JPH0315324A - Tank for cultivating algae and method for using it - Google Patents

Abstract

PURPOSE: To culture algae and more particularly Chondrus crispus at a high yield by arranging obstacles on the course of a liquid medium driven by the impellers of an alga culture tank. CONSTITUTION: The culture tank 10 which has a somewhat flat elliptic annular form delineated between an outside wall 11 and a central nucleus 12 and includes at least one of the radial impellers 14 and discharge pipes 22 consist of at least two groups of the obstacles 18, 20. The one 20 is arranged on the axis of the central nucleus 12 and another 18 is arranged downstream of the impellers 14. The obstacle 18 has an angle of 90 to 160 deg. with the flow and the length thereof, if longest, is equal to half the width of the fluid flow. The sea water is supplied to this culture tank 10 which is then replenished with a carbon source, nitrogen source and phosphorus source. The pH of the medium is maintained at 8 to 9. The pH of the medium is maintained at 8.5 to 8.8 by adding an inorg. acid to the tank in some cases during long-term photosynthesis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an outdoor tank for culturing macroalgae, in which algae float in seawater flowing within the tank, and a culture method using this tank.

Algae are widely used as raw materials in the pharmaceutical, chemical and food industries. Several species of algae are eaten as-collected or rehydrated in various countries. However, the availability of natural algae is decreasing, especially on the French coast. Therefore, it is desirable to produce at least some species of algae by cultivation in tanks supplied with seawater, located outdoors in coastal areas and away from storms and tides. .

Many algae species can be cultured in this way. For example, Chondrus crlspusSGlg
artina stellata, Callble
pharis cillata et lanceol
ataSLailnarfa sp. , Sol1er
la Chordalls, CysLoclonlu
m purpurua, Palmarla pa
lmata, Gracilaria sp. , Ulv
a sp. , EnLeromorpha sp. ,
Bryopsis sp. etc.

For example, Chondoma, a red algae from which carrageenan, a polysaccharide that acts as a food thickener, is extracted, and Chond, which is processed in particularly large numbers in Europe,
For S. rus crlspus, it is highly desirable to find economically competitive culture conditions. Several groups of experts are already studying this problem. For example, Canada's R. G. S. Bidvell's research group, this group is rBotanic
a Marlna J Vol. 28, pp. 87-97 (19
In 1985), Chondrus cr1spus
(also called tochaca), which is supplied with seawater, nutrients and carbon dioxide,
Five tanks were used in which agitation of the algae was performed by blowing air from the bottom of the tank, which was approximately 80 ca+ deep.

According to the authors, this device ensures intermittent light reception for the algae, which is favorable for algae growth, and provides a regular supply of carbon sources and other necessary nutrients that are well known to experts. can be distributed. On the other hand, a pallet car device has previously been used for stirring by Simpson et al. and r Bot. Mar. J Vol. 2l, No. 229-2
35 (1978), but this is clearly less efficient and less profitable. This is because the flow of the plants is poor and the plants tend to settle to the bottom of the tank, resulting in slow growth, epiphyte elongation and disease proneness. It would have been desirable to find another device. This is because tank agitation by air blowing presents various drawbacks. These disadvantages include high consumption of energy and carbon dioxide, and high cost of manufacturing the tank. These tanks must be equipped with non-corrosive air supply pipes;
Also, to obtain proper agitation, the depth of the tank should be 4 to 5 times the depth of light penetration.

The tank according to the invention, by virtue of its shape and the presence of suitably placed obstacles in the path of the liquid medium driven by the impeller, can be used in a moderate manner, such as on the coast of the English Channel and on the Atlantic coast in France. In warm, sunny areas, algae, especially Chondrus crlsp.
This makes it possible to culture US with high yield.

Algae grow rapidly in conventional culture conditions. These culture conditions are described, for example, by R. G.J. BIdwel in the above-mentioned document. Alternatively, as described in the Canadian Journal of' by Nelsh et al.
Botany J Vol. 55, pp. 2263-227l (
(1977).

