WO2011007250A2

WO2011007250A2 - Industrial photobioreactor and structure of the same, of low cost and with high productive yield for occupied surface site

Info

Publication number: WO2011007250A2
Application number: PCT/IB2010/001751
Authority: WO
Inventors: Angelo Fontana; Marcello Maria Diano; Maddalena Parente
Original assignee: M2M Engineering S.A.S.; Neotica S.R.L.
Priority date: 2009-07-17
Filing date: 2010-07-16
Publication date: 2011-01-20
Also published as: WO2011007250A3; IT1402625B1; ITRM20100394A1; WO2011007250A4

Abstract

The present invention relates to a photobioreactor for industrial cultures of microalgae or other photosynthetic organisms, having low costs of manufacturing and annual operations, as well as high production yields due to the capability to obtain a large lighted surface and to install high volumes of culture for unit of occupied surface area. Said photobioreactor and the structure of the same, include a substantially cylindrical hollow element made of flexible or deformable material, upper and lower stoppers made of rigid material and placed to close the hollow element, semicylindrical upper and lower cages, so that the rigid cylindrical structure derived from the connection of the two cages, supports and contains the culture flexible chamber composed by the stoppers and the hollow element, which thus takes the form of the cylindrical structure. The industrial photobioreactor is also characterized by that the cylindrical rigid structure is fixed to a framework provided with adjustable supports to set the photobioreactor to the ground, so that the regulation of the supports allows to adapt the inclination to the horizontal plane (tilt angle) and direction to the North-South axis (azimuth angle). The Tilt and Azimuth angle are depending by the latitude, longitude, and other characteristics of the installation plant site. The device covered by this patent is the basic module for the construction of industrial large scale installations, consisting of parallel rows of "N" adj acent and parallel photobioreactors.

Description

IND USTRIAL PHOTOBIORE A CTOR AND STR UCTURE OF THE SAME. OF LO W COST AND WITH HIGH PROD UCTIVE YIELD FOR OCCUPIED SURFA CE SITE. TECHNICAL FIELD

The finding covered by said invention relates to a photobioreactor for industrial cultures of microalgae or other photosynthetic organisms, having low costs of manufacturing and annual operations, as well as high production yield due to the capability to obtain a large lighted surface and to install high volumes of culture for unit of occupied surface area.

BACKGROUND ART

It is known that unicellular photosynthetic organisms are cultured in aqueous means housed in natural environments or in artificial structures for the production of biomass from which commercial value products are obtained. Artificial cultures of photosynthetic organisms, usually algae and cyanobacteria, are much preferred because of their greater management flexibility. Massive cultures of microalgae or other photosynthetic organisms exploit two key technologies: the open ponds (Raceway Ponds) and the closed photobioreactors.

Raceway Ponds are wide and open tanks with a depth of a few tens of centimetres, usually made of concrete or rigid plastic, located in places with high exposure to the sunlight throughout the year. The ponds, supplied continuously with water and nutrients, are shuffled by rotor blades' systems in order to let the culture circulate within the pond along a predetermined path to avoid the stagnation thereof. The raceway ponds have the advantage of being cheaper and more productive than open non-dynamic culturing systems. However, they suffer a high risk of contamination from external organisms, large water losses due to evaporation and low photosynthetic efficiency (fraction of light energy converted into chemical energy during photosynthesis), which yields low biomass production for each unit of surface occupied.

In contrast, closed photobioreactors have the advantage of greater productivity for occupied surface area, due primarily to a higher photosynthetic efficiency, low water losses due to evaporation and a low degree of contamination due to the fact that access of external agents is controlled by the isolation of the cultures.

At the present state of the technique, the use of closed photobioreactors is substantially limited by the high financial costs of these installation mainly due to the high cost of transparent materials (methacrylate, glass, polycarbonate) that are used for the culture chamber, from the costs of the pumps (centrifugal and peristaltic pumps) for the forced circulation of the microalgae biomass within the culture chamber and from the costs of air temperature control plants based on immersion systems (for example cooled or heated coils), water sprays or, in a simplest but less effective manner, shading.

