WO2014184717A1

WO2014184717A1 - Arrangement for improving growth

Info

Publication number: WO2014184717A1
Application number: PCT/IB2014/061276
Authority: WO
Inventors: Ari Ketola; Annkaisa ELO; Jukka ROPPONEN; Janne Aaltonen
Original assignee: Ductor Oy
Priority date: 2013-05-15
Filing date: 2014-05-07
Publication date: 2014-11-20

Abstract

The invention provides methods and systems for cultivating photosynthetic organisms by illuminating the photosynthetic organisms with modulated light, wherein the modulated light exhibits a pulsed ON/OFF cycle, and wherein the light comprises modulated sunlight, with optional supplemental artificial light.

Description

ARRANGEMENT FOR IMPROVING GROWTH

TECHNICAL FIELD

The present invention relates generally to processes and systems for modulating illumination to provide improved growth rates for photosynthetic organisms. The invention provides for illuminating photosynthetic organisms with discrete intervals of illumination. The illumination is provided e.g., by sunlight, where the illumination is modulated by alternately turning the illumination on and off, with light/dark time intervals, and the ratio of light to dark durations, selected to accelerate growth of photosynthetic organisms that are cultivated in photobioreactors and greenhouses and the like.

BACKGROUND OF THE INVENTION

Sunlight is the ultimate natural energy source for photosynthetic organisms.

For this reason, optimization of light use is essential for any cultivation system for photosynthetic organisms. Photosynthetic organisms are organisms containing chlorophyll that are capable of photosynthesis, i.e., forming longer carbon chains from carbon dioxide. Only limited wavelengths of solar radiation are useful in

photosynthesis. The wavelengths that support photosynthesis are generally between

400nm (nanometers) and 700nm and are referred to as "photosynthetic active radiation" and comprise, on an energy basis, 43% of solar radiation.

An overall equation describing photosynthesis i.e., wherein CO₂ and water, in the presence of light, form sugars and oxygen, is as follows.

6C0₂ + 6H₂0 + light→ C₆H₁₂0₆ + 60₂

In particular, photosynthesis involves at least two different steps, a light reaction and a dark reaction. In the first step, or light reaction, light energy is absorbed by chlorophyll. The light reaction transfers electrons from H₂0 to ADP (adenosine diphosphate) to form ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). In the second step, or dark reaction (the Calvin-Benson Cycle), ATP and NADPH from the light cycle are used to fix carbon into sugars according to the following general equation.

6C0₂ + 18 ATP + 12H₂0 + 12NADPH→ C₆H₁₂0₆ + 12Pi + 18ADP + 12NADP⁺

The amount of available light energy often limits productivity of the photosynthetic process, but light should be used under conditions promoting the highest possible efficiency. For example, too little light results in slow growth of the illuminated photosynthetic organism, and in some situations, might even prohibit growth. In addition, a considerable part of the incoming excitation energy cannot be utilized in the photosynthetic reaction centers in a cell because their capacity is limited. Thus, only part of the excitation energy is utilized by photosynthetic apparatus of the organisms and a considerable amount of the incident light energy is dissipated as heat or fluorescence. An overdose of excitation energy usually leads in to photo-inhibition and a decrease in the growth rate and thus productivity.

One way to provide additional illumination for photosynthetic organisms, e.g., algae cultivations or other plants, is to use artificial light. For example, the yield of algal oil from microalgal ponds illuminated by sunlight is 100-130 m³ /hectare (hectare is abbreviated herein as "ha"), but the yield can reach 172 m³/ha with artificial lighting (Malcata, 2011 Trends in Biotechnology, 29(11):542-549). However, the high cost of installing and operating artificial light sources remains a major drawback, even though the efficiency and quality of the light for photosynthetic organisms has been improved, e.g., by using light emitting diode ("LED") lamps.

It has also been demonstrated that fast alternations between high light intensities and darkness, the so called "flashing light effect" can greatly enhance photosynthetic efficiency (Phillips and Myers, 1954, Plant Physiology, 29(2): 152). This effect has been observed under very short light/dark cycles, ranging from less than 40μβ up to Is. This effect is more efficient with shorter cycles, and when the dark period is longer than light period. Gordon and Polle, 2007, Appl Microbiol Biotechnol 76:969-975 describe how a low duty factor, high peak irradiance, illuminating light can greatly accelerate algae growth.