The production rate per unit of surface area is 10 to 15 times higher than when the algae are in their natural environment. Furthermore, slight differences in appearance, especially in composition, were observed between the natural algae and the algae cultured in tanks according to the invention. This is because almost no mu fraction, which is a precursor of kappa lageenan, is found in cultured algae, and only this carrageenan is found. In order to convert the precursors and extract all of the carrageenan from natural plants, the pH
A base treatment with 12 is necessary, which makes it possible to carry out the extraction by dissociation of the plant in slightly alkaline water.

The tank according to the invention has a flat oval crown (
It has a ring) shape. This inner core can also be a simple plane, which is located in the long sleeve of the ellipse. This surface is, for example, specifically represented as a wall. This wall terminates on either side at a distance approximately equal to the short axis of the ellipse from the outer wall of the tank so that the liquid medium can flow continuously around the central core. On land, an equivalent tank, although requiring a larger area and with slightly less performance, consists of a cylindrical crown between two ellipses of substantially similar shape. The length of the long sleeve is 2 to 8 times the length of the short axis, and the wall thickness is approximately 8 cm-t. It is preferable that it is just right to ensure aoc-.

For example, the tank 10 shown in plan view in FIG. 1 has an elongated oval shape. In the figure only half of the tank is shown, the other half being symmetrical with respect to the transverse vertical plane indicated by the line xx''.

The tank is defined between an outer wall 11 and a central core 12. In this embodiment, the central core 12 is simplified as a wall terminating at a predetermined distance from the two ends of the tank. This defines a closed circulation circuit within the tank for the water contained in the tank.

The tank can be installed in the ground with only half buried or embedded in the ground. In addition, this tank is equipped with at least one impeller 14. The rotation of the impeller ensures the circulation of the liquid medium around the central core 12 of the tank. This axis therefore coincides with the radius of the tank at that point. The vanes 16 are immersed in water to a depth sufficient to drive the liquid medium over their entire length. Those skilled in the art will understand that the rate of movement of the liquid is due to parasitic macrophytes (n+aerophytes).
Enough to prevent heavy algae growth (actually 0)
．． 30m/sec or more).
Depending on the size of the blades, the height of the immersed part in the water, the shape and size characteristics of the tank, and especially depending on the height of the water, it would be possible to calculate the rotation speed of the shaft.

In order to avoid the formation of dead zones next to the well-stirred zone, two impellers 14, 14 are installed at predetermined positions in the tank, in particular in diametrically opposed positions in annular tanks.
′ is preferably placed.

Alternatively, in the case of a tank with a flat central core, it is preferable to locate the two streams in an elongated section of the ellipse that cuts in opposite directions as shown in FIG. However, the impeller need not be within the axis of symmetry of the tank. The distance between their axes is 2 of the length of the tank
It may be up to 73.

The height of the water in the tank depends on the species of algae being cultured, their density and size, as well as adequate sunlight. This height is generally between 0.3 and 1-20 lbs. to ensure sufficient liquid flow and sufficient light reception to the maximum depth position.
, preferably about 0.40a.

Finally, and this is also an important feature of the invention, the tank is equipped with at least two groups of obstacles 18.20 located in the path of the liquid medium. These obstacles consist, for example, of vertical or slightly inclined small walls, preferably low, just below the upper level of the liquid. Its length is at most equal to half the width of the body stream. One of these groups is located substantially along the long sleeve of the tank and is an extension of the central core 12. The other is downstream of the impeller or impellers 14, 14' and makes an angle with this flow of 90 to 160 degrees, preferably 130 degrees. This obstruction creates a vortex and locally accelerates the flow, which ensures better homogenization of the medium and re-rising of the algae to the water surface. The production rate of the culture is very significantly improved in the presence of several obstacles as described below. That is, such obstructions are preferably located appropriately in zones where the flow is laminar or where the flow velocity is to be slowed down.

On the other hand, increasing the number or size of obstacles is disadvantageous.

Therefore, in the case of the tank shown in Figure 1, which is equipped with four obstacles, the average annual production rate is:
This is 2.5 times as large as a tank of the same shape but agitated only by an impeller.