Said factors, together with the low utilization of the surface occupied due to the reduced volume of the cultures installed for area unit (usually described as volume of culture per hectare), determine manufacturing and management costs of the production plants that are depreciable over a span of time that does not allow large-scale industrial investments.

The state of the current technique does not offer solutions that allow overcoming these problems, making industrially accessible culturing of microalgae, both in open ponds and in closed systems, only when the biomass has a high-added value, such as in the case of substances intended for pharmaceutical, nutraceutical, cosmetic or food purposes.

However, the current status of the technique and the existing patents can not solve these critical aspects.

DISCLOSURE OF INVENTION

The finding here described aims to overcome techniques and equipments known and very well known in the field of photobioreactors for cultivation of microalgae and other photosynthetic organisms of industrial or research purposes.

One of the main tasks of said discovery consists in solving the disadvantages and problems described in the above section, thus giving rise to a photobioreactor that is characterized by high biomass yields for unit of occupied surface area.

The finding takes form of a photobioreactor that allows a high ratio between illuminated and occupied surface, thus leading to an efficient use of the occupied area in relation with the culture volumes installed on it. The discovery aims to achieve a photobioreactor that has the advantage of having low manufacturing and operating costs. In light of the aforesaid issues and others, together with and according to the invention, the present finding consists of a low-cost photobioreactor and structure of the same, which include a substantially cylindrical hollow element made of flexible or deformable material, an upper and lower rigid stopper placed on the closure of said hollow element, a lower semicylindrical rigid cage, an upper semicylindrical rigid cage complements the lower one. The rigid cylindrical structure derived from the connection of the two cages is placed to support and contain the flexible culture chamber composed by the stoppers and the hollow element, that thus takes the form of the cylindrical structure.

The industrial photobioreactor is also characterized by that the cylindrical rigid structure is supported by a metal framework to set the device on a plane. Said framework is provided of adjustable elements to regulate the inclination and position of the culture chamber in relation to the characteristics of the installation site.

The device covered by this patent is the basic module for the construction of industrial large scale plants, consisting of parallel rows of "N" adj acent and parallel photobioreactors.

With special reference to below mentioned figures, the subj ect of this patent application, is an industrial photobioreactor and its structure for massive culture of microalgae or generic unicellular photosynthetic organisms, capable to give high biomass yield per unit of occupied surface area. Said photobioreactor and structure of the same, include a substantially cylindrical hollow element ( 1 ) made of flexible or deformable material , an upper (2) and lower (3) stopper, both made of rigid material placed on the closure of said hollow element ( 1 ), a semicylindrical lower rigid cage (5), an upper semi-cylindrical rigid cage (6). The rigid cylindrical structure (7) derived from the connection of the two cages (5, 6) is placed to support and contain the culture flexible chamber (4) composed by the stoppers (2, 3 ) and the hollow element ( 1 ), which thus takes the form of the cylindrical structure (7).

The so realized culture chamber (4) limits the culture space and makes it inaccessible to external contaminant agents.

The hollow substantially cylindrical element ( 1 ) is preferably completely or partially transparent, translucent or slightly opaque, made of low cost material that allows light absorption of algal cultures and offers low porosity and roughness of the internal surface in order to permit both reduction of biofouling effects and regular washing of the photobioreactor. Said item ( 1 ) can be coloured to facilitate absorption and scattering of spectral light in order to select specific frequencies which promote the massive growth of the photosynthetic organisms. The lower part of the hollow element ( 1 ) may be provided wholly or partially with reflective material to increase and standardize, like a parabolic solar concentrator, the incident radiation throughout the volume of the culture.

According to the invention, the material of the hollow element ( 1 ) has a mechanical strength to withstand the hydrostatic and hydrodynamic load of the volume of the culture media, in relation to the angle "a" and the containment and support strength provided by the cylindrical cage (7). According to the invention, the hollow element ( 1 ) is advantageously made of a film or sheet ( I a) of flexible material folded on itself and welded to its ends, in order to form a cylinder with a substantially circular or elliptical section. The film or the sheet of flexible material will have a thickness from a few microns up to 6 mm and could be transparent, translucent or slightly opaque, coloured, reflective or semi- reflective.

