation

We will now describe various aspects relating to a sizing of the bioreactor by considering a discontinuous light supply, that is to say by considering that each light source 22 generates a discontinuous light radiation composed of a close alternation. dark phases and illuminated phases (flashes), for example at a frequency between 10 and 50 kHz.

By way of indication, FIG. 9 illustrates the difference between discontinuous lighting 31 and continuous lighting 32.

Such a discontinuous supply of light indeed makes it possible to act positively on crop yield in terms of biomass. As illustrated below, the change from a continuous light supply to a discontinuous light supply makes it possible to increase the distance between two adjacent light diffusers 21 (between 2 and 10 centimeters, preferably between 4 and 8 centimeters, and even more preferably substantially equal to 6 centimeters), while maintaining the other parameters identical to those calculated previously.

2.2.7. Calculation of an optimal distance between adjacent lighting devices

Or a system with a continuous average intensity of 1000 pmol.nr ² .s ¹ at the light diffusers 21.

When this average intensity (continuously) is set in “flashes” while maintaining an average irradiance of 1000 pmol.m ² .s ¹ , it is then possible to obtain flash waves of 10,000 pmol.nr ² .s ¹ :

The cycle time t _cycie is such that: tcycie = tiight + tdark (s) / or the frequency (Hz) where tiig _ht corresponds to an illuminated phase and t _dark corresponds to a dark phase; The light fraction f is such that: f = (tng _ht / (tng _ht + t _dark ))

Integrated irradiance: l _m = I _f f with f = 10%; lm = 1000 pmol.nr ² .s ¹ lm = I _f f pmol.nr ² .s ¹ I _f = 10,000 pmol.nr ² .s ¹

This wave of photons makes it possible to increase the distance of entry of photons into the medium, and therefore to increase the distance between the light diffusers 21 with an identical biomass concentration.

As emerges from Figure 10 illustrating concentration curves 33, 34 in microalgae as a function of a distance between two adjacent lighting devices: in the case of continuous lighting on the one hand (curve referenced 33), and in the case of discontinuous lighting (curve referenced 34) on the other hand, the mean distance can then be extended to 0.055 meters in flash with a concentration of 1.5 g / L. In other words, the lighting devices can be arranged so that the distance between two adjacent light diffusers 21 is substantially equal to 11 centimeters. 3. Other embodiments

In the preceding description, various variants of bioreactors have been described, in particular bioreactors intended for industrial applications allowing the treatment of the gases emitted. Of course, the teachings of the present invention are not limited to bioreactors of large dimensions intended for industrial applications.

In particular, in an alternative embodiment, the bioreactor can be of smaller dimensions. For example, the bioreactor can include: a tank with transparent or translucent walls: o of length between 1 and 10 meters, o of width between 50 centimeters and 5 meters, o of thickness between 4 and 30 centimeters, a single lighting device integrated into the tank, an injection system including one (or more) diffusion units.

Such a bioreactor can in particular be used in urban applications to replace certain existing panels such as one (or more) wall (s) of a Bus Shelter®, or any type of shelter.

Of course, the shape of the tank is not necessarily parallelepiped, and depends on the intended application (cylindrical shape, etc.). Likewise, for certain applications, the walls of the tank may not be transparent or translucent.

In all cases, the lighting device is preferably placed in the tank so as to extend: parallel to the side walls of the tank of larger dimensions, (including a light diffuser composed of a pair of plates, and at equal distance from said side walls of larger dimensions.

Such a lighting device comprises a light diffuser preferably composed of a pair of micro-etched plates contiguous by their rear faces, said plates having substantially the same shapes and dimensions as the side walls of larger dimensions of the tank ( plate dimensions = 90-100% side wall dimensions of larger dimensions). The lighting device also comprises a light source as described above. Preferably, the dimensions of the tank are adapted so that the illumination of the mass to be treated by the lighting device is optimal. In particular, the distance separating: the light diffuser and each side wall of larger dimensions of the tank may be between 1 and 15 centimeters, preferably between 2 and 10 centimeters, and even more preferably between 3 and 6 centimeters.

4. Conclusions

The solution described above makes it possible to increase the energy and biomass production yields of the reactor, in particular thanks to a homogeneous conduction of light, and to an optimal sizing of the various components of the reactor as a function of the maximum quantity of biomass desired in the reactor. reactor.