It has been hypothesized that a basis for the flashing light effect is that photosynthesis is comprised of a cycle of nearly instantaneous photic reactions followed by slower thermochemical reactions. The photosynthetic reaction turnover time is controlled by the slower thermochemical reaction time scale of approximately 1-15 ms (Carvalho, 2011, Appl Microbiol Biotechnol 89: 1275-1288). For example, according to Tomohisa Katsuda et al. 2006, Journal of Bioscience and Bioengineering 102(5). 442-446, the rate of algae production was higher with a lower amount of total illumination, when the light was administered as light/dark pulses. It has been also demonstrated that by alternating light and dark cycles, algae can efficiently exploit even high levels of light energy without damaging the photosynthetic apparatus of the organism (Sforza et al. 2012, PloS one, 7(6), e38975). However, if the provided alternation of light and dark is not optimal, radiation damage may occur and photosynthetic productivity is greatly reduced. Experiments by e.g., Sforza et al. 2012, Id. confirmed that the frequency of light changes has an enormous effect on biomass productivity. For example, with light pulsed at 30Hz, the cell number in an algae growth environment was about two times higher than with light at a pulse frequency of 10Hz, after 10 days of growth.

A growth experiment with Chlamydomonas reinhardtii resulted in 35% higher biomass production with illumination by light pulsed at 100Hz, relative to illumination with continuous light (Vejrazka et al. 2011, Biotechnology and Bioengineering,

108(12): 2905-2913). In addition, a method for plant growth utilizing LED

illumination has been described by US Patent No. 8,302,346B2, by Hunt.

A related method is described by US Patent Publication No. 2012/0306383, by Munro, that disclosed a method of modulating sunlight using mirrors to provide light to algae. The drawback to the Munro method is that it requires photovoltaic solar panels to generate electricity to provide modulated illumination and/or requires fiber optics for conducting light to algae.

US Publication No. 2004/0109302, by Yoneda, described a method for improving plant growth by administering pulsed light. The drawback to the Yoneda system is that it required both artificial light and a control unit to control the light.

Broadly, the difficulty with all of the above-described solutions is the need for LED lights, or other artificial light source, which require energy. Another difficulty is that above described solutions are very difficult to scale up and implement in large scale growth setups such as pond, cultures, green houses or photobioreactors. SUMMARY OF THE INVENTION

Accordingly, the invention provide a method for cultivating photosynthetic organisms, the method comprising illuminating the photosynthetic organisms with modulated light, wherein the modulated light exhibits a pulsed ON/OFF cycle, and wherein the light comprises modulated sunlight.

In one embodiment, the modulated light is pulsed, for example, at a frequency ranging from about 1 through about 10,000 Hz. The modulated light can also be pulsed at a frequency ranging from about 10 through about 5,000 Hz, at a frequency ranging from about 20 through about 1,000 Hz, at a frequency ranging from about 20 through about 500 Hz, at a frequency ranging from about 40 through about 100 Hz, at a frequency ranging from about 10 through about 50 Hz, and/or at a frequency of from 1 to about 5 Hz.

The modulated light also has a duty cycle, that can be pulsed at a 1/2 duty cycle with a ratio of 1 time unit on and 1 time units off, a 1/3 duty cycle with a ratio of 1 time unit on and 2 time units off, or with a 1/10 duty cycle with a ratio of 1 time unit on and 9 time units off, and/or at other ratios that may be selected, e.g., duty cycles ranging from 20/1 to 1/20 or greater.

Further, the light intensity reaching the plants ranges from about 4^mol/m²/sec to about 2000μιηο1/ιη²/8εϋ, optional light intensity being from about 4^mol/m²/sec to about 400μιηο1/ιη²/8εϋ

Generally, the photosynthetic organisms are any organisms with chlorophyll, including, e.g., corn, beans, wheat, rice, vegetables, tomatoes, flowers, grass, salad, photosynthetic bacteria e.g. cyanobacteria, algae, e.g., microalgae. In particular, the microalgae are Nannochloropsis salina or Chlamydomonas reinhardtii, although other art-known algae are readily cultivated according the invention.

In a further embodiment, the invention also provides a system for cultivating photosynthetic organisms with modulated light, wherein the system comprises a light valve for modulating illumination from a light source, a controller operatively connected to the light valve and at least one sensor operatively connected to the controller, wherein the light valve is located between the light source and the photosynthetic organisms to be illuminated with modulated light.

In certain embodiments, the system further comprises at least one sensor for measuring light from the light source and at least one sensor for measuring parameters selected from the group consisting of light intensity, ON/OFF frequency, duty cycle and combinations thereof of the intensity of the modulated light, and wherein the at least one sensor is operatively connected to the controller. The light source preferably comprises sunlight, although supplemental artificial light is optionally provided.

The modulated light is provided, for example, by a liquid crystal valve under the control of the controller and a power source that powers the controller and a driver logic that drives the liquid crystal valve is also provided.

In certain alternative embodiments, the light valve comprises, e.g., at least one mirror, at least one lens, at least one prism and combinations thereof, wherein the lens, prism or mirror can be rotated in a circular or reciprocal movement to alternately direct the light source towards and away from the photosynthetic organism(s).

