CA2997994A1

CA2997994A1 - Bioreactors supported within a rack framework and methods of cultivating attached cultures of microorganisms therein

Info

Publication number: CA2997994A1
Application number: CA2997994A
Authority: CA
Inventors: Soheyl Mottahedeh
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-12
Filing date: 2018-03-12
Publication date: 2019-09-12

Abstract

A photobioreactor comprising a vertical framework, which supports reaction troughs, thereby creating a column of easily accessible reaction troughs. In one embodiment, the reaction troughs are constructed from vacuum molded stiff plastic. Each reaction trough is operatively associated with an illumination system that is attached to the reaction trough immediately above it. The photobioreactor includes harvesting system, comprising scraper wands that move the biomass towards the funnel positioned at the end of each reaction trough. Each trough has media, gas and nutrient supplies that are operatively associated with it. The bioreactor can be used to grow single-celled micro-organisms and other small multi-cellular organisms.

Description

BIOREACTORS SUPPORTED WITHIN A RACK FRAMEWORK AND
METHODS OF CULTIVATING ATTACHED CULTURES OF
MICROORGANISMS THEREIN
FIELD OF THE INVENTION
The invention relates to systems and methods for cultivating photoautotrophic microorganisms. The invention further relates to a photobioreactor system and method for growing and harvesting algae in a mass production environment.
BACKGROUND OF THE INVENTION
Microorganisms are very diverse and include all the bacteria, the archaea and almost all of the protozoa. They also include some fungi, algae and certain animals such as rotifers. Many macro animals and plants have juvenile stages, which are also microorganisms. A photoautotrophic microorganism is an organism that is capable of generating its own sustenance from inorganic substances using light as an energy source. As an example, photosynthetic microscopic algae, hereinafter referred to as algae, are photoautotrophs.
Algae are unicellular organisms, which produce oxygen by photosynthesis, and may include flagellates, diatoms, and blue-green algae. More than 100,000 species of algae are known.
The current energy crisis has prompted interest in alternative energy, bringing a great deal of attention to the production of algae biofuels. Beyond biofuels, commercial algae farming is also important to medicine, food, chemicals, aquaculture and production of feedstocks. One major obstacle to algae farming is the commercial scale-up for mass culture, temperature control of algae and the high cost associated with such a culture.

As a result, during the past decade, much focus has been aimed at the production of algae for commercial purposes. This focus is evidenced by the manifestation of many new industries and uses of algal production.
The vast number of different bioreactor concepts is testimony that the best algal farming bioreactors are still to be found. Most bioreactor designs are not suitable for commercial use due to cost and scale-up problems.
A closer look at the systems disclosed in prior documents people skilled in the art have strongly discouraged suspending or supporting horizontally-oriented structures above ground, particularly carrying heavy loads of liquids over suspended structures. This discouragement has been extended even further when liquids were to be carried and contained in flexible or semi-rigid containers.
Objectors have argued that such an undertaking calls for extra support costs, requires additional structural stability or may be subject to environmental risks.
Serpentine Processing: Serial Processing through the reaction chambers One strategy for replicating the effectiveness of a raceway pond within a small footprint is to vertically stack a series of horizontally-oriented reaction chambers such that the liquid media from the higher chamber flows into the one immediately below it usually following a serpentine path. The length of the serpentine path creates the length of the "raceway" for the reaction of the algae as each of the reaction chambers are linked in a series.
In U.S. Patent Number 8,372,632 Kertz teaches a method and apparatus for sequestering CO2 using algae comprising a plurality of vertically suspended bioreactors, each bioreactor being translucent and including a flow channel formed by a plurality of baffles. A culture tank contains a suspension of water and at least one species of algae and includes a plurality of gas jets for introducing a CO2-containing gas into the suspension. The culture tank is in fluid communication with an inlet in each channel for flowing the suspension through the channel in the presence of light. A pump pumps the suspension into the channel inlet.

2 In U.S. Patent Number 8,415,142 Kertz provides a method and apparatus for growing algae for sequestering carbon dioxide and then harvesting the algae including a container for a suspension of algae in a liquid and a bioreactor having a translucent channel in fluid communication with the container to absorb CO2 and grow the algae. A monitor determines the reaction of the algae in the channel. A separator separates the grown algae from the suspension and an extractor extracts biomaterials from the grown algae.
In US Patent No. 8,713,850, Seebo describes a bioreactor in the form of an algae growing assembly that comprises a plurality of growing trays vertically stacked together and retained within a transparent housing. Each growing tray is configured to flowingly transport nutrient enriched water to the growing tray positioned immediately beneath it. Each growing tray is composed of a stiff transparent plastic sheet having a pliable transparent gas permeable membrane affixed thereon. A carbon dioxide gas infusion system is fluidly connected to each of the plurality of growing trays such that carbon dioxide gas is able to (1) inflate respective carbon dioxide gas chambers, and (2) diffuse into the nutrient enriched water.
Vertical Spacing of the Trays/Shelves allows for exposure to natural light There are a series of photo-bioreactor patent documents relating to the arrangement of the vertically stacked growing trays that allows for maximal exposure to natural sunlight.
The photobioreactor disclosed by Levin in US Patent Application No.
2007/0155006 teaches the construction of a photobioreactor, which is based on application of parallel sets of multi-level troughs intended for flowing a microalgae suspension, these troughs are irradiated therewith by the sun light. The troughs are arranged in each set one above the other. The width of the gaps between the neighboring sets of the troughs is significantly larger than the width of the troughs themselves. Optical elements, which reflect and disperse the light, are positioned between the neighboring sets of the troughs. The broth with

3 microalgae is flowing from the troughs into a collecting trough and thereupon this suspension is accumulated in a tank. The suspension is supplied again from the tank by a pumping means into the feeding pipes and thereafter--to the troughs.
In US Patent Application No 2011/0300614, Tian Kian Wee teaches a photobioreactor comprising a base; a supportive frame extending upwardly from the base; a plurality of trays for culturing phototropic microorganisms, ranking vertically from a uppermost tray to a bottommost tray, supported co-axially on the supportive frame and spaced apart one and other in a predetermined gap at the vertical plane to optimize exposure to a light source; and a protective member located on top of the uppermost tray by mounting onto the supportive frame wherein the plurality of trays and the protective member are made of light permeable material.
Primarily Defined by Natural Light Sources, Supplemented by Artificial Light Sources Rusiniak in US Patent No. 8,800,202 discloses a biomass production apparatus comprising a stack of trays, each tray, in use, being in receipt of a respective layer of liquid, the layers being spaced apart from one another such that each layer has associated therewith a respective headspace. Light sources are provided for each layer and are disposed in the headspace associated with said each layer, to illuminate, at least in part, said each layer.
SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The bioreactor can be used to grow single-celled micro-organisms and other small multi-cellular organisms.

4 The foregoing has outlined rather broadly certain features of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features of the invention will be described hereinafter that form the subject of the claims. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed bioreactor. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying figures incorporated in and forming a part of the specification, illustrate several aspects of the present invention and together with the description serve to explain the principles of the invention.
FIG. 1 is a perspective view illustrating general aspects of one framework unit and harvesting system according to one embodiment.
FIG. 2 is a cross section of one embodiment showing general aspects of the lateral edge of a reaction trough and some of the associated elements.
FIG. 3 is a perspective view of a reaction trough in one embodiment.
FIG. 4 is a perspective view of an embodiment of the framework illustrating a configuration comprising three central support members positioned between the end support members.
FIG 5A is a perspective view from the second end of one column of reaction troughs supported by the framework, illustrating certain aspects in an embodiment of the design of the reaction trough, which play a role in the harvesting of the biomass. FIG. 5B shows an enlarged view of the area circled in FIG. 5A, illustrating the details of the front end of this embodiment of the photobioreactor.

FIG. 6A is a cross section of one embodiment of the a section of a central support member depicting five cantilevered arms, the top arm supporting aspects of a lighting system and the second arm supporting a reaction trough positioned over the light guide. FIG. 6B shows an enlarged view of the square area in FIG.
6A, illustrating the details of the lateral edge of this embodiment of the photobioreactor.
Fig. 7A illustrates aspects of a cross section of one embodiment of the reaction trough and light system. FIG. 7B is a cross-sectional side view of a fleece-like substrate or lofted fabric according to one embodiment having substantially continuous fiber-free pathways or channels formed thereon. FIG. 7C illustrates the warp and weft elements that create a woven substrate. FIG. 7D is a magnified photographic plan view of a knitted geotextile according to one embodiment. FIG. 7E is a cross-sectional view of the knitted geotextile sown in FIGS. 7D and FIG. 7F is an enlarged plan view of a section of the knitted geotextile shown in FIG. 7D, enlarged approximately 5 times.
FIG. 8 is a side view of key components of one embodiment of the illumination system including a light source and a light guide panel.
FIG. 9 is a plan view of a bottom surface of one embodiment of a light guide designed for even illumination with edge lighting along each longitudinal side.
FIG. 10 is a plan view of a bottom surface of one embodiment of a light guide designed for even illumination with two light input surfaces at opposite sides thereof respectively.
FIG. 11 is a plan view of a bottom surface of one embodiment of a light guide designed for even illumination with edge lighting along only one longitudinal edge of the light guide.
FIG. 12 is a plan view of a bottom surface of one embodiment of a light guide illustrating that the dots can form non-uniform patterns of light if desired for a specific application.

