FR3145166A1 - LIGHT DIODE REACTOR - Google Patents

Abstract

The present invention relates to a reactor including a tank (1) and a lighting device (2a-2g) arranged in the tank (1), said lighting device being flexible in at least one direction.

Description

LED REACTOR FIELD OF THE INVENTION.

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

BACKGROUND OF THE INVENTION.

The concept of bioreactor here refers to a reactor within which biological phenomena develop, such as the growth of cultures of a single type or of a consortium of micro-organisms (notably microalgae), in very varied fields such as the treatment of effluents, the production of biomass containing biomolecules of interest (i.e. biomolecules that we know how to valorize) and/or metabolite products.

• la production de biomasse, ou pour
• la production d'un métabolite, ou pour
• la bioconversion d'une molécule d'intérêt.

A bioreactor typically comprises a tank (cylindrical or parallelepiped) containing a culture medium for biological species (yeasts, bacteria, microscopic fungi, algae, animal and plant cells) for:

• biomass production, 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; we thus know, in particular, autotrophic (or photoautotrophic) growth regimes with a supply of light (also called photosynthesis). 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 supply of light during culture can therefore be useful even when the microorganisms are heterotrophic.

In the following, we will focus more specifically on photo-bioreactors, i.e. 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 supply is provided from inside the tank. Document US 3,986,297 proposes in particular a photo-bioreactor in which the light supply is provided by immersion, in the culture medium, of illumination means (such as xenon lamps). A disadvantage of this solution is that the efficiency of the photo-bioreactor is inversely proportional to its dimensions. 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 supply is provided from outside the tank. In particular, a well-controlled configuration consists of equipping the tank with portholes allowing the penetration of light generated from outside the tank (natural or artificial light). A disadvantage of such a configuration is that the portholes limit the illumination surface and absorb or reflect a significant portion of the photons emitted by the lighting source.

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

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

• la majeure partie des photons émis par la source de lumière ne peuvent pas être consommée biologiquement par le micro-organisme du fait d’une surcharge en énergie,
• la dissipation de la chaleur générée par la source de lumière est mal maîtrisée,
• il est complexe et coûteux de réaliser des photo-bioréacteurs de grandes dimensions.

Furthermore, whatever the light source chosen to illuminate the culture medium (Neon, LEDs, Natural Light), its contribution in photonic energy is carried out in a very localized manner, so that:

• most of the photons emitted by the light source cannot be biologically consumed by the microorganism due to an energy overload,
• the dissipation of heat generated by the light source is poorly controlled,
• It is complex and expensive to produce large photo-bioreactors.

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

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

BRIEF DESCRIPTION OF THE INVENTION.

• une cuve destinée à contenir une masse à traiter, la cuve comprenant une paroi inférieure formant fond, une paroi supérieure opposée à la paroi inférieure, et au moins une paroi latérale entre les parois inférieure et supérieure,
• un ensemble de dispositifs d’éclairage flexibles contenu dans la cuve et destiné à favoriser le traitement de la masse,
• au moins un module d’alimentation en énergie électrique connecté à chaque dispositif d’éclairage,

remarquable en ce que chaque dispositif d’éclairage flexible comprend :

• un cadre périphérique composé :
  • de deux bordures longitudinales flexibles, et
  • de deux bordures transversales,

chaque bordure transversale s’étendant entre une paire d’extrémités libres respective des bordures longitudinales, et

• une nappe centrale flexible sur les bords de laquelle est monté le cadre périphérique, la nappe centrale flexible incluant :
  • au moins une plaque flexible,
  • une couche de revêtement flexible transparente au rayonnement lumineux, ladite couche de revêtement s’étendant sur la plaque flexible,
  • un groupe de diodes lumineuses s’étendant entre la plaque flexible et la couche de revêtement flexible, lesdites diodes lumineuses étant orientées de sorte à générer le rayonnement lumineux dans une direction opposée à la plaque flexible.

For this purpose, the invention proposes a reactor including:

• a tank intended to contain a mass to be treated, the tank comprising a lower wall forming a bottom, an upper wall opposite the lower wall, and at least one side wall between the lower and upper walls,
• a set of flexible lighting devices contained in the tank and intended to promote the treatment of the mass,
• at least one electrical power supply module connected to each lighting device,

remarkable in that each flexible lighting device includes:

• a peripheral frame composed of:
  • of two flexible longitudinal edges, and
  • of two transverse borders,

each transverse edge extending between a respective pair of free ends of the longitudinal edges, and

• a flexible central sheet on the edges of which the peripheral frame is mounted, the flexible central sheet including:
  • at least one flexible plate,
  • a flexible coating layer transparent to light radiation, said coating layer extending over the flexible plate,
  • a group of light emitting diodes extending between the flexible plate and the flexible coating layer, said light emitting diodes being oriented so as to generate the light radiation in a direction opposite to the flexible plate.

This solution provides a more ergonomic photo-bioreactor in which the extraction of lighting devices is facilitated. Indeed, the flexibility of each lighting device allows it to be extracted by moving it in a horizontal direction above the tank, for example by making it circulate on rollers of a roller conveyor positioned above the tank. It is thus possible to reduce the height required to extract said lighting device(s) from the tank, for example as part of a maintenance operation.

This solution also 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 flexibility of each lighting device allows it to be conformed to the geometry of the photo-bioreactor, and thus to maximize the ratio of illuminated surface area/volume illuminated directly in contact with the culture medium.

Furthermore, the flexibility of the plate(s) makes it possible to improve the kinetics of movement of the medium in certain areas of the photo-bioreactor, in particular by limiting the formation of circular secondary flows around a main flow of the medium, as will be described in more detail below with reference to the figures.

• chaque diode lumineuse peut être une diode électroluminescente organique flexible (OLED), chaque diode lumineuse étant en contact avec une diode lumineuse adjacente ;
• chaque diode lumineuse peut être choisie parmi une diode électro-luminescente conventionnelle (LED), ou une mini diode électro-luminescente (mini LED), les diodes lumineuses étant espacées les unes des autres d’une distance supérieure ou égale à 50µm ;
• chaque bordure transversale peut être flexible de sorte que le cadre périphérique est flexible selon deux directions orthogonales ;
• chaque bordure transversale peut être rigide de sorte que le cadre périphérique est flexible selon une unique direction parallèle aux bordures longitudinales ;
• chaque bordure transversale peut inclure une armature rigide et un brin rigide de longueur inférieure à l’armature rigide, l’armature rigide et le brin étant reliés par une liaison pivot de sorte que le brin est apte à pivoter relativement à l’armature ;
• chaque bordure flexible peut comprendre une succession de segments rigides raccordés entre eux par des liaisons pivot de sorte que chaque segment est apte à pivoter relativement à un segment adjacent ;
• chaque bordure flexible peut consister en un boudin réalisé dans un matériau identique à un matériau constituant la plaque flexible ;
• ledit et au moins un dispositif d’éclairage peut être de forme parallélépipédique, le réacteur incluant une structure support rigide comportant des logements, chaque logement étant destiné à recevoir un dispositif d’éclairage flexible respectif et étant configuré de sorte à recourber le dispositif d’éclairage dans la cuve ;
• chaque diode lumineuse peut comprendre un empilement de structures, chaque structure étant adaptée pour émettre un rayonnement lumineux dans une gamme de longueurs d’onde respective ;
• le réacteur peut également comprendre au moins un contrôleur (6) configuré pour piloter ledit et au moins un module d’alimentation (5) en énergie électrique ;
• ledit et au moins un contrôleur peut être configuré pour contrôler une variation d’énergie fournie par ledit et au moins un module d’alimentation afin de modifier au cours du temps le spectre d’émission dudit et au moins un dispositif d’éclairage ;
• ledit et au moins un contrôleur peut être configuré pour :
  • contrôler l’activation continue dudit et au moins un module d’alimentation en énergie électrique de sorte que ledit et au moins un dispositif d’éclairage (2a, 2b) génère un rayonnement lumineux continu,
  • contrôler l’activation discontinue dudit et au moins un module d’alimentation en énergie électrique de sorte que ledit et au moins un dispositif d’éclairage (2a, 2b) génère un rayonnement lumineux discontinu sous forme de flashs composé d’une alternance de phases obscures et de phases éclairées, par exemple à une fréquence comprise entre 10 et 50 kHz ;
• le matériau constituant ladite couche de revêtement peut être du verre souple ;
• le matériau constituant la couche de revêtement peut être une résine synthétique ou semi-synthétique choisie parmi les résines (méth)acryliques réticulées, les résines de styrène réticulées, les résines de polyuréthane, les résines de polyester, les résines de silicone, les résines fluorées, les résines préparées à partir de substances inorganiques telles que la silice, le carbonate de calcium et le sulfate de baryum ;
• au moins deux diodes lumineuses de la pluralité de diodes lumineuses peuvent être de tailles différentes ;
• la pluralité de diodes lumineuses peut comprendre :
  • au moins une diode lumineuse à émission ultraviolet, et/ou
  • au moins une diode lumineuse phosphorescente.

