Patent Description:
Patent Document <NUM> discloses an algae culturing method for promoting growth by irradiating algae with artificial light. In this algae culturing method, an irradiation cycle including a red light irradiation procedure for irradiating the algae with red light and a blue light irradiation procedure for irradiating the algae with blue light is performed at least twice within a certain period of time.

It is confirmed that haptophytes grow and yet decrease in a short period of time when the haptophytes are cultured by being irradiated with the red or blue light pertaining to the algae culturing method described in Patent Document <NUM>. An object of the present disclosure is to provide a culturing method and a culturing device enabling to extend the life of the haptophytes.

The present inventor has found that the period from the initiation of culturing by light irradiation to a decrease in population is longer when haptophytes are irradiated with both yellow light and non-yellow visible light than when the haptophytes are irradiated with the non-yellow visible light alone.

Based on the above findings, the haptophyte culturing method according to the present disclosure includes irradiating culture liquid containing the haptophytes with both yellow light and non-yellow visible light. According to this haptophyte culturing method, the haptophytes grow by receiving the yellow light and the non-yellow visible light. As a result, by this culturing method, the life of the haptophytes can be extended as compared with the case of irradiation with the non-yellow visible light alone.

In one embodiment, the haptophytes may be Pavlova lutheri. In this case, the life of Pavlova lutheri can be extended.

The haptophyte culturing device according to another aspect of the present disclosure includes: a culture tank storing culture liquid containing the haptophytes; a first light source irradiating the culture liquid in the culture tank with yellow light; and a second light source irradiating the culture liquid in the culture tank with non-yellow visible light. According to this haptophyte culturing device, haptophytes are cultured in the culture liquid of the culture tank. The haptophytes grow by receiving both the yellow light emitted from the first light source and the non-yellow visible light emitted from the second light source. As a result, with this culturing device, the life of the haptophytes can be extended as compared with the case of irradiation with the non-yellow visible light alone.

The haptophyte culturing device according to one embodiment may further include a control unit configured to control the first light source and the second light source such that the culture liquid is irradiated with both the yellow light and the visible light. In this case, the haptophytes in the culture liquid are capable of receiving both the yellow light from the first light source and the non-yellow visible light from the second light source, which are emitted under the control of the control unit.

According to the present disclosure, the life of haptophytes can be extended.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. It should be noted that the same or equivalent elements are denoted by the same reference numerals without redundant description in the following description and drawings. The dimensional ratios in the drawings do not necessarily match those described. The terms of "up", "down", "left", and "right" are based on illustrated states and are for convenience.

A culturing method according to the present embodiment is a method for efficiently growing haptophytes and extending the life of the grown haptophytes. The haptophytes to be cultured are algae that are a nutritious feed for seedlings of crustaceans such as shrimps and crabs and shellfish such as clams and ark shells. Examples of the haptophytes include Pavlova lutheri, Isochrysis galbana, and Isochrysis sp.

<FIG> is an overall perspective view illustrating a culturing device according to the embodiment. The culturing method of the present embodiment is carried out by, for example, a culturing device <NUM> illustrated in <FIG>. The culturing device <NUM> illustrated in <FIG> is a device for culturing haptophytes <NUM>. The culturing device <NUM> includes a culture tank <NUM>, a first illumination <NUM>, a second illumination <NUM>, an underwater illumination <NUM>, a control unit <NUM>, and a ventilation unit <NUM>. The culture tank <NUM> is a container where the haptophytes <NUM> and culture liquid <NUM> are stored. The culture liquid <NUM> is water suitable for the growing environment of the haptophytes <NUM> to be cultured. The culture liquid <NUM> is, for example, water containing more nutrient salt such as nitrogen and phosphorus than seawater. The haptophytes <NUM> grow by photosynthesis in the culture liquid <NUM>.

A box-shaped space with, for example, an open upper part is defined in the culture tank <NUM>. The haptophytes <NUM> and the culture liquid <NUM> are stored in the culture tank <NUM>, and a water surface <NUM> is formed in the culture tank <NUM>. A bottom surface <NUM> is provided at the lower end in the culture tank <NUM>.

The first illumination <NUM> and the second illumination <NUM> irradiate the haptophytes <NUM> and the culture liquid <NUM> in the culture tank <NUM> with light. The first illumination <NUM> and the second illumination <NUM> are disposed above, for example, the water surface <NUM>. The first illumination <NUM> and the second illumination <NUM> perform the light irradiation with light-emitting surfaces directed toward the bottom surface <NUM> of the culture tank <NUM>.