The methods and systems of the invention provide for optimized growth of photosynthetic organisms, and in certain embodments, provides for optimized lipid production. In particular, the invention further provides for a method of enhancing lipid production in cultivated photosynthetic organisms comprising cultivating the photosynthetic organisms with modulated light, wherein the modulated light exhibits a pulsed ON/OFF cycle, and wherein the light comprises modulated sunlight, wherein the cultivated photosynthetic organisms yield enhanced lipid content relative to the same photosynthetic organism cultivated under the same growth conditions, under equivalent intensity continuous illumination.

The lipid content is generally enhanced by about 20 to 200 percent, relative to the lipid content of the same photosynthetic organisms cultivated in equivalent continuous illumination. Preferably, the lipid content is enhanced by about 80 percent, relative to the lipid content of the same photosynthetic organism cultivated under the same growth conditions, under equivalent intensity continuous illumination.

In a preferred embodiment, the photosynthetic organism is an algae, and more preferably, a microalgae, such as, e.g., Nannochloropsis salina or Chlamydomonas reinhardtii.

Preferably, the pulse frequency ranges from 0.1 to 5 Hz, the duty cycle from 20/1 to 1/10, and the light intensity from 50 to 200 μΕ m^'V¹. More preferably, the pulse frequency is 1 Hz, the duty cycle is 1/2 and the light intensity is 150 μΕ m^'V¹.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system according to the invention wherein a light source illuminates a modulator or light valve. Illumination from the light source, modulated by the modulator or light valve, under the control of a controller and sensors falls on photosynthetic organism(s).

FIG. 2 illustrates a system according to the invention where the modulator is a liquid crystal valve under the control of controller wherein the modulated light illuminates photosynthetic organisms. A power source powers the controller and driver logic which drives the liquid crystal valve. Parameters for the modulator are configured by user interface (5102)

FIG. 3 illustrates the intensity of light from the sun. Graph (600) shows intensity of the light (604) as function of time. Graph (602) shows intensity of modulated light as a function of time, providing a light intensity wave form.

FIG. 4 illustrates a greenhouse with liquid crystal valve panels for light modulation in place of some or all of the windows.

FIG. 5A illustrates lenses that focus light onto the leftmost third of a sample of a photosynthetic organism(s).

FIG. 5B illustrates the lenses of FIG. 5 A, repositioned in order to focus light onto a middle third of a sample of photosynthetic organism(s).

FIG. 5C illustrates the lenses of FIG. 5 A, repositioned to focus light onto a rightmost third of a sample of photosynthetic organism(s).

FIG. 6 illustrates a top view of the lenses of FIGs. 5A-5C.

DETAILED DESCRIPTION

Accordingly, the present invention provides improved methods and systems for growing photosynthetic organisms. Broadly, the inventive methods and systems provides for modulating a light source, e.g., sunlight, with a light valve or analogous light control means, to provide optimized, pulsed illumination with alternating light and dark cycles. A light valve according to the invention includes, e.g., one or more electronically controlled liquid crystal light valves, reflectors with optional movable components, such as mirrors (including micromirrors), lens or prism systems with optional movable components and analogous optical hardware.

Light supply plays a key role in a photo bioreactor design. At high cell densities, a more intense photosynthetic photon flux helps photons penetrate deeper, e.g., into a culture of photosynthetic microorganisms, thus reducing mutual shading, as well as increasing the ratio of cells receiving enough light to perform photosynthesis (Malcata 2011, Id.). Alternating light and dark cycles permit greater illumination of the photosynthetic organisms while minimizing the possibility of light induced damage to such organisms.

In order to more clearly appreciate the invention, the following terms are defined. The terms listed below, unless otherwise indicated, will be used and are intended to be defined as indicated. Definitions for other terms can occur throughout the specification. It is intended that all singular terms also encompass the plural, active tense and past tense forms of a term, unless otherwise indicated.

The term "photosynthetic organism" is intended to broadly encompass all organisms that contain chlorophyll or bacteriochlorophyll a or b and carry on photosynthesis in order to meet all or part of their nutritional requirements. These include, without limitation, photosynthetic bacteria, photosynthetic plants e.g., multicellular and unicellular plants and preferably photosynthetic plants of commercial, e.g., agricultural, interest, both terrestrial and aquatic in origin. In addition organisms might have other photosensitive components such as carotenoid pigments.

Example plants related to horticultural production in a greenhouse environment can include, for example and without limitation; vegetables (such as tomatoes, cucumber), potted vegetables (such as lettuce), berries, herbs, cut flowers, potted flowers, ornamental plants seedlings and cuttings. In open field growth example plant products can include, e.g., vegetables (such as onion, carrot, cabbages, spinach), berries (strawberry, blueberries), fruits (apples, oranges), wine, nurseries, cut flowers and green cuttings.

In one embodiment, the photosynthetic organisms employed in the practice of the invention are plants grown in greenhouse environment.