Conveniently, the hollow element ( 1 ) is manufactured by using a disposable bag or a deformable and flexible sack of transparent, slightly translucent or opaque or coloured or reflective or semi-reflective plastic, with a thickness from some microns up to 2 mm.

Preferably, the flexible or deformable material of the substantially cylindrical hollow element ( 1 ) is PE, LDPE, LLDPE, HDPE, PMMA, PMA, PUR, PVC or other similar new or traditional plastic substances that match the requirements of transparency and strength necessary to house the cultures.

According to the invention, the upper stopper (2) with circular or elliptical cross-section, is made of rigid or slightly flexible plastic material that can be transparent or translucent or slightly opaque or coloured or reflective. The upper stopper is provided with plant system slots (2b) capable to house the monitoring and control devices, as well as any other sensors and equipment necessary to permit automation and operating procedures such as washing, loading and unloading of liquid and biomass, gas injection. The external surface of the stopper has two grooves of which one is to house (2a) one of the semicircle rigid elements of the cage (5b and 6b) and another one is to house an expansion collar (2c) used to tighten the hollow element ( 1 ) to the upper stopper (2). Said tight connection is carried out by inserting the end of the film, sheet or bag of the hollow element ( 1 ) between the groove of the upper stopper (2) and the expansion collar (2c), followed by the adjustment from outside of the collar in order to compress the film, sheet or bag of the hollow element ( 1 ) against the groove surface of the stopper (2).

Conveniently, said system allows easy access to the workers and technicians for the replacement of the film, sheet or bag, as well as for the maintenance of the above said technologies.

Similarly, the lower stopper (3) is composed of rigid or slightly flexible plastic material that can be transparent or translucent, slightly opaque or coloured or reflective, with circular or elliptical cross-section. The lower stopper is also provided with plant system slots (3b) able to house the monitoring and control devices, as well as any other equipment necessary to permit the automation and operating procedures, such as washing, loading and unloading of the liquid and biomass, gas injection. The external surface of the stopper has two grooves of which one (3 a) is to house one of the semicircle rigid elements of the cage (5b and 6b) and another one is to house an expansion collar (3 c) used to tighten the hollow element ( 1 ) to the lower stopper (3 ). Said tight connection is carried out by inserting the end of the film, sheet or bag of the hollow element ( 1 ) between the groove surface of the lower stopper (3) and the expansion collar (3 c), followed by the adjustment from outside of the collar in order to compress the surface of the hollow element ( 1 ) against the inner part of the lower stopper (3 ).

In relation to the type of organism and intensity of agitation required, air or other gas mixtures are inj ected through the plant system slots (2b, 3b) of the lower or upper stoppers in order to aerate and maintain in suspension the photosynthetic cells.

Conveniently, said stoppers (2 and 3 ) allow easy access to the workers and technicians for the replacement of the hollow item ( 1 ) and for the maintenance of the above technologies.

The support and containment structure (7) of the culture chamber (4) consists of a rigid semi-cylindrical lower support and containment cage (5) and a rigid semi-cylindrical upper containment cage (6).

The culture chamber (4) is lodged in the lower cage (5). The structure (7) is designed and sized according to the hydrostatic and hydrodynamic loads of the culture liquid into the hollow element ( 1 ) and the mechanical forces, as dependent on the angle of inclination "α", to which the culture chamber (4) is subjected. Upper and lower cages (5 and 6) may have a semicircular or semi-elliptical cross section, so as to define a cylindrical structure (7) with transversal or elliptical cross section.