Preferred but non-limiting aspects of the assembly according to the invention are as follows:

• each light emitting diode may be a flexible organic light emitting diode (OLED), each light emitting diode being in contact with an adjacent light emitting diode;
• each light emitting diode may be selected from a conventional light emitting diode (LED), or a mini light emitting diode (mini LED), the light emitting diodes being spaced apart from each other by a distance greater than or equal to 50µm;
• each transverse border can be flexible so that the peripheral frame is flexible in two orthogonal directions;
• each transverse edge may be rigid so that the peripheral frame is flexible in a single direction parallel to the longitudinal edges;
• each transverse edge may include a rigid frame and a rigid strand of lesser length than the rigid frame, the rigid frame and the strand being connected by a pivot connection such that the strand is capable of pivoting relative to the frame;
• each flexible border may comprise a succession of rigid segments connected together by pivot links so that each segment is able to pivot relative to an adjacent segment;
• each flexible border may consist of a bead made of a material identical to a material constituting the flexible plate;
• said and at least one lighting device may be of parallelepiped shape, the reactor including a rigid support structure comprising housings, each housing being intended to receive a respective flexible lighting device and being configured so as to curve the lighting device in the tank;
• each light emitting diode may comprise a stack of structures, each structure being adapted to emit light radiation in a respective wavelength range;
• the reactor may also comprise at least one controller (6) configured to control said and at least one electrical energy supply module (5);
• said and at least one controller can be configured to control a variation of energy supplied by said and at least one power supply module in order to modify over time the emission spectrum of said and at least one lighting device;
• said and at least one controller may be configured to:
  • controlling the continuous activation of said and at least one electrical energy supply module so that said and at least one lighting device (2a, 2b) generates continuous light radiation,
  • controlling the discontinuous activation of said and at least one electrical energy supply module so that said and at least one lighting device (2a, 2b) generates discontinuous light radiation in the form of flashes composed of an alternation of dark phases and illuminated phases, for example at a frequency of between 10 and 50 kHz;
• the material constituting said coating layer may be flexible glass;
• the material constituting the coating layer may be a synthetic or semi-synthetic resin selected from crosslinked (meth)acrylic resins, crosslinked styrene resins, polyurethane resins, polyester resins, silicone resins, fluorinated resins, resins prepared from inorganic substances such as silica, calcium carbonate and barium sulfate;
• at least two light emitting diodes of the plurality of light emitting diodes may be of different sizes;
• the plurality of light emitting diodes may comprise:
  • at least one ultraviolet emitting light diode, and/or
  • at least one phosphorescent light diode.

BRIEF DESCRIPTION OF THE FIGURES.

• est une représentation schématique en perspective d’un exemple de bioréacteur ;
• est une représentation schématique d’un premier exemple d’une nappe centrale d’un dispositif d’éclairage ;
• est une représentation schématique en coupe transversale d’un exemple de structure de diode lumineuse ;
• est une représentation schématique de la répartition lumineuse de la lumière émise par une diode électroluminescente conventionnelle (LED) ;
• est une représentation schématique de la répartition lumineuse de la lumière émise par une diode électroluminescente organique (OLED) ;
• est une représentation schématique d’un deuxième exemple de nappe centrale d’un dispositif d’éclairage ;
• est une représentation d’un troisième exemple de nappe centrale d’un dispositif d’éclairage ;
• est une représentation schématique en coupe transversale d’un bioréacteur de l’art antérieur ;
• est une représentation schématique partielle d’un écoulement dans le bioréacteur illustré à la ;
• est une représentation schématique en coupe transversale d’une variante de réalisation d’un bioréacteur selon l’invention ;
• est une représentation schématique d’un système de maintenance de bioréacteur selon l’invention ;
• est une représentation schématique d’une autre variante de réalisation du bioréacteur selon l’invention ;
• est un graphique représentant la productivité d’une chlorelle dans la variante de réalisation du bioréacteur illustrée à la ;
• est une courbe illustrant la concentration maximum en microalgues en fonction d’un écartement entre deux dispositifs d’éclairage adjacents ;
• est un schéma de principe illustrant la différence entre un éclairage continu et un éclairage discontinu ;
• représente des courbes de concentration en microalgues en fonction d’un écartement entre deux dispositifs d’éclairage adjacents dans le cas d’un éclairage continu d’une part et dans le cas d’un éclairage discontinu d’autre part,
• est une représentation schématique en vue de face d’un dispositif d’éclairage,
• est une représentation schématique en vue de côté d’une bordure de cadre périphérique,
• est une représentation schématique en vue de dessus d’une bordure de cadre périphérique.

Other advantages and characteristics of the reactor according to the invention will emerge more clearly from the following description of several variant embodiments, given as non-limiting examples, from the attached drawings in which:

• is a schematic perspective representation of an example bioreactor;
• is a schematic representation of a first example of a central sheet of a lighting device;
• is a schematic cross-sectional representation of an exemplary light emitting diode structure;
• is a schematic representation of the light distribution of light emitted by a conventional light-emitting diode (LED);
• is a schematic representation of the light distribution of light emitted by an organic light-emitting diode (OLED);
• is a schematic representation of a second example of a central sheet of a lighting device;
• is a representation of a third example of a central sheet of a lighting device;
• is a schematic cross-sectional representation of a prior art bioreactor;
• is a partial schematic representation of a flow in the bioreactor illustrated in ;
• is a schematic cross-sectional representation of an alternative embodiment of a bioreactor according to the invention;
• is a schematic representation of a bioreactor maintenance system according to the invention;
• is a schematic representation of another variant embodiment of the bioreactor according to the invention;
• is a graph representing the productivity of a chlorella in the embodiment variant of the bioreactor illustrated in ;
• is a curve illustrating the maximum concentration of microalgae as a function of a spacing between two adjacent lighting devices;
• is a schematic diagram illustrating the difference between continuous lighting and discontinuous lighting;
• represents microalgae concentration curves as a function of a spacing 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,
• is a schematic representation in front view of a lighting device,
• is a schematic side view representation of a peripheral frame border,
• is a schematic top view representation of a peripheral frame border.

DETAILED DESCRIPTION OF THE INVENTION.

We will now describe different examples of photo-bioreactors according to the invention with reference to the figures. In these different figures, equivalent elements are designated by the same numerical reference.

1. General

• une cuve 1 destinée à recevoir une masse à traiter,
• une pluralité de dispositifs d’éclairage 2a-2g,
• une pluralité d’unités de diffusion 3 de dioxyde de carbone (CO₂) sous forme de bulles de gaz ou sous forme d’un fluide constitué de CO₂dissout dans un milieu aqueux,
• un module d’alimentation 5 en énergie électrique,
• un contrôleur 6 permettant de piloter la pluralité de dispositifs d’éclairage 2a-2g, la pluralité d’unités de diffusion 3, et le module d’alimentation en énergie électrique 5.

In reference to the , the bioreactor may include:

• a tank 1 intended to receive a mass to be treated,
• a plurality of lighting devices 2a-2g,
• a plurality of diffusion units 3 of carbon dioxide (CO ₂ ) in the form of gas bubbles or in the form of a fluid consisting of CO ₂ dissolved in an aqueous medium,
• a 5-phase electrical power supply module,
• a controller 6 for controlling the plurality of lighting devices 2a-2g, the plurality of diffusion units 3, and the electrical energy supply module 5.

Each lighting device is intended to be integrated into the tank 1 for the treatment of a culture medium 4 contained in the tank 1. These lighting devices 2a-2g are intended to be completely immersed in the culture medium 4. The lighting devices 2a-2g may be of different heights. Alternatively, the lighting devices 2a-2g may all be of identical height. This makes it possible to simplify the installation of the lighting devices by an operator.

In the following, the bioreactor will be described with reference to the treatment of a biomass formed by microorganisms, for example microalgae. It is understood, however, that the following description also applies to other types of reactors in the field of microbiology.

• un premier groupe 2a, 2c, 2e, 2g de dispositifs d’éclairage disposés à une distance non nulle du fond de la cuve, et
• un deuxième groupe 2b, 2d, 2f de dispositifs d’éclairage en contact avec le fond de la cuve.

In the embodiment illustrated in , the bioreactor includes:

• a first group 2a, 2c, 2e, 2g of lighting devices arranged at a non-zero distance from the bottom of the tank, and
• a second group 2b, 2d, 2f of lighting devices in contact with the bottom of the tank.