In another embodiment, the photosynthetic organisms employed in the practice of the invention are algae. As used in the art, the term "algae" refers to a large and diverse group of typically heterotrophic, eukaryotic organisms that can be found growing in fresh, salt or brackish water. While the group encompasses multicellular seaweeds, the algae referred to herein are preferred to belong to the unicellular variety, i.e., microalgae. Generally, the term "algae" as employed herein references microalgae, unless otherwise indicated.

The methods and systems of the invention provide for light control devices configured to provide a ON/OFF (i.e., light/dark) illumination cycle of "modulated light." The modulated light can be provided in a range of frequencies, including, for example, from about 1 through about 10,000Hz, from about 10 through about 5,000 Hz, from about 20 through about 1,000 Hz, from about 20 through about 500 Hz, from about 40 through about 100 Hz, from about 10 through about 50 Hz and from about 20 to about 40 Hz. In one embodiment, 30 Hz is employed.

The modulated light can be provided in a range of duty cycles. A duty cycle identifies the ratio of ON (light) verses OFF (dark) phases of the modulated light. Thus, the modulated light can be controlled to have, for example, light ON for 1 unit and light OFF for 19 units i.e. 1/20 as a duty cycle. Using a 1/2 ratio as a duty cycle results in 1/2 of the sunlight reaching the illuminated photosynthetic organisms in a given time period, relative to unmodulated, continuous light illumination. Using a 1/3 ratio as a duty cycle results in 1/3 of the sunlight reaching the illuminated

photosynthetic organisms in a given time period, relative to unmodulated, continuous light illumination.

Continuous light illumination can be converted to modulated light, for example, by means of a liquid crystal based light valve based on nematic liquid crystals. Light valves and display devices and nematic liquid crystal compounds useful therein are described, for example, in U.S. Pat. No. 3,322,485 by Williams, incorporated by reference herein. Such light valves are controlled by an electric field and operate when the liquid crystal material is in its mesomorphic state. Generally, with no electric field applied to the nematic liquid crystal material, the material is slightly turbid in appearance and scatters light to some extent. However, a thin layer of such a material is relatively transparent to light incident thereon. The direction of alignment of the liquid crystal molecules (which in the absence of an electric field exist in randomly oriented domains), in an electric field depends upon the direction of the dipole moment of the molecule with respect to its molecular axis. The aligned crystals can be configured to operate as a polarization filter, thus forming the basis for a functioning, electrically controlled light shutter when combined with a parallel polarization filters patterned at right angles to the aligned crystals of liquid crystal panel when the electric field is applied.

Such light valves or shutters are commercially available. For example, simply by way of example, there is MagicFoil™ from MediaVision in Germany (www dot media-vision dot de) that is a liquid crystal based material that is transparent when the current is flowing, and opaque in the absence of current. The manufacturer BMG MIS from Germany, Ulm also sells liquid crystal based products such as a liquid crystal based wall (a large liquid crystal element) and related control electronics that can be adapted to the purposes of the present invention.

For higher frequency modulation, active liquid crystal light valves with typically thin film transistor embedded in the structure are preferably employed. Such active liquid crystal light valves are art known, e.g., as described by U.S. Patent Nos. 5,245,455 and 6,133,897.

Modulated light can also be obtained from continuous light by employing other light control devices, such as, for example, mirrors, lenses and/or prisms that can be rotated in a circular or reciprocal movement to alternately direct the light source, e.g., sunlight, towards and away from the photosynthetic organism(s) that are under cultivation.

In a first embodiment of the invention, as illustrated by FIG. 1, example system (100) includes a light source (102) that radiates light (1020). Preferably the light source (102) is the sun. Optionally, light source (102) can be one or more artificial lights or can include a portion of artificial light in combination with, or alternating with, sunlight. The spectrum of light (1020) can include visible and non- visible light.

Typically, light energy from the sun corresponds to about 1000 Watts/square meter (m²). An alternative way to measure energy from the sun is with units of μπιοΐ/ιη²/ sec i.e., how many photons arrive per square meter per second. Typically there is about 2000 μιηο1/ιη²/8 of photons in sunlight reaching the surface of the Earth. The amount of light arriving at the Earth's surface is typically far more than is needed for growth, leading to photoinhibition.

Photosynthetic organism(s) (106) use the energy from the sun to grow (as in the photosynthesis reactions). Examples of photosynthetic organisms include, without limitation, algae, corn, beans, wheat, rice, vegetables, tomatoes, flowers, grass, salad, and any other art-known useful crop. The photosynthetic organisms (106) can grow in soil, in water, in air, etc. as appropriate. Typically, the photosynthetic organisms are fed with fertilizers, water, nutrients from time to time, using, for example, automatic systems (116).

When the photosynthetic organisms are plants growing in soil, or in a hydroponic apparatus or systems, an example of an automated system will also include an automated watering system. When the photosynthetic organisms are algae, an example of an automated system will also include an automated CO₂ feeding system to provide CO₂ for photosynthesis. The automated systems (116) can be connected to controller (110). The controller (110) can receive sensor data from sensor (112) to measure the effect of direct sunlight (1020) without modulation / modification and from sensor (114) to measure modulated light (1022).

