JPH0724570B2 - Algae culture method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for aseptically culturing microalgae such as Chlorella and Spirulina.

[Conventional technology]

Artificial culture of microalgae, such as chlorella and spirulina, which can be used for medicines, foods, feeds, etc., has been studied from an early stage, and many culture devices for that purpose have been proposed. The main ones are as follows.

Open pond culture method Open circulation culture method Open flow channel culture method Glass flat bottle culture method Vertical cylindrical culture method Among these, the open type that allows large-scale culture is contaminated with other algae and contamination by various bacteria. It has the drawback that it tends to occur and the quality and yield of the harvested algae are not stable. Further, in the culturing method using sunlight, in order to expand the light-receiving surface, the culture device must be expanded horizontally, but since the light-receiving surface cannot be made larger than the installation area of the culture device, large-scale culture is possible. To do that requires a vast site. Aseptic culture is possible with the culture method using a glass flat bottle, but mass culture is not possible.

In the vertical cylindrical culture method, a cylindrical culture tank made of a light-transmitting material such as glass or acrylic resin is blown with air to perform culture while irradiating light, so that large-scale culture is possible, and heterogeneous algae and other bacteria are also available. It has the feature that it is not easily contaminated with. However, vigorous agitation is required to prevent precipitation of algae during culture and adhesion of alga bodies to the inner surface of the culture tank. However, if the amount of aeration is increased, algae adhere to and accumulate on the tank wall in the gas phase portion above the culture tank, and if left unattended, the yield will decrease, so frequent cleaning is necessary. In addition, aeration causes significant water evaporation and foaming. Effervescence is particularly prominent in the culture of substances that release polysaccharides outside the algal cells, such as Spirulina and porphyridium, and the algal cells are discharged out of the culture tank along with the bubbles, causing a decrease in yield and contamination. .

[Problems to be Solved by the Invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the vertical cylindrical culture method, to provide an algae culture method that requires a small amount of aeration and is capable of large-scale culture.

[Means for Solving the Problems]

The present invention succeeded in achieving the above-mentioned object is that a cylindrical culture tank made of a transparent material is vertically arranged, a means for aerating the inside of the culture tank from the bottom of the culture tank and a means for illuminating the inside of the culture tank from around the culture tank. When culturing microalgae with a batch-type culturing apparatus additionally provided, a reflux tube consisting of a cylindrical body having a diameter smaller than that of the culture tank is arranged vertically in the culture tank, and a gas-liquid separation chamber is provided at the top of the reflux tube. The top of the culture tank and the gas-liquid separation chamber are connected by a pipe, and the bottom of the culture tank and the bottom of the reflux pipe are connected by a pipe. It is characterized in that the culture is continued while supplying carbon dioxide gas and stirring in the tank by aeration.

[Action]

The apparatus used in the culture method of the present invention is a transparent cylindrical culture tank provided with a ventilation means and a lighting means similar to those used in the conventional vertical cylindrical culture method, and comprises a tubular body having a diameter smaller than that of the culture tank. The reflux tube is arranged vertically in line with the culture tank, a gas-liquid separation chamber is provided at the top of the reflux tube to connect the culture tank top and the gas-liquid separation chamber with a pipe, and the culture tank bottom and the reflux tube bottom are connected with a pipe. Keep in communication. Then, this apparatus is used in a state where aeration and stirring are performed so that the entire culture tank is filled with the culture solution and no gas phase remains in the upper portion of the culture tank. When the culture is started by irradiating light from the surroundings in this state, air bubbles blown from the bottom of the tank rise in the culture solution and enter the gas-liquid separation chamber from the top of the culture tank through the pipe. At this time,
Since the culture tank is filled with the culture solution, the culture solution is gradually sent to the gas-liquid separation chamber through the pipe due to the airlift effect.

The upper part of the gas-liquid separation chamber communicates with the atmosphere through an exhaust pipe, and the lower part communicates with the reflux pipe. The culture solution that has entered here flows downward in the reflux pipe due to its own weight, and returns to the bottom of the culture tank through the pipe. Bubbles are separated from the culture medium in the process, gather in the upper part of the gas-liquid separation chamber, and after the bubbles are broken, only gas is released into the atmosphere through the exhaust pipe. The gas-liquid separation chamber shall have sufficient space for bubble destruction, but when the foaming of the culture solution is not so remarkable, a "chamber" made of a special material is not provided as the gas-liquid separation chamber and the top of the reflux pipe is used for it. It can also be used.

Although the culture solution circulates between the culture tank and the gas-liquid separation chamber as described above, it does not come into contact with the contaminated ambient air, which enables stable algae growth in a clean environment.

〔Example〕

In the culture apparatus shown in the figure, the culture tank 1 has a bottom plate 2 of a closed structure in which both ends of an upright acrylic resin cylinder are closed, and a diffuser plate 3 for ventilation is attached to the bottom plate 2 of the tank, and a water passage pipe 4 for temperature control is attached. It is fixed to the applicable location in the tank.

The air diffuser plate 3 is made of porous ceramics and is connected to the air supply device 6 by a pipe 5. The air supply device 6 is composed of a compressor 7 for air pressure feeding, a carbon dioxide gas cylinder 8 for supplying carbon dioxide gas, a flow rate control device 9 for adjusting the air flow rate, an air filter 10 for cleaning the air flow, etc., and has a constant carbon dioxide gas concentration. It is possible to supply the air having a raised level to the diffuser plate 3 at a constant flow rate.

The water pipe 4 is connected to a temperature-adjustable water supply device 11, receives cold water or hot water of a constant temperature from the water supply device 11 to cool or warm the culture solution, and keeps the culture solution temperature at a suitable value. .