The first illumination <NUM> irradiates the culture liquid <NUM> in the culture tank <NUM> with yellow light. The yellow light is light with a wavelength range of substantially <NUM> or more and <NUM> or less. The wavelength range is the range of the wavelength in which the peak wavelength of the light exists. The upper limit value of the wavelength range of the yellow light may be <NUM>. The lower limit value of the wavelength range of the yellow light may be <NUM>. The lower limit value of the wavelength range of the yellow light may be <NUM>. Here, the yellow light may be, for example, light in which the half-value width of the peak wavelength falls within any of the above wavelength ranges. The first illumination <NUM> is, for example, a surface light source configured by a plurality of yellow light-emitting diodes (LEDs) fixed on a substrate and having the light-emitting surface on one surface.

The second illumination <NUM> irradiates the culture liquid <NUM> in the culture tank <NUM> with non-yellow visible light. The non-yellow visible light is visible light with a wavelength range of substantially less than <NUM> or more than <NUM>. The non-yellow visible light may be visible light with a wavelength range of more than <NUM>. The non-yellow visible light may be visible light with a wavelength range of less than <NUM>. The non-yellow visible light may be visible light with a wavelength range of less than <NUM>. Here, the non-yellow visible light may be, for example, light in which the half-value width of the peak wavelength falls within any of the above wavelength ranges. The second illumination <NUM> is, for example, a surface light source configured by a plurality of LEDs fixed on a substrate and having the light-emitting surface on one surface.

The underwater illumination <NUM> is disposed in the culture tank <NUM> and irradiates the haptophytes <NUM> and the culture liquid <NUM> in the culture tank <NUM> with light. The underwater illumination <NUM> is disposed at, for example, the upper end of a scaffold <NUM> extending upward from the bottom surface <NUM>. The underwater illumination <NUM> is disposed in the culture liquid <NUM> away from the water surface <NUM> and the bottom surface <NUM>. The underwater illumination <NUM> is disposed along a plane parallel to the bottom surface <NUM>. The underwater illumination <NUM> is disposed with light-emitting surfaces on both surfaces directed toward the water surface <NUM> and the bottom surface <NUM>.

The underwater illumination <NUM> emits yellow light or non-yellow visible light. The wavelength range of the yellow light in the underwater illumination <NUM> is the same as the wavelength range of the yellow light in the first illumination <NUM>. The wavelength range of the non-yellow visible light in the underwater illumination <NUM> is the same as the wavelength range of the non-yellow visible light in the second illumination <NUM>. The underwater illumination <NUM> is, for example, a surface light source configured by laminating the substrates of two LED plates configured by a plurality of LEDs fixed on the substrates and having the light-emitting surfaces on both surfaces.

The underwater illumination <NUM> is covered with, for example, a translucent resin member. The underwater illumination <NUM> is waterproofed since the underwater illumination <NUM> is disposed in the culture liquid <NUM>. A power source is provided in the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM>. The electric power of the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM> may be supplied from an external power source by wiring or the like.

The control unit <NUM> controls the first illumination <NUM>, the second illumination <NUM>, and the underwater illumination <NUM> such that the culture liquid <NUM> is irradiated with both the yellow light and the non-yellow visible light. The control unit <NUM> is, for example, a central processing unit (CPU). The control unit <NUM> is connected to the first illumination <NUM>, the second illumination <NUM>, and the underwater illumination <NUM>. The control unit <NUM> controls the timings at which the first illumination <NUM>, the second illumination <NUM>, and the underwater illumination <NUM> perform the light irradiation.

The control unit <NUM> performs control such that, for example, the inside of the culture tank <NUM> is simultaneously irradiated with the yellow light from the first illumination <NUM> (an example of a first light source) and the non-yellow visible light from the second illumination <NUM> (an example of a second light source). The control unit <NUM> may perform control such that the inside of the culture tank <NUM> is simultaneously irradiated with the yellow light from the underwater illumination <NUM> (an example of the first light source) and the non-yellow visible light from the second illumination <NUM> (an example of the second light source). The control unit <NUM> may perform control such that the inside of the culture tank <NUM> is simultaneously irradiated with the yellow light from the first illumination <NUM> (an example of the first light source) and the non-yellow visible light from the underwater illumination <NUM> (an example of the second light source).