To increase the mixing and homogenization of the mass to be treated, the diffusion units 3 can be arranged every two lighting devices so that two successive diffusion units 3 are separated by two adjacent lighting devices.

In particular and with reference to the , the diffusion units 3 of the injection system can be arranged periodically downstream of each lighting device of the first group 2a, 2c, 2e, 2g (the reactor being devoid of diffusion unit 3 downstream of lighting device of the second group 2b). Thus, after having circulated under the lighting device of the first group 2a, 2c, 2e, 2g, the mass to be treated is driven vertically towards the top of the tank 1 (i.e. direction opposite to the bottom) by the CO ₂ bubbles (or the fluid containing the dissolved CO ₂ ) emitted (or emitted) by the diffusion units 3. The mass to be treated passes above the lighting device of the second group 2b, 2d, 2f and falls back towards the bottom of the tank 1 by gravity. This creates a circulation of the mass to be treated through the tank 1, which improves the mixing and homogenization of the mass to be treated.

The power supply module 5 makes it possible to supply each lighting device 2a-2g with electrical energy. In particular, each lighting device 2a-2g is electrically connected to the power supply module 5 via one (or more) electrically conductive connection cable(s). The electrical energy provided by the power supply module 5 is then converted into light radiation by each lighting device 2a-2g to illuminate the culture medium 4.

• le (ou les) régime(s) d'excitation de chaque dispositif d’éclairage (par exemple régime continu pour certains dispositifs d’éclairage, et régime flash à une fréquence comprise entre 1 et 150 kHz pour d’autres dispositifs d’éclairage), et/ou
• le (ou les) spectre(s) d’émission de chaque dispositif d’éclairage (par exemple en lumière blanche pour certains dispositifs d’éclairage et en lumière bleu pour d’autres dispositifs d’éclairage), etc.

The controller 6 is used to control the bioreactor. In particular, the controller 6 is used to control the electrical power supply module to vary:

• the excitation regime(s) of each lighting device (for example continuous regime for certain lighting devices, and flash regime at a frequency between 1 and 150 kHz for other lighting devices), and/or
• the emission spectrum(s) of each lighting device (for example in white light for certain lighting devices and in blue light for other lighting devices), etc.

The reader will appreciate that within the same lighting device, different excitation regimes and/or emission spectra can be implemented, as will be described in more detail below.

2 . Tank

The tank 1 is intended to contain the culture medium 4. It comprises a bottom and at least one side wall.

In the embodiment illustrated in , the tank 1 is substantially parallelepipedal. It is composed of a base, four side walls and an at least partially removable cover.

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

The material constituting the walls of the tank 1 may be stainless steel or equivalent. Of course, other materials may 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.).

3 . Lighting device

Each lighting device is flexible. The flexible nature of each lighting device allows it to be shaped to the shape of the tank, for example by curving it (totally or partially) in the case of a cylindrical tank.

In the context of the present invention, a component is said to be “flexible” when it is made of a material having mechanical properties allowing elastic deformation of said component.

• un module d'élasticité supérieure à 0.05 Mpa, par exemple compris entre 0.1 Mpa et 300 Gpa, et
• une limite à la rupture supérieure à 100 MPa, par exemple compris entre 200 MPa et 5GPa.

The flexible material can for example have:

• a modulus of elasticity greater than 0.05 Mpa, for example between 0.1 Mpa and 300 Gpa, and
• a breaking limit greater than 100 MPa, for example between 200 MPa and 5GPa.

Flexibility is further achieved through the geometry of the 2a-2g lighting device, in particular its thickness.

• un cadre périphérique 51, et
• une nappe centrale 52.

As illustrated in the , the flexible lighting device 2 comprises:

• a peripheral frame 51, and
• a central tablecloth 52.

As will be described in more detail hereinafter, the frame 51 and the sheet 52 are flexible in at least one direction.

3.1. Peripheral frame

• deux bordures longitudinales 511 s’étendant parallèlement l’une à l’autre, et
• deux bordures transversales 512 s’étendant parallèlement aux bordures longitudinales 511,

chaque bordure transversale 511 s’étendant entre une paire d’extrémités libres respective des bordures longitudinales 512.The peripheral frame 51 makes it possible to support the central sheet 52. As illustrated in , the peripheral frame 51 comprises:

• two longitudinal edges 511 extending parallel to each other, and
• two transverse edges 512 extending parallel to the longitudinal edges 511,

each transverse edge 511 extending between a respective pair of free ends of the longitudinal edges 512.

The edges 511, 512 of the peripheral frame 51 constitute reinforcements for the central sheet 52. In particular, they make it possible to protect the central sheet 52 during handling of the lighting device 2, and thus limit the risks of degradation of the central sheet 52.

Furthermore, the edges 511, 512 can make it possible to constrain the sheet 52 according to a desired shape in the absence of external stress. For example, in the embodiment illustrated in , the edges 511, 512 make it possible to conform the central sheet 52 in a plane when the lighting device is suspended (and no force is applied to the edges to bend the lighting device).

For this purpose, the edges may be rigid or have non-zero flexibility. To constrain the shape of the sheet when its flexibility is non-zero, each edge 511, 512 has a stiffness coefficient greater than the stiffness coefficient of the central sheet 52. In the following, each edge 511, 512 of non-zero flexibility will be referred to as a “flexible edge”, even if the stiffness coefficient of said edge is greater than the stiffness coefficient of the central sheet 52.

In some embodiments, the four edges 511, 512 are flexible. In this case, the peripheral frame 51 is flexible in two orthogonal directions D1, D2.

In other embodiments, only two parallel edges 511 (e.g. the longitudinal edges) are flexible, the other two edges 512 (e.g. the transverse edges) being rigid. In this case, the peripheral frame 51 is flexible in a single direction. The fact that the peripheral frame 52 is flexible in only one direction makes it possible to improve its holding (shape retention) in a direction orthogonal to its movement when the lighting device is handled, for example during a maintenance operation.

Each edge 511 may be rigid over only a portion of its length. For example, in the embodiment illustrated in , each transverse edge 512 is composed of a rigid frame 512' and a strand 512'' of a length less than the rigid frame 512', the rigid frame 512' and the strand 512'' being connected by a pivot connection 512''' so that the strand 512'' can move in rotation relative to the rigid frame 512'. This makes it possible to create a fin (forming a deflector) at a transverse edge of the lighting device 2, for example to improve the mixing of the mass to be treated, etc.

In reference to the , each flexible edge 511 may consist of a succession of rigid segments 513 connected together by pivot connections 514 allowing each segment to pivot about an axis of the pivot connection relative to at least one of the segments adjacent to it. This makes it possible to bend the end of the lighting device to conform it to the geometry of the photobioreactor, as will be described in more detail below with reference to FIGS. 8 to 10. Alternatively, each flexible edge may consist of a bead made of the same material as the plate. This makes it possible to simplify the design of each lighting device. In particular, the material constituting each flexible edge may be polymethyl methacrylate (PMMA), or a methacrylic resin (such as methyl methacrylate, ethyl ether, butyl methacrylate, propyl or isopropyl methacrylate), or a resin of the polystyrene, polycarbonate or polyacrylate type.

Advantageously, a rigid support structure (not shown) comprising housings in each of which is housed a respective flexible lighting device may be provided in the tank.

Such a support structure – each housing of which can be defined by one (or more) guide rail(s) in which the associated lighting device is able to slide – makes it possible to conform the flexible lighting device in order to curve its end in the photo-bioreactor.

3.2. Central tablecloth

• une plaque 21 flexible, et
• au moins une diode lumineuse 22, 22a, 22b, 22c montée(s) sur la (ou les) plaque(s) 21 flexible(s).

With reference to figures 2, 6 and 7, the sheet 52 of the lighting device 2 comprises:

• a flexible plate 21, and
• at least one light diode 22, 22a, 22b, 22c mounted on the flexible plate(s) 21.

For example in the embodiment illustrated in , the lighting device 2 comprises a single light diode 22 (for example with a surface area of 6m²).

Alternatively and as illustrated in Figures 6 and 7, each lighting device 2 comprises a plurality of light diodes 22, 22a, 22b, 22c (each having a surface area of between 0.01 m² and 6 m²).

Each light diode 22, 22a, 22b, 22c can be glued to the flexible plate 21.

Alternatively, each light diode 22, 22a, 22b, 22c may be laminated on the flexible plate 21 using a lamination interlayer.

3 .2.1. Flexible plate

Each flexible plate 21 may be substantially rectangular. However, each plate 21 may have another shape.

• une autre résine méthacrylique transparente telle que le méthacrylate de méthyle, le éthacrylate d'éthyle, le méthacrylate de butyle, le méthacrylate de propyle ou d'isopropyle, ou
• une résine transparente de type polystyrène, polycarbonate, polyacrylate, ou
• un verre / une silice fondue.