Furthermore, like a conventional tank, there is a seawater inlet, not shown, as well as a water outlet pipe 22, preferably at the other end. This drain pipe is advantageously located behind the obstruction so that the density of algae in the zone is low. Water supply may be continuous or sequential. The water supply is
It must be sufficient to provide the necessary amounts of trace elements and potassium for algae growth and to compensate for natural evaporation.

This tank shape prevents water recirculation, which is common in rectangular tanks, to create flow in the medium.

Another subject of the invention is a method for the production of macroalgae, comprising culturing the algae in a tank according to the invention supplied with seawater and supplemented with carbon, nitrogen and phosphorus sources. be. The normal nutrients nitrogen and phosphorus are injected at regular intervals, preferably with the seawater circuit interrupted.

This improves the absorption of the compound by the algae and
and large losses in the effluent are prevented.

Similarly, carbon is introduced into the culture medium in the form of carbon dioxide, carbonates or carboxylic acids. Cultured vX pl+
In order to maintain pi in this range, generally between 8 and 9, preferably between 8.5 and 8.8, during long photosynthesis times, an indefinite acid may be introduced into the medium.

According to another aspect of the invention, alkalinity is added in the tank during cultivation if the proportion of algae foreign to the culture resulting from the germination of spores introduced by seawater becomes troublesome. Introduce an oxidized water solution containing hypochlorite. The amount of NaOCj depends on the characteristics of the tank and the amount of algae present.

A person skilled in the art will be able to easily determine this.

Able to process quickly. During this process, the oxidizing agent is destroyed after a few minutes by the addition of a reducing agent, such as thiosulfate or alkaline hydrogen sulfide, or by a simpler process of allowing the oxidizing agent to be removed naturally. In the latter case, the initial concentration must be lower, clearly 15-25% lower.

The long sleeves are 7.2 times the length of the short sleeves, the depth is 40c+e, and there are two obstacles with a length of Im and two obstacles with a length of 2m arranged as shown in Figure 1. about 980 with
Chondru with a dry weight of 253 g/m2 by culturing for 4 weeks in an oval tank of m2.
A red plant of the species S crlspus was collected. Carrageenan was extracted from this.

For comparison, we simultaneously cultured the same enriched marine medium in a small round tank with a diameter of 3 m stirred by strong air blowing, and the result was 234 g/m2.
Only a few algae were collected. Furthermore, if air agitation is taken into account, it is clear that the operating cost is higher.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an algae culture tank according to an embodiment of the present invention. 11...Outer wall, 12...Central core, 14.14-...
・Impeller, 16.16-...Blade, 18.20...
Obstacle, 22...Exhaust pipe

Claims (9)

[Claims] (1) Culture tank 1 for macroalgae supplied with water
0, having a more or less flat elliptical ring form defined between the outer wall 11 and the central core 12; and comprising at least one radial impeller 14; Two groups of obstacles 18, 20, one of which is located on the axis of the central core 12 and the other downstream of the impeller 14, the flow is 90 to 1
Culture tank, characterized in that it is provided with an obstruction that forms an angle of 60 degrees and whose width is at most equal to half the width of the liquid stream. (2) The culture tank according to claim 1, wherein the central core 12 is simplified and has a flat surface. (3) Claim 1, wherein the obstruction is a small vertical or inclined wall that is just below the upper level of the liquid.
Or the culture tank described in 2. (4) Chondr comprising culturing algae in the culture tank according to any one of claims 1 to 3, which is supplied with seawater and supplemented with carbon, nitrogen, and phosphorus sources.
Method for producing us crispus. (5) The method according to claim 4, wherein the carbon source is carbon dioxide, carbonate, or carboxylic acid. (6) The method according to claim 4 or 5, characterized in that the pH of the medium is maintained at 8-9. 7. Process according to claim 6, characterized in that during the long-term photosynthesis, the pH of the medium is maintained between 8.5 and 8.8, optionally by adding an inorganic acid. (8) The method according to any one of claims 4 to 7, further comprising adding alkaline hypochlorite to remove foreign algae. (9) Excess hypochlorite is destroyed by adding thiosulfate or hydrogen sulfide.
The method described in.