The lower cage (5) consists of a net or a sheet (5a) together with rigid elements with the shape of semi-ellipses or semi-circles (5b). The sheet or net (5a), that are made of metal, plastic or composite, can be transparent or reflective, rigid or deformable material, with a semicircular or half-elliptic profile, so that the culture chamber (4) may assume the form designed to maximize the production efficiency. When the lower cage consists of a sheet, the material may be partially or totally reflective in order to increase and standardize, like a parabolic solar concentrator, the incident radiation throughout the culture chamber (4). Preferably, the rigid elements (5b), spaced each other to form a semi-cylindrical framework with a semicircular or semi-elliptic profile to sustain and contain the culture chamber, are fixed to the net or the sheet (5a).

Said semi-cylindrical lower cage (5) is fixed to a framework (8) provided with supports (8a, 8b, 8c) to set the photobioreactor on a plane in order to adapt the inclination with respect to the horizontal plane and direction with respect to the south.

Preferably said framework (8) consist of at least four vertical supporting telescopic bars (8a), made of low cost and high mechanical strength metal, anchored to the ground wide plates (8b). The telescopic bars are connected by longitudinal beams (8c) that are also fixed to the rigid elements (5b) of the lower cage (5 ). The number, sections, profiles, lengths of the above bars and beams are determined by structural calculation of mechanical resistance according to the weight of the culture chamber, lateral mechanical stress caused by installations in windy areas, mechanical interactions with other photobioreactors in industrial large scale installation.

Preferably the upper cage (6), that is designed to contain the culture chamber, has a semi-cylindrical or semi-elliptical shape that completely or partially cover the upper part of the culture chamber (4). The upper containment cage is designed to prevent the deformation or expansion of the culture chamber. The upper cage (6) is sized according to the mechanical forces due to the angle of inclination "α" established with respect to latitude and other characteristics of the installation site.

The upper containment semi-cylindrical cage (6) consists of a net

(6a) together with rigid elements (6b) with the shape of semi-ellipses or semi-circles. The net (6a), that is made of metal or plastic or composite, can be transparent or reflective, rigid or deformable material, so that the culture chamber (4) is above delimited by the shape designed to maximize the production efficiency.

Preferably, the rigid elements (6b), spaced each other to form a semi- cylindrical frame with a semicircular or semielliptic profile to form a containment above the culture chamber (4), are fixed to the net (6a) and secured to the connecting longitudinal beams (8c) by a rotary or generally movable joints. These said rotary or movable joints are functional to the opening of the upper containment structure (6) in case of maintenance or replacement of the culture chamber (4). In this case, the upper containment structure can be opened like a casket .

With respect to the horizontal plane, the telescopic bars (8a) allow one to regulate the inclination of the culture chamber (4) in order to set an angle "α" depending on the characteristics (latitude, longitude, shading of the surrounding area) of the installation site. The angle "α" is established to maximize the incident solar energy on the photobioreactor and then to optimize the biomass productivity. The framework (8) allows one to vary the angle "β" that the culture chamber (4) forms with respect to the South. This angle depends on the characteristics of the installation site (latitude, longitude and shading of the surrounding area). The angle "β" is established to maximize the incident solar energy on the photobioreactor and then to optimize the biomass productivity. The telescopic bars can be adjusted manually or mechanically.

Advantageously, the industrial photobioreactor and its structure for massive culture of microalgae or generic unicellular photosynthetic organisms is characterized by the fact that it forms the basic module for the installation of industrial large-scale plants, consisting of parallel rows of "N" adj acent and parallel photobioreactors according to identical angles "a" and "β". The "rows" of the photobioreactors are arranged in parallel and are separated by a space " D", calculated according to the terrestrial latitude and longitude of the installation site, in order to minimize shading between the parallel rows and thus to optimize the absorption of the solar radiation on the whole industrial plant.

The following summarizes the advantages of the invention covered by application rights:

> Volume of the culture chamber variable between 30 1 for laboratory culture and 1 5000 1 for applications on industrial or semi-industrial scale;

> Good photosynthetic efficiency for high diameters (> 80 cm) of the culture chamber; > High production yield of algal biomass for unit of occupied surface area (biomass productivity per hectare);

> Low cost of the materials used for the culture chamber, with commercial availability, great versatility and interchangeability of transparent parts;

> Low operating cost of both individual photobioreactor and production plants;

> Absence of culture recirculation pumps;

> Angle of inclination "α"(Fig. 10) adjustable in relation to the characteristics of the installation site, in order to optimize the light absorption of the photosynthetic cultures and to maximize production yield;

> Angle of direction "β"(Fig. 1 1 ) adjustable in relation to the characteristics of the installation site, in order to optimize the light absorption of the photosynthetic cultures and to maximize production yield;

> Modularity and scalability of the industrial installation made by series of photobioreactors (Fig. 12, 13 );

> Simplified recovery of microalgal biomass from the lower base of the cylinder by gravity.