The material constituting each plate 21 may be polymethyl methacrylate (PMMA) or another transparent material known to those skilled in the art which allows the plate 211 to conduct – by transmission between its front and rear faces – the luminous flux emitted by the light diode(s), such as for example:

• another transparent methacrylic resin such as methyl methacrylate, ethyl ether, butyl methacrylate, propyl or isopropyl methacrylate, or
• a transparent resin such as polystyrene, polycarbonate, polyacrylate, or
• a glass / a fused silica.

Alternatively, the material constituting each plate 21 may be a metal.

In some embodiments, the plate may comprise a layer of material reflecting the light flux generated by the light diode(s). This layer of reflective material preferably extends between the plate 21 and the light diode(s). It makes it possible to reflect, orient and focus the light produced by the light diode(s). The layer of reflective material may consist of a film of reflective material such as a metallized aluminum film, or a paint.

3 .2.2. Light diode

3 .2. 2 .1. Structure

• l’une des électrodes – appelée anode – est agencée sous la (ou chaque) couche de matériau électroluminescent, et
• l'autre des électrodes – appelée cathode – est agencée sur la (ou chaque) couche de matériau électroluminescent à l'opposé de l'anode.

Each light emitting diode comprises one (or more) layer(s) of electroluminescent material(s) framed by two electrodes:

• one of the electrodes – called the anode – is arranged under the (or each) layer of electroluminescent material, and
• the other of the electrodes – called the cathode – is arranged on the (or each) layer of electroluminescent material opposite the anode.

It will be understood hereinafter that when a layer A is referred to as being "on" (respectively "under" ) a layer B, the latter may be directly on (respectively under) the layer B, or may be located above (respectively below) the layer B and separated from said layer B by one or more intermediate layers. Furthermore, it will be understood that when a layer A is referred to as being "on" (respectively "under" ) a layer B, the latter may totally or partially cover the layer B (respectively be totally or partially covered by the layer B).

Each light emitting diode emits light by electroluminescence using the recombination energy of holes injected from the anode and electrons injected from the cathode.

Advantageously, the anode and the cathode can be made of a transparent material, so that the emitted photons pass through each electrode to provide light outside the light diode through its two faces.

• une première électrode 221 en contact avec la plaque flexible 21,
• une unité d’émission rouge 222 directement sur la première électrode 221 et recouverte d’une gamme chimique qui émet dans le rouge,
• une deuxième électrode 223 directement sur l’unité d’émission rouge 222,
• une unité d’émission verte 224 directement sur la deuxième électrode 223 et recouverte d’une gamme chimique qui émet dans le vert,
• une troisième électrode 225 directement sur l’unité d’émission verte 224,
• une unité d’émission bleue 226 directement sur la troisième électrode 225 et recouverte d’une gamme chimique qui émet dans le bleu,
• une quatrième électrode 227 directement sur l’unité d’émission bleue 226.

In reference to the , an example structure for each light-emitting diode has been illustrated. This structure includes:

• a first electrode 221 in contact with the flexible plate 21,
• a red emitting unit 222 directly on the first electrode 221 and covered with a chemical range which emits in the red,
• a second electrode 223 directly on the red emission unit 222,
• a green emitting unit 224 directly on the second electrode 223 and covered with a chemical range which emits in the green,
• a third electrode 225 directly on the green emission unit 224,
• a blue emitting unit 226 directly on the third electrode 225 and covered with a chemical range which emits in the blue,
• a fourth electrode 227 directly on the blue emission unit 226.

Stacking several emission units 222, 224, 226 makes it possible to vary the emission spectrum of the light radiation emitted by the light diode.

More specifically, with such a structure the color of the light rays emitted by the light diode can be modified to make it particularly suitable for a specific maturation or growth method, as will be described in more detail below.

• une Diode Electro-Luminescente conventionnelle DEL (ou« LED »selon l’acronyme anglo-saxon« Light-Emitting Diode »),
• une Diode Electro-Luminescente organique DELO flexible (ou« OLED »selon l’acronyme anglo-saxon« Organic Light-Emitting Diode »),ou
• une mini Diode Electro-Luminescente (ou« mini LED »selon l’acronyme anglo-saxon« Mini Light-Emitting Diode »).

Each light diode 22, 22a, 22b, 22c can be chosen from:

• a conventional Light- Emitting Diode ( LED ),
• a flexible organic light- emitting diode ( OLED) or
• a mini Light-Emitting Diode (or “mini LED” according to the English acronym “Mini Light-Emitting Diode” ).

The flexible nature of OLED light emitting diodes allows the flexibility of lighting devices to be maintained even when the OLED light emitting diodes (arranged on the flexible plate) are in contact with each other.

When the light diodes are of a type other than an OLED, they are spaced apart from each other by a sufficient distance to allow the lighting device to be bent at an angle greater than or equal to 60°, preferably at an angle greater than or equal to 90°, more preferably at an angle greater than or equal to 120°, and even more preferably at an angle equal to 180°. In particular, the light diodes may be spaced apart from each other by a distance greater than or equal to 50 µm.

The use of mini LED type light diodes makes it possible to have smaller light sources than conventional LED type light diodes (size less than 500 µm), which makes it possible to increase the number of light sources per unit area (improving brightness and contrast), and to reduce the thickness of the lighting devices.

3 .2. 2 .2. Advantage associated with using OLED

As illustrated in Figures 4 and 5, the use of flexible OLED type light diodes 22 makes it possible to increase the homogeneity of the light 228 emitted by the lighting device according to the invention in comparison with the light 92 emitted by a conventional LED type light diode 91.

• l’angle incident 2α de la lumière 92 émise par une diode lumineuse de type LED 91 est de 120°, comme illustré à la , tandis que
• l’angle incident 2α de la lumière 228 émise par une diode lumineuse de type OLED flexible est de 178°, comme illustré à la .

Especially :

• the incident angle 2α of the light 92 emitted by a LED type light diode 91 is 120°, as illustrated in , while
• The incident angle 2α of the 228 light emitted by a flexible OLED type light diode is 178°, as shown in .

Thus, the use of OLED type light diodes ensures better homogeneity of light, and makes it possible to optimize the illuminated volume in the bioreactor.

3 .2.3. Layer of exterior coating

In reference to the , each lighting device 2 may optionally comprise an external coating layer 23 covering the light diode(s) and possibly the flexible plate(s) 21.

This coating layer 23 protects the light diode(s) and the plate(s) 21 against possible mechanical damage (scratches due to friction, etc.). It also ensures the sealing of the lighting device.

In some embodiments, the coating layer 23 also makes it possible to improve the diffusion of the light emitted by the light diode(s). Indeed, when light is applied to a material, part of the light is reflected, part is absorbed and another part is transmitted through. These parameters can be determined by a person skilled in the art using conventional photometry and optical methods. In the context of the present invention, the external coating layer 23 can be a transmission layer making it possible to promote the transmission of the light radiation emitted by the light diode(s) to the outside. In particular, the material constituting the coating layer 23 can be a resin including transparent particles, in particular a thermoplastic resin. In the latter case, the resin may be a synthetic or semi-synthetic resin and be selected from crosslinked (meth)acrylic resins, crosslinked styrene resins, polyurethane resins, polyester resins, silicone resins, fluorinated resins, resins prepared from inorganic substances such as silica, calcium carbonate and barium sulfate. Among these resins, synthetic resins are preferred, in particular, crosslinked (meth)acrylic resins, crosslinked styrene resins, crosslinked (meth)acrylic-styrene copolymer resins and silicone resins are preferred. Crosslinked (meth)acrylic resins, crosslinked styrene resins and their copolymers are particularly preferred since it is possible to prevent their discoloration by ultraviolet rays in particular by crosslinking processes. The latter therefore have a better lifespan than the other resins. Preferably, the coating layer 23 comprises a diffusing material having a transmittance preferably of at least 90%, still preferably of at least 95%, still still preferably between 95% and 98%.

Preferably, when the coating layer has the function of improving the diffusion of the light emitted by the light diode(s), it is configured so that the light emitted by the light device has a degree of dispersion preferably greater than or equal to 170°, still more preferably greater than or equal to 175°, still more preferably between 175° and 180°.

Advantageously, the coating layer 23 can also have a function of filtering the wavelengths of the light emitted by the lighting device. In particular, the material constituting the coating layer can be chosen to allow the transmission of light radiation whose wavelengths are between 380 nm and 800 nm, preferably between 400 nm and 720 nm, even more preferably between 420 and 690 nm.