The control unit <NUM> may perform control such that the inside of the culture tank <NUM> is simultaneously irradiated with the yellow light from the combination of the first illumination <NUM> and the underwater illumination <NUM> (an example of the first light source) and the non-yellow visible light from the second illumination <NUM> (an example of the second light source). The control unit <NUM> may perform control such that the inside of the culture tank <NUM> is simultaneously irradiated with the yellow light from the first illumination <NUM> (an example of the first light source) and the non-yellow visible light from the combination of the second illumination <NUM> and the underwater illumination <NUM> (an example of the second light source).

The control unit <NUM> may control the wavelength and intensity of the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM>. The wavelength and intensity controlled by the control unit <NUM> are set based on, for example, the density, growth rate, or number of days of culturing of the haptophytes <NUM> in the culture tank <NUM>. The control unit <NUM> controls the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM> based on the set wavelength and intensity.

The ventilation unit <NUM> performs ventilation from the bottom surface <NUM> toward the water surface <NUM> with a gas <NUM> containing carbon dioxide and oxygen. The gas <NUM> contains carbon dioxide and oxygen. The haptophytes <NUM> perform photosynthesis using the carbon dioxide ventilating the culture liquid <NUM> and perform respiration using the oxygen. The ventilation unit <NUM> has an air cylinder <NUM>, a supply pipe <NUM>, and a discharge pipe <NUM>. The air cylinder <NUM> stores the carbon dioxide- and oxygen-containing gas <NUM>. The air cylinder <NUM> may be an air pump. One end of the supply pipe <NUM> is connected to the air cylinder <NUM>, and the other end of the supply pipe <NUM> is connected to the discharge pipe <NUM>. The supply pipe <NUM> is made of, for example, a silicon tube. The supply pipe <NUM> acquires a predetermined amount of the gas <NUM> from the air cylinder <NUM>. The supply pipe <NUM> supplies the acquired gas <NUM> to the discharge pipe <NUM>.

The discharge pipe <NUM> is disposed on the bottom surface <NUM>. The discharge pipe <NUM> is a long pipe member. The discharge pipe <NUM> is made of, for example, a vinyl chloride pipe. A pipe line <NUM> is defined in the discharge pipe <NUM>, and a plurality of small holes <NUM> are formed at predetermined intervals in the upper portion of the discharge pipe <NUM>. The plurality of small holes <NUM> allow the inside of the culture tank <NUM> and the pipe line <NUM> to communicate with each other. As for the discharge pipe <NUM>, the gas <NUM> supplied from the supply pipe <NUM> to the discharge pipe <NUM> passes through the pipe line <NUM> and is discharged into the culture tank <NUM> from the plurality of small holes <NUM>.

The amount of the gas <NUM> that the supply pipe <NUM> acquires from the air cylinder <NUM>, the size of the discharge pipe <NUM>, the shapes and sizes of the cross sections of the pipe line <NUM> and the small holes <NUM>, and the disposition interval of the small holes <NUM> in the discharge pipe <NUM> are appropriately set in accordance with, for example, the density, growth rate, or number of days of culturing of the haptophytes <NUM>. The control unit <NUM> may control the ventilation unit <NUM>. The control unit <NUM> controls, for example, the amount of the gas <NUM> ventilating the culture liquid <NUM> and the rate at which the gas <NUM> is supplied. A water flow circulating in the culture tank <NUM> is generated by the ventilation unit <NUM> ventilating the culture liquid <NUM> with the gas <NUM>. As a result, the haptophytes <NUM> move along the water flow and the inter-individual bias in the amount of light reception is suppressed.

Next, a method for culturing the haptophytes <NUM> will be described. The haptophytes <NUM> and the culture liquid <NUM> are stored in the culture tank <NUM>. The ventilation unit <NUM> ventilates the culture liquid <NUM> with the gas <NUM> under the control of the control unit <NUM>. The water flow circulating in the culture tank <NUM> is generated by the ventilation unit <NUM>, and the haptophytes <NUM> move in the culture tank <NUM> along the water flow. Under the control of the control unit <NUM>, the haptophytes <NUM> in the culture liquid <NUM> stored in the culture tank <NUM> are irradiated with both the yellow light from the first illumination <NUM> or the underwater illumination <NUM> and the non-yellow visible light from the second illumination <NUM> or the underwater illumination <NUM>. As a result, the haptophytes <NUM> grow by photosynthesis by receiving both the yellow light and the non-yellow visible light.

