WO2010077638A1

WO2010077638A1 - Light transport in a bioreactor system

Info

Publication number: WO2010077638A1
Application number: PCT/US2009/067110
Authority: WO
Inventors: Miguel Olaizola
Original assignee: Sapphire Energy Inc
Current assignee: Sapphire Energy Inc
Priority date: 2008-12-08
Filing date: 2009-12-08
Publication date: 2010-07-08
Anticipated expiration: 2011-06-08

Abstract

Disclosed herein are devices, systems, and methods configured to cultivate a photosynthetic organism and can be configured to improve the growth of organism (for example, algae). The photosynthetic organism can be used to produce a product, such as fuel product. The bioreactor devices and systems can be inexpensive and can increase the efficiency of light utilization by a photosynthetic biomass.

Description

Aquatic photosynthεtic organisms (for example, algae and photosynthetic bacteria such as Cyanobacteria) are often cultivated to produce commercial products. The organisms themselves may be the product or the organisms may synthesize a product that is used and/or sold. Therefore the amount of product produced from such commercial endeavors that utilize aquatic photosynthetic organisms may be directly correlated to the amount of biomass that can be produced. The method of producing a large biomass thai is most desired from a commercial prospective is the fastest and least expensive method. 100021 There are many ways to optimize growth and production of a photosynthetic biomass. Nutrients, such as carbon, nitrogen, phosphorus and potassium can be added to a bioreactor system. Gases such as CO2 may be introduced into the system by various means. Attempts can be made to adjust environmental conditions such as adjusting the temperature of the bioreactor, whether it is an open system (for example, a raceway pond that is exposed to the elements) or a closed system (for example, a photobioreaclor chamber). All of these methods can increase the growth and production of a biomass, but the cost of such methods do not always outweigh the commercial bcneilts of obtaining a larger, faster growing biomass.

[0003] A photosynthcsizing biomass also requires light energy to drive photosynthesis. The primary source of light energy for an open bioreactor system is sunlight. In some cases artificial light is provided. However, only a fraction of the light impinging on the surface of the bioreactor is available to drive photosynthesis. A considerable amount of light energy is lost due to reflection and refraction at the aqueous surface. Wherein the light enters the aqueous medium, the light energy available to drive photosynthesis may decrease in a manner proportional to the distance from the surface through which the light entered. In addition the amount or density of light absorbing substances (dissolved or particulate) present in the culture medium can also affect the available light energy.

[0004] In an aspect, a bioreactor is provided that comprises: a liquid medium; a gas/liquid medium interface; and a plurality of light transporters configured to transfer light from at or near the gas/liquid medium interface into the liquid medium; wherein the light is from an irradiation source and wherein the liquid medium comprises at least one species of a photosynthetic organism. [0005] A light transporter of the plurality of light transporters can comprise: a top surface; a bottom submerged in the liquid medium; a longitudinal shaft connecting the top surface to the bottom, wherein the longitudinal shaft is at least partially transparent to a wavelength of light capable of driving photosynthesis; and a float configured to maintain the top surface at or near the gas/liquid medium interface. A light transporter can further comprise a weight attached to the bottom wherein the weight maintains the longitudinal shaft about perpendicular to the gas/liquid medium interface, 100061 In an embodiment, the bottom of a light transporter is submerged into the liquid more than 30, 50, 70, or 90% of the depth of the liquid.

[0007] A longitudinal shaft of a light transport can transmit or reflect light from the gas/liquid medium interface into the liquid. The longitudinal shaft can comprise two or more planar surfaces. In some instances, the longitudinal shaft is up to 30 cm in length. A longitudinal shaft can be solid, rigid, or hollow. A cross sectional shape of the longitudinal shaft can be circular, oval, square, rectangular, triangular, hexagonal, polygonal or any variation or mixture thereof.

[0008] A light transporter can comprise a prism, at least one mirror, and/or a fluorescent material. In some embodiments, the light transporter comprises a polymer, such as a plastic, and can be selected from the group consisting of polyethylenes, poiypropylenes, polyethylene terephthalates, polyacrylates, polyvinylchlorides, polycarbonates, and polystyrenes. In some instances, a light transporter comprises quartz, glass or resin-supported fiberglass. A light transporter can comprise a filter. [0009] A light transporter may further comprise a fin, bumper or a guide. In an embodiment, a bumper is a ring with a diameter of at least 2 cm wherein the ring is: fixed to the longitudinal shaft; surrounds the longitudinal shaft; and the geometric plane defined by the ring is perpendicular to the longitudinal shaft.

[0010] A top surface of a light transporter can be partly flat, convex, or concave. In some instances the top surface has a surface area between 0.01 cπr to 20 cm',

100111 A float of a light transporter can be an air bubble. In many instances, the float is at least partially transparent to light of a wavelength capable of driving photosynthesis. The float can be an inherent property of the light transporter.

[00Ϊ2] An irradiation source can be sunlight. In other instances, an irradiation source is an artificial light source.

100131 A bioreactor may further comprise a driver configured to move the liquid medium.

[0014] A liquid medium of a bioreactor can comprise a photosynthetic organism such as algae. A photosynthetic organism can be genetically modified.