Preferably, the thickness of the coating layer 23 is between 0.1 mm and 5.0 mm, preferably between 0.5 mm and 3.0 mm, even more preferably between 0.5 mm and 2.0 mm. For the same thickness, a lighting device according to the invention comprising a coating layer 23 made of flexible diffusing material as defined above, has a better diffusion capacity than the lighting devices of the prior art and therefore a better W/Lumen/unit surface yield. Thus, for an equivalent microorganism biomass yield, a culture method using a bioreactor comprising a lighting device according to the invention will require less electrical energy. Furthermore, the lighting device described above is safer because it only requires low voltages.

The coating layer 23 may also be made of a material (or be covered with a material) that limits its soiling (in particular by preventing the deposition of microalgae on its surface). The coating layer 23 may for example consist of a flexible glass of the Corning type (with a thickness of between 0.1 mm and 0.7 mm). Such a sealed glass coating also allows for better exchange of the heat emitted by the light diode(s) towards the culture medium (which can promote the growth of microorganisms contained in the culture medium 4). Such a sealed glass coating also constitutes a better barrier to the gases injected into the bioreactor.

3 .2. 4 . Examples of lighting devices

Referring to Figures 6 and 7, other examples of lighting devices are illustrated.

In these embodiments, the central sheet of the lighting device 2 comprises a flexible plate 21 and a plurality of light diodes 22, 22a, 22b, 22c mounted on the flexible plate 21.

The use of a plurality of light diodes 22, 22a, 22b, 22c makes it possible to improve the modularity of the lighting device 2, and in particular to vary its size and dimensions in order to adapt them to the size and dimensions of the tank 1.

In the embodiment illustrated in , the light diodes are of identical size, and identical structure.

Alternatively, the light emitting diodes may be of different size and/or type (LED, OLED, mini LED), and/or structure, as illustrated in .

• une (ou plusieurs) diode(s) lumineuse(s) fluorescente(s) 22a,
• une (ou plusieurs) diode(s) lumineuse(s) à émission ultraviolet 22b (par exemple « UVOLED », acronyme de l’expression anglo-saxonne « Ultra-Violet Organic Light-Emitting Diodes »), et/ou
• une (ou plusieurs) diode(s) lumineuse(s) phosphorescente(s) 22c (par exemple « PHOLED », acronyme de l’expression anglo-saxonne « Phosphorescent Organic Light-Emitting Diodes »).

For example, each lighting device 2 may comprise:

• one (or more) fluorescent light diode(s) 22a,
• one (or more) 22b ultraviolet emitting light diode(s) (for example “UVOLED”, acronym for the Anglo-Saxon expression “Ultra-Violet Organic Light-Emitting Diodes”), and/or
• one (or more) 22c phosphorescent light-emitting diode(s) (for example “PHOLED”, acronym for the Anglo-Saxon expression “Phosphorescent Organic Light-Emitting Diodes”).

The presence of one (or more) ultraviolet emitting light diode(s) 22b allows the emission of UV-C radiation to sterilize the culture medium, and/or eliminate a contaminated culture in a compartment of the bioreactor and/or cause metabolic stress of the culture medium.

3 . 2.5 . Advantages of the lighting device according to the invention

• les pertes de charge dans le flux de circulation du milieu de culture sont réduites,
• les zones non éclairées le long de ce chemin de circulation sont limitées.

The flexible nature of the lighting device makes it possible to define a circulation path for the growing medium in which:

• pressure losses in the circulation flow of the culture medium are reduced,
• Unlit areas along this traffic path are limited.

These phenomena will now be presented with reference to Figures 8 to 10 to enable those skilled in the art to better understand the advantages associated with the use of a flexible lighting device.

• un dispositif d’éclairage 7b, 7d, 7f, 7h en contact avec le fond de la cuve 1 est adjacent à deux dispositifs d’éclairage 7a, 7c, 7e, 7g, 7i en contact avec le couvercle de la cuve 1,
• un dispositif d’éclairage 7a, 7c, 7e, 7g, 7i en contact avec le couvercle de la cuve 1 est entouré par deux dispositifs d’éclairage 7b, 7d, 7f, 7h en contact avec le fond de la cuve 1.

In reference to the , when non-flexible lighting devices 7a-7i are integrated into a parallelepiped tank 1 (of the type comprising a base, four side walls and a cover), these are conventionally arranged transversely to the length of the tank, and offset vertically to come into contact successively with the cover and the base of the tank 1. Thus:

• a lighting device 7b, 7d, 7f, 7h in contact with the bottom of the tank 1 is adjacent to two lighting devices 7a, 7c, 7e, 7g, 7i in contact with the cover of the tank 1,
• a lighting device 7a, 7c, 7e, 7g, 7i in contact with the cover of the tank 1 is surrounded by two lighting devices 7b, 7d, 7f, 7h in contact with the bottom of the tank 1.

This makes it possible to delimit a slotted circulation path for the culture medium 4.

However, such a notched shape induces the presence of “shadow zones” 8 along the circulation path, namely zones at the level of which the culture medium 4 is not (or not sufficiently) illuminated.

Furthermore, this notched shape induces pressure losses. In particular and as illustrated in , when passing between two successive slots of the circulation path, the main flow (or flux) F _p of the culture medium is subdivided, each subdivision forming a circular secondary flow F _s which recombines with the main flow F _p , then subdivides again and so on. This succession of subdivisions and recombinations of the secondary flows F _s with the main flow F _p induces pressure losses.

The flexibility of the lighting devices 2a-2j according to the invention makes it possible to bend the end of the lighting device in order to form an access path composed of a succession of segments rounded at their ends, as illustrated in .

It is thus possible to illuminate the environment at the junction between two successive segments, which reduces the “shadow zones” along the circulation path.

Furthermore, the rounded U shape (obtained by bending the end of the successive lighting devices) helps to limit pressure losses at the junction between two successive segments.

3 . 3 . Power Supply Module and Controller

As indicated previously, the power supply module 5 illustrated in FIGS. 1 and 2 makes it possible to supply the electrical energy necessary for the generation of light radiation by each light diode 22, 22a, 22b, 22c.

Each lighting device 2 can be independently connected to the electrical energy supply module 5. This allows each lighting device 2 to be individually removed from the bioreactor during operation thereof.

When the lighting device comprises a plurality of light diodes, each light diode can be individually connected to the power supply module 5. More specifically, the power supply module 5 is electrically connected to the electrodes of each light diode. This makes it possible to individually control the light radiation emitted by each light diode.

• d’activer/désactiver sélectivement chaque diode lumineuse du dispositif d’éclairage, par exemple en fonction d’un taux de remplissage du bioréacteur ; il est ainsi possible d’optimiser l’efficacité du bioréacteur ainsi que sa monté en puissance électrique,
• de définir individuellement le régime d'excitation (régime continu ou flash) de chaque diode lumineuse.

For this purpose, the power supply module 5 is in communication (wired or wireless) with the controller 6 which is configured to emit control signals allowing in particular:

• to selectively activate/deactivate each light diode of the lighting device, for example depending on a filling rate of the bioreactor; it is thus possible to optimize the efficiency of the bioreactor as well as its electrical power increase,
• to individually define the excitation regime (continuous or flash regime) of each light diode.

In addition, the presence of a controller connected to the light diodes makes it possible to detect a possible fault in one (or more) light diode(s). This detection makes it possible to locate the faulty light diode(s) in order to replace it (or them) if necessary.

When the light diode(s) of the flexible lighting device have the structure illustrated in , the controller 6 and the power supply module 5 also make it possible to individually define the emission spectrum (white light, blue, red, green, etc.) of each light diode.

Indeed, in this case, the power supply module 5 is electrically connected to the first, second, third and fourth electrodes 221, 223, 225, 227. To vary the emission spectrum of each light diode, the controller 6 controls the quantity of electrical energy supplied by the power supply module 5 to each of the first, second, third and fourth electrodes 221, 223, 225, 227, in order to modulate the intensity of the radiation emitted by each respective emission unit 222, 224, 226. By mixing, the red, green and blue light radiation emitted by the emission units then makes it possible to obtain a specific spectrum (white, yellow, violet light, etc.) adapted to a given application.

For example, the growth of a microalga of the Oscillatoria sp type is faster in the case of light radiation whose wavelengths are included in a blue spectrum. Similarly, chlorophyll and carotenoid pigments are observed at high concentrations in blue light radiation. To induce the emission of blue light by a light diode, the controller 6 commands the power supply module 5 to supply only the third and fourth electrodes 225, 227 between which the blue emission unit 226 extends with electrical energy.

The growth of a microalga of the Ankistrodesmus type is faster in the case of green light radiation. To induce the emission of green light by a light diode, the controller 6 commands the power supply module 5 to supply electrical energy only to the second and third electrodes 223, 225 between which the green emission unit 224 extends.