FIG. 13 is a plan view of a bottom surface of one embodiment of a light guide illustrating that the dots can form non-uniform patterns of light if desired for a specific application.
FIG. 14A shows a simplified side view of a "single channel" leadscrew system according to one embodiment of the harvesting system. FIG. 14B shows a simplified side view of a "dual-channel" leadscrew system according to one embodiment of the harvesting system.
FIG. 15 is a perspective view illustrating a chain-drive system with a motor according to one embodiment of the harvesting system.
FIG. 16 is a perspective view illustrating aspects of the harvesting system according to one embodiment of the harvesting system, as viewed slantwise from above.
FIG. 17 is a perspective view illustrating aspects of the "moving platform"
according to one embodiment of the harvesting system, as viewed slantwise from under (back side).
FIG. 18 is a cross sectional view through a central support member and a harvesting apparatus, illustrating how the scraper arms of the harvesting apparatus engage with the cantilevered arms of the central support members.
FIG. 19A is a side view illustration of one embodiment of the harvesting system depicting three scraping blades connected directly to support arms. FIG. 19B
is a side view illustration of one embodiment of the harvesting system depicting three scraping blades connected to lateral extensions of the support arms.
FIG. 20 is a sectional view of a portion of steel, which has been laser cut to produce 8 cantilevered arms and 8 corresponding support arms, illustrating how the central support members can be laser cut from the same piece of steel as the support arms of the harvesting system according to one embodiment.
FIG. 21 is a sectional view of a portion of steel, which has been laser cut to produce 8 cantilevered arms and 8 corresponding support arms, illustrating how the corresponding support arms and scraper blades inter-relate with the corresponding cantilevered arms supporting the reaction troughs according to one embodiment.
FIG. 22 is a sectional view of a portion of steel, which has been laser cut to produce 8 cantilevered arms and 8 corresponding support arms, illustrating how the corresponding support arms and scraper blades inter-relate with the corresponding cantilevered arms supporting the reaction troughs according to one embodiment.
FIG. 23 is a cross section of one embodiment of the bioreactor framework depicting four columns of reaction troughs and four sets of harvesting arms.
FIG. 24 is a perspective view of a photobioreactor illustrating the central horizontal cross bars that support the reaction troughs.
FIG. 25 is a cross section of one embodiment of a section of a central support member depicting multiple cantilevered arms where length of the toppest and the bottommest cantilevered arms are longer for their respective edges to be supported by a column positioned at a distance from the shorter arms for a traveling harvesting system to move in a space along edges of the shorter cantilevered arms.
FIG. 26 is a cross section of one embodiment of the bioreactor framework having toppest and bottommest cantilevered arms supported by a vertical support with a harvesting system having arms engaged over reaction troughs.
FIG, 27 is a perspective side view illustration of one embodiment of the harvesting system depicting multiple scraping blades configured as horizontally-oriented scoopers connected directly to support arms.
FIG, 28 is a perspective side view illustration of one embodiment of the harvesting system depicting multiple scoopers of FIG. 27 adopting a dumping inclined position when they reach the end of reaction troughs.

DETAILED DESCRIPTION OF THE INVENTION
A photobioreactor system and method for growing and harvesting photosynthetic organisms is disclosed in various embodiments. The framework of the photobioreactor is modular and hence may be configured to meet a number of different site requirements. Likewise, the system may be reconfigured while in use to accommodate changing needs and conditions. Hence, it is to be understood that the photobioreactor may be implemented in a number of embodiments; and while the photobioreactor will be explained with regard to some specific embodiments, other embodiments are within the scope of the invention and will be readily apparent to those of skill in the art.
However, one skilled in the relevant art will recognize that the various embodiments may be practiced without one or more of the specific details, or with other replacement and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention.
Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the invention. Nevertheless, the invention may be practiced without specific details.
Furthermore, it is understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.
Reference throughout this specification to "one embodiment" or "an embodiment"

or variation thereof means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, but do not denote that they are present in every embodiment. Thus, the appearances of the phrases such as "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

Nonetheless, it should be appreciated that, contained within the description are features which, notwithstanding the inventive nature of the general concepts being explained, are also of an inventive nature.
This photobioreactor is designed to support the reaction and cultivation of photo-autotrophic and microorganisms. The design and use of the photobioreactor will be described and taught using algae as an example. It is to be understood, however, that the photo-bioreactor can be used to cultivate photo-trophic microorganisms and is not to be restricted to just algae. For example, in some situations it may be desirable to cultivate cyanobacteria, which is a phylum of bacteria that obtain their energy through photosynthesis and therefore require a light source.
In some embodiments, a mixotropic culture system is provided wherein the culture may additionally include non-phototrophic microorganisms such as certain forms of bacteria. It may be desirable to culture such non-phototrophic microorganisms either in a mixed culture with phototrophic organisms, or separately wherein some or all of the reaction troughs are designed without a light source, or wherein the light source is simply not turned on. The parallel processing capacity exhibited by the rack support allows for a multiplicity of culturing conditions within the same footprint of floor space.
The Overview of the Photobioreactor The photobioreactor comprises a vertical framework, which supports the reaction troughs, thereby creating a column of easily accessible reaction troughs. In one embodiment, the reaction troughs are each constructed from a flexible plastic film positioned over a hard flat surface created by light guide panels that illuminates the reaction trough immediately below it or are constructed from vacuum molded stiff plastic. Each reaction trough is operatively associated with an illumination system that is attached to the reaction trough immediately above it. The photobioreactor includes harvesting system, comprising scoop pans or scraper wands that move the biomass towards the end of each reaction trough and dumps the collected microorganisms. Each trough has media, gas and nutrient supplies operatively associated with it. The bioreactor can be used to grow single-celled micro-organisms and other small multi-cellular organisms.
An introduction to certain embodiments of the photobioreactor 10 is shown in FIG. 1. and 2, wherein a photobioreactor 10 comprises one vertical framework unit assembled with reaction troughs 100 to create a rack structure. The framework unit in one embodiment comprises two vertical end-support members 16 and one or more vertical center-support members 17, connected by superior longitudinal connecting members 18 and inferior longitudinal connecting members 20. The center-support members 17 have cantilever arms 25 enabling unimpeded access from the front side 11. Some embodiments, such as the one illustrated in FIG. 3 will have two framework units combined back-to-back, such that two columns of reaction troughs (viewed from one end) are accessible from both sides of the photobioreactor 10. In another embodiment of the framework such as illustrated in FIGS. 25 and 26, the toppest and the bottommost cantilever arms 21 are longer and their edges are supported by a column 19 which location creates an open access to shorter cantilever arms 25. The embodiment of this self-standing framework provides stability to vertical center-support members 17.
Furthermore, adding support columns 19 enables center-support members 17 to carry collectively a nutrient tank above closed support member 26. The combination center-support members 17 with support column 19 create a closed cantilevered support 26 that is optionally made of two connected parts or made of a single unit as shown in FIG. 26.
A flow-through photobioreactor design will be used for the purposes of introducing the structure of a photobioreactor 10, wherein the first end 13 will be considered to be the end of the photobioreactor 10 where the inputs such as media, water, nutrients, and CO2 are stored and provided to delivery tubes (not shown) operatively attached to the reaction troughs 100. The second end 14 will be considered to be the end of the photobioreactor 10 where algae is harvested.