[0015] In some instances, a bioreactor comprises at least ten light transporters per square meter of the las/liquid medium interface. A bioreactor can comprise at least one hundred light transporters per square meter of the gas/liquid medium interface. In another instance, a bioreactor can comprise up to 10,000 light transporters per square meter.

[0016] In some instances, the liquid medium has an irradiation level of greater than 100 μE rrf^" s^"1 when measured at a depth of 1, 2, 3, 5, or 10 inches, when the irradiation source provides 1500-3000 μE m^"~ s^" ^f at the gas/liquid medium interface.

[0017] The liquid medium can have an average irradiation level greater than 250 μE m^"2 s^"1 when measured at a depth of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 inches below the gas/liquid medium interface and when the irradiation source provides 1500-3000 μE m^"~ s^~! at the gas/iiquid medium interface. [0018] In some instances, the bioreactor is an open raceway pond. [0019] A plurality of light transporters can be positioned randomly in the liquid medium. In some instances, the plurality of light transporters occupies more than 10, 20, 50, or 90% of the area of the gas/liquid medium interface.

[0020] A bioreactor can comprise beads and in some instances, the beads remove algal deposits from the bioreactor and/or from the light transporter. [0021] The amount of light available from the irradiation source for driving photosynthesis, when measured at a depth of 7.5 cm, can be greater than that measured in an equivalent apparatus that does not comprise a light transporter. The amount of light available may be increased by 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%, In other embodiments, the amount of light available is increased by greater than 100%. [0022] In some instances, upon exposing the gas/liquid medium interface to 1500 μE m^"2 s^"1 of sunlight, the amount of light available for driving photosynthesis, when measured at a depth of 6.0 cm, is increased as compared to a reactor that docs not comprise light transporters. The amount of light available may be increased by 5%, 10%. 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%», 80%, 85%, 90%, 95%, or 100%. In some instances, the increase can be as much as 2-fold or more as compared to a reactor that does no! comprise light transporters.

[0023] One aspect provides a method of growing a photosynthetic organism comprising: providing a liquid medium comprising a photosynthelic organism in a bioreactor; inserting a plurality of light transporters into the liquid medium in the bioreactor, wherein the plurality of light transporters are configured to transfer light from an irradiation source from at or near the gas/liquid medium interface into the liquid medium; and providing light from an irradiation source to liquid medium within the bioreactor. A method can further comprise moving the liquid medium within the bioreactor. In some instances, a method comprises harvesting the organism, [0024] All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

ESCR

|0025| Features of the invention are set forth with particularity in the appended claims. A better understanding of many features and advantages of the disclosure will be obtained by reference to the following detailed description thai sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: [0026] Figure 1 illustrates an open raceway pond for growing algae comprising a plurality of light transporters randomly distributed and floating within the liquid medium.

[0027] Figure 2 illustrates a closed photobiorcactor containing a liquid medium and a plurality of light transporters.

[0028] Figure 3 demonstrates an exemplary embodiment of a bioreactor or biorcactor system as described herein comprising a light transporter.

[0029] Figure 4A illustrates an exemplary embodiment of a light transporter can have a top surface of the transporter that is circular and flat.

[0030] Figure 4B illustrates a light transporter with a different shape that comprises a float near the top of the longitudinal shaft. [00311 Figure 4C illustrates a rectangular light transporter that may be composed of a reflective material in order to transport, reflect, or transmit light along the longitudinal shaft.

[0032] Figure 4D illustrates a light transporter with a concave top surface that can direct light into the longitudinal shaft.

[0033] Disclosed herein are devices and methods configured to cultivate a photosynthetic organism. In many embodiments, the photosynthetic organism can be used to produce a product. The methods and devices described can be configured to produce improved growth of a photosynthetic organism (for example, algae). In some aspects, inexpensive devices and methods are presented that increase the efficiency of light utilization by a photosynthetic biomass in a biorcactor system. A biorcactor system with light transporters as described herein can optimize growth conditions by transporting light below the surface of a liquid medium wherein the organisms are grown. For example, in an open raceway pond, photo synthetic organisms are circulated and/or cycled within the pond in an attempt to have all the organisms and cells achieve a similar amount of light.

[0034] In an aspect, a bioreactor comprises: a liquid medium; a gas/liquid medium interface; and a plurality of light transporters configured to transfer light from an irradiation source from at or near the gas/liquid medium interface into the liquid medium; wherein the liquid medium comprises at least one species of a pholosynthctic organism.

[0035] In some instances, the irradiation source comprises a natural or artificial source of light. Light, as referred to herein, is any photonic energy that is available for driving photosynthesis in a photosynthetic organism. Examples of irradiation sources include, but are not limited to, sunlight, filtered sunlight, light bulbs, and light emitting diodes (LEDs). The irradiation source can be near the gas/liquid interface of the biorcactor or distant from it (for example, the sun).