Lipid accumulation is high in yellow light radiation compared to other light radiation in Ankistrodesmus. To induce the emission of yellow light by a light diode, the controller 6 commands the power supply module 5 to supply only electrical energy to the first, second and third electrodes 221, 223, 225 between which the red and green emission units 222, 224 extend. The mixture of the red and green light radiation from the red and green emission units 222, 224 then produces yellow light.

It is also possible to favor the emission of light radiation in the ultraviolet spectrum in order to stimulate the production of vitamins, in particular vitamin D3.

Thus, the combination of a light diode including a stack of structures 222, 224, 226, a power supply module 5 (connected to the light diode) and a controller 6 (controlling the power supply module 5) makes it possible to modulate the emission spectrum of the light diode.

Advantageously, this modulation of the emission spectrum of the light diode can vary over time, to adapt to conditions of biomass growth and/or stress and/or production of metabolites.

• à un stade initial, moduler le spectre d’émission des diodes lumineuses de sorte à induire l’émission de rayonnements lumineux de couleur bleue afin d’augmenter la croissance de microalgues, puis
• à un stade ultérieur, modifier le spectre d’émission des diodes lumineuses de sorte à induire l’émission de rayonnements lumineux de couleur jaune afin d’augmenter l'accumulation de lipides par les microalgues.

For example, a user of the bioreactor according to the invention can:

• at an initial stage, modulating the emission spectrum of the light diodes so as to induce the emission of blue-colored light rays in order to increase the growth of microalgae, then
• at a later stage, modifying the emission spectrum of the light diodes so as to induce the emission of yellow-colored light rays in order to increase the accumulation of lipids by the microalgae.

3 . 4 . Broadcast unit

The 3 diffusion units illustrated in the allow the bioreactor to be supplied with nutrients, particularly _CO2 .

• de fournir le dioxyde de carbone nécessaire au développement du milieu de culture 4, et
• de mettre en suspension les particules supports de microorganismes contenus dans le milieu de culture.

In particular, the 3 diffusion units allow:

• to provide the carbon dioxide necessary for the development of the culture medium 4, and
• to suspend the microorganism support particles contained in the culture medium.

• sous forme de bulles de gaz, ou
• sous forme d'une solution aqueuse pompée ou poussée dans le bioréacteur.

The supply of carbon dioxide can be continuous or discontinuous in response to certain criteria such as time or pH. Carbon dioxide can be introduced:

• in the form of gas bubbles, or
• in the form of an aqueous solution pumped or pushed into the bioreactor.

The introduction of carbon dioxide in the form of gas bubbles allows a better distribution of _CO2 in tank 1.

• dans le cas de CO₂gazeux, les unités de diffusion 3 peuvent consister en des têtes de micro-bullage pour la diffusion de bulle de différents diamètres,
• dans le cas de CO₂dissout dans un milieu aqueux, les unités de diffusion 3 peuvent consister en des buses d’éjection de fluide pour la diffusion du fluide contenant du CO₂dissout.

The diffusion units 3 may be of different types known to those skilled in the art, for example diffusers made of microporous composite materials, with membrane (EPDM, silicone, etc., preferably EPDM), ceramic or slot, etc.:

• in the case of gaseous _CO2 , the diffusion units 3 may consist of micro-bubbling heads for the diffusion of bubbles of different diameters,
• in the case of _CO2 dissolved in an aqueous medium, the diffusion units 3 may consist of fluid ejection nozzles for the diffusion of the fluid containing dissolved _CO2 .

The diffusion units 3 may also comprise a membrane contactor. A membrane contactor is a device comprising at least two fluid circulation circuits separated by a transfer membrane. The fluids circulating in said membrane contactor are also referred to as circulation fluid(s). The membrane contactor thus comprises a first circulation circuit for a first circulation fluid for supplying carbon dioxide ( _CO2 ), called CO2 supply fluid in contact with a first face of the transfer membrane, and a second circulation circuit for a second circulation fluid for receiving _CO2 , called _CO2 receiving fluid, in contact with the second face of the transfer membrane. Each fluid circulation circuit is independent of one another, and may be closed or open. Such a membrane contactor associated with a reactor is described in particular in international application PCT/EP2022/087329.

Each diffusion unit 3 is preferably arranged in the immediate vicinity of the bottom of the tank 1. 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 distinct from the lighting devices 2a, 2b surrounding the other diffusion units 3. In other words, each diffusion unit 3 is separated from the closest diffusion unit 3 (or closest units) by two lighting devices 2a, 2b.

The diffusion units 3 are connected to a CO ₂ supply unit – such as a booster (in the case of gaseous CO ₂ ) or a pump (turbine type in the case of fluid CO ₂ ) – preferably equipped with a non-return valve in order to prevent the sludge or effluents from rising to the CO ₂ supply unit. Such a CO ₂ supply unit is known to those skilled in the art and will not be described in more detail below.

4 . Maintenance system

The flexible nature of the lighting device(s) contained in the tank also makes it easier to maintain the bioreactor according to the invention.

• une grue montée sur un châssis fixe ou mobile, et
• un outil de préhension 100 (crochet, grappin, ou analogue) monté à l’extrémité libre de la grue,
• une pluralité de rouleaux de guidage 101, 102 pour le déplacement par roulement de chaque dispositif d’éclairage 2.

In reference to the , an example of a maintenance system is illustrated. This system includes:

• a crane mounted on a fixed or mobile chassis, and
• a gripping tool 100 (hook, grapple, or the like) mounted at the free end of the crane,
• a plurality of guide rollers 101, 102 for rolling movement of each lighting device 2.

Each lighting device 2 comprises a gripping element (such as a cavity) intended to cooperate with the gripping tool 100 of the maintenance system. The operating principle of the maintenance system is as follows.

In a first step, the gripping tool 100 is attached to the gripping element of the lighting device 2. Once attached, the gripping tool 100 is moved in a vertical direction towards the outside of the tank 1.

In a second step, the gripping tool 100 is moved horizontally between a lower roller 101 and an upper roller 103 of the plurality of guide rollers 101, 102 arranged above the tank 1. The lighting device 2 bends 90°. An upper portion of the lighting device 2 (located between the lower roller 101 and an upper edge of the lighting device 2) then moves in a horizontal direction, while a lower portion (located between the lower roller 101 and a lower edge of the lighting device 2) moves vertically upwards.

In a third step, when the entire lighting device 2 extends horizontally between the plurality of guide rollers 101, 102, the gripping tool 100 is immobilized.

Thus, the flexible nature of the lighting device(s) 2 makes it possible to reduce the height required to extract said lighting device(s) 2 from the tank 1 for the implementation of a maintenance operation.

5 . Characteristics of the photo-bioreactor

We will now describe different aspects relating to the sizing of the bioreactor allowing optimal use of the luminous flux from the lighting devices.

5 .1. Photon capture model

To understand whether the photon flux from the lighting devices is optimally used by the mass to be treated, we propose to use a model on the capture of photons by microalgae as a function of an emission surface and 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 overall model of the surface efficiency of a photo-bioreactor is as follows:

• f_dest la fraction volumique non éclairée par conception du réacteur (fd = 0 si toute la surface du réacteur est éclairée),
• ρ_Mest le rendement énergétique maximum de conversion de l’énergie lumineuse en énergie physico-chimique,
• φ est le rendement quantique molaire de la photosynthèse,
• α est le module de diffusion linéaire,
• a_lightest la surface spécifique éclairée du réacteur sur volume,
• K correspond à une constante de demi-saturation de la photosynthèse (dépend du micro-organisme),
• ň correspond au degré de collimation moyen du rayonnement incident,
• q_nest la densité de flux moyenne de photon sur la surface du bioréacteur.

Or :

• f _d is the design unilluminated volume fraction of the reactor (fd = 0 if the entire surface of the reactor is illuminated),
• ρ _M is the maximum energy efficiency of converting light energy into physicochemical energy,
• φ is the molar quantum yield of photosynthesis,
• α is the linear diffusion modulus,
• a _light is the illuminated specific surface area of the reactor over volume,
• K corresponds to a half-saturation constant of photosynthesis (depends on the microorganism),
• ň corresponds to the average degree of collimation of the incident radiation,
• q _n is the average photon flux density on the bioreactor surface.

The maximum performance of a photobioreactor can be characterized by some simplifications of the constants in an ideal case.