The system of FIG. 1 also includes a modulator (104) (light valve) to modulate radiated light (1020) to modulated light (1022). The modulator is optionally controlled by controller (110). Parameters to control include the frequency and duty cycle.

Example duty cycles include those where the modulator is at the "ON"-stage (i.e., allows light to pass through) for 1 unit of time and is at the "OFF"-stage (i.e. blocking the light) for 2 units of time i.e., having 1/3 as duty cycle (for ON time). Alternative duty cycle can be for example having light ON for 1 unit and OFF for 9 units i.e. 1/10 as duty cycle. Using 1/3 as duty cycle results in 1/3 of the sun light to reach the material 106. Using 1/10 as duty cycle results in 1/10 of the sun light to reach the material 106.

In a second embodiment, as illustrated by FIG. 2, the modulator is a liquid crystal light valve (512). The modulator is used to modulate incoming light (502) to modulated light (504). The modulated light (504) is used by plants (or other organisms needing light) (522). The liquid crystal light valve is controlled by a controller (500). Controller (500) has power source (5100) to provide electricity for the driver logic (5104) which drives the liquid crystal light valve (512). Power source (5100) can be battery or it can be transformer receiving power from power outlet.

In FIG. 2, driver logic (5104) provides alternative voltage via control wires (510) to liquid crystal light valve transparent electrodes that are in the top part (506) and bottom part (508) of the liquid crystal light valve. Typically the top part and bottom part have polarization filters. The filters are aligned at 90 degree angle to each others. When no voltage is applied to the transparent electrodes light passes via the light valve, since the liquid crystal material rotatates light 90 degrees. When a voltage difference is applied to the electrodes the resulting electric field aligns liquid crystal molecules in such a orientation that the light is not rotated, thus blocking the light from passing through the valve (OFF stage).

In FIG. 2, controller (500) optionally includes an user interface (5102) to enable a user to program / configure parameters (duty cycle and frequency) of the controller as well as display status / settings for the users. The frequency can vary from 0 Hz (ON or OFF all the time) to several 100 's of Hz with liquid crystal light valves, or higher (1000's) depending on implementation. Typically, lower frequencies can be achieved with cost efficient passive liquid crystal light valves. For higher frequencies it might be beneficial to use active liquid crystal light valves with typically thin film transistor embedded in the structure. Thus, for example, the frequency ranges from about 10 through 5,000 Hz, more particularly from about 20 through about 1,000 Hz, from about 20 through about 500 Hz, from about 40 through about 100 Hz, and from about 10 through about 50 Hz.

The duty cycle can be used to modify the total amount of light (as integrated over time) (504) for the plants (522). For example intensity of incoming light (502) from the sun during the midday can be in range of 2000μπιο1/ιη²/8εϋ (designated as I_sun). In case modulating the light (502) with duty cycle ½ then total amount of light for the plants (522) is I_totai = Isun/2 i.e., about 1000μιηο1/ιη²/8εϋ when integrated over time. Intensity value during the ON time is I_SUn and during OFF time intensity value is 0 (depending on the transmission characteristics of the light valve).

If the duty cycle is 1/10 the total amount of light energy is I_totai ⁼ Isun /10 i.e., about 200μπιο1/ιη²/8εϋ. As with previous example during the ON time plants (522) get full light intensity of I_sun and during the off time the plants (522) do not get any or limited amount of light.

In preferred embodiments light intensity (504) is set to 1/10 or less of the normal midday sun in equator using duty cycle of 1/10 to 1/20. During dawn or dusk or during cloudy days the duty cycle migh be varied to take in account lower incoming intensity of light (502). For example during cloudy day I_SUn cloudy can be 20% of I_SUn (normal day) i.e., about 400μπιοι/ιη²/8εϋ. Adjusting the duty cycle to 1/2 would lead to an integrated amount of light of 200μπιο1/ιη²/8εε i.e., giving same total amount of light for the plants as during a sunny day. In 8mbodim8nts during times of lower intesity of light from the sun, duty cycles are selected to be from 1/2 to 1/9 to compensate for a lower incoming radiation intensity.

Based on these embodiments the duty cycle can be modified based on intensity of incoming light.

The controller can also optionally include a set of pre-programmed parameters and programs for different types of environments and photosynthetic organisms. The pre-programmed parameters can be also be dynamic and change as function of time and environment. Change of the parameters can be deterministic (change of duty cycle as function of growing time, first week for example 1/10, second week 1/9, third week 1/8 etc. Change of parameters can also be done automatically based on environment such as weather and stage of the growth.