[0036] In many algal-cultivation systems, light only penetrates the top few inches of the liquid medium. As the algae grow and multiply, the organisms become so dense that they block light from reaching deeper into the pond or tank. The light at the surface of the system can often be significantly higher than can be efficiently utilized by the organisms resulting in inefficient light utilization. Further, too much light for the algae can damage the organism. In order, to avoid this issue, many systems circulate arid cycle the algae through the system, to receive the flashing-light effect. As described, herein, light transporters can direct light from the surface of the system to deeper within the bioreactor, [0037] Apart from agitation, another means of supplying light aside from natural light such as sunlight or moonlight to algae is incorporating an artificial light source in the system. In the absence of a light transporter, much of the light delivered to a bioreactor may be reflected off the surface of the liquid medium or absorbed near the surface of the liquid medium. The light that enters the liquid medium decreases exponentially as the depth of the liquid increases. A photosynthetic organism located at a depth of 10 cm or greater has very little light available to it for driving photosynthesis. A light transporter can deliver additional light to photosynthetic organisms in a liquid medium and thereby increase viability and growth of the photosynthetic organisms. Currently, in an open raceway pond used for growing algae, the medium is circulated within the bioreactor and a carbon source is often provided to the bioreactor. [0038] In bioreactors, various methods have been used to agitate the liquid medium within, thus circulating the algae so that it does not remain on the surface or the bottom of the reactor. Algae that is not circulated can be overexposed at a surface and/or underexposed to light at the bottom. Paddle wheels can be used to circulate or stir the liquid medium in a reactor. Compressed air can be introduced into the bottom of a pond or tank to agitate the liquid medium, bringing algae from the lower levels up with it as it makes its way to the surface.

[0039] Algae can be cultured in open bioreactors, such as ponds, or closed systems, such as photobioreaclors. Raceway ponds may be less expensive to maintain and utilize. Raceway ponds and culture lakes are open to the atmosphere and can be referred to as open systems. A major benefit of an open system is the cost of construction and the cost of cultivation. Also open systems have some of the largest production capacities relative to oilier systems of comparable size and cost. In some instances, open culture can be viable when the particular algae in question requires (or is able to survive) some sort of condition that many other algae can not survive. For example, SpiruHna can grow in medium with a high concentration of bicarbonate at a high pH and Dunaliella will grow in high salinity medium. Figure 1 illustrates an open raceway pond for growing algae, wherein the pond comprises a paddle wheel to circulate the liquid medium within the pond and a plurality of light transporters randomly distributed and floating within the liquid medium. j 00401 Algae can also be grown in a closed photobioreactor. A photobioreactor can be a system that is not open to the environment and receives light from a natural or artificial source. Examples of photobioreactors include, but are not limited to, tanks provided with a light source, polyethylene sleeves or bags, and glass or plastic tubes. Figure 2 illustrates a closed photobioreactor containing a liquid medium. In this example, the photobioreactor comprises a material that allows sunlight to pass through the wall of the bioreactor. Light transporters are distributed throughout the bioreactor wherein the longitudinal shaft of the light transporter is submerged in the liquid medium and the top surface is at or near the gas/liquid medium interface within the bioreactor.

[0041] In an embodiment, a pond can have a transparent or translucent barrier, such as those that cover a pond or pool with a greenhouse. A covered pond that may be closed to the environment can also comprise light transporters. Because photobioreactor systems are closed, essential nutrients must be introduced into the system to allow algae to grow and be cultivated. A photobioreactor can be operated in batch mode, but it is also possible to introduce a continuous stream of sterilized water containing nutrients, air, and carbon dioxide, As the algae grows, excess culture overflows and is harvested. 100421 A bioreactor can comprise a liquid medium and a gas/liquid medium interface wherein the liquid medium comprises at least one species of a photosynthetic organism and at least one light transporter that is configured to transfer light from at or near the air/liquid interface into the liquid medium. The photosynthetic organism can be a non- vascular photosynthetic organism, such as an algae. [0043] The light transporter can be transparent or at least partially transparent to light in order to transfer light frυrn at or near the gas/liquid interface mto the liquid medium, In many embodiments, the light transporter makes more light available for photosynthesis beneath the surface of the gas/liquid medium interface than in a bioreactor without a light transporter, 100441 In an aspect a light transporter comprises: a top surface; a bottom submerged in the liquid medium; a longitudinal shaft connecting the top surface to the bottom, wherein the longitudinal shaft is at least partially transparent to a wavelength of light capable of driving photosynthesis; and a float configured to maintain the top surface at or near the gas/liquid medium interface. Figure 3 demonstrates an exemplary embodiment of a bioreaclor or bioreactor system as described herein comprising a light transporter, The light transporter comprises a float that maintains the top surface of the light transporter near the gas-'liquid medium interface. When light (for example, sunlight) enters the bioreactor, often much of it is reflected off of the interface and some of it is absorbed m the liquid medium very near the interface as shown by the light energy diagrammed on the right side of Figure 3. When light energy as diagrammed in Figure 3 enters a light transporter as described herein through the top surface, the light energy can be transported down the longitudinal shaft and be made available much deeper in the liquid medium.