• La fraction sombre« S _x », qui correspond au ratio volumique non éclairé (fd=0) : Sx = (1-fd)ln(1+q/K) en kg/m²/J
• Où q est la densité de flux moyenne de photon sur la surface du bioréacteur (s’exprime en µmolphotons/s/m²⁾, et où K est la constante de demi-saturation de la photosynthèse (30000 µmol/kgx/s),
• La production surfacique« P _x »dû à la captation du flux de photons surfacique capté : Px = Sx * a_Lumièreen kg/m³/J avec facteur correctif de 20%
• La production volumique en fonction du flux de photons surfacique capté rapporté au volume total : a_Lumière= S_Lumière/V_r, où V_rest le volume du bioréacteur_.

Therefore production will depend on the following elements:

• The dark fraction “S _x ” , which corresponds to the unlit volume ratio (fd=0): Sx = (1-fd)ln(1+q/K) in kg/m²/J
• Where q is the average photon flux density on the bioreactor surface (expressed in µmolphotons/s/m ^{2 )} , and where K is the half-saturation constant of photosynthesis (30000 µmol/kgx/s),
• Surface production “P _x ” due to the capture of the surface photon flux captured: Px = Sx * a _Light in kg/m ³ /J with correction factor of 20%
• Volumetric production as a function of the surface photon flux captured relative to the total volume: a _Light = S _Light /V _r , where V _r is the volume of the bioreactor _.

• une plaque d’acrylique de 0.1m de large et 0.1m de long
• une lumière incidente de 350µmol/m2/s,
• un volume total de réacteur de 0.008 m³,
• aucune zone d’ombre (fd=0),
• alors la productivité volumique théorique maximale est estimé à 139 mg/L/J, comme illustré par le tableau ci-dessous.

By applying the previous calculation rules for:

• an acrylic plate 0.1m wide and 0.1m long
• incident light of 350µmol/m2/s,
• a total reactor volume of 0.008 ^m3 ,
• no shadow area (fd=0),
• then the maximum theoretical volumetric productivity is estimated at 139 mg/L/J, as illustrated by the table below.

Reactor geometry case Length 0.40 m Width 0.20 m Illuminated surface 0.08 m ² Qn 350.00 µmol/m2/s K 30000.00 µmol/kgx/s Vr 0.008 m ³ In the light 10 m ¹ fd 0.00 nd Sx 0.01 Kg/ ^m2 /J Px 0.08 Kg/m ³ /J Px correction 0.13918963 Kg/m ³ /J Theoretical maximum production 139 mg/L/J

This is confirmed in an experiment using the bioreactor shown in which includes a parallelepiped tank 1, eight lighting devices of 0.1 m sides (0.01 m²) and each including a WOLED (White OLED) placed in contact on five sides of the tank.

An average production of 172 mg/L/D over 55 hours (minimum: 100 mg/L/D, maximum: 230 mg/L/D) is obtained, as illustrated in the which represents a summary graph of the productivity of a chlorella in the bioreactor illustrated in .

Adding air with 2% _CO2 ensures mixing and provides carbon.

5 . 2. Determining the optimal amount of lighting devices

The aim is to determine the optimum area for diffusion of the luminous flux for the reactor. Of course, the number and arrangement of lighting devices can vary depending on the quantity of biomass that one wishes to produce.

To produce 711 mg/L/J of biomass per ^m3 of culture in a volume of 1 ^m3 , by applying the formulas of the global modeling described above, 24 m² of lighting devices emitting 750 µmol/m²/s are necessary.

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

We obtain the following table:

Reactor geometry case Surface Column Ext 24.00 M² Q _n 750.00 µmol/m²/s K 30000.00 µmol/kgx/s V _r 1.00 m ³ a _light 24 m ¹ f _d 0.00 Nd S _x 0.02 Kg/m²/J P _x continuous 0.59 Kg/m ³ /J P _x continuous correction rdt 0.711147243 Kg/m ³ /J Theoretical maximum production 711 mg/L/J

5 .3. Determination of a maximum quantity of biomass not to be exceeded

The objective is to determine the maximum concentration of biomass not to be exceeded in order to avoid having a dark zone in the environment (i.e. maintain an f _d = 0),

In the following, we consider a bioreactor with a tank with the following dimensions: 1 meter x 1 meter x 1 meter (L*W*H in meters). The volume of the tank is therefore 1 ^m3

It is also assumed that each lighting device has dimensions of 1 meter per side and emits on both sides. The emitting surface of each lighting device is therefore 2 m².

Reactor characteristic Length - m 1 Width - m 1 Depth - m 1 Volume - m3 1

The spacing between the different lighting devices is then given by the following formula:

D = (L – E _tot ) / (½ x Nb _Plates ) = (1 - 0.06)/ (½ x 12), and d _free = D - thickness of a lighting device

• L : Largeur d’un dispositif d’éclairage ;
• E_tot: Epaisseur totale ;
• Nb : nombre de dispositifs d’éclairage ;
• D : Distance entre deux dispositifs d’éclairage,
• d : espace libre en deux dispositifs d’éclairage.

With :

• L: Width of a lighting device;
• E _tot : Total thickness;
• Nb: number of lighting devices;
• D: Distance between two lighting devices,
• d: free space in two lighting devices.

Plate characteristics Number of simple lighting devices 12 Thickness “½e” of a lighting device - m 0.005 Total thickness - m 0.06 Spacing “D” between the rear faces of two successive lighting devices - m 0.156
Free space “d” between lighting devices - m 0.145

In case the lighting devices have dimensions of 1*1 meter, twelve lighting devices are required in the bioreactor.

Arranging them in a sandwich, the total thickness of the lighting devices measures 0.06 meters.

The lighting devices are placed every 0.156 m in the middle and with a free space of 0.145 m.

It is necessary to determine the maximum concentration that must not be exceeded in order to avoid having a dark zone in the culture medium and to maintain an f _d = 0, i.e. a sufficient photon flux up to the adjacent zone.

Ideally, a concentration of 0.3 g/L/J should not be exceeded, as illustrated in the representing a maximum concentration of microalgae as a function of the spacing between adjacent lighting devices.

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

• I₀correspond à la lumière incidente,
• K_aest un coefficient d’absorption,
• B correspond à la concentration en biomasse,
• Z correspond à la longueur de la cuve.

Or :

• I ₀ 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.

If we consider that from 50 µmol/m²/s, the quantity of light is insufficient to have sufficient yields, it is possible to determine the maximum concentration not to be exceeded.

Here with 0.03 meters (due to the lighting devices placed in sandwich) the maximum concentration not to be exceeded is 1.5 g/L.

5 .4. Homogeneity of light

The homogeneity of light from a lighting device including an OLED is greater than or equal to 99%, ensuring better performance than a lighting device including an LED.

A PMMA plate with prisms has a diffusion capacity of 70% to 90% depending on the thickness and the quantity of LEDs placed on the sides.

The amount of energy to be sent to the surface is therefore less in the case of a lighting device including an OLED.

For an equivalent biomass yield per unit volume, it will be necessary to inject between 10 and 30% more electrical energy in the case of a lighting device including an LED.

5 .5. Useful volume of the bioreactor

The useful volume of the bioreactor is larger (economic advantage) with a lighting device including a flexible lighting device.

• l’épaisseur d’une plaque de pmma ou de polycarbonate peut mesurer 0.01 m et 0.08 m, et que
• l’épaisseur d’un dispositif d’éclairage flexible de 0.005 m.

This use of flexible lighting device makes it possible to optimize the useful volume of the reactor by two to sixteen times, given that:

• the thickness of a pmma or polycarbonate plate can measure 0.01 m and 0.08 m, and that
• the thickness of a flexible lighting device of 0.005 m.

5 .6. Incident angle

The homogeneity of light by the incident angle of the OLED layers of 178° in opposition to LEDs of 120°.

This ensures better homogeneity of light in the bioreactor.

We preferred to use an OLED with the widest possible angle: greater than 120°.

Indeed, it is difficult to obtain an angle greater than 120° with LEDs. This reduces the volume of culture optimized for microalgae culture.

This angle allows an improvement in the coverage of the illuminated volume of 20% compared to a classic LED plate with a power of 700 µE and 0.1 g/L of algal concentration.

The illuminated volume is therefore defined by the following formula: Illuminated volume = ((παr²)/360°) *L*n _Sides )+(L*l*h)*n faces in ^m3 .

The table below provides a comparison of the volumes illuminated with a classic LED type diode and an OLED type diode.