In FIG. 2, the controller (500) can also include communication interface to connect to external computing device (520) over communication network such as Internet over communication module (5106). The connection can be wired or wireless. The external computing device (520) can be for example server or servers. Said servers can be used to remotely configure controller (500) in dynamic manner. Remote configurability enables to update controller with frequency and duty cycles if needed. In some embodiments duty cycles and frequencies can be tuned based on type of organism / plant to be grown. In further embodiments control parameters might be modified based on weather, time of the year, time of the day, type/maturity /age of the plant, desired end product composition (such as size, amount of nutrients, amount of sugar).

An example of modulation according to the invention is illustrated by FIG. 3. In FIG. 3, the flux of light from the sun is about I_sun = 2000μπιο1 / sec / m² (equator, midday). The graph (600) shows the intensity of the light (604) as function of time. As the light is modulated, a light intensity wave form as shown in (602) is presented. There is ON time (606) and OFF time (608) of the light, depending on the parameters.

Integrated total energy is related to the duty cycle i.e., I_totai ⁼ dutycycle x I_sun i.e., with duty cycle 1 N the energy is 1/N of the sun intensity.

In a third embodiment of the invention, as illustrated by FIG. 4 there is provided a greenhouse (400) built using liquid crystal light valve modulators / light valve foil (402). The windows in the greenhouse are replaced (all or some) or covered with liquid crystal light valve glass (or folio) (402) in the roof and/or ceilings (404). Additionally windows (406) which can be opened, can include an liquid crystal light valve modulator. The glass is used to modulate the light to produce the flashing / modulated light effect for the plants which are grown in the green house.

In a fourth embodiment, as with above described greenhouse an, open pond algae growth facility can be covered with a light modulating material. In addition, algae growth facilities implemented using transparent pipes for pumping an aqueous algae growth medium under sunlight can be covered with a light modulating layer, e.g., a liquid crystal light valve panel. The layer can be set above the pipes or it can optionally be an integral part of the pipes. In a fifth embodiment, the systems as illustrated by FIGs. 1 and 2, discussed above, optionally further include artificial lights, such as light emitting diodes (LEDs), installed close to the photosynthetic organism(s). The LEDs can be used to simulate modulated light during the night time, and other times when the sun is not available. In practice there can be a set of LEDs which are providing light in dedicated wave lengths and are modulated (duty cycle and frequency) to correspond to similar environment as modulated from the sun.

Alternatively, the light provided by the LEDs is modulated in different manner than with a modulating layer. In a further alternative, the LEDs are used together with sunlight to further enhance the growth of the photosynthetic organism(s).

In a sixth embodiment, a prism, lenses, or other mechanical means for providing light valve functionality is optionally provided. For example, Figure 5A illustrates an arrangement with three lenses (200), (202) and (204). The lenses can be rotated around axis (206). The incoming light (2000) consists of parallel light. Lenses are used to direct light towards the photosynthetic organisms in a way that provides on/off illumination as a function of the direction of light focused by each respective lens to a first third of the growing area, to a second third of the growing area, and to the last third of the growing area, with repetitions, as in Figure 5A. The system provides on/off illumination as a function of the direction of light focused by each respective lens to a first third of the growing area, to a second third of the growing area, and to the last third of the growing area, with repetition.

Figure 5B illustrates a situation where the lenses of Figure 5 A have been rotated counter clockwise and light is directed to the middle portion of the growing area of the photosynthetic organisms (210). Figure 5C illustrates the light rays (2010) directed to the photosynthetic organisms to the rightmost portion of the growing area of the photosynthetic organisms. Using this arrangement, a duty cycle of 1/3 is achieved. In addition, the total amount of light provided to the photosynthetic organisms is the same as with direct illumination, since the light is not blocked. In essence, light is concentrated to one part of the material at a time and tracked across the surface of the photosynthetic organisms to be grown, resulting in an on off illumination cycle.

Further, the arrangement of Figures 5A, 5B and 5C, respectively, are shown from the top (i.e., from the direction of light source) in Figure 6 in order to provide an overview. Prisms/lenses (300) are arranged in groups of 3 (for 1/3 duty cycle) designated with A, B, C. Each of the prisms (300) are rotated by motor(s) (302). The motor(s) (302) are controlled by controller (304). In one embodiment each A prism or lens is in same angle as other A prism or lens, each B prism or lens is in the same angle as other B prisms/lens and each C prism/lens is in the same angle as other C prism/lens. In alternative embodiment each prism/lens is controlled separately. Based on one embodiment, and to simplify, the prisms are preferably directed in a North - South direction.

EXAMPLES FOR ALGAE

In the following example the growth and lipid production of the following microalgal species is assessed in flat-bed bioreactors. An excess of CO₂ and nitrogen is provided in order to avoid growth limitation due to these nutrients.

