JPH07155167A - Culture device for fine alga - Google Patents

Abstract

PURPOSE:To provide a culture device for fine algae capable of maintaining activity of cell at the maximum and increasing productivity of alga by control ling an amount of light rays supplied according to a cell density of a culture solution. CONSTITUTION:A great number of glass tubes are arranged in a cylindrical container 1 made of glass, a light amount variable type fluorescent tube 3 is inserted into each glass tube 2 and an illumination meter 4 is inserted into an arbitrary glass tube 2. A culture solution 6 is agitated by a stirrer 7 and air from a vent pipe 5 is aerated. Change of cell density is measured by an illuminance monitor 8 and a quantity of light supplied is regulated by a light amount controller 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a culture apparatus for microalgae which efficiently increases the production amount of microalgae cells by supplying a minimum amount of light regardless of the cell density in a microalgae culture solution.

[0002]

2. Description of the Related Art Currently, industrial culture of microalgae represented by Chlorella and Spirulina is carried out using a pond. In this culturing method, since the light source is limited to sunlight, the depth of the pond is as shallow as 50 cm or less, and a vast site is required to increase the production of cells or metabolites. Become. In addition, since this culture method is an open system, it has a drawback that there is a high risk of contamination with bacteria or other algae.

In order to improve these drawbacks, a microalgae culturing device, which is a photosynthetic bioreactor in a closed system using various artificial light sources, has been developed. Typically,
In order to efficiently culture and produce microalgae, it is necessary to grow the microalgae at a high density. Therefore, in the photosynthetic bioreactor used, it is necessary that the amount of light necessary for cell growth be supplied to the cells in the reactor as uniformly as possible. However, many microalgae are extremely sensitive to the amount and wavelength of light provided, and excessive light and wavelengths that inhibit growth can cause cell damage or death.

Therefore, in consideration of the optical path length from the light source to the cells and the cell density, it is important to make uniform the amount of light and the wavelength of light required for growth, which is constant for all cells. It becomes a factor. In culture production of microalgae as well as in conventional fermentation production, it is desirable that the ultimate cell density be as high as possible. However, since the optical path length becomes shorter as the cell density increases, it is necessary to irradiate the cells with light from a position closer thereto. To meet these requirements, a light supply method is used in which the optical path length from the light source to the cells is shortened, and at the same time, the light irradiation surface per volume of the culture solution is increased.

[0005]

When considering the regulation of the amount of light supplied during the culture of microalgae, for example, in a photosynthetic bioreactor of the type in which a light emitter is inserted in the reactor, it is necessary to control the number of lights of the light emitter. There is. However, in this case, even if the mounting amount of the light emitters is uniform, even if the number of light emitter lamps is uniform, the optical path length from the light source to the cell varies, and switching of the light supply amount is performed by the light emitter 1. Since the work is done in units of this unit, variations occur and it is difficult to perform fine control.

[0006] In culture production of microalgae, the culture format is usually batch culture as in conventional fermentation production. In batch culture, the cell density in the culture solution changes 10 times or more from the start to the end of the culture, but the average light intensity received by the cells decreases with increasing cell density and is supplied to all cells in the culture solution. The average amount of light emitted is reduced. The effect becomes more remarkable in high-density culture with a cell density of 0.5 g / 1 or more, and there is a big problem in which cell density the light amount is set.

For example, cell density (C1) at the initiation stage of culture
When the amount of light is set in, the average amount of light received by cells decreases as the cell density increases, and the growth rate decreases, resulting in a decrease in algal cell production. On the other hand, when the amount of light is set at the cell density (C2) at the stage of culturing, light is excessively supplied at the stage of culturing, the cells are damaged, and the amount of algal cells produced decreases. Further, even when the amount of light is set at the cell density (Cn) at an arbitrary stage in the culture solution, the amount of light is oversupplied at a cell density lower than Cn, and the amount of light becomes insufficient at a high density.

[0008] Therefore, an object of the present invention is to cultivate a microalgae in which the activity of cells is maximally maintained and the productivity of algal cells is increased by adjusting the amount of light supplied according to the cell density in the culture solution. Is provided.

[0009]

[Means for Solving the Problems] As a result of research on a method of supplying appropriate light to cells regardless of cell density, the present inventors have shortened the optical path length from the light source to the cells and, at the same time, per volume of culture solution. It is possible to maintain the cell growth ability and metabolite production ability by combining the light supply method with more light irradiation surface and the variable light source, and as a result, increase the algal cell production and metabolite production. Then, they have completed the present invention.

That is, the present invention is an apparatus for culturing microalgae, which is provided with a device for measuring a change in cell density of microalgae and a device for varying a light amount according to the change.

In the present invention, an illuminometer or a turbidimeter is used as a device for measuring changes in cell density, and the light supply amount is measured at any time by this, and the light amount is adjusted by the measured value. When culturing microalgae, the measurement value measured by a luminometer or a turbidimeter decreases as the cell density increases. That is, the supplied light amount is increased so that the measurement value measured by the illuminance meter or the turbidity meter becomes constant. For example, an illuminometer or a turbidimeter is installed in the culture solution, and the amount of light is adjusted from the measured value.

In the present invention, a light source of variable light amount is used as a light source for supplying light to cells, and the optical path length from the light source to the cells is short, and at the same time, the light irradiation surface per volume of the culture solution is increased. Is preferred. For example, a cylindrical luminous body is inserted into a culture solution at uniform intervals, and the amount of light emitted from the luminous body is adjusted as the cell density increases.