BRIEF DESCRIPTION OF DRAWINGS

Other features and advantages of the invention will be included in the following description of the invention without limiting the invention to the specifics of the examples. The drawings follow the general statement of the invention, in which:

Figure 1 shows an overall front view of the finding according to the invention in which are shown the parts composing the photobioreactor and structure of the same;

Figure 2 shows an overall rear view of the finding according to the invention in which are shown the parts composing the photobioreactor and structure of the same;

Figure 3 shows an overall front view of the finding according to the invention in which are shown the parts composing the photobioreactor and structure of the same;

Figure 4 shows a detail of the lower stopper (3 ) and the containment structure (7);

Figure 5 shows a rear view of a fixing system of the lower stopper (3 ) and the hollow element ( 1 );

Figure 6 shows a detail view of a fixing system of the upper stopper (2) and the hollow element ( 1 );

Figure 7 shows a detail view of the hollow element ( 1 );

Figure 8 shows an overall view of the culture chamber (4) and its components;

Figure 9 shows an overall view of the support and containment structure (7);

Figures 10, 1 1 respectively describe the angles "α" and "β" ;

Figures 12, 13 show overall views of the industrial large scale installations; Figures 14, 1 5, 1 6 show views of the invention with details of micro and macro-injection of gas to aerate and mix the cells in the culture chamber;

Figure 1 7 shows a representation of the light scattering effect induced by micro-injection of gas;

Figure 1 8 shows a representation of the effects of the invention on growth rates and yields with the microalga Thalassiosira sp. The term

"New Photobioreactor" indicates the growth curve obtained with the use of the present invention, while the term "Traditional " indicates the growth curve obtained with a traditional annular photobioreactor;

Figure 19 shows the effect on a culture of the microalga Thalassiosira recorded with the use of micro-and macro-injection in the photobioreactor that is the subject of the present patent (New

Photobioreactor) and in a annular photobioreactor (Traditional Photobioreactor);

Figure 20 shows the increase in photosynthetic efficiency on a culture of the microalga Thalassiosira sp recorded with the use of micro-and macro-injection in the photobioreactor that is the subject of the present patent (New Photobioreactor) and in a annular photobioreactor (Traditional Photobioreactor);

Figure 21 shows the increase in major chemical components (lipids, proteins and carbohydrates) in the biomass of the microalga Thalassiosira sp. by using either the photobioreactor that is the subject of the present patent (black column, New Photobioreactor) or a traditional annular photobioreactor (gray column, Traditional Photobioreactor);

Figures 22, 23 show the driving forces and the motions generated by the combination of micro-and macro-inj ection in the invention, with a clear indication of vortices and turbulences generated;

Figure 24 shows the measurements of turbulence by using an ADV (Acoustic Doppler Velocimeter) for traditional inj ection and microinj ection in the photobioreactor that is the subject of this patent. BEST MODE FOR CARRYING OUT THE INVENTION

Advantageously the industrial photobioreactors that is the subject of this application for right, is complemented by a system for insufflation (9) (Figures 14, 1 5 , 16) of gas mixtures that agitates the photosynthetic microorganisms and controls the temperature of the liquid inside the culture chamber (4); control and automation devices for operating procedures, such as loading and unloading of the liquid and biomass; sensors to monitor chemical and physical parameters such as pH, salinity, level of biomass growth, conductivity, temperature, dissolved oxygen and absorption degree of injected gases inside the culture chamber (4).

Said insufflation technology of gas mixtures consists of a microinjection ( 12) and macro-injection ( 13 ) (Fig. 14).