High power, wide spectrum Cool white LED lamps are used to mimic sunlight in these experiments. The lamps are configured to provide light intensities which are relative to light intensity from the sun. Higher light intensity of about 2000 μπιοΐ m^"2 s^"1 is used to simulate high light conditions of midday (midday test) and lower light intensity of about 300 μπιοΐ m^"2 s^"1 is used to simulate lower light conditions such as during cloudy day or at dawn / dusk (cloudy day test).

A liquid crystal light valve panel (LCLV) based modulator panel is installed between the light source and the photobioreactor. Light is modulated with a variety of frequencies and duty cycles with the LCLV. Growth is measured by daily changes in optical density of the microalgae suspension in the growth medium at OD_750. The specific growth rate is calculated by the slope of the logarithmic phase for number of cells.

As a control, to get a reference point, growth without LCLV between the light source and photobioreactor is studied.

Light is modulated with different duty cycles and different frequencies. The microalgae species in this example are the art-known, good lipid producer

Nannochloropsis salina. EXAMPLE 1

Light intensity has been suggested to have an influence in algal lipid production, with strong illumination inducing lipid accumulation. By switching the light conditions during cultivation it is possible to change the production from biomass growth towards lipid production.

In order to study the effect of pulsed light on the lipid production, an algal cultivation was subjected to low light intensity of 150μΕ nfV¹ (equals 150μιηο1 m^"V ^:), which normally doesn't support lipid production (Sforza et al. 2012, Id.) The algal species Nannochloropsis salina was selected due to its good lipid producing ability. Cellular lipid content is indicated by fluorescence intensity of Nile Red stained cells at 580 nm. The Nile Red lipid detection method was adapted from Sforza. et al 2012 Id- using a Biotek Synergy #1 Hybrid Reader photometer for measuring fluorescence emission at 580nm. A standardized amount of cells (2xl0⁶) from each replicate sample was used in the measurements.

The light was provided by 120W LedGrow Warm white panels consisting of 55x2W light emitting diodes (Epistar Bridgelux) and provided by LEDFinland. The light valve with trade name ^"'MagicFoil" was provided by MediaVision

(http://www.media~yisj0r3.de), and was controlled by a purpose-built pulse-width modulation module, provided by Mediakum Ltd.

Pulse frequency in the test: 1 Hz.

Duty cycle in the test: ½.

Light intensity: ^Ο μΕ πΤ ¹.

The algae were grown in 400 ml volume in aerated photobioreactors with CO2 addition.

The algae Nannochloropsis salina Tests I, II and III was maintained in sea water supplemented with Guillard's ill nutrients (Sigma Chemicals) as described by Sforza et al. 2012, Id, The growth medium was supplemented with 5 mM \: !( ^'() : as CO2 source and 1.5 g/l a O to prevent nitrogen starvation. For each test group condition three or four individual replicates were grown and analyzed

Test I: algae grown under the modulator panel in "open" non-pulsing mode; control.

Test II: algae grown under the modulator panel in pulsed mode (1 Hz, DT ½). Test III: algae grown in direct light without panel; control.

After 14 days of growth, fluorescence intensity of Nile Red stained cells was determined. Then the algae were harvested, dried, weighed and the respective weights compared. Under this low light intensity the algae biomasses did not show significant variation between different test conditions. The mean biomass in test I, modulator panel in non-pulsing mode, was slightly lower than in pulsing or direct light (Table 1).

However, lipid content in cells showed significant differences between different experimental conditions. Based on Nile Red fluorescence at 580 nm, lipid content per cell was highest in Test II, where algae were grown under pulsed light (Table 1). Even considering variation between individual replicates, the data suggests pulsed light has an increasing effect on lipid production. Individual replicates, e.g. IIA and IID show even higher cellular lipid content so that the difference between the highest (IID) and lowest (IIIB) recorded intensity is almost 80%. This confirms that modulated light has a high potential to improve algae lipid production and boost e.g. biofuel production.

Attorney Docket No. 44545.1006-W

TABLE 1

Lipid content as reflected by fluorescence intensity of Nile Red stained cells and the biomass (dry weight) of algae as grown in Example 1.

REFERENCES CITED

U.S. PATENT DOCUMENTS

US 8,302,346 B2 11/2012 Hunt et al.

US 2012/0306383 Al 12/2012 Munro US 2004/0109302 Al 06/2004 Mori & Yoneda

US 3,322,485 A 05/1967 Williams

US 5,245,455 A 09/1993 Sayyah & Wu

US 6,133,897 A 10/2000 Kouchi

OTHER REFERENCES

Carvalho, A. P., Silva, S.O., Baptista, J.M., Malcata, F.X. 2011. Light requirements in microalgal photobioreactors: an overview of biophotonic aspects. Applied

Microbiology and Biotechnology 89(5): 1275-88.

Gordon J.M., Polle, J.E.W. 2007. Ultrahigh bioproductivity from algae. Applied Microbiology and Biotechnology 76: 969-975.