The haptophytes <NUM> cannot be grown even if the haptophytes <NUM> are cultured by being irradiated with the yellow light alone. By irradiating the haptophytes <NUM> with the non-yellow visible light, the haptophytes <NUM> can be grown, and yet the haptophytes <NUM> decrease in a short period of time. By culturing the haptophytes <NUM> with the combination of the non-yellow visible light and the yellow light, which does not contribute to the growth of the haptophytes <NUM>, the haptophytes <NUM> can be grown and the phenomenon in which the haptophytes <NUM> decrease in a short period of time is improved. By means of the method for culturing the haptophytes <NUM> and the culturing device <NUM> according to the present embodiment, the life of the haptophytes <NUM> can be extended by irradiating the haptophytes <NUM> with both the yellow light and the non-yellow visible light.

Although various exemplary embodiments have been described above, various omissions, substitutions, and changes may be made without being limited to the exemplary embodiments described above. For example, the side surface and the bottom surface <NUM> of the culture tank <NUM> may have a structure blocking light from the outside such that, for example, light other than the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM> does not enter the culture liquid <NUM>.

In addition, the culturing device <NUM> may lack the first illumination <NUM>. In this case, the underwater illumination <NUM> is used as a light source for yellow light irradiation. The culturing device <NUM> may lack the second illumination <NUM>. In this case, the underwater illumination <NUM> is used as a light source for non-yellow visible light irradiation. The culturing device <NUM> may lack the first illumination <NUM> and the second illumination <NUM>. In this case, the underwater illumination <NUM> emits both the yellow light and the non-yellow visible light. The culturing device <NUM> may lack the underwater illumination <NUM>. In this case, the first illumination <NUM> is used as a light source for yellow light irradiation and the second illumination <NUM> is used as a light source for non-yellow visible light irradiation. The first illumination <NUM> or the second illumination <NUM> may be disposed so as to emit light from the side surface or the bottom surface <NUM> of the culture tank <NUM>.

The culturing device <NUM> may lack the control unit <NUM>. In this case, a worker may control the light irradiation performed by the first illumination <NUM>, the second illumination <NUM>, or the underwater illumination <NUM>, the amount of the ventilation that the ventilation unit <NUM> performs with the gas <NUM>, or the supply rate. The culturing method of the present disclosure may be applied to other phytoplankton similar in absorbance characteristics to the haptophytes <NUM>. The phytoplankton are, for example, plankton having low absorbance in the wavelength range of yellow light. As for the culturing method, the irradiation with the yellow light may be performed after the haptophytes have grown by the non-yellow visible light irradiation.

Hereinafter, various experiments carried out for verifying the effects of the method and device according to the present disclosure will be described. It should be noted that the present disclosure is not limited to the following experiments. In the following experiments, Pavlova lutheri was used as an example of the haptophytes <NUM>.

The absorption spectrum of Pavlova lutheri was measured by absorptiometry. A device was used in which a light source, opal glass, a sample cell, and a spectroscopic detector are arranged in a straight line in this order. The absorption spectrum of Pavlova lutheri was obtained by storing Pavlova lutheri and water in the sample cell, irradiating the sample cell with scattered light, and detecting the light transmitted through the sample cell for each wavelength. The measurement conditions are as follows.

Only water was stored in the sample cell for comparison, and the absorption spectrum of the water was obtained under the above measurement conditions. The results are shown in <FIG>.

<FIG> is a graph showing the absorption spectrum of Pavlova lutheri. The horizontal axis of <FIG> is the wavelength (nm), and the vertical axis of <FIG> is the absorbance. <FIG> shows the half-value widths of the peak wavelengths of the red, yellow, green, blue, and white light emitted from the light source used in the example to be described later. The peak wavelength of the red light is <NUM>, and the half-value width of the red light is in the range of <NUM> or more and <NUM> or less. The peak wavelength of the yellow light is <NUM>, and the half-value width of the yellow light is in the range of <NUM> or more and <NUM> or less. The peak wavelength of the green light is <NUM>, and the half-value width of the green light is in the range of <NUM> or more and <NUM> or less. The peak wavelength of the blue light is <NUM>, and the half-value width of the blue light is in the range of <NUM> or more and <NUM> or less. The peak wavelengths of the white light are <NUM> and <NUM>, the half-value width of the short wavelength-side peak is in the range of <NUM> or more and <NUM> or less, and the half-value width of the long wavelength-side peak is in the range of <NUM> or more and <NUM> or less.