In an embodiment illustrated in FIG.1, the substrate 130 is distributed over a flexible impermeable plastic laid over the flat floor of a reaction trough 100. In this embodiment, culture media introduced on one side of reaction troughs 100 saturates the substrate 130 and moves through the substrate fibers by capillary action, un-affected by minor height variations along the full length and width of the substrate 130. Continuous delivery of fresh media guarantees that the substrate 130 remains saturated with fresh nutrients thereby guaranteeing that microorganisms have continuous access to fresh media.
In another embodiment of the photobioreactor 10 illustrated in FIG. 2, some of the components operatively associated with reaction trough 100 are illustrated in a cross-section view. The reaction troughs 100 are supported within the cantilevered arms 25 and positioned by edge supports 120. In this embodiment, the reaction trough 100 is a stiff plastic material, which has been vacuum molded with upward facing protrusions 114. FIG. 3 shows a surface view of one embodiment depicting a trough 100 suspended within the framework, without a substrate, such that the pattern of upward facing protrusions 114 and channels 116 wherein culture media can flow are evident. FIG. 2 shows a substrate 130, which has a textured and oftentimes "hairy" surface is placed upon the reaction trough 100, to create an extensive surface area upon which the microbiological cells can attach and grow. A wedge 122 is used to attach the longitudinal edge of the substrate 130 to the longitudinal edge of the reaction trough 130.
In an embodiment (not shown) the two lateral borders of the substrate 130 incorporate a bulged edge comprising a welting cord. These lateral bulged edges act as guides for engaging the substrate with the scoop pans 484 and also prevent the growth of microorganisms beyond the lateral borders of the substrate 130. To further reduce growth of microorganisms on the bulged edge are covered by a plastic film. To control the movement of substrate 130 during harvesting, the substrate ends are stretched.
In the embodiment shown in FIG. 2, LED's 200 are attached to an LED support plate 201 to generate edge-lighting. The supports 201 are oriented parallel to the longitudinal connecting members 18 and positioned with LED's 200 facing towards the center of the longitudinal line of the reaction trough 100 such that the light enters a light guide panel 220. The light guides 220 are positioned below the reaction troughs 100, with the lateral edges supported within the edge support 50. The combination of the LED's 200, the LED supports 201, the light reflector sheet 202 (not shown) and the light guide 220 functions as a lamp directing light in a substantially homogeneous manner downwards to the entire upper substrate surface 131 of the substrate 130 located in the reaction trough 100 immediately below.
FIG. 4 illustrates the framework for one embodiment of the photobioreactor 10 demonstrating the scalability of the system. This design could be termed a bilateral photobioreactor, wherein two framework units are placed "back to back"
and extended in the longitudinal direction by including multiple central support members 17. It can be seen that neighboring framework units share upright end support members 16 and central support members 17, which have been generated in a symmetrical mirror-like fashion. Reaction troughs 100 (not pictured) would extend continuously throughout each level of the framework 15 and would be harvested by one apparatus positioned alongside each of the open sides of a bilateral photobioreactor.
Optionally as illustrated in FIGS. 25 and 26 multiple closed support members can extend the photobioreactor 10 to a desired length.
The bioreactor 10 can be used to grow single-celled microorganisms and other small multi-cellular organisms. The disclosed photobioreactor is generally directed to use for mass culture of algal biomass in the form of attached culture being exposed to artificial light, solar light or to a combination thereof.
In one embodiment of the invention, the multilevel bioreactor is contained within a building such as a warehouse, a greenhouse, or contained within a shipping container.

The Framework The framework of the photobioreactor and its harvesting system generally defines the outer perimeter of the photobioreactor 10. It is designed to take into account the production requirements and the space capabilities of the microorganism production facility. The greater the number of cantilevered arms 25 and reaction troughs 100, the greater the quantity of biomass that can be produced on the same footprint. The number of reaction troughs 100 is dependent on the overall height of the framework and on the vertical distance provided between the reaction troughs. The distance between the reaction troughs is limited by the distance required by the illumination system and the space required for the harvesting system.
The design of the framework of the photobioreactor 10 allows the bioreactor 10 to be expandable. The selection of materials used to construct the framework will take into account factors such as weight, cost, and space considerations, etc.
In some embodiments, it may be preferable to use a material such as stainless steel or powder coated metal, as rust is a concern. In some embodiments, it may be preferable to use a weight bearing plastic, especially if weight and cost is a concern. One skilled in the art would appreciate that the strength of the materials used to construct the framework would need to be appropriate to adequately support the weight of the column(s) of reaction troughs 100.
For example, if one were to construct a relatively small and inexpensive photobioreactor 10 with only a few shelves, then a material such as plastic might be more appropriate. If on the other hand, one were to construct a large, durable photo-bioreactor for long-term industrial use, a material such as stainless steel or a powder coated metal might be more appropriate. The material may be flat, tubular or of some other appropriate shape.

The Design of the Framework In an embodiment of the photobioreactor 10 shown in FIG. 1 each framework unit will be designed with two end support members 16 located at first and second ends 13 and 14, respectively, attached to superior and inferior longitudinal connecting members 18 and 20, respectively. The height of the end support member 16 can range from about 50 cm to about 8 m. In general, the height will range from about 2.4 m to about 3.6 m. In one embodiment, the height will be between 1.0 m to 2.4 m. The length of the photobioreactor 10 can range from about 1.2 m to about 100 m long. In practice the length will be about 1.2 m to about 2.4 m. In one embodiment the length will be between about 2.4 m to 50 m long.
In the embodiment shown in FIGS. 25 and 26, each framework unit will be designed with multiple closed modular support members 26.
In embodiments where the microorganisms will be cultured within reaction troughs oriented in parallel, such that the culture media within one reaction trough only enters and exits that trough (without flowing through another trough, positioned at a lower elevation) there will generally be a front end of the photo-bioreactor where the media and inoculum enter the reaction troughs and a back end where the culture media exits the reaction trough upon harvesting. Such a flow-through photobioreactor design will be used for the purposes of introducing the structure of a photobioreactor 10, wherein the first end 13 will be considered to be the end of the photobioreactor 10 where the inputs such as media, water, nutrients, and CO2 are stored and provided to delivery tubes operatively attached to the reaction troughs 100. The second end 14 will be considered to be the end of the bioreactor 10 where the algae is harvested.
There are various embodiments of the design of the system. Harvesting can be achieved at either end of the photobioreactor 10, depending on which end better suits the overall design of the system and the environment in which it is positioned. In some embodiments the photobioreactor 10 will be configured such that the supply of inputs (gas, water, nutrients, media, etc.) will be located at the same end that the algae will be harvested from and will be delivered through pipes or tubes to the appropriate location within the reaction troughs 100. In some embodiments, the algae will be harvested from both ends of the system.
Nonetheless, one skilled in the art will understand how to appropriately modify the instructions provided for a flow-through photobioreactor to the specific design of interest.
Expandability of the Framework Units As illustrated in FIG. 4 these framework units can be combined side-by-side to construct a "bilateral" photobioreactor with two vertical racks of shelves positioned respectively back-to-back. This can be accomplished with either a common central support 17, or with the inner supports 16 connected in an appropriate manner. In some embodiments, the common central supports 17 between the two framework units are specifically configured with a mirrored symmetry to provide the central support system to two columns of reaction troughs 100. In accordance with these embodiments, the two framework units share common vertical support members 16 and central support members 17.
FIG. 24 illustrates the central horizontal cross bars that support the reaction troughs.
In the embodiment shown in FIGS. 25 and 26, expandibility of photobioreactor is achieved by placing side-by-side multiple closed vertical supports 26 and associated components.
The Reaction Troughs As illustrated in FIGs. 1, 25 and 26 a reaction trough 100 is constructed from a flexible impermeable plastic material that is laid generally flat over a rigid flat surface provided by the collection of light guide panels that illuminates the photobioreactor. Borders of the flexible plastic material are slightly elevated to prevent leakage of the culture media.