[0045] Λ light transporter can further comprise a weight attached to the bottom wherein the weight maintains the longitudinal shaft about perpendicular to the gas/liquid medium interface, The weight can be a solid weight, such as a metal, or can be a dense plastic or other dense material. In an embodiment, the shaft is hollow and the weight is not hollow. As demonstrated in Figure 4A, an exemplary embodiment of a light transporter can have a top surface of the transporter that is circular and flat. The longitudinal shaft can transparent to light and is cylindrical in shape. At the bottom of the light transporter is a weight, such that when floating in a liquid medium, the weight maintains the top surface perpendicular to and at or near the gas/liquid medium interface. [0046] In order Io deliver light into the bioreactor, the bottom of the light transporter can be submerged into the liquid more than 10, 20, 30, 40, 50, 60. 70, 80 or 90% of the depth of the liquid. For example, a light transporter can extend about 1, 2, 3, 4, 5, 6, 7, 8, or 9 in into a 10 in deep liquid medium, In another example, a raceway pond may be configured to contain about a foot of liquid depth and the depth of the can vary based on surface waves in the reactors. A plurality of light transporters can be submerged in the liquid medium to more than 10, 20, 30, 40, 50, 60, ^"0, 80 or 90% of the average depth of the liquid medium. A longitudinal shaft can transmit, transfer, or reflect light from a gas/liquid medium interface into the liquid medium. i7| In an example, the longitudinal shaft comprises two or more planar surfaces and is in contact with the top surface. The longitudinal shaft can be, for example, solid, rigid, and/or hollow, and the cross sectional shape of the longitudinal shaft can be circular, oval, square, rectangular, triangular, hexagonal, polygonal or any variation or combination thereof. A light transporter can comprise a prism, a mirror, and/or a fluorescent material.

[0048] Manufacturing of a light transporter can comprise making, molding, or shaping a light transporter from one or more polymers or plastic such as polyethylene;_*, polypropylenes, polyethylene tcrephthalates, polyacrylatcs, polyvinykhloridcs, polycarbonates, and polystyrenes. In other instances, a light transporter comprises quartz, glass or resin-supported fiberglass. [0049] A light transporter can further comprise a filter, a fin, a bumper or a guide. In an embodiment, the bumper is a ring that is fixed to the longitudinal shaft; surrounds the longitudinal shaft: and the geometric plane defined by the ring is perpendicular to the longitudinal shaft.

[0050] The top surface of a light transporter can be flat, partly flat, convex, or concave. The top surface can have a surface area between 0.01 cm^" to 100 cnτ\ The top surface of the light transporter can be of any suitable shape that permits absorption and/or transmission of light. The top surface can be any suitable shape (for example, square, rectangular, oval, or circular). The surface area of the top surface can occupy up to 0.5, 1, 2, 3, 5, 20, 30, 40, 50, 60, 70, 80. 90 or 100 cm^" of the gas/liquid medium interface. In some aspects the top surface absorbs light of a visible wavelength and transmits that light into the longitudinal shaft where the light is directed into the liquid medium. Sn another embodiment, the top surface is transparent and light is directed through the longitudinal shaft into the liquid medium. The top surface can selectively reflect, absorb, or transmit light of specific wavelengths. For example, the top surface can reflect light outside of the visible wavelength spectrum (for example, by means of a filter or reflective coating). The top surface can be designed to collect light originating from a plurality of angles, with respect to the plane of the gas/liquid medium interface, and transmit that light into the longitudinal shaft, The top surface of the light transporter can comprise a mirror to direct light into the longitudinal shaft.

[0051] A light transporter can comprise a float or floating means. The float or floating means can be defined by the density and or shape of the material in which the light transporter is made, (n another aspect the float can be an air bubble or a plurality of air bubbles trapped inside the light transporter. In some aspects a float can be integrated into, attached or associated with the light transporter.

[0052] A float of a light transporter can be an air bubble attached to or built into a light transporter. In many instances, the float is at least partially transparent to light of a wavelength capable of driving photosynthesis. The float can comprise a material less dense than water. In an embodiment, the float material is less dense than the liquid medium. The float can comprise a plastic that is less dense than the liquid medium. The float can be an object, such as a ring, filled with air such that when attached to the light transporter, it floats in the liquid medium. In some instances, the float is an inherent property of the light transporter.

[0053] In many instances, the light transporter floats freely in the liquid medium. The light transporter can travel with the liquid medium. When there is a plurality of light transporters, the light transporters can be randomly distributed throughout the bioreactor and float freely within the bioreacter. For example, in a raceway pond where the liquid medium is circulated by a paddle wheel, light transporters can travel around the raceway pond with the liquid medium and can travel through the paddle wheel. In other instances, the light transporter can be held in position (for example, by a tether or an anchor). In some aspects the light transporter is held in position by its buoyant properties (for example, size, shape and/or density). The light transporter can be held in position by a weight, for example wherein the weight is placed at or near the bottom. In another aspect this is accomplished by an anchor, a tether, or a float. The liquid medium of the bioreactor, wherein the light transporter is located, can be in motion. Therefore the light transporter can be in motion as well. The position of a light transporter with respect to the gas/liquid medium interface can be dynamic and defined, in part, by the wave dynamics of the liquid, The position of the light transporter with respect to the gas/liquid medium interface is given as an approximate position. In some instances, groups of light transporters can be attached together by a flexible tether. In another embodiment, a group of light transporters can be attached by a rigid or solid tether. For example, a group of light transporters can be attached to a grid or frame and the light transporters can be submerged in the medium. A grid of light transporters can be fixed or can be mobile in the liquid medium. [0054] The light transporter can comprise a bumper. A bumper can be any structure that helps maintain a minimal spacing between other light transporters in the liquid medium. A bumper can be attached to a light transporter. In some aspects a bumper is a wheel like ring that is situated in a plane that is perpendicular or near perpendicular to the longitudinal shaft. The top surface of the light transporter is situated in the center of the ring. One or more radial spokes can secure the ring to the light transporter. In some aspects a single spoke secures the ring to the top end of the light transporter. The diameter of the ring can be from 0.5 cm up to 10 cm in diameter. In some aspects the diameter of the ring is from 2 cm up to 6 cm. The bumper can be designed to allow an optimal amount of light to irradiate the gas/liquid medium interface that is not occupied by the top end of the light transporter. In some aspects the bumper further acts as a float.