The said micro-injection technology ( 12) is the subject of a separate Italian patent application filed on June 1 , 2010 with No. RM2010A000297. The micro-injection technology is composed by at least four micro- perforated tubes ( 12a) that are inserted into the culture chamber (4) through the slots (2b, 3b) of the upper and lower stoppers (2, 3) (Fig.14). Said perforated tubes are changeable and their characteristics can be varied in function of the photosynthetic species in culture. The punched surface of these tubes ( 12a) contains a large number of microscopic holes ( 12b) of 10-50 microns in diameter and with a linear density of about 1500-3500 holes per linear meter. Gas introduction through said holes generates micro-bubbles ( 12c) of dimensions ( 1 - 100 microns) comparable with the size of the cells ( 12d) in the culture chamber (Fig. 1 5).

The size and the linear density of the micro-holes, as well as the elasticity of the material used to make the tubes, are variable and can be used depending on the biological characteristics (size, cell structure, growth rate) of the photosynthetic species in culture. The result is that the micro-injection technology ( 12a) can be adjusted so that the size of the micro-bubbles is as large as the rough size of the cells, as well as the density of the micro-bubbles (number per litre of culture) is related to the number of cells at different stages of growth.

This micro-injection technology, through the division of the gaseous flow, provides the following advantages :

- increase of the contact surface between cells and injected gas;

prolong of the permanence of the gas in the culture;

- allow the efficient use of the gaseous flow to control the temperature in the culture chamber; increase the cellular absorption of gaseous components that can be metabolized (e.g. , CO2 and NOx);

induce an effect of micro-turbulence (Fig. 1 6) uniform and distributed within the culture;

- generate a flashing light-dark effect at high frequency that promotes and increases the production of biomass;

- induce the light scattering effect and the diffusion of radiation (Fig. 1 7) even in the lower layers of cells, thus prompting an effect of light-dilution and the decrease of self-shading effect of the culture;

- generate a widespread and sensitive effect of stirring that allows the massive cultivation of cells prone to lyse under physical stress (turbulence, pressure variations).

These advantages lead to increase the production yields and growth rates of cultures in comparison to traditional technologies (Figures 1 8 and 1 9), as well as to achieve massive cultures of biological species

(such as diatoms or dinoflagellates) whose cells undergo cell damage with other mixing systems (recirculating pumps and traditional air-lift).

The effects of flashing and scattering caused by the micro-injection allow a significant increase of the thickness of the culture chamber while keeping high photosynthetic efficiency.

Conveniently, said micro-inj ection technology coupled to the photobioreactor subject of this patent application, allows the use of culture chamber having a significantly increased diameter (80- 1 00 cm) while keeping high biomass productivity and photosynthetic efficiency, as a result of the efficient use of the light radiation (Figure 20). The increase of the diameter of the culture chamber allows to enhance the culture volume for occupied surface area, thus leading to improve the biomass productivity per unit of occupied surface area (total production of biomass per hectare of culture).

According to the invention, the mixing of the photosynthetic microorganisms in the culture chamber is further improved by combining said micro-injection technology ( 12) with a traditional lift-up apparatus ( 13) that produces macro-bubbles ( 13b) of 1 -3 cm in diameter (Fig. 14). The gas flow is injected into the culture chamber through the lower cap (3 ) by a nozzle or a circular hole ( 1 3 a) with a diameter of approx. 5 cm (Fig. 16). Said macro-bubbles run up to the surface of the water slipping longitudinally below the upper surface of the culture chamber (Fig. 22, 23).