In another embodiment, as depicted in FIG. 3, a reaction trough 100 is constructed from a rigid material, which is constructed with an uneven surface allowing for protrusions 114 creating channels 116 where fluid can flow. The protrusions 114 support a substrate 130 above the channels, such that the culture media can flow below the substrate within the channels in addition to along the upper surface of the substrate. The pattern of the protrusions 114 and their placement within the reaction troughs 100 will influence the amount of media that exits the reaction trough 100 as the scraper blade 480 of the harvesting system moves longitudinally above and along the reaction trough 100 towards the end lip 150 and funnel 410 (pictured in FIGS. 5A and 5B).
In some embodiments it may be preferable to form the reaction trough 100 from one material and to overlay another layer of the same material or another material to create the surface with the protrusions 114 and channels 116 such as in bubble mats. In some embodiments, such as illustrated in FIG. 2, it may be preferable to generate the reaction trough 100 and the protrusions from the same material, such as a rigid plastic material, which has been vacuum molded with upward facing protrusions 114.
The rigid reaction troughs can be constructed from thermoformable plastic materials such as, but not limited to ABS, HDPE, HIPS, PETG, PC, Acrylic, or from metallic materials such as metallic bubble wraps.
The flexible reaction troughs can be constructed from water-impermeable polymeric sheet materials such as but not limited to PE, PP and PET.
In a traditional flow-through system, a photobioreactor may use gravity to transport the medium from one end of the system to the other end of the system.
Furthermore, gravity may be used at the end of such a traditional photobioreactor to collect the excess media and recirculate it with a pump. However, in the flow-through embodiment of this invention capillary action is being used to move culture media through fibers of substrate 130 provided with wicking properties. In such a system using capillary action, the shelves at the entry-point end may or may not be slightly higher in elevation than the exit-point end. However, to optimize this capillary action, only a small substrtae portion located at the very end of the wickable substrate 130 may be hanged or positioned lower than at entry point to allow dripping and flow through the fibers of the saturated substrate 130. At the end hanging portion of the substrate 130, excess culture media exits from the substrate fibers and can be pumped back to the other end of the substrate 130.
The Substrate In the embodiments of the present invention, the substrate 130 material can be laid over a flat surface as shown in FIGS. 1, 7B, 27 and 28 or on any rippled surface such as shown in FIG. 2.
FIGS. 2, 7A and 7B illustrate embodiments employing a substrate 130, which has an upper substrate surface 131 comprising lofted fibers 134 rendering a textured, "hairy" or fleece-like surface. The substrate 130 with lofted fibers 134 is placed upon the reaction trough 100, to create an extensive surface area upon which the microbiological cells can attach and grow. In one embodiment, depicted in FIG. 2, a wedge 122 is used to attach the longitudinal edge of the substrate 130 to the edge support 120 at the longitudinal edge of the reaction trough 100.
In an embodiment of the invention, the substrate 130 is wickable and transfers liquids along its fibers by capillary action such that the nutrient media moves through the fabric.
As known by people skilled in the art capillary action is not affected by minor height variations, therefore the culture media can move through the full length of the horizontally-oriented trough 100 and feed microorganisms positioned over the substrate 130 in a self-regulated manner. This method of feeding microorganisms with a minimal amount of cultures media is completely opposite of the large traditional amounts of media used to cultivate microorganisms such as algae. Notwithstanding that the prior method requires agitation of the aqueous media to reduce the amount of shadow on the cultivated algae and requires a serious dewatering phase to separate the suspended microorganisms from the rest of the water. Capillary action provides a measured and direct supply of nutrients to photosynthetic microorganisms such as algae and recognizes the principle that a photosynthetic process is based on surface exposure to light and not on the volume of water in which suspension of the algae occurs.
In other embodiments, the substrate 130 is porous, such that the nutrient media permeates the fabric from below to reach the microbiological organisms growing on the upper surface of the substrate. In some embodiments, a porous fabric will be used and in other embodiments, a non-porous fabric will be used but will be rendered more porous by altering its configuration. In yet other embodiments, a non-porous but wickable fabric will be used.
In one embodiment the microorganisms will be grown in a photobioreactor wherein the media, supplied from underneath the substrate will soak into the substrate keeping it continuously damp, such that the substrate will not be significantly submerged within the media. In one embodiment, the height of the longitudinal sides of the reaction troughs will be significantly higher than the upper surface of the substrate to allow for nutrient to flow both above and below the substrate, such that the substrate will be submerged within the media.
Depending on the application for the microorganisms, the substrate can be an appropriate material taking into account what is suitable for a species of microorganism and the eventual application to which the microorganism will be applied. For example, nutritional or medical applications could require a food-grade substrate, whereas other species of microorganisms and applications such as phytoremediation may require an industrial quality substrate.
In one embodiment the substrate may comprise a relatively smooth and even upper surface. In one embodiment, the upper surface of the substrate has a "fuzzy" surface, comprised of a multitude of lofted fibers 134 or "hairs,"
which facilitate attachment of microbiological organisms along the sides of each hair in order to increase yield. Various materials with a nap/pile and/or tufted surface can be used. In general, these kinds of materials will be referred to as "fleece-like."
A fleece-like material is a material with a pile or nap on at least one side.
A
common example is a flannel, which is a soft woven fabric made from wool, cotton, or synthetic fiber. The cotton in this instance acts as a wick.
Another example, Polar fleece is a soft napped insulating synthetic fabric made from polyethylene terephthalate (PET) or other synthetic fibers. It does not absorb moisture as it is hydrophobic, holding less than 1% of its weight in water.
In one embodiment the substrate will comprise a nap, a raised, fuzzy surface on certain tines of cloth following the raising process, which draws out the ends of the fibers to create lofted fibers 134 and thereby a nap. In one embodiment, the material used for a substrate will also include tufts 136, being clusters of small, usually soft and flexible hairs, attached or fixed closely together at the base and loose at the upper ends. In one embodiment, some combination of a substrate with a nap and tufts will be employed. Yarn pile height may be varied through a substrate or substantially constant through the substrate. In one embodiment a geotextile will be used as a substrate, especially when a more heavy-duty material is required. In said embodiment, wickable fibers may be woven into the geotextile.
The color of the substrate may be chosen to facilitate light penetration and/or reflectance. White, tan, or other light colors, for example, may facilitate such functions. In addition to yarn texture characteristics, other yarn characteristics may also be configured to improve microbiological growth and attachment. As one example, yarn having a high luster may increase light reflection to facilitate or improve photosynthetic activity. As another example, continuous filament yarn may be selected to provide greater strength and/or minimize or eliminate loss of filaments associated with natural or stapled fibers. Such yarn may also improve product stability during a potentially disruptive harvesting process, for example, in which algae is mechanically scraped or pulled from the product.