Katsuda, T., Shimahara, K., Shiraishi, H., Yamagami, K. Ranjbar, R., Katoh, S. 2006. Effect of flashing light from blue light emitting diodes on cell growth and astaxanthin production of Haematococcus pluvialis. Journal of Bioscience and Bioengineering 102(5): 442-446. Malcata, F.X. 2011. Microalgae and biofuels: A promising partnership? Trends in Biotechnology 29(11): 542-549.

Phillips, J.N., Myers, J. 1954. Growth Rate of Chlorella in Flashing Light. Plant Physiology 29(2): 152-161.Sforza, E., Simionato, D., Giacometti, G.M., Bertucco, A., Morosinotto, T. 2012. Adjusted Light and Dark Cycles Can Optimize Photosynthetic Efficiency in Algae Growing in Photobioreactors. PloS One 7(6): e38975. Vejrazka, C, Janssen, M., Streefland, M., Wijffels, R.H. 2011. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light. Biotechnology and Bioengineering 108: 2905-2913.

INCORPORATION BY REFERENCE

Numerous references are cited throughout this application, each of which is incorporated by reference herein in its entirety.

CLAIM OF BENEFIT

This application claims the benefit of US Provisional Application Ser. No. 61/823,544, filed on May 15, 2013, the contents of which are incorporated herein by reference in their entirety.

Claims

WE CLAIM:

1. A method of cultivating photosynthetic organisms comprising illuminating the photosynthetic organisms with modulated light, wherein the modulated light exhibits a pulsed ON/OFF cycle, and wherein the light comprises modulated sunlight.

2. The method of claim 0.1 wherein the modulated light is pulsed at a frequency ranging from about 1 through about 10,000 Hz.

3. The method of claim 1, wherein the modulated light is pulsed at a duty cycle ranging from 20/1 to 1/20.

4. The method of claim 1, wherein the light intensity ranges from about 40μιηο1/ιη²/8εϋ to about 4000μιηο1/ιη²/8ε

5. The method of claim 1, wherein the photosynthetic organisms are selected from the group consisting of algae, corn, beans, wheat, rice, vegetables, tomatoes, flowers, grass, salad and combinations thereof.

6. The method of claim 5, wherein the photosynthetic organisms are microalgae.

7. The method of claim 6, wherein the microalgae comprise Nannochloropsis salina or Chlamydomonas reinhardtii.

8. A system for cultivating photosynthetic organisms with modulated light, wherein the system comprises a light valve for modulating illumination from a light source, a controller operatively connected to the light valve and at least one sensor operatively connected to the controller, wherein the light valve is located between the light source and the photosynthetic organisms to be illuminated with modulated light.

9. The system of claim 8, wherein the system further comprises at least one sensor for measuring light from the light source and at least one sensor for measuring parameters selected from the group consisting of light intensity, ON/OFF frequency, duty cycle and combinations thereof of the intensity of the modulated light, and wherein the at least one sensor is operatively connected to the controller.

10. The system of claim 8, wherein the light source comprises sunlight or artificial light.

11. The system of claim 8, wherein the light valve is a liquid crystal valve under the control of the controller.

12. The system of claim 11 that further comprises a power source that powers the controller and a driver logic that drives the liquid crystal valve.

13. The system of claim 8 wherein the light valve is selected from the group consisting of at least one mirror, at least one lens, at least one prism and combinations thereof, wherein the mirror, lens or prism can be rotated in a circular or reciprocal movement to alternately direct the light source towards and away from the

photosynthetic organism(s).

14. A method of enhancing lipid production in a cultivated photosynthetic organism comprising cultivating the photosynthetic organism with modulated light, wherein the modulated light exhibits a pulsed ON/OFF cycle, and wherein the light comprises modulated sunlight, wherein the cultivated photosynthetic organism yields enhanced lipid content relative to the same photosynthetic organism cultivated under the same growth conditions, under equivalent intensity continuous illumination.

15. The method of claim 14 wherein the lipid content is enhanced by about 20 to 200 percent, relative to the lipid content of the same photosynthetic organism cultivated under the same growth conditions, under equivalent intensity continuous illumination.

16. The method of claim 14 wherein the lipid content is enhanced by about 80 percent, relative to the lipid content of the same photosynthetic organism cultivated under the same growth conditions, under equivalent intensity continuous illumination.

17. The method of claim 14 wherein the photosynthetic organism is a microalgae.

18. The method of claim 17 wherein the microalgae comprise

Nannochloropsis salina or Chlamydomonas reinhardtii.

19. The method of claim 14 wherein the pulse frequency ranges from 0.1 to 5 Hz, the duty cycle from 20/1 to 1/20, and the light intensity from 50 to 200 μιηοΐ m^'V¹ 20. The method of claim 19 wherein the pulse frequency is 1 Hz, the duty cycle is 1/2 and the light intensity is 150 μιηοΐ m^'V¹.