As shown in <FIG>, the absorbance of the water changed near <NUM> in the wavelength range of <NUM> or more and <NUM> or less. From this, it was confirmed that the effect of the water on the absorption spectrum is small. The absorbance of Pavlova lutheri resulted in a peak around the wavelength range of the blue or red light. In other words, it was confirmed that Pavlova lutheri easily absorbs light around the wavelength range of the blue or red light. This result suggests that the photosynthesis of Pavlova lutheri can be performed more efficiently by using the light around the wavelength range of the blue or red light than by using the yellow or green light.

The time change in Pavlova lutheri cell density was measured for each irradiation light color. Red, yellow, green, and blue light were used as the irradiation light. The peak wavelengths and half-value widths of the red, yellow, green, and blue light are as described above. The culturing device <NUM> was prepared for each irradiation light color. The light irradiation was performed using only the underwater illumination <NUM> without using the first illumination <NUM> and the second illumination <NUM>. The culture conditions are as follows.

The cell density of Pavlova lutheri cultured under the above culture conditions was measured for each culture day. The cell density of Pavlova lutheri was measured by collecting <NUM>µL of the culture liquid <NUM> from the inside of the culture tank <NUM> and using a one-cell counter (disposable hemocytometer). This measurement was repeated four times, the average was calculated, and the average was used as the cell density of Pavlova lutheri in the culture liquid <NUM> of that day. The results are shown in <FIG>.

<FIG> is a graph showing the time change in Pavlova lutheri cell density at a time of culturing with light different in wavelength range. The horizontal axis of <FIG> is the number of days of culturing (days), and the vertical axis of <FIG> is the Pavlova lutheri cell density (×<NUM><NUM> cells/ml). The culturing was initiated on day <NUM>. Each graph shown in <FIG>, which pertains to Pavlova lutheri culturing by means of reception of any one of red, yellow, green, and blue light, plots the Pavlova lutheri cell density for each light and represents an estimated cell density between data points by an approximate line.

As shown in <FIG>, it was confirmed that the Pavlova lutheri population can be increased the most by the red light among the red, yellow, green, and blue light. As shown in <FIG>, the red light is easily absorbed by Pavlova lutheri. In other words, it is expected that Pavlova lutheri absorbed a large amount of light and actively photosynthesized by using the red light and the Pavlova lutheri population increased as a result.

However, in the case of culturing using the blue light, which is easily absorbed by Pavlova lutheri, the population did not grow as much as in the case of using the red light and, rather, the population did not grow more than in the case of using the green light, which is lower in absorbance. This result suggests that the absorbance is not the only Pavlova lutheri growth factor. One possible factor is light transmittance. The light transmittance of the culture tank <NUM> where Pavlova lutheri is present is higher in the order of yellow, red, green, and blue light. Blue light has extremely low transmittance compared to light of other colors. In other words, although blue light is easily absorbed by Pavlova lutheri, the light is hard to reach Pavlova lutheri in a culture tank large in scale as in the present experimental environment, and thus it is presumed that the light contributed less to the population growth than green light.

Further, as shown in <FIG>, it was confirmed that the yellow light hardly contribute to the growth of Pavlova lutheri despite irradiation. As described above, the yellow light is the light with the highest transmittance although it is not easily absorbed by Pavlova lutheri. Accordingly, it is unlikely that the yellow light did not contribute to the growth of Pavlova lutheri because it did not reach Pavlova lutheri. Microscopic confirmation suggested that Pavlova lutheri was active and photosynthesizing. Then, it can be said that Pavlova lutheri is not growing while performing photosynthesis. In other words, it was confirmed that the yellow light has a unique and extraordinary effect that it does not contribute to growth (suppresses growth) while giving the energy required for the activity of Pavlova lutheri.