In some embodiments, it may be advantageous to include wickable tufts 136 to facilitate both capillary action for flow of nutrients while enabling attachment of the microorganisms. Tufts 136 can be formed of staple or filament yarns protruding as single strand portions, loops, cut-loops, or otherwise and may be made from a variety of natural or synthetic materials. A tufted product may comprise one or more different types of tufts, e.g., comprising both loops and cut loops. A tufted product may be configured with high texture and/or other yarn characteristics that facilitate growth. High texture yarn, for example, may facilitate attachment of microorganisms. High texture yarns may be formed by crimping and/or through the use of multiple filaments to provide increased surface area.
Channels in the Substrate In one embodiment, the substrate includes substrate channels 150 to promote flow of the media along the surface of the substrate. The fabric comprising the substrate includes patterns of "open" channels in the underlying panel that are devoid of the lofted fibers, which provides a substrate channel 150 free of lofted fibers. FIG. 7B is a cross-sectional side view of a fleece or lofted fabric wherein the underlying material is knitted with the lofted fibers 134 in the lofted portions.
The fabric panel also includes a plurality of substantially continuous fiber-free pathways or substrate channels 150 formed therein. The channel portion of the underlying fabric can be either discontinuous, with short substrate channels or can be a substantially continuous substrate channel 150 that is substantially devoid of lofted fibers along the entire continuous length of the reaction trough 100.
Certain embodiments involve yarn tufts 136 spaced to balance the objective of providing increased surface area for algae growth and attachment with the objective of allowing water flow amongst the yarn tufts. The tufting pattern can be such that substrate channels 150 are formed within the substrate encouraging the flow of fluid media through the channels.
Geo textile Geotextiles are permeable fabrics consisting of synthetic fibers rather than natural ones such as cotton, wool, or silk. They are typically made from polypropylene or polyester. These synthetic fibers are made into flexible, porous fabrics by standard weaving machinery or are matted together in a random non-woven manner. Some are also knitted. Geotextiles are porous to liquid flow across their manufactured plane and also within their thickness, but to a widely varying degree. The knitted structure of the geotextile is configured to have a porosity that allows the passage of a fluid such as water there through and that retains fluid-suspended solids, such as microorganisms, thereon. The combination of the knitted structure with the polyester and polypropylene materials of construction provides a durable geotextile that is resistant to ultraviolet degradation.
FIGS. 7C, 7D, 7E and 7F are used to illustrate one example of a woven geotextile demonstrating some of the kinds of design features that may be taken into account. FIG. 7C shows the basic pattern to a woven fabric comprising warp 138 and weft fibers 140. In general, a woven geotextile includes in general a plurality of continuous load bearing fibers, also known as yarns, that are inlayed into the structure substantially parallel to each other across the width of the fabric and substantially parallel to each other across the length of the fabric, and a grid-like structure of knitting fibers, also known as yarns, that hold the load bearing fibers in position. FIG. 7D shows a knitted geotextile including a pattern of oriented warp fibers 138 positioned substantially parallel to each other, a pattern of oriented weft fibers 140 positioned substantially parallel to each other and substantially perpendicular to the oriented warp fibers138.
In one embodiment, as shown in FIGS. 7E and 7F, a geotextile can also include a nonwoven fleece 148, and oriented knitting fibers 142 that interconnect the warp fibers 138, the weft fibers 140, and the nonwoven fleece 148 as a knitted structure. The pattern of weft fibers 140 overlays the pattern of warp fibers and the nonwoven fleece 148 overlays the pattern of weft fibers 140. A
configuration that incorporates the nonwoven fleece 148 as part of the knitted structure, the geotextile is able to retain even fine-grained material (i.e., smaller microbiological organisms) A knitted geotextile provides an open mesh that includes a plurality of apertures or openings 146 resulting from the pattern of oriented warp fibers 138 positioned substantially parallel to each other that is overlaid with the pattern of oriented weft fibers 140 positioned substantially parallel to each other and substantially perpendicular to the oriented warp fibers 138. The knitted structure is configured to have a porosity that allows the passage of a fluid such as water and nutrient to the upper substrate surface 131, while retaining the microbiological organisms on the upper substrate surface 131.
As shown in FIG. 7F, each warp fiber 138 has an undulating configuration. The warp fibers 138 have a pattern of repeating opposed minor undulations across a centerline of the warp fiber. One function of the undulating warp fiber configuration, also known as "relaxation in the stitch," is to provide a location 141 at which adjacent warp fibers 138 are in relatively close proximity to each other such that the warp fibers can be secured to one another with the knitting fiber 142. The undulating warp fiber configuration enhances the structural integrity of the resulting geotextile. Moreover, fabricating the geotextile with weft insertion knitting with fleece capability, not only are the warp fibers 138 and weft fibers 140 connected by the knitting fiber 142, but the nonwoven fleece 148 is knitted into the geotextile as well.
The materials of construction of the oriented fibers, i.e., the warp fibers 138, the weft fibers 140, and the knitting fibers 142, can be selected from, for example, polyester, polypropylene, polyethylene, coir, sisal, jute, flax, nylon, Kevlar , aramid, carbon, and glass. The materials of construction of the non-oriented fibers, i.e., the fibers of the nonwoven fleece 148, can be selected from, for example, polyester, polypropylene, polyethylene, coir, sisal, jute, flax, and cotton for acting as a wickable material. The geotextile can be constructed of various combinations of the warp fibers 138, the weft fibers 140, the nonwoven fleece 148 fibers, and the knitting fibers 142 that represent various combinations of the aforementioned fiber materials of construction. According to still another possible embodiment of the invention, the knitting fibers 142 can be constructed of a non-oriented fiber.
Although the knitted geotextile has been described as including the nonwoven fleece 148, other embodiments of the invention that do not include the nonwoven fleece are possible. For example, the knitted geotextile can simply include a pattern of oriented warp fibers 138 positioned substantially parallel to each other, a pattern of oriented weft fibers 140 positioned substantially parallel to each other and substantially perpendicular to the oriented warp fibers 138, and oriented knitting fibers 142 that interconnect the warp fibers 138 and the weft fibers as a knitted structure.
The Illumination System In one embodiment, the biomass is illuminated using a system comprising a light guide with LEDs positioned along one or more edges of a light guide. In some embodiments a light guide panel is used. In some embodiments a light guide film is used.
Light Guides Illuminate Uniformly Light travels throughout the panel or film, staying within the guide due to total internal reflection at its front planar surface and back planar surface. This light applied into the light guiding panel or film is repeatedly reflected between a light exit surface (upper surface) and a reflective surface (lower surface) of the light guiding panel or film. When the angle formed between the reflected light and the normal line to the light exit surface is smaller than the critical angle, the reflected light permeates and exits through the light exit surface. In order to direct the light to exit the light guide, light may be directed out of the guide by an extraction feature located at specific places on the panel or film.
For example, the light incident through the side face of the light guide plate is diffused by action of a light distribution pattern provided on the back side of a light guide plate or film (e.g., a light distribution pattern comprised of light scattering dots). Light components with angles of not less than the critical angle emerge from an exit surface of the light guide plate, thereby supplying the surface light. For making the luminance of its light emission surface uniform, the light guide plates are provided with such gradation as to change the density of the light distribution pattern from coarse to dense with distance from the light source.
FIG. 8 illustrates the basic elements of a light guide system, wherein the light source, in this case an LED 200 is positioned at the edge of the light guide (in FIG. 8, the light guide is a panel). The light guide is a rectangular sheet and includes at least a first light input surface 222, a light output surface 224, adjoining the light input surface 222, a bottom surface 226 opposite to the light input surface 222, and an arrangement of dots 228 formed on the bottom surface 226. The LED 200 is positioned adjacent to the light input surface 222. A
material of the light guide is selected from the group consisting of polymethyl methacrylate (PMMA), polycarbonate (PC), and other suitable transparent resin materials. In one embodiment the light guide is made of pure acrylic PMMA
resin.
FIG. 7 shows an embodiment comprising a light reflector sheet. It is generally a flat film of white color and can be of any water-resistant or waterproof material resistant to molds and microbes.
FIGS. 9 to 13 illustrate that different patterns and shapes of dots can be used to create the illumination pattern that is optimal for the species of microorganism of interest, wherein various arrangements of the dots 228 on the bottom surface 226 of the light guide panel 220 is shown. The dots 228 are used to diffuse light incident thereon. The dots 228 are arranged in a series of adjacent columns, all of which are parallel to the light input surface 222. Each column contains a line of adjacent dots 228.
The distance between adjacent column axes 232 (FIG. 11) is configured vary according to varying distances of the columns from the light input surface 222, 223, and the dots 228 in a same column are arranged closely together.

Therefore, even though the dots 228 in columns near the light input surface 222, 223 are relatively small, a clearance between adjacent columns near the light input surface 222 can be configured to be very small. Thus a great majority of the bottom surface 226 is used for light diffusion, and the dots 228 near the light input surface 222 provide efficient dispersal of light rays incident at that part of the bottom surface 226. Further, each dot 228 in each column is offset relative to the adjacent dots 228 in each of the adjacent columns. There are no straight clearances between adjacent rows of dots; and therefore there are no corresponding bright lines in the output light.
In FIGS. 9 and lithe dots 228 are square when viewed from directly below. In FIGS. 9, 10, and 11, the dots 228 within each column have a same size, and are closely adjacent each other in a same column and the distance between centers of two adjacent dots 218 in a same column is constant.
FIGS. 9 and 10 illustrate light guides 220 wherein the system includes a first and second light input surfaces 222, 223 at two opposite sides thereof respectively.
Sizes of the dots 228 increase with increasing distance of the columns from the first light input surface 222 to the center axis 230. Sizes of the dots 228 increase with increasing distance of the columns from the second light input surface to the center. A distance between two adjacent column axes increases with increasing distance from the first light input surface 222 to the center axis, and a distance between two adjacent column axes increases with increasing distance from the second light input surface 223 to the center axis. It is to be understood that if the light sources have different light outputted brightness, any suitable axis between the two light input surfaces 222, 223 can be defined instead of the surface center axis 230.
In FIG. 11 illustrating a light guide with the light source positioned only on one side (the light input surface 222 is on the left side of the sketch) the distance between two adjacent column axes progressively increases with increasing distance from a leftmost column nearest the light input surface 222 to a rightmost column furthest from the light input surface 222. The size of the dots 228 in each column progressively increases with increasing distance of the columns from the leftmost column nearest the light input surface 222.
The sizes of at least some of the dots 228 in each column can be configured to be different from each other, according to a position and/or a distribution of the light source 200. As illustrated in FIGS. 12 and 13, the sizes of the dots 228 in a same column progressively increase or decrease along the length of a column.
An area of the dots 228 when viewed from directly below is preferably in the range from about 1 x 10-7 square millimeters to about 1 x 10-4 square millimeters.
The array of the dots 228 are manufactured by printing or chemical etching with a pattern mask. A material of the dots 228 can be selected from a group consisting of printing ink or a suitable modified printing ink. The modified printing ink is formed by uniformly dispersing a plurality of scattering particles into a printing ink matrix material. Alternatively, the dots 228 can be configured to be micro-scattering structures etched on the bottom surface 226.
The Gas Delivery System It is well known that absorption efficiency of gas bubbles by a liquid is a function of the contact time. Thus, efficient CO2 gas absorption will occur in an apparatus designed to generate the prolonged contact of substantially uniform size bubbles with the water. One example of such an apparatus is a downf low bubble contact aeration apparatus as described in US. Patent No. 3,643,403.
One embodiment of such an apparatus comprises submerging a downwardly diverting funnel of uniform slope as shown enclosing a flow chamber having an increasing flow area in a downward direction. A forced downf low of water through the flow chamber is induced by rotation of an impeller located at the upper inlet end of the flow chamber operatively connected to the upper inlet of the flow chamber in order to conduct a downf low stream of water from the inlet end of the flow chamber to the larger outlet end with the velocity of the water decreasing from a maximum value at the inlet end to a minimum value at the outlet end. In one embodiment, the apparatus is constructed such that an appropriate hydrostatic head forces the downf low of water through the funnel.