[0055] Figure 4B illustrates a light transporter with a different shape that comprises a float near the top of the longitudinal shaft. The float may also be an air bubble within the longitudinal shaft. Figure 4C illustrates a rectangular light transporter that may be composed of a reflective material in order to transport, reflect, or transmit light along the longitudinal shaft. The light transporter also comprises an exemplary bumper that can prevent the light transporter from bumping into the walls of the bioreactor or other light transporters in a bioreactor. Figure 4D illustrates a light transporter with a concave top surface that can direct light into the longitudinal shaft. In this embodiment, the top surface area is larger than that of the longitudinal shaft and the top surface can rest slightly above the gas/liquid medium interface. In this manner, the light transporter may occupy less volume available to the liquid medium in the bioreactor, while achieving more surface area to receive light at the top of the bioreactor. [0056] The longitudinal shaft can be designed to collect light originating from the top surface of the light transporter and transmit or reflect that light along the length of the shaft, ultimately transmitting or reflecting the light into the liquid medium. The longitudinal shaft of the light transporter can be of any suitable shape that permits transmission and/or reflection o f light in the visible spectrum. The longitudinal shaft can be flat, partially flat, convex or concave. The longitudinal shaft can be any suitable shape, wherein the cross sectional shape of the longitudinal shaft is circular, oval, square, rectangular, triangular, hexagonal, polygonal or any variation or mixture thereof. The longitudinal shaft can define the shape of the light transporter wherein the light transporter has a shape selected from the group consisting of the following: a cylinder, a pyramid, a cone, a rod, a blade, a diamond, and a hexahedron. The longitudinal shaft can comprise two or more planar surfaces. The longitudinal shaft can taper in width, from wide to narrow, in the direction from the top end to the bottom end. The longitudinal shaft can be solid or hollow. The longitudinal shaft can be rigid or flexible. The longitudinal shaft can comprise a liquid or a gas, for example a liquid or gas with fluorescent properties. The longitudinal shaft can further comprise a fin or a guide.

[0057] A light transporter can extend from the gas/liquid medium interface to depths of up to several meters. Therefore, the length of the longitudinal shaft can be up to 10, 20, 30, 40, 50, 100, 200 or 300 cm in length. In some aspects the longitudinal shaft can be up to 10 or 20 cm in length. In some aspects the longitudinal shaft can be from 3 era in length up to 10 or 20 cm in length.

[0058] The bottom of the light transporter can be of any suitable shape. The bottom can comprise an anchor, a weight, or a tether that can serve to help maintain the position of the light transporter in the liquid medium wherein the vertical shaft is positioned perpendicular or near perpendicular to the gas/liquid medium interface, The position can be movable relative Io the bioreactor, wherein the light transporter travels with the liquid medium, but remain perpendicular to the gas/liquid medium interface. Wherein the bottom comprises an anchor or a tether, the anchor or tether can restrict the movement of the light transporter in the liquid medium. Wherein the liquid medium is in motion, (for example, comprises a current), the anchor or tether can prevent net movement of the light transporter in the direction of the current. Wherein the bottom comprises an anchor, the anchor may restrict, but not prevent movement of the light transporter in the direction of the current. In one non-limiting example, an anchor can drag on the bottom of the bioreactor thus allowing movement of the light transporter in the direction of the current, but restricting movement to a speed that is slower than that of the current.

[0059] In some instances, a light transporter can be made of a single material or can comprise a plurality or mixture of materials. The light transporter can comprise a material that contributes to the buoyant properties of the light transporter, such as less dense plastic, or a hollow plastic or other hollow material. Any suitable material can be used that allows the light transporter to float in the liquid medium. In other embodiments, the top surface and/or longitudinal shaft of the light transporter comprise material that does no! float in the liquid medium, but is attached to a float, In some instances, the light transporter comprises a material that contributes to the optical properties of the light transporter. For example, the light transporter can comprise a material that allows selected wavelengths to travel through to the liquid medium and other wavelengths to be blocked or reflected. In another example, a light transporter comprises reflective material that reflects the light along the longitudinal shaft into the liquid medium. (006Oj A light transporter can comprise a polymeric material. The polymeric material can be a plastic or can be a polymer selected from the group of polycthylenes, polypropylencs, polyethylene tcrcphthalates, polyacrylates, poiyvinylchlorides, polycarbonates, and polystyrenes or a mixture thereof. The light transporter can comprise quartz, glass or resin-supported fiberglass. The light transporter can comprise a prism, a mirror, crystal or any suitable reflective material. The light transporter can comprise a fluorescent material. A fluorescent material can allow absorption of light at a wavelength not suitable to drive photosynthesis followed by emission of light that is more suitable to drive photosynthesis. The light transporter can comprise a coating, for example with a coating that prevents algae or other material from sticking to the light transporter. In some aspects the light transporter can comprise a filter. The filter can be a coating. The filter can be configured to filter out radiation that generates heat or radiation that can damage the photosynthetic organisms. The filter can be configured to allow only visible light (for example, light of 350 - 700 nrn wavelength) to enter the light transporter. A bioreactor (for example, an open bioreactor) can comprise from one up to several thousand light transporters per square meter of air/liquid interface. In some aspects an open bioreactor comprises at least 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 light transporters per square meter of gas/liquid medium interface. In another aspect an open bioreactor comprises at least 200, 300, 400, 500, 600, 700, 800, 900, 1 ,000, 5,000, or 10,000 light transporters per square meter of gas/liquid medium interface. A plurality of light transporters in an open bioreactor system can occupy up to 10, 20, 30, 40, 50, 60, 70, 80, 90 or 95% of the area of the gas/liquid medium interface. In some aspects the light transporters can be positioned randomly in the liquid medium of the bioreactor system. [0062J A bioreactor can comprise a plurality of light transporters wherein all of the light transporters are identical. In another aspect a bioreactor can comprise a plurality of light transports of different shapes and/or sizes. In yet another aspect a bioreactor can comprise a plurality of light transporters wherein some or all of the light transports comprise different optical characteristics.