Since only the yellow light has a growth inhibitory effect, it can be said that the non-yellow visible light (e.g. red, green, blue, or white light) needs to be emitted for Pavlova lutheri growth. However, it was confirmed that Pavlova lutheri grown by the red, green, or blue light decreases with the passage of culture days. The Pavlova lutheri population reached <NUM> on day <NUM> when grown in the blue light and on day <NUM> when grown in the green light. Even when grown in the red light, the Pavlova lutheri population significantly decreased on day <NUM> and was expected to reach <NUM> within a few days. In this manner, it was confirmed that the red, green, and blue light are capable of growing Pavlova lutheri and yet the grown Pavlova lutheri population cannot be maintained for over a week or so and rapidly decreases subsequently.

As an example, Pavlova lutheri was cultured by means of the culturing device <NUM>, the yellow light, and the non-yellow visible light and the time change in cell density was measured. White light was used as an example of the non-yellow visible light. The peak wavelengths and half-value widths of the yellow and white light are as described above. The yellow light was emitted using the underwater illumination <NUM>, and the white light was emitted using the second illumination <NUM>. The culture conditions are as follows.

The cell density of Pavlova lutheri cultured under the above culture conditions was measured by the method described above for each culture day.

As a comparative example, Pavlova lutheri was cultured only with white light and using another culturing device <NUM> and the time change in cell density was measured. The white light was emitted using the second illumination <NUM>. The culture conditions and the cell density measurement method were the same as those of the example with the exception of the yellow light not emitted in the comparative example. The results are shown in <FIG>.

<FIG> is a graph showing the time changes in Pavlova lutheri cell density according to the example and comparative example. The horizontal axis of <FIG> is the number of days of culturing (days), and the vertical axis of <FIG> is the Pavlova lutheri cell density (×<NUM><NUM> cells/ml). The culturing was initiated on day <NUM>. Each graph shown in <FIG> plots the Pavlova lutheri cell density according to the example or comparative example and represents an estimated cell density between data points by an approximate line.

As shown in <FIG>, the Pavlova lutheri cell density according to the comparative example decreased with the passage of culture days from day <NUM> although the density increases in a short period of time from the culturing initiation as in the case of the non-yellow visible light shown in <FIG>. Specifically, the increase in cell density slowed down from day <NUM> and the cell density was maintained at <NUM> to <NUM> (×<NUM><NUM> cells/ml) from day <NUM> to day <NUM>. The cell density decreased after day <NUM>. The Pavlova lutheri population was <NUM> (×<NUM><NUM> cells/ml) or more for <NUM> days.

In contrast, it was confirmed that Pavlova lutheri according to the example grows with stability although the growth rate from the culturing initiation is slightly lower than that of the comparative example. Specifically, the cell density increased until day <NUM>. The increase in cell density slowed down from day <NUM>, and the cell density was maintained at <NUM> to <NUM> (×<NUM><NUM> cells/ml) from day <NUM> to day <NUM>. The cell density decreased after day <NUM>. The Pavlova lutheri population was <NUM> (×<NUM><NUM> cells/ml) or more for <NUM> days.

As described above, in the example, it was confirmed that the period from the initiation of culturing by light irradiation to a rapid decrease in population is <NUM> days, which is <NUM> days longer than in the comparative example. In the example, it was confirmed that the maximum value of the cell density was maintained for <NUM> days, which is five days longer than in the comparative example. In the examples, it was confirmed that <NUM> (×<NUM><NUM> cells/ml) or more was maintained for <NUM> days, which is <NUM> days longer than in the comparative example. In this manner, it was confirmed that the culturing method according to the example is longer in every evaluation period than the method according to the comparative example. Accordingly, it was confirmed that the culturing method according to the example enables life extension for haptophytes such as Pavlova lutheri as compared with the method according to the comparative example.

Further, in the example, the maximum value of the cell density was <NUM> to <NUM> (×<NUM><NUM> cells/ml), which is higher than <NUM> to <NUM> (×<NUM><NUM> cells/ml) of the comparative example. In this manner, it was confirmed that the maximum value of the Pavlova lutheri cell density can be increased by the culturing method according to the example as compared with the method according to the comparative example.

Claim 1:
A method for culturing haptophytes comprising simultaneously irradiating culture liquid containing the haptophytes with both
- yellow light the half-value width of the peak wavelength of which falls within the wavelength range of <NUM>-<NUM>, using a first light source, and
- non-yellow visible light the peak wavelength of which falls within the wavelength range of < <NUM> or within the wavelength range of > <NUM>, using a second light source.