This is valid for cultures in mixotrophy, in autotrophy on photosynthetic organisms but also for cultures in mixotrophy predominantly heterotrophic where light is not important for photosynthetic activity but for example for the induction of molecules of interest. such as pigments (WO2017050917), and / or oil. The invention presented above has many applications, and can for example be used to achieve a carbon sink allowing, by absorption of the carbon contained in the atmosphere (carbon monoxide / dioxide), to reduce the amount of carbon dioxide. atmospheric carbon.

The reader will understand that many modifications can be made to the invention described above without materially departing from the new teachings and advantages described here.

For example, in the above description, the lighting and heating device was integrated in a reactor including a rotating assembly intended to ensure mixing of this mass of microorganisms. It is obvious to those skilled in the art that the lighting and heating device described above could be integrated in a reactor without a rotating assembly.

Therefore, all such modifications are intended to be incorporated within the scope of the appended claims.

Claims

1. Reactor including a vessel (1) intended to contain: o a mass to be treated, and o at least one lighting device (2a, 2b) intended to promote the treatment of this mass, characterized in that each device of lighting (2a, 2b) comprises: a light diffuser (21), the diffuser (21) including at least one micro-etched plate (211) transparent to light radiation (23), said plate (211) having rear faces and opposing front (2113, 2114) and at least two slices (2111) between the rear and front faces (2113, 2114), the area of each face being greater than the area of each slice, the rear face (2113) including a plurality of micro-patterns (2112), a light source (22) for generating the light radiation (23), the light source (22) being disposed on at least one wafer of the plate (211) and being oriented so that the light radiation (23) that it generates propagates in the plate (211).

2. Reactor according to claim 1, wherein each plate (211) is substantially planar and comprises four slices (2111), each light source (22) including a plurality of light emitting diodes disposed on at least one of the more slices. small dimensions.

3. Reactor according to claim 1, wherein each plate (211) is cylindrical and comprises two wafers, each light source (22) including a plurality of light emitting diodes disposed on at least one of the two wafers.

4. Reactor according to one of claims 2 or 3, wherein the diodes of the plurality of light emitting diodes are arranged on the edge of the plate (211) furthest from the bottom of the vessel (1).

5. Reactor according to any one of claims 1 to 4, wherein each light diffuser (21) comprises a pair of micro-etched plates (211) arranged so that their rear faces (2113) extend facing the 'one from the other.

6. Reactor according to any one of claims 1 to 5, wherein each light diffuser (21) further comprises at least one layer of material reflecting (212) the light radiation (23), each layer of reflecting material (212). ) extending over the rear face (2113) of a respective plate (211).

7. Reactor according to any one of claims 1 to 6, wherein each light diffuser (21) further comprises at least one transmission layer (213), each layer of transmission material (213) extending over the. front face (2114) of a respective plate (211).

8. Reactor according to any one of claims 1 to 7, which comprises a plurality of light diffusers (21), two adjacent light diffusers (21) being spaced at a distance of between 2 and 10 centimeters, preferably between 4. and 8 centimeters, and even more preferably substantially equal to 6 centimeters.

9. Reactor according to claim 8, wherein the light source (22) of each lighting device (2a, 2b) is adapted to generate continuous light radiation.

10. Reactor according to any one of claims 1 to 7, which comprises a plurality of light diffusers (21), two adjacent light diffusers (21) being spaced at a distance between 8 and 150 centimeters, preferably between 10. and 50 centimeters, and even more preferably substantially equal to 11 centimeters.

11. Reactor according to claim 10, wherein the light source (22) of each lighting device (2a, 2b) is adapted to generate a discontinuous light radiation in the form of flashes composed of an alternation of dark phases and of illuminated phases, for example at a frequency between 10 and 50 kHz.

12. Reactor according to any one of claims 1 to 11, wherein the vessel has a capacity of 100m ³ , the area covered by the plates of the light diffusers (21) being between 2000 and 3000m ² , preferably between 2250. and 2750m ² , preferably substantially equal to 2500m ² .

13. Reactor according to any one of claims 1 to 12, wherein the lighting devices are composed of: o a first group (2a) of lighting devices with a first height (h _a ), and o a second group (2b) of lighting devices with a second height (h) less than the first height (h _a ), a lighting device of the second group (2b) being arranged between two devices of successive lighting of the first group (2a).

14. Reactor according to any one of claims 1 to 13, which further comprises an injection system including a plurality of diffusion units (3), each diffusion unit (3): extending between two diffusers of light (21) adjacent, and o being separated from the other diffusion units (3) by at least two successive light diffusers (21).

15. Reactor according to any one of the preceding claims, wherein each lighting device (2a, 2b) is independently connected to an electric power supply module so that each lighting device (2a, 2b) can be removed individually from the reactor while the reactor is in operation.