[0063] In the presence of at least one light transporter or a plurality of light transporters, the liquid medium may have an average irradiation level at a depth of 3 or more inches that is greater than that of a liquid medium in the absence of a light transporter. In a bioreactor comprising a plurality of light transporters, the amount of light available for driving photosynthesis, when measured at a depth of 7,5 cm, can be greater than that measured in an equivalent bioreactor that does not comprise a light transporter. In some aspects, upon exposing the gas/liquid medium interface to 1500 μE m ² s^"! of natural sunlight, the amount of light available for driving photosynthesis, when measured at a depth of 4.0, 5.0, 6.0, 7.0 or 7.5 cm, is increased. In some aspects a bioreactor comprising a liquid medium, a gas/liquid medium interface, at least one species of a photosynthetic organism and a plurality of light transporters has an irradiation level of greater than 100, 125, 150 or 200 μE m^"2 s^"1 when measured at a depth of 10 cm, when a light source provides 1500-3000 μE m^"" s^"1 at the gas/liquid medium interface and the liquid medium has a typical algal density as found in a typical raceway pond. In some aspects a bioreactor comprising a plurality of light transporters has an average irradiation level greater than 250, 300, 350 or 400 μE m^"2 s^"1 when measured at a depth of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 inches below the gas/liquid medium interface when the liquid medium has a typical algal density as found in a typical raceway pond. In some embodiments, an irradiation source provides 1500-3000 μE nϊ'^' s^~l at the gas/liquid medium interface. [0064] A bioreactor can comprise a liquid medium. The liquid medium can be configured for growth of a photosynthetic organism. In some embodiments, the liquid medium is comparable in salt content to lake water. In other embodiments, the liquid medium is comparable in salt content to ocean water. In another embodiment the salinity of the liquid medium is much greater than the salinity of ocean water. Additives can be added to the liquid medium to provide additional nutrients to the photosynthelic organism. Some non-limiting examples of nutrients additives include carbon, nitrogen, phosphorus or potassium. Additional non-limiting examples of nutrient additives include complex carbohydrates, simple sugars, lipids, fatty acids, proteins, amino acids, vitamins and gases (e.g. CO₂, nitrogen, or oxygen). A liquid medium can be water. A liquid medium can be a cell growth culture medium. In some instances, a liquid medium comprises a pholosynthetic organism and nutrients for cultivating the organism. The content of a liquid medium can be customized according to the type of photosynthetic organism io be cultivated. [00651 ^m some biorcactor systems (for example, a raceway pond), the system has a liquid medium current wherein the medium is in constant motion

[0066] A bioreactor can comprise a gas/liquid medium interface that defines a separation between the liquid medium and the gas provided to the bioreactor. In some instances, the gas/liquid medium interface does not include bubbles or pockets of gas surrounded on all sides by liquid medium. In other instances, the surface of the liquid comprises bubbles and the gas/liquid medium interface is the interface between the liquid surrounding the bubbles and the gas within the reactor. In an open bioreactor system, the gas can be atmospheric air, wherein the air is unadulterated and provided by nature, In an open bioreactor system the air is not confined by a vessel. The ratio of the volume of air to the volume of liquid in an open bioreactor system is typically greater than 10: 1, 100:1, 1000: 1 or 10,000:1. In some aspects the ratio of the volume of air to the volume of liquid in an open biorcactor system is greater than 1000:1. An open bioreactor can sometimes comprise a fixed or removable cover. Often times, there is air or gas between the cover and the liquid medium. In this embodiment, the gas/liquid medium interface is interface of the gas and liquid medium at the surface of the liquid medium. Similarly, in a closed biorcactor, there is often room for some hcadspacc above the liquid medium that comprises a gas. In this embodiment, the gas/liquid medium interface is the interface at the surface of the liquid medium in contact with the hcadspace.

