Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process...
Patent
1987-11-06
1990-06-05
Maff, David M.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
435174, 43524023, 43524025, 43524046, 435261, 435286, 435288, 435313, 435315, 435813, 435818, 210780, C12P 100, C12N 1100, C12N 502, C12M 140
Patent
active
049313886
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a method for treating a liquid mixture containing biocatalysts or comparable particles, in which liquid from the mixture is allowed to pass through an oscillated screen surface while particles are retained, and to a corresponding device comprising a container for receiving the mixture, a screen device for removing liquid from the mixture, which screen device admits this mixture during operation and retains particles of a predetermined minimum size; it is also directed to possible devices for introducing gas and/or nutrients or for the drainage of the liquid which has passed through the screen device.
It is known to immobilize biocatalysts, such as microorganisms, cell cultures, carriers or similar particles with or without bound, biologically active substances, etc., against flushing by means of mechanical mechanisms, such as screens, whose openings have passage widths which are narrower them to the size of the particle to be retained, or by means of attaching the biocatalysts to installations or carrier particles which are static or suspended in the liquid, or by means of the inclusion of the cells in gels such as alginates or the like, or also by means of sedimentation. However, all of the methods mentioned have considerable disadvantages in practice. For example, screens have a strong tendency to shift, since the particles are forced into the through-openings of the screen because of the liquid currents, and these through-openings are therefore opened from time to time, and the particles must be put in suspension again. Also, it is possible to cancel the retaining action only by means of special steps, such as removing the screen or flushing at a high through-flow rate. When biocatalysts are attached to packing bodies or installations, the culture is very sensitive, since an operation diverging from the ideal conditions often causes the biocatalysts to fall off. Moreover, the portion of the biocatalysts needed for the attachment is blocked for the reaction. The same applies for biocatalysts included in gels or the like, in which diffusion barriers occur and particles which are no longer effective biologically remain in the reaction space as ballast. The biocatalysts, as such, are therefore often kept in suspension in the reaction vessel, wherein the particles which are flushed from the reaction vessel in the course of obtaining the reaction product are mechanically separated from the liquid, for example, by means of separation, sedimentation or the like.
In addition, a method and a device for classifying solids suspended in liquids are known from Swiss Patent No. CH-PS-602 102, in which the mixture is fed to an oscillated screen basket through which the liquid and the desired small particles pass, while the particles which do not pass through the screen opening are retained, but the vibration prevents a filter cake from being built up. However, this procedure does not concern the retention of particles which are smaller than the screen openings.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a method and a device for treating a liquid mixture containing biocatalysts or similar particles of the type mentioned in the beginning, which enables the biocatalysts and similar particles to be