Immediately next to the culture tank 1, there is a reflux tube 12 which stands upright in parallel with the culture tank 1. The reflux tube 12 is a top plate 13 of the culture tank 1.
At a position higher than that, a pipe 14 is connected to the top plate 13. A pipe 15 is connected between the reflux tube 12 and the bottom of the culture tank 1.

In the pipe 14, a thick pipe 17 having almost the same diameter as that of the reflux pipe 12 is used in a connecting portion 16 with the reflux pipe 12, and the reflux pipe 12 in this portion and the pipe mounting portion constitutes a gas-liquid separation chamber 18. ing.

The pipe constituting the reflux pipe 12 is an exhaust pipe 19 above the gas-liquid separation chamber 18, and the vicinity of the tip is bent horizontally to prevent suspended dust from entering. .

Fluorescent lamps (not shown) are arranged around the culture tank 1 at substantially equal intervals so that the culture solution in the light-transmissive culture tank 1 can be illuminated.

Next, a culture experiment of chlorella (Chlorella pyrenoidosa) using this culture device will be described. The culture conditions were as follows.

Culture solution temperature: 27 ℃ Illuminance: 20klux (measured value on the inner wall of the culture tank) Initial algal cell concentration: 0.4g / Aeration rate: 8.8 / min / Culture solution 100 Carbon dioxide concentration in the blown air: 5% Culture solution (MC Medium) Composition: KNO ₃ 125mg MgSO ₄・ 7H ₂ O 125mg KH ₂ PO ₄ 125mg Fe mixed solution 0.1ml A ₅ metal mixed solution 0.1ml Distilled water 99.8ml pH 7.2 Fe mixed solution FeSO ₄ / 7H ₂ O 1g Distilled water 500ml H ₂ SO ₄ 2 drops A ₅ Metal mixture H ₃ BO ₃ 286mg MnSO ₄・ 7H ₂ O 250mg ZnSO ₄・ H2O 22.2mg CuSO ₄・ H ₂ O 7.9mg Na ₂ M _O O ₄ 2.1mg Distilled water 100ml When the whole 1 is filled and the culture is started, the culture solution is gradually sent to the gas-liquid separation chamber 18 via the top connecting pipe 14 together with the air bubbles generated by the air blowing from the diffuser plate 3, and the gas-liquid separation chamber 18 is supplied there. Is separated, the air is exhaust pipe
The culture solution was released into the atmosphere from 19, and the culture solution descended through the reflux pipe 12 into the pipe 15 and was refluxed to the culture tank 1. The inside of the culture tank 1 was well stirred by the rising bubbles, and almost no chlorella cells proliferating or settling on the wall surface were observed.

Culture was continued for 10 days while collecting and analyzing the culture solution once every two days.

As a comparative example, the same experiment was performed using a culture tank having the same structure except that the gas-liquid separation chamber and the reflux tube were not provided and bubble destruction was caused on the liquid surface of the culture solution in the culture tank. The lighting conditions were the same, but the aeration rate was set to 4 times, and the culture volume was limited to 90% in order to increase the aeration rate.

In the culture according to the comparative example, algal cells that adhered and proliferated and precipitated in the part above the liquid surface of the culture liquid in the culture tank were observed, even though vigorous agitation was performed than in the examples. .

The experimental results are shown in Tables 1 and 2.

Table 2 Changes in algal cell concentration (g /) Number of days of culture Comparative example 0 0.4 0.4 2 1.3 1.2 4 2.4 2.1 6 3.4 2.8 8 4.3 3.5 10 5.2 4.0 [Effect of the invention] According to the present invention, which is filled with a culture solution and aerated and stirred so as to cause bubble destruction in a gas-liquid separation chamber different from the culture tank, the culture tank wall is reduced even if the aeration amount is reduced to weaken the aeration and stirring. There is no accumulation of algal cells that stick to the
The substantial capacity of the culture tank is also increased, and extremely efficient culture can be performed. Further, since it is not necessary to increase the amount of aeration so much, there is no difficulty in breaking bubbles even when culturing algae that easily foams.

When the algal cell production capacity per unit area of the culture tank was calculated based on the results of the examples, it was 34.1 g / m ² / day, which is the average alga of the open-type circular culture tank currently being conducted in Southeast Asia. The body production capacity, ie, about 15 g / m ² / day or more, is twice or more, which shows that the culture method of the present invention is advantageous.

[Brief description of drawings]

The drawings are perspective views showing the outline of the culture apparatus used in the examples of the present invention. 1: Culture tank, 3: Air diffuser 6: Air supply device, 12: Reflux pipe 18: Gas-liquid separation chamber, 19: Exhaust pipe

Claims (1)

[Claims] 1. A batch-type culture in which a cylindrical culture tank made of a transparent material is vertically arranged, and a means for aerating the bottom of the culture tank into the tank and a means for illuminating the inside of the culture tank from around the culture tank are additionally provided. When culturing microalgae with the device, a reflux tube consisting of a cylinder with a diameter smaller than that of the culture tank is arranged vertically in the culture tank, and a gas-liquid separation chamber is provided at the top of the reflux tube to establish the top of the culture tank and the gas-liquid separation chamber. With the pipe, and the bottom of the culture vessel and the bottom of the reflux tube are communicated with the pipe, and while the entire culture vessel is filled with the culture solution, the carbon dioxide gas is supplied from the bottom of the culture vessel to the inside of the vessel by the aeration means. A method for cultivating algae, which comprises continuing culturing while stirring.