[0067J In an open bioreactor, often the gas is the atmosphere. In some instances, the atmosphere can comprise flue gas or waste gas such as those concentrated in carbon dioxide. The flue gas or waste gas can be utilized by the photosynthetic organism in the bioreactor. The flue gas or waste gas may be at the gas/liquid medium interface, or may be bubbled or diffused into the liquid medium at another place within the biorcactor. Ϊ8] In many instances with an open biorεactor system, the irradiation source is natural sunlight and the intensity varies with the daily cycles of sunlight and the weather. Sunlight can be captured by mirrors or other light capture devices and then provided as an irradiation source to a bioreactor as described herein. Moonlight, or sunlight reflected from a body in space, may also provide an irradiation source to a bioreactor. A bioreactor can be positioned such that is receives the maximum amount of sunlight possible throughout a day. Sunlight can also be provided to a closed bioreactor. A closed bioreactor can have a vessel wall that is composed of a translucent or transparent materia] that allows photons and light energy to pass through the wall. The materials of the wall can be varied depending on the wavelength or intensity of light that is selected to pass. [0069] An irradiation source can also be a light bulb, light emitting diode, or any other man-made lighting device that can be utilized for growing photosynthetic organisms. An artificial irradiation source can be customized to deliver selected wavelengths and intensities. However, in a dense or dark liquid medium, the light energy still may not travel deep into the liquid medium. A light transporter can be used with a bioreactor that has an artificial irradiation source, in order to deliver light energy in a better manner throughout the liquid medium, In some instances, sunlight may provide light energy during the daylight hours and an artificial irradiation source may provide energy during dark hours or periods of the day.

[0070J The bioreactor system described herein can comprise at least one species of a photosynthetic organism. In some instances, the photosynthetic organism can be genetically altered to produce or provide a product (for example, a commercial product such as biofuel, gasoline, pharmaceuticals, or fragrances). Non-limiting examples of products produced or provided by photosynthetic organisms and genetically altered photosynthetic organisms arc biofuels, feedstocks, and recombinant proteins (for example, bio-degrading enzymes). Non-limiting examples of some prokaryotic non-vascular photosynthetic organisms include, but are not limited to, cyanobacteria (for example, Synechococcus, Synechocγslls, Athrospirά). Some non-limiting examples of eukaryotic τιoπ~vascular photosynthetic organisms include Chlainydomonas reinhardtii, Dunalϊella salϊna, Dunaliella terciolecta, and Haematococcus pluvialis . Additional non-limiting examples of non-vascular photosynthetic organisms contemplated for use herein include cyanophyta, prochlorophyta, rhodophyta, chlorophyta, hcterokontophyta, tribophyta, glaucophyta, chlorarachniophytes, euglenophyta, euglenoids, haptophyta, chrysophyta, cryptophyta, cryptomonads, dinophyta, dinoflagellata, pyrmnesiophyta, bacillariophyta, xanthophyta, custigmatophyta, raphidophyta, phacophyta, and other phytoplankton. A bioreactor system can comprise a vessel that contains liquid medium. A vessel can be a natural structure or a man-made structure or both. A vessel used in an open bioreactor system can comprise a bottom or base structure and at least two vertical walls connected to the base structure. Wherein an open vessel is filled with a liquid medium, the top of the vessel can be defined by the gas/liquid medium interface. Non-limiting examples of vessels used for open bioreactor systems include lakes, ponds, pools (for example, man-made pools), canals, channels, rivers, bays, lagoons, fiords, reservoirs, and raceway ponds. The walls and bottom or base structure of a vessel can be constructed of any suitable material including, but not limited to dirt, cement, wood, plastic, rock or fiberglass. In some aspects a vessel (for example, a raceway channel) can be built in concrete, or compacted earth, and can be lined with polymeric films such as white plastic. In some aspects an open bioreactor system comprises a vessel wherein the vessel is a raceway pond. A raceway pond can be a closed loop recirculation channel. Mixing and circulation can be produced by a paddle wheel, pump, airlift, or Archimedes screw. Flow can be guided around bends by baffles placed in the flow channel. The paddlcwheel can operate continuously to prevent sedimentation. |0072] The volume of the vessel can be from 100 to up to 10,000, 20,000, 30,000, 100,000 liters or more. A vessel (for example, a vessel used in an open bioreactor system) can be from 10 cm to up to 200 cm deep. Wherein the vessel is a natural or manmade structure (e.g. a lake or lagoon) the volume can be greater than 100,000 liters and deeper than 200 era. Wherein the vessel is a raceway pond, the vessel can be from 10 to 60 cm deep. [0073] A vessel can comprise a means Io generate a current (e.g. a paddle wheel, pump, airlift, or

Archimedes screw). A vessel can also comprise an aeration system that allows introduction of gas into the liquid medium.

100741 A bioreactor can further comprise beads. Beads can be used to remove algal deposits from the vessel or from the light transporters. For example, beads may travel with the liquid medium and through friction or oilier force can prevent some or all cells or organisms or gunk in the liquid medium from attaching to the sidewalls of the bioreactor. The beads can also prevent deposits on the light transporters themselves. As described herein, the light transporters can also be coated to prevent deposits. 100751 In an aspect, a method of growing a photosynthetic organism comprising: providing a liquid medium comprising a photosynthetic organism to a bioreactor; inserting a plurality of light transporters into the liquid medium in the bioreactor, wherein the plurality of light transporters are configured to transfer light from the irradiation source from at or near the gas/liquid medium interface into the liquid medium; and providing light from an irradiation source to liquid medium within the bioreactor. In an embodiment, a method described herein further comprises moving the liquid medium within the bioreactor. A method can also comprise harvesting the organism after cultivation. [0076] While embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

CLAIMS WHAT IS CLAIMED IS:

1 . A bioreactor comprising: a. a liquid medium: b. a gas/liquid medium interface; and c. a plurality of light transporters configured to transfer light from at or near the gas/liquid medium interface into the liquid medium, wherein the light is from an irradiation source; wherein the liquid medium comprises at least one species of a photosynthetic organism.