A suitable source of CO2 under a static pressure greater than that of the water is provided and mounted at a suitable location for supply through the conduit to a gas bubble disperser located within the chamber in spaced adjacency below the impeller at the inlet end. Thus, gas bubbles are continuously injected into the downflow stream of water conducted through the flow chamber. The upward buoyant velocity of the gas bubbles emerging from the bubble disperser, is less than the downward velocity of the water so as to prevent any escape of bubbles from the upper end of the apparatus. The bubbles are accordingly conveyed downwardly. However, as the bubbles approach the lower outlet end of the flow chamber, the decreasing velocity of the downf low of water becomes less than the upward buoyant velocity of the bubbles. Accordingly, the gas bubbles are "trapped" inside the flow chamber for a prolonged contact time. Bubbles of relatively uniform size are eventually displaced from the lower end of the flow chamber, out of the influence of the downf low, by virtue of the continuous injection of bubbles causing "crowding" of the bubbles at the lower outlet end.
Following such a process of carbonation, nutrients are added to the water.
This carbonated medium is then circulated in the channels throughout the reaction troughs and soaks into the substrate, supplying water, nutrients and CO2 to the microorganisms growing on the superior surface of the substrate.
In one embodiment, CO2 gas is mixed with the air that is circulated throughout the room or structure (e.g., shipping container) containing the photobioreactor in a manner that effectively delivers air/CO2 to the microorganisms growing on the surface of the substrate, due to the positive pressure of the air/CO2 created therein.
Following such a process of carbonation, nutrients are added to the water.
This carbonated medium is then circulated in the channels throughout the reaction troughs and soaks into the substrate, supplying water, nutrients and CO2 to the microorganisms growing on the superior surface of the substrate.

In one embodiment, CO2 gas is mixed with the air that is circulated throughout the room or structure (e.g., shipping container) containing the photobioreactor in a manner that effectively delivers air/CO2 to the microorganisms growing on the surface of the substrate, due to the positive pressure of the air/CO2 created therein.
The Nutrient Delivery System In one embodiment, the nutrient is circulated by using a capillary action to move the aqueous media through the fibers of a wickable substrate. To optimize this capillary action, only the end portion of the substrate is positioned at a slightly lower height than at entry point or is hanged to allow dripping and flow through the fibers of the saturated substrate.
In another embodiment, the nutrient is circulated under the substrate within the trough channels. The height of the trough is configured to provide a flow level that exceeds the level of saturation of the substrate and therefore able to continue to circulate excess medium passing through the trough channels under the substrate until it exits from the other end of the substrate without losing its potency. This excess medium feeds microorganisms such as algae located in another tray either adjacent to this first tray or located under it. In this embodiment, tubes are not required as the trough channels act as the delivery means.
In one embodiment, nutrients may be delivered to the reaction trough by delivery tubes, positioned internal, external or some combination thereof to the reaction troughs. These tubes may augment the flow of nutrients within the trough channels and may deliver the nutrient medium along the upper surface of the substrate, or below it into the trough channels.
The amount of nutrient that is delivered in the embodiment using a capillary action or using simple irrigation is controlled by a computerized controller that operates a peristaltic pump. To determine how much nutrient is required, a number of sensors log continuously the amount of oxygen released by the culture under controlled temperature, pH and carbon dioxide levels (in the form of water dissolved carbon) all based on a known amount of delivered nutrients.
This knowledge verifies the amount of nitrogen and carbon that has been delivered to the culture and is matched against the amount of nitrogen and carbon present in the harvested biomass. This collection of knowledge is translated into a single reading of the amount of oxygen released daily by the biomass, which in turn will determine the amount of nutrient the pump will deliver.
The Biomass Harvesting System In certain embodiments a harvesting system will be employed that comprises scoop pans 484 or scraping blades 480 supported by arms which are supported by a vertical support positioned on a travelling platform. In one embodiment, the travelling platform moves longitudinally alongside the open side of the framework causing scoop pans to scoop microorganisms cultivated over the substrate and dump the collected load when reaching the reaction trough end. In another embodiment, scraping blades scrape the substrates within each reaction trough causing biomass to move towards funnels located at the connection end of the framework.
In practice only 30% to 50% of the production is harvested at any time, leaving behind enough inoculum to grow for the next harvest.
The Travelling Platform In some embodiments, a leadscrew system with a nut assembly is used to move the travelling platform alongside the open side of the framework. A leadscrew is a screw, or threaded rod, that may be used, in conjunction with a corresponding nut, to convert rotational motion into linear motion. In a typical leadscrew system, a leadscrew is coupled to a motor that rotates the leadscrew. As the leadscrew rotates, the corresponding nut, which is screwed onto the leadscrew and also connected to a guide rod, moves up or down along the leadscrew shaft. The direction of the nut's linear motion depends on the leadscrew's direction of rotation and thread characteristics.
FIG. 14A shows a simplified side view of such a leadscrew system comprising leadscrew 426, motor 428, corresponding screw nut 430, guide rod 432, collar 434, connecting strut 436, and end support 438. Motor 428 and guide rod 432 are rigidly attached to end support 438. Leadscrew 426 is (i) parallel to guide rod 432 and (ii) connected to motor 428 so as to be rotated by motor 428 relative to end support 438, as indicated by rotational directions 426a and 426b. The thread of screw nut 430 complements the thread of leadscrew 426. The materials of leadscrew 426 and screw nut 430 are such as to allow them to have relatively low-friction interaction and, consequently, allow leadscrew system to have relatively efficient translation of the rotational motion of leadscrew 426 into corresponding linear motion of screw nut 430. The materials and shape characteristics of guide rod 432 and collar 434 are such that collar 434 can slide along guide rod 432 with relatively low friction. Collar 434 may comprise a bearing or a guide. Connecting strut 436 rigidly connects screw nut 430 to collar 434 so that screw nut 430 does not rotate when leadscrew 426 rotates, but, instead, screw nut 430 moves linearly along leadscrew 426. This allows for relatively precise control of the linear motion and placement of screw nut 430 relative to base end supports 438. The travelling platform 424 is attached to the superior surface of screw nut 430 and the vertical support 420 of the harvesting apparatus is attached to the superior surface of the travelling platform 424.
If leadscrew 426 rotates in direction 426a, then screw nut 430, along with connecting strut 436 and collar 434, moves away from end support 438, while, if leadscrew 426 rotates in opposite direction 426b, then screw nut 430, along with connecting strut 436 and collar 434, moves toward end support 439.
FIG. 14B illustrates one embodiment employing two guide rods for further stability, for example when a bilateral harvesting apparatus is employed servicing two columns of reaction troughs 100, the system further comprises (i) leadscrew 426, (ii) guide rods 432 and 433, and (iii) end supports 438, 439, which hold and stabilize leadscrew 426 and guide rods 432 and 433. The system can either include a motor configuration as in FIG. 14A, or it can include a different motor configuration as depicted in FIG.14B., with motor 442, gear 440, and gear 441.

Motor 442 drives gear 440, which, in turn, drives gear 441. Gear 441 is mounted on leadscrew 430 so that when motor 442 is operating, leadscrew 426 is rotated by motor 442 via gears 440 and 441.
In one embodiment illustrated in FIG. 15, a motor-driven chain-drive moves the harvesting apparatus forward or backward along a rail. In this chain-drive system, a sprocket gear attached to the motor, forces a transmission chain to travel along a rail and return to its original position after passing around an idler-wheel positioned at the end of the rail. The movement of the chain is transmitted to the harvesting system. In one embodiment, this chain drive can be positioned in an elevated position located above the harvesting apparatus 402, with an inverted travelling platform 424 attached thereto supporting the harvesting apparatus from above. In one embodiment, the motor-driven chain drive is positioned at the bottom of the photobioreactor, in a manner that is similar to the embodiments depicted in FIGS. 16 and 17 for the travelling platform powered by a leadscrew system.
FIGS. 16 and 17 illustrate one embodiment of the harvesting apparatus 402 mounted on the travelling platform 424, supported by two guide rails 432, 433.