Usually, the growth curve of microalgae draws a curve as shown in FIG. A few hours after the start of the culture, a time lag (a) occurs, and then several hours show a logarithmic growth phase (b), which becomes a linear growth phase (c) as the cell density in the culture medium increases, and the supply of light is insufficient or The stationary phase (d) is reached due to lack of nutrients in the medium. In the linear growth phase (c), the amount of cell growth per hour becomes constant, so
In order to efficiently culture microalgae, it is necessary to maintain the logarithmic growth phase (b) as long as possible.

The cause of the transition from the logarithmic growth phase (b) to the linear growth phase (c) is largely due to the insufficient supply of light.
Therefore, in order to maintain the logarithmic growth phase (b) for a long time, it is necessary to increase the supply light amount immediately before the supply light amount becomes insufficient.

[0015]

[Figure 1]

[0016]

Therefore, when the culture apparatus for microalgae of the present invention is used, the amount of light supplied can be increased as the cell density increases, and the logarithmic growth phase (b) can be maintained for a long time. As a result, the cell activity is maintained well and efficient culture of microalgae can be performed.

[0017]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. Example

FIG. 2 shows a schematic view of a culture apparatus for microalgae used in this example. (1) has an inner diameter of 85 mm and a height of 25
It is a 0 mm glass cylindrical container, and 46 glass tubes (2) having an inner diameter of 5 mm, an outer diameter of 7 mm and a length of 230 mm are arranged at 3 mm intervals from the top plate of the cylindrical container (1). , The number is shown as three). Into this glass tube (2), a variable light quantity type fluorescent lamp (3) (outer diameter 3 mm, light emitting part length 15 mm) capable of adjusting the surface illuminance of the glass tube in the range of 3 klx to 30 klx is inserted as a light source. ing. Also, inner diameter 3 mm, outer diameter 5 m
A glass tube (2) with a length of m and a length of 200 mm is placed at an arbitrary position from the top plate of the cylindrical container (1), and an outer diameter of 1 is placed therein.
An illuminometer (4) having a length of mm and a length of 180 mm is inserted.
The culture liquid volume was set to 1 liter, and 300 ml / m of air was supplied from the ventilation pipe (5) inserted from the center of the top plate of the cylindrical container (1).
Aerated at a rate of in. The stirrer (not shown) was used to stir the culture solution (6), and the stirrer (7) with a length of 2 cm was used to
It was stirred at 50 rpm. The temperature of the culture solution (6) was controlled to 22 to 23 degrees by placing the cylindrical container (1) in a temperature-controllable water tank (not shown). (8) is an illuminance monitor, and (9) is a light quantity controller.

[0019]

[Fig. 2]

The microalgae used in this example are the coccolithophorid Pleurochrysis cartere (Ple) belonging to the phytophyta Haptophyta.
urochrysis carterae) was used. As a culture medium, natural seawater is supplemented with inorganic salts such as nitrates and phosphates and various trace metals (Epp)
ley's) medium was used.

In a cylindrical container (1), 1 liter of Eple's medium was placed, and a culture solution of Pleurocrisis cartere was added to the cell culture medium having an initial cell density of 0. D. (Optical Densit
100 ml was inoculated so that y) = 0.05. The amount of light supplied can be adjusted to 0. D. The illuminance of the illuminance meter (4) was measured by the illuminance monitor (8), and the light amount was manually adjusted by the light amount controller (9). The initial value of the amount of light emitted from the light emitter is set to 3 klx, and O.I. D. Is 0.05 to 0.2
Up to 3 klx, from 0.2 to 0.5 up to 6 klx, 0.
9 klx from 5 to 0.7, 12 from 0.7 to 1.0
Culture was performed as klx. As a result, the production amount of algal cells reached 585 mg / l on the 6th day of culture.

Comparative Example As a comparison, Pleurocrisis cartel was cultured without adjusting the amount of light and keeping the amount of luminescence constant at 6 klx. In this case, the alga body production was 320 mg / l on the 6th day.

From the above, if the amount of luminescence is adjusted according to the alga body density and culturing is performed using the culturing apparatus of the present invention,
The cell activity was maintained well, and the amount of algal cells produced could be increased 1.8 times that of the comparative example.

[0024]

By using the culture apparatus for microalgae of the present invention, cell growth ability and metabolite production ability can be maintained throughout the culturing period, so that the alga body production amount and the metabolite production amount can be increased.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the culture time of microalgae and the yield of algal bodies.

FIG. 2 Microalgae culture device used in this example

[Explanation of symbols]

 a Time lag b Logarithmic growth phase c Linear growth phase d Stationary phase 1 Cylindrical container 2 Glass tube 3 Variable light intensity fluorescent lamp 4 Illuminance meter 5 Vent tube 6 Culture solution 7 Stirrer 8 Illumination monitor 9 Light intensity controller

Claims (3)

[Claims] 1. An apparatus for culturing microalgae, comprising: a device for measuring a change in cell density of microalgae; and a device for varying a light amount according to the change. 2. The culture apparatus for microalgae according to claim 1, wherein the apparatus for measuring the change in cell density of the microalgae is an illuminometer or a turbidimeter. 3. The apparatus for culturing microalgae according to claim 1, wherein the device for changing the light amount is a variable light type fluorescent lamp.