2. The bioreactor of claim 1, wherein a light transporter of the plurality of light transporters comprises: a. a top surface; b. a bottom submerged in the liquid medium; c. a longitudinal shaft connecting the top surface to the bottom, wherein the longitudinal shaft is at least partially transparent to a wavelength of light capable of driving photosynthesis; and d. a float configured to maintain the top surface at or near the gas/liquid medium interface,

3. The bioreactor of claim 2, wherein the light transporter further comprises a weight attached to the bottom wherein the weight maintains the longitudinal shaft about perpendicular to the gas/liquid medium interface.

4. The bioreactor of claim 2, wherein the bottom of the light transporter is submerged into the liquid more than 30, 50, 70, or 90% of the depth of the liquid.

5. The bioreactor of claim 2, wherein the longitudinal shaft transmits or reflects light from the gas/liquid medium interface into the liquid.

6. The bioreactor of claim 2, wherein the longitudinal shaft comprises two or more planar surfaces.

7. The bioreactor of claim 2, wherein the longitudinal shaft is solid.

8. The bioreactor of claim 2, wherein the longitudinal shaft is rigid.

9. The bioreactor of claim 2, wherein the longitudinal shaft is hollow.

10. The bioreactor of claim 2, wherein a cross sectional shape of the longitudinal shaft is circular, oval, square, rectangular, triangular, hexagonal, polygonal or any variation or mixture thereof.

11. The bioreactor of claim 2, wherein the light transporter comprises a prism.

12, The bioreactor of claim 2, wherein the light transporter comprises at least one mirror.

13, The bioreactor of claim 2, wherein the light transporter comprises a fluorescent material.

14. The bioreactor of claim 2, wherein the light transporter comprises a polymer.

15. The bioreactor of claim 14, wherein the polymer is plastic.

16. The bioreactor of claim 14, wherein the polymer is selected from the group consisting of polycthylenes, polypropylcncs, polyethylene tcrephlhalates, polyacrylatcs, polyvinylchlorides, polycarbonates, and polystyrenes.

17. The bioreactor of claim 2, wherein the light transporter comprises quartz, glass or resin- supported fiberglass,

18, The bioreactor of claim 2, wherein the light transporter comprises a filter.

19. The bioreactor of claim 2, wherein the light transporter further comprises a fin, bumper or a guide.

20. The bioreactor of claim 19, wherein the bumper is a ring, wherein the ring is: a. fixed to the longitudinal shaft b. surrounds the longitudinal shaft: and, c. the geometric plane defined by the ring is perpendicular to the longitudinal shaft.

21. The bioreactor of claim 2, wherein the top surface is partly flat, convex, or concave,

22. The bioreactor of claim 2, wherein the top surface has a surface area between 0.01 cm^z Io 20 cm².

23, The bioreactor of claim 2, wherein the float is an air bubble,

24. The bioreactor of claim 2, wherein the float is at least partially transparent to light of a wavelength capable of driving photosynthesis,

25. The bioreactor of claim 2, wherein the float is an inherent property of the light transporter.

26. The bioreactor of claim 1, wherein the irradiation source is sunlight,

27, The bioreactor of claim 1 , wherein the irradiation source is an artificial light source.

28. The bioreactor of claim 1 further comprising a driver configured to move the liquid medium,

29. The bioreaclor of claim 1, wherein the photosynthetic organism is algae.

30. The bioreactor of claim 1, wherein the photosynthetic organism is genetically modified.

31. The bioreactor of claim 1 further comprising at least ten light transporters per square meter of the gas/liquid medium interface.

32. The bioreactor of claim 1 further comprising at least one hundred light transporters per square meter of the gas/liquid medium interface. , The bioreactor of claim 1, wherein the bioreactor is an open raceway pond. , The bioreactor of claim 1 , wherein the plurality of light transporters are positioned randomly in the liquid medium. , The bioreacior of claim 1, wherein the plurality of light transporters occupies more than 10, 20, 50, or 90% of the area of the gas/iiquid medium interface. , The bioreactor of claim 1 further comprising beads. , The bioreactor of claim 36, wherein the beads remove algal deposits from the bioreactor or from the light transporter. , The bioreactor of claim 1, wherein the amount of light available from the irradiation source for driving photosynthesis, when measured at a depth of 7.5 cm, is greater than that measured in an equivalent apparatus that does not comprise a light transporter. , A method of growing a photosynthetic organism comprising: a. providing a liquid medium comprising a photosynthetic organism to a bioreactor; and b. inserting a plurality of light transporters into the liquid medium in the bioreactor, wherein the plurality of light transporters are configured to transfer light from the irradiation source from at or near the gas/liquid medium interface into the liquid medium; and c. providing light from an irradiation source to liquid medium within the bioreactor. , The method of claim 39 further comprising moving the liquid medium within the bioreactor., The method of claim 39 further comprising harvesting the organism.

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