The macro-bubbles ( 13b) generated by the traditional lift-up apparatus produce a hydraulic thrust along the top surface layer and parallel to the major axis of the culture chamber. The longitudinal hydraulic thrust generated by the traditional lift-up ( 1 3) combines and overlaps over the vertical hydraulic thrust generated by the microinjection ( 12). The synergistic combination of these two thrusts result in re-circulation and vortex movement that affect mainly the layers of the culture close to the upper surface of the culture chamber (Figures 22, 23). The size and intensity of these circulation motions depend on both the contribution of the two gas flows used and the angle of inclination "α". Since the vortices induce rapid mixing of the culture in the area of the photobioreactor exposed to the direct light radiation, the effect of the combination of micro-inj ection and lift-up technologies leads to a further increase in photosynthetic efficiency due to a continuous renewal of the superficial cell layer illuminated by the solar radiation (Fig. 22, 23). Said vortex motions transfer cells from shaded layers to high radiation zones, thus affecting in a positive manner the productivity of photosynthetic cultures (Figures 19, 20).

The vortex motions are regulated and controlled in order to meet the physiological requirements of the biological species in culture and to optimize the absorption of the incident light radiation.

Synergy and complementarity of the two technologies of gas injection is due to the following characteristics summarized briefly:

• the micro-inj ection creates a vertical thrust from the bottom to the top, with a turbulence generated by small low power vortices, a power fairly flat spectrum also distributed at high frequency (Figures 16, 22, 23 , 24);

• the macro-injection generates an oblique thrust with an angle "α", along the major axis of the photobioreactor and adj acent to the upper surface of the cylinder, with a turbulence generated by large vortices, concentrated at low frequency (Figures 22, 23 , 24).

Both characteristics have been evaluated experimentally in the laboratory by ADV velocimeter measurements whose results are shown below (Fig. 24).

In analogy with the micro-injection technology, ( 12) size and number of macro-bubbles are under control of an injection devise through the nozzle or the hole in the lower stopper of the culture chamber. The operating parameters can be varied according to the species under cultivation, the type of macro-turbulences and micro-turbulences desired in the cultivation, in order to achieve mixing motions to optimize biomass production and to increase in the cell growth.

In practical operations, the materials used, the form and the dimensions of the invention may be varied according to any requirements.

The well understood invention is not limited to the description given but can receive improvements and modifications by a professional without impairing the scope of the patent.

Claims

1. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, comprising:

- An hollow element (1) substantially with cylindrical shape made in flexible or deformable material;

- An upper (2) and lower (3) stopper in rigid material placed to close said hollow element (1);

- A semi-cylindrical rigid lower cage (5);

- A semi-cylindrical rigid upper cage (6) placed to close the lower cage;

characterized from the fact that the cylindrical rigid structure (7) derived by juxtaposition of the two cages (5, 6), is placed to support and contain the flexible culture chamber (4), which assumes the shape of the cylindrical structure (7), being said chamber constituted by the hollow element (1) and stoppers (2, 3).

2. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the hollow element (1) is a film or a leaf (Ia) of flexible or deformable material, wrapped on itself and welded to the extremity.

3. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the flexible or deformable material used for the hollow element (1) is as of PE, LDPE, LLDPE, HDPE, PMMA, PMA, PUR, PVC.

4. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the lower and upper stoppers (3, 2) are provided with a socket (3a, 2a), with plant system slots (3b, 2b) and with an expansible collar (3c, 2c).

5. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the rigid material used for the upper (2) and lower (3) stoppers is made of plastic or composite material.

6. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1 , characterized from the fact that the semi-cylindrical rigid cages (5, 6) of metallic, plastic or composite material, is composed by a net or leaf (5a, 6a), and by rigid elements

(5b, 6b), to a large extent of semicircular or semi-elliptic shape, spaced at fixed distance.

7. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the realized cylindrical rigid structure (7) is lodged on a framework (8) of adjustable inclination in relation to the south direction.

8. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1 , characterized from the fact that the framework (8) is equipped of supports (8a, 8b, 8c) to sustain and regulate the culture chamber inclination to the horizontal plane , which depends on the latitude , longitude, and other characteristics of the installation site.

9. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as claimed in claim 1, characterized from the fact that the said photobioreactor is the basic module for the realization of large-scale industrial plant, deriving by installation of parallel rows of "N" adjacent and parallel photobioreactors.

10. Industrial photobioreactor and structure of the same, of low cost and with high productive yield per occupied surface site, as according to how much inferable from the description and the designs.