FIG. 16 is a perspective view showing the harvesting apparatus 402 mounted on the vertical adjuster unit 444, according to the first embodiment, as viewed slantwise from above. The travelling platform 424 travels on the guide rails 432, 433.
FIG. 17 is a perspective view showing the travelling platform 424, according to the first embodiment, as viewed slantwise from under. The leadscrew 426 is arranged in a manner to be interposed by the two guide rails 432, 433, and torque of the ball leadscrew 426 moves the travelling platform 424 through the screw nut 430 mounted to the underside of the travelling platform 424. The wheels 446 mounted to the underside of the travelling platform are arranged in a manner to travel on the guide rails 432, 433.
The Scraper Blades & Scoop pans Scraper blades 480 can be positioned and attached to support arms in one of a number of possible configurations. FIG. 18 illustrates one embodiment where the scraper blades 480 are attached directly to the support arms 482. In one embodiment, using the same configuration as depicted in FIG. 18, no scraper blades are used and the scraper arms are used to collect the biomass. FIG. 19A

illustrates one embodiment where the scraper blades 480 are attached to the ends of the support arms 482. FIG. 19B illustrates one embodiment where scraper blades 480 are attached to extensions of the support arms 482.
FIG. 20 illustrates how, in one embodiment, the central support members 17 can be laser cut from the same steel as the harvesting apparatus 402. The central support members 17 have a flat surface on the upper edge of the arm, whereas the scraper arms 422 on the harvesting apparatus 402 have a flat surface on the lower edge of the scraper arm 422. In one embodiment, blades are made of flexible materials such as rubber or of silicon rubber.
FIGS. 18, 21 and 22, depict how the scraper arms 424 of the harvesting apparatus 402 interact with the reaction troughs 100 and the central support members 17.
FIGS. 27 and 28 illustrate an embodiment of scoop pans in which scoop pans 484 are configured in the shape of horizontally-oriented pans that cooperate hingingly with harvester arms 482 in a manner that, when reaching the end of reaction troughs 100, they tilt and adopt an inclined position for dumping their biomass content as depicted in FIG. 28.

Automated Continuous Harvesting As illustrated in FIG. 16, the vertical support 420 is mounted on a cart 424 that moves the vertical support along the shelves to operationally engage the scraper blades 424 or the scoop pans 484 with the substrate 130 while collecting the biomass.
A Bilateral Scraper Arm Configuration FIG. 23 is a cross section of one embodiment of the bioreactor framework depicting four columns of reaction troughs and four sets of harvesting arms.
In one embodiment a bilateral scraper arm configuration is used wherein the upright support has arms directed in180 degree orientation and the travelling platform is positioned between two columns of reaction troughs, the harvesting system will be configured to scrape and collect biomass from two columns at the same time.
Parallel Processing of Reaction Troughs Having multiple reaction troughs so densely located next to each other enables one to subject algae to collaborative processes including extreme environmental conditions and shocks that stimulate algae reaction. Such environmental treatment may include subjecting the algae to high or low electromagnetic fields, high or low flashes of light, flashes of heat, exposure to sound waves, and a combination thereof. As an example, a plurality of upper levels of reaction troughs may be engaged in culture of an algae species receiving air, CO2 and nutrients, whereas one or more lower levels of algal medium may be cut off from nutrients to undergo a starvation process forcing them to transform their biomass into oil, and finally one or more of the lowest levels may be used as transfer surfaces to maintain continuity of the process.
To engage different individual troughs or groups of reaction troughs to perform different tasks or processes in a same photobioreactor, valves may be opened or closed manually or automatically enabling fluid flow in a reaction trough in a vertical downward direction (for example to maintain fluid at a predetermined level in the trough), in a horizontal sideways direction from left to right or vice-versa (for example, between adjacent reaction troughs), or follow a pattern programmable by a controller means (not shown).
In the disclosed photobioreactor, biofilm or attached culture in a reaction trough may be removed by displacing manually, automatically or by pressure differential means a movable cleaning head (not shown) over the reaction trough surface.
To achieve this, a scraper-shape cleaning head may be used.
The Optional Dewatering System After stopping culture media, dewatering is achieved by slow gravity permeation of the extra water using capillary force through the body of the substrate towards a lower hanging portion of the substrate one end or both ends and by channeling the collected water away from the substrate. The level of water content of the harvest is controlled by the amount of nutrient or the lack thereof provided by the photobioreactor feeding system.
The Thermal Regulation System In certain embodiment, the bioreactor may include a thermal regulator system to maintain the temperature of the culture within the reaction trough(s) within a predetermined range. In one embodiment of invention as illustrated in FIG. 2, thermal regulation of the reaction trough 100 is provided by two different means.
Heating or cooling is provided by increasing light intensity of the LED system (200) or lowering the temperature of the LED water cooling system (not shown), which in turn generates more or less heat that can be transmitted to the metal profiles 120 supporting the reaction troughs. Cooling is also provided by displacing ambient air over the substrate. It is known that air movement over a wet surface causes faster evaporation and reduces surface temperature.

The Optional Fluid Collector In certain embodiments, the bioreactor may optionally comprise a fluid collector to collect spills, overflow, leaks and the like. In some embodiments, the fluid collector channels and collects water from spills or leakage from the reaction troughs, and comprises a waterproof sheet loosely stretched between the opposing sides of the framework, positioned at the lowest level of the photobioreactor. The waterproof sheet is further provided with a drainage means (such as a funnel collector) connected to hoses that carry water spills away.
Optional Processing Systems In certain embodiments, the photobioreactor provides a controlled environment in which multiple parallel or serial processes may occur within a reaction trough of the photobioreactor itself or in association with equipment and accessories that are in air or fluid communication with reaction trough, or are introduced in said reaction trough. As an example, in some embodiments, the reaction trough may be configured to support multiple strips of substrates of different materials some functioning as filtering membranes. When dealing with fluids of different densities, internal layers may transfer or filter fluids via osmosis or reverse osmosis.
In another example, introducing carbonated water into the algal medium creates micro bubbles that separate solids from liquids and lift agglomerated cells over the fluid surface making harvesting of nnicroalgae easy as a simple skimming process. Other processing steps within the bioreactor reaction trough may include electro flocculation, bioflocculation, biofloatation, fermentation, lysing, hydrogenation, localized heat treatment, localized light flash treatment, localized high or low magnetic field treatment; some of said processes causing stresses that may increase biomass productivity or influence it.
The Biomass Monitoring System The compactness provided by the present multilevel bioreactor improves monitoring and control of factors that influence generally the operation of a bioreactor. Such factors include temperature, light, pH, agitation, gas flow and liquid flow and physical factors of the like.
The Optional Outer Protective Cover In some situations, it may be desirable to include an outer protective cover to the photobioreactor. Such a cover may be as simple as a tarp securely attached over the outer frame, a greenhouse structure or as secure as a steel container, such as a shipping container. The cover may be provided with a reflective material that reflects LED light back towards the reaction troughs.
Some embodiments of photobioreactor are adapted to operate indoors, inside a warehouse, a shipping container or inside any other closed structure or building.
In one embodiment of the invention, the multilevel bioreactor is surrounded by a circular-shape greenhouse in which the lower portion of the cover close to the ground takes on a parabolic shape covered by a reflective material.
In one embodiment, the photobioreactor is configured to operate outdoors, protected from weather conditions under structures such a greenhouse or an inflatable structure. In one embodiment, the photobioreactor is located at the center of a tunnel-shape greenhouse with the cover being adapted to provide optimum photosynthetically active radiation (PAR) within wavelengths ranging about 400nm to 700nm with about 95% light diffusion. The lower portion of the greenhouse is provided with a reflective portion having a parabola-shape configuration. The reflective material comprising the reflective portion may be flexible or semi-rigid and is adapted to reflect incoming light towards the reaction troughs. In one embodiment, the outer protective cover is a geodesic building.
In one embodiment of the photobioreactor is encased and installed in a steel structure such as a shipping container. Grouping multiple shipping containers together can quickly scale-up the production capability of an algae production facility.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A photobioreactor for culturing at least one of phototrophic and mixotrophic microorganisms comprising:
a plurality of horizontally-oriented generally flat reaction troughs composed of a water-impermeable material, a porous substrate distributed over each reaction trough having wicking fibers for liquids to travel along the surface of the fibers by capillary force, and a support structure comprising a framework defining first and second sides and a first and second end, and configured to support the plurality of reaction troughs in horizontally oriented vertically spaced relation, each of the reaction troughs extending from the first to the second end of the framework.
2. The photobioreactor according to claim 1, wherein the framework reaction trough support comprising horizontally-oriented cantilevered arms.
3. The photobioreactor according to claim 1, wherein the plurality of cantilevered arms are configured to enable access to the reaction troughs from one side.
4. The photobioreactor according to claims 1, 2 and 3 wherein the length of the toppest and of the bottommest cantilevered arms are longer for their respective edges to be supported by a common column; the space created between the shorter cantilevered arms and the column enabling a traveling harvesting system to move along the edges of the shorter cantilevered arms.
5. The photobioreactor according to claim 1, wherein the substrate comprising lofted fibers on the upper surface of the substrate.
6. The photobioreactor according to claim 1, wherein the substrate comprising tufts.
7. The photobioreactor according to any ones of claims 1 and 6, wherein the substrate comprising a combination of lofted fibers and tufts.