LED Cases r 0.385 0.195 0.13 0.1 0.08 0.065 0.055 0.05 0.045 0.04 0.035 0.03 0.03 Alpha angle 30 30 30 30 30 30 30 30 30 30 30 30 30 Total volume - m3 1,391 0.549 0.331 0.242 0.187 0.148 0.123 0.110 0098 0.087 0.075 0.064 0.064 OLED Cases r 0.385 0.195 0.13 0.1 0.08 0.065 0.055 0.05 0.045 0.04 0.035 0.03 0.03 Alpha angle 88 88 88 88 88 88 88 88 88 88 88 88 88 Total volume - m3 1.68 0.62 0.36 0.26 0.20 0.16 0.13 0.12 0.10 0.09 0.08 0.07 0.07 Gain % OLEDs VS LEDs 20.83 13.53 9.99 8.08 6.70 5.59 4.82 4.42 4.02 3.61 3.19 2.76 2.76

5 .7. Possibility to vary the distance between the lighting devices depending on the light flow in continuous or flash mode

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

Consider a system with a continuous average intensity of 1000 µmol.m ^{- 2} .s ^-1 at the lighting devices.

When this continuous average intensity is then set to flash while maintaining an average irradiance of 1000 µmol.m ^{- 2} .s ^-1 it is then possible to obtain flash waves of 10000 µmol.m ^{- 2} .s ^{- 1} .

• le temps de cycle est donné par la formule suivante : tcycle = tlight + tdark (s) / ou la fréquence (Hz)
• la fraction lumineuse est donnée par la formule suivante : φ : (tlight / (tlight + tdark ))
• l’irradiance intégrée est donnée par la formule suivante : I_m= I_f· φ

For information purposes, the illustrates the difference between discontinuous lighting 31 and continuous lighting 32:

• the cycle time is given by the following formula: tcycle = tlight + tdark (s) / or the frequency (Hz)
• the light fraction is given by the following formula: φ : (tlight / (tlight + tdark ))
• the integrated irradiance is given by the following formula: I _m = I _f · φ

• φ = 10% ;
• I_m= 1000 µmol.m^{- 2}.s^-1,
• I_m= I_f· φ µmol.m^{- 2}.s^-1,
• I_f= 10000 µmol.m^{- 2}.s^-1.

With :

• φ = 10% ;
• I _m = 1000 µmol.m ^{- 2} .s ^-1 ,
• I _m = I _f · φ µmol.m ^{- 2} .s ^-1 ,
• I_f= 10000 µmol.m^{- 2}.s^-1.

This wave of photons makes it possible to increase the distance of entry of the photons into the medium and therefore to increase the distance between the lighting devices with an identical biomass concentration.

Indeed, as illustrated in the , switching from a continuous light supply to a discontinuous light supply makes it possible to increase the distance between two adjacent lighting devices while maintaining the other parameters identical.

In reference to the , the distance between two adjacent lighting devices can be extended to 0.055 meters in flash with a concentration of 1.5 g/L.

6 . Conclusions

• l’hydraulique du photo-bioréacteur via des dispositifs d’éclairage flexibles est améliorée, notamment grâce à une optimisation du flux de circulation du milieu de culture dans certaines zones du photo-bioréacteur,
• la maintenance du photo-bioréacteur est facilitée grâce à la flexibilité des dispositifs d’éclairage,
• le volume utile du photo-bioréacteur est plus important (avantage économique) en comparaison aux solutions d’éclairage existantes,
• la flexibilité des dispositifs d’éclairage à OLED permet également d’apporter plus de lumière dans des zones mortes du photo-bioréacteur,
• l’utilisation d’une plaque et d’une couche de revêtement externe en verres minces permet
  • de diminuer l’effet de collage (« fouling ») des microalgues sur les dispositifs d’éclairage,
  • une meilleure insulation des composants électroniques entre eux, limitant les risques électriques,
  • une meilleure transmittance optique,
  • une meilleure stabilité chimique,
  • une meilleure barrière aux gaz injectés dans le photo-bioréacteur,
  • un meilleur échange des calories générées par les diodes lumineuses des dispositifs d’éclairage,

en comparaison à une couche de revêtement extérieur de pmma ou de polycarbonate.The solution described above has many advantages:

• the hydraulics of the photo-bioreactor via flexible lighting devices is improved, in particular thanks to an optimization of the circulation flow of the culture medium in certain areas of the photo-bioreactor,
• photobioreactor maintenance is made easier thanks to the flexibility of the lighting devices,
• the useful volume of the photo-bioreactor is larger (economic advantage) compared to existing lighting solutions,
• The flexibility of OLED lighting devices also allows more light to be brought into dead zones of the photobioreactor,
• the use of a plate and an external coating layer made of thin glass allows
  • to reduce the fouling effect of microalgae on lighting devices,
  • better insulation of electronic components between them, limiting electrical risks,
  • better optical transmittance,
  • better chemical stability,
  • a better barrier to gases injected into the photo-bioreactor,
  • better exchange of calories generated by the light diodes of lighting devices,

compared to an outer coating layer of PMMA or polycarbonate.

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

Claims (17)

Reactor including:

• a tank (1) intended to contain a mass to be treated, the tank (1) comprising a lower wall forming a bottom, an upper wall opposite the lower wall, and at least one side wall between the lower and upper walls,
• a set of flexible lighting devices contained in the tank and intended to promote the treatment of the mass,
• at least one electrical power supply module connected to each lighting device,

characterized in that Each flexible lighting device includes:

• a peripheral frame composed of:
  • of two flexible longitudinal edges, and
  • of two transverse borders,

each transverse edge extending between a respective pair of free ends of the longitudinal edges, and

• a flexible central sheet (52) on the edges of which the peripheral frame is mounted, the flexible central sheet (52) including:
  • at least one flexible plate (21),
  • a flexible coating layer (23) transparent to light radiation, said coating layer extending over the flexible plate,
  • a group of light emitting diodes (22, 22a, 22b, 22c) extending between the flexible plate and the flexible covering layer, said light emitting diodes being oriented so as to generate the light radiation in a direction opposite to the flexible plate.

The reactor of claim 1, wherein each light diode is a flexible organic light emitting diode (OLED), each light diode being in contact with an adjacent light diode. Reactor according to claim 1, in which each light diode is selected from a conventional light-emitting diode (LED), or a mini light-emitting diode (mini LED) , the light diodes being spaced from each other by a distance greater than or equal to 50µm. Reactor according to any one of claims 1 to 3, in which each transverse edge is flexible so that the peripheral frame is flexible in two orthogonal directions (D1, D2). Reactor according to any one of claims 1 to 3, in which each transverse edge is rigid so that the peripheral frame is flexible in a single direction (D1) parallel to the longitudinal edges. A reactor according to any one of claims 1 to 3, wherein each transverse edge includes a rigid frame (512') and a rigid strand (512'') of less length than the rigid frame (512'), the rigid frame (512') and the strand (512'') being connected by a pivot connection such that the strand (512'') is capable of pivoting relative to the frame (512'). Reactor according to any one of claims 1 to 6, in which each flexible border comprises a succession of rigid segments (513) connected together by pivot links (514) so that each segment is able to pivot relative to an adjacent segment. Reactor according to any one of claims 1 to 6, in which each flexible border consists of a bead made of a material identical to a material constituting the flexible plate. A reactor according to any one of claims 1 to 8, wherein said and at least one lighting device is of parallelepiped shape, the reactor including a rigid support structure comprising housings, each housing being intended to receive a respective flexible lighting device and being configured so as to bend the lighting device in the tank. Reactor according to one of claims 1 to 9, in which each light diode comprises a stack of structures (222, 224, 226), each structure being adapted to emit light radiation in a respective wavelength range. Reactor according to claim 10, which further comprises at least one controller (6) configured to control said and at least one electrical energy supply module (5). Reactor according to claim 11, wherein said and at least one controller (6) is configured to control a variation of energy supplied by said and at least one power supply module (5) in order to modify over time the emission spectrum of said and at least one lighting device (2, 2a-2j). Reactor according to any one of claims 11 or 12, in which said and at least one controller is configured to:

• controlling the continuous activation of said and at least one electrical energy supply module so that said and at least one lighting device (2a, 2b) generates continuous light radiation,
• controlling the discontinuous activation of said and at least one electrical energy supply module so that said and at least one lighting device (2a, 2b) generates discontinuous light radiation in the form of flashes composed of an alternation of dark phases and illuminated phases, for example at a frequency of between 10 and 50 kHz.

A reactor according to any one of claims 1 to 13, wherein the material constituting said coating layer is flexible glass. Reactor according to any one of claims 1 to 13, in which the material constituting the coating layer is a synthetic or semi-synthetic resin selected from crosslinked (meth)acrylic resins, crosslinked styrene resins, polyurethane resins, polyester resins, silicone resins, fluorinated resins, resins prepared from inorganic substances such as silica, calcium carbonate and barium sulfate. A reactor according to any one of claims 1 to 15, wherein at least two light emitting diodes of the plurality of light emitting diodes are of different sizes. A reactor according to any one of claims 1 to 16, wherein the plurality of light emitting diodes comprises:

• at least one ultraviolet emitting light diode (22b), and/or
• at least one phosphorescent light diode (22c).