Chemistry: molecular biology and microbiology – Apparatus – Bioreactor
Reexamination Certificate
2002-02-01
2003-06-17
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Bioreactor
C435S101000, C435S134000, C435S257100, C435S257300, C047S001400
Reexamination Certificate
active
06579714
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for culturing algae having an ability of producing highly unsaturated fatty acids, photosynthetic pigments, and/or polysaccharides to manufacture the algae containing these substances in algal cells, more specifically relates to the method for culturing algae having an ability of producing the highly unsaturated fatty acids, the photosynthetic pigments, and/or the polysaccharides in a culture medium under light irradiation and/or aeration condition to manufacture efficiently algae containing these highly unsaturated fatty acids, photosynthetic pigments, and/or polysaccharides in algal cells in a high concentration using a certain cultivation apparatus.
BACKGROUND ART
Development of a cultivation method for algae, wildly growing, is needed for stable, high yield production of the photosynthetic pigment used as a safe feed for a cultured fish and as a safe food additive and unsaturated fatty acid, photosynthetic pigment, and/or polysaccharide used for a medical drug and a health food. However, cultivation method has been limited to a few numbers and thus, very limited species such as Chlorella and Spirulina were studied and a method for an efficient cultivation is has not been yet established.
Algae perform biosynthesis of a useful substance by photosynthesis through absorption of carbon dioxide. In addition, it is important that algal cultivation is carried out efficiently and therefore, an apparatus for cultivation is necessary for efficient photosynthesis. Hence, improving the apparatus for cultivation and developing a new apparatus for cultivation are being conducted.
So far, as the apparatus for cultivation for algae, for example, a cultivation pond, a raceway type cultivation apparatus, a tubular type cultivation apparatus, a liquid membrane-forming cultivation apparatus have been well known. In the cultivation pond, a concrete-made cultivation pond or cultivation vessel are prepared in the outdoors to build up a pond in which a culture solution is filled and a species of a microalgae exemplified by Chlorella is cultured in the pond using sunlight. However, this type of the cultivation apparatus requires such area as 3000 m
2
for the pond resulting in a huge volume.
In addition, cultivation of microalgae by using the cultivation apparatus of this type causes a high concentration of algal cells containing in the culture solution according to progress of cultivation resulting in thick green coloration of the culture solution to disturb reaching of sunlight to a bottom of the pond. From such phenomenon, the following problem comes up: unless algal cell density necessary for cultivation is reduced, a total algal photosynthetic efficiency is lowered.
Consequently, a depth of the pond must be set to 15 cm or smaller and a land for mass cultivation of algal cells must be vast. Further, a concentration of the culture solution cannot be made higher and thus, in collection of a culture from the solution, the following problem comes up: the culture must be collected from a huge amount of a low density culture solution.
On the other hand, the cultivation pond must be stirred to make algal photosynthesis easy. However, a large amount of energy is required for stirring the huge volume of the low concentration liquid. In addition, the cultivation pond is located in the outdoors and in an opened state and hence, such exogenous matters as dust and waste are easy to contaminate the liquid and airborne microorganisms and cells of other species of microalgae contaminate the pond to propagate resulting in the following problem: culture of a high purity and a high quality cannot be yielded.
The cultivation pond is located in the outdoors and thus, a temperature thereof changes according to a change of weather to cause very difficulty to maintain the temperature of the pond in a constant value. Particularly, there is a defect that in winter in a certain locality, the temperature drops excessively.
Caused by such status, cultivation of algae by using the cultivation pond cannot be applicable to other algal genera than Chlorella, Spirulina, and Dunaliella, which can grow under a unique condition such as a high pH and a high salinity.
The raceway type cultivation apparatus has a circulatory path, for culture solution, made by partitioning of an inside of the cultivation vessel with a straightening vane and is used for cultivation of algae by the method by which the culture solution is circulated in this circulatory path by using means for circulation. This system is of an improved circulation system of the culture solution and a photosynthetic rate of algae lowers, similar to the cultivation method using the cultivation pond, according to progress of cultivation and therefore, does not allow efficient use of light energy. Consequently, the following problem also comes up: an efficiency of carbon dioxide is low. In order to achieve efficient use of light, irradiation of sunlight to the liquid through an optical fiber has been proposed (Japanese Utility Model Application Laid-Open No. 5-43900).
In operating algal cultivation by using this system, the liquid is circulated by mechanical stirring and thus, the following inevitable defects occur: algal cells are broken and a shear stress occurs (a phenomenon in which algal cells are cut by a shear stress to cause reduction of cellular activity resulting in a low propagation rate).
The tubular type cultivation apparatus is the apparatus for algal cultivation by using the cultivation apparatus comprising a light transmission tube. Algal cultivation by using this apparatus allows no contamination of the culture solution by non-objective bacteria and making culture concentration high and thus, is a very beneficial method for collection of the useful substance, which is produced by algae, by separating algae from the culture solution.
However, after long-time algal cultivation, algae attach to an internal wall of the tube to disturb light pass through the tube very. These facts make efficient algal cultivation difficult and also make removal of algae attached to the internal wall of the tube difficult.
In order to solve these problems, the following method has been proposed: a cleaning ball is put in the tube an the ball is always circulated together with the culture solution to clean the internal wall of the tube (Japanese Patent Application Laid-Open No. 6-90739). However, even by this method, the following and other many problems remain: dirt and algal attachment of the internal wall of the tube cannot be continuously removed completely, the ball must be collected to clean and also, the ball must be always circulated in the tube. In addition, a further problem of this system for algal cultivation is that cultivation operated inside the tube allows oxygen gas, which is generated by algal photosynthesis to stay, in the tube and oxygen inhibits algal photosynthesis. Based on these facts, a device of the apparatus has been proposed to suppress a bad effect caused by oxygen, generated by photosynthesis, on cultivation (Japanese Patent Application Laid-Open No. 9-121835).
In the liquid membrane-forming cultivation apparatus, a dome-shaped, light-passing lid body is installed on an top face of the cultivation vessel and culture solution is jetted from a bottom to an internal face of an apical part of the dome-shaped lid body to form a liquid membrane on the internal face of the lid body and irradiate a light on this liquid membrane (Japanese Patent Application Laid-Open No. 8-38159).
However, there are problems: this system proposed requires a circulation pump for continuation of formation of the liquid membrane, is not suitable for mass cultivation, and does not allow using sunlight.
A panel type cultivation apparatus is used for algal cultivation by installing a thin box-like apparatus, which is prepared by using two resin-made panel boards, with inclination.
This apparatus itself is a closed type similar to the tubular type cultivation apparatus, for example, and has an advantage of no contamination o
Hirabayashi Seishiro
Prilutsky Alexander
Sadamatsu Hisato
Armstrong Westerman & Hattori, LLP
Beisner William H.
Micro Gaia Co., Ltd.
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