8. The photobioreactor according to claim 1, wherein controlled feeding of microorganisms is achieved by controlling the amount of medium moved by capillary action through the porous substrate.
9. The photobioreactor according to claim 1, wherein capillary action through the porous substrate overcomes minor height variation along the length and width of the reaction troughs.
10. The photobioreactor according to claim 1, wherein microorganisms attach to the substrate surface while fresh medium moves through the porous substrate.
11. The photobioreactor according to claim 1, wherein the framework comprises two vertical end-support members and, optionally, at least one vertical center-support member for supporting the plurality of reaction troughs, wherein the center-support member comprises a plurality of arms configured to enable access to the reaction troughs from one side.
12. The photobioreactor according to claims 1 to 11, wherein the substrate lateral borders incorporate a bulged edge.
13. The photobioreactor according to claim 12, wherein the substrate bulged edge comprising a welting cord for engaging the two lateral edges of the substrate.
14. The photobioreactor according to claim 11, wherein the bulged edge is covered by a plastic film.
15. The photobioreactor according to any ones of claims 1 to 14, wherein the substrate ends are stretched.
16. A photobioreactor for culturing at least one of phototrophic and mixotrophic microorganisms comprising:
a plurality of reaction troughs composed of a rigid water-impermeable material, each of the reaction troughs having a floor configured to define a plurality of protrusions, a water permeable substrate distributed over each reaction trough, and a support structure comprising a framework defining first and second sides and a first and second end, and configured to support the plurality of reaction troughs in horizontally oriented, vertically spaced relation, each of the reaction troughs extending from the first to the second end of the framework.

17. The photobioreactor according to claim 14, wherein the floor of each reaction trough comprises a plurality of protrusions defining one or more channels.
18. The photobioreactor according to claim 14, wherein the water permeable substrate is suspended over the plurality of protrusions.
19. The photobioreactor according to claims 14 to 16 wherein the reaction trough is composed of a rigid thermoformable plastic material.
20. The photobioreactor according to claim 14, wherein the reaction trough is composed of a rigid thermoformable plastic material, which has been vacuum molded to define the plurality of protrusions on the floor of the reaction trough.
21. The photobioreactor according to any one of claims 1 to 20 wherein the water-impermeable reaction troughs are selected from the group of materials consisting of flexible plastic, rigid plastic and metal.
22. The photobioreactor according to claim 21, wherein the metallic material has been molded to define the plurality of ridges on the floor of the reaction trough.
23. The photobioreactor according any one of claims 16 to 22, wherein the reaction trough comprises an inner liner disposed therein and configured to provide the plurality of protrusions on the floor of the reaction trough.
24. The photobioreactor according to claims 1 to 23, wherein the substrate is a geotextile fabric.
25. The photobioreactor according to claim 24, wherein the geotextile fabric includes strands of wicking fibers and of non-wicking fibers.
26. The photobioreactor according to any one of claims 1 to 25 further comprising an illumination system operatively associated with one or more of the plurality of reaction troughs to provide light thereto.
27. The photobioreactor according to claim 26, wherein the illumination system comprises light emitting diodes and a transparent light guide panel, wherein the light emitting diodes are positioned at one or more edges of the light guide panel.

28. The photobioreactor according to claim 26, wherein the light emitting diodes and the light guide panels are located underneath each reaction trough and configured to primarily illuminate the reaction trough immediately below.
29. The photobioreactor according to claim 26, wherein the light guide panel comprises surface dots to diffuse light incident thereon.
30. The photobioreactor according to claim 26, wherein the light guide panel is transparent and imbeds reflective particles that diffuse light incident thereon.
31. The photobioreactor according to claims 26 to 30, wherein the illumination system further comprises a light reflector sheet positioned between the light guide panel and the reaction trough.
32. The photobioreactor according to any one of claims 1 to 31, further comprising a harvesting apparatus operatively associated with the plurality of reaction chambers for removing biomass therefrom.
33. The photobioreactor according to claim 32, wherein the harvesting apparatus comprises a vertical support, a plurality of horizontal support arms, a plurality of scraper blades operatively associated with each of the plurality of support arms.
34. The photobioreactor according to claim 32, wherein the harvesting apparatus is supported on a travelling platform configured to move longitudinally along an open side of the framework.
35. The photobioreactor according to claim 32, further comprising a leadscrew system with a nut assembly configured to move the travelling platform alongside the open side of the framework.
36. The photobioreactor according to claim 32, further comprising a motor-driven chain-drive configured to move the travelling platform alongside the open side of the framework.
37. The photobioreactor according to claims 32 to 36, wherein the travelling platform further comprises a vertical adjustor unit operatively associated with the harvesting apparatus.
38. The photobioreactor according to any one of claims 1 to 37 further comprising one or more nutrient supply systems operatively associated with each of the plurality of reaction troughs.

39. The photobioreactor according to any one of claims 1 to 38 further comprising one or more gas supply systems operatively associated with the plurality of reaction troughs.
40. The photobioreactor according to claim 39, wherein the gas is diffused into the liquid nutrient supply system operatively associated with each of the plurality of reaction troughs.
41. The photobioreactor according to claim 1 to 40, wherein each of the reaction troughs comprises one or more delivery tubes for delivering nutrients and gas to the culture medium.
42. The photobioreactor according to one of claims 1 to 41, wherein the framework further comprising a plurality of metal profiles extending from the first to the second end of the framework, each of the metal profiles configured to hold an edge of a reaction trough and positioned relative to a trough such that when holding an edge of the reaction trough disposed on thereon, the edge of the reaction trough is in an elevated position.
43. The photobioreactor according to claim 42, wherein at least one of the metal profiles is configured to also support an edge of a light guide panel operatively configured therein.
44. The photobioreactor according to any one of claims 1 to 43 further comprising an end lip positioned at the second end of each reaction trough.
45. The photobioreactor according to any one of claims 14 to 44 further comprising a funnel operatively associated with the second end of each reaction trough.
46. The photobioreactor according to any one of claims 1 to 45 further comprising a thermal regulator operatively associated with each of the reaction chambers for regulating the temperature of the culture within the reaction troughs.
47. The photobioreactor according to any one of claims 14 to 46, wherein the support structure comprises two framework units disposed side-by-side.
48. The photobioreactor according to claim 47, wherein the two framework units share common vertical end supports and central supports.
49. A method of culturing at least one of phototrophic and mixotrophic microorganisms comprising the steps of:

introducing said microorganisms into one or more reaction troughs of the photobioreactor of any one of claims 1 to 48 to provide a culture of at least one of phototrophic and mixotrophic microorganisms, and supplying light, gas and nutrients to the one or more reaction troughs.
50. A reaction trough for culturing at least one of phototrophic and mixotrophic microorganisms, the reaction trough configured with a horizontally-oriented water-impermeable flat surface covered with a porous substrate distributed thereon and wherein controlled feeding of microorganisms with liquid nutrients is achieved by capillary action.
52. A photobioreactor for culturing at least one of phototrophic and mixotrophic microorganisms comprising:
a framework comprising a plurality of cantilevered arms configured to support a plurality of water-impermeable reaction troughs in horizontally oriented vertically spaced relation, each of the reaction troughs extending from a first to a second end of the framework and accessible from one side, a wickable porous substrate distributed over each reaction trough, an illumination system comprising plural light guide panels supporting the reaction troughs and providing light to the reaction trough immediately below, and at least one nutrient delivery tube saturating one end of each substrate for transporting culture medium through the substrate using capillary action.
53. A harvesting system for collecting microorganisms over a substrate distributed over each of a plurality of rectangular horizontally-oriented reaction troughs supported by a framework comprising a self-standing support structure securing a plurality of vertically-oriented cantilevered arms in vertically spaced relation and extending from a first to a second end and accessible from one side;
the harvesting system comprising a traveling vertical support supporting a plurality of horizontally-oriented cantilevered arms, each securing hingingly a scoop pan;

the outline of the horizontally-oriented cantilevered arms of the harvester matching male-femalingly the outline of the vertically-oriented cantilevered arms of the framework; and wherein moving the traveling support at least in one direction causes scoop pans to collect microorganisms.
54. The harvesting system of claim 53, wherein each of the horizontally-oriented scoop pans tilts downwardly at the end of the horizontally-oriented reaction troughs for dropping the collected microorganisms.
55. A method of harvesting at least one of phototrophic and mixotrophic microorganisms comprising the steps of:
moving the traveling harvesting system of claim 53 along an open side of the reaction troughs for collecting on scoop pans microorganisms cultivated over the upper surface of the substrate; and unloading the collected microorganisms when the scoop pans reach the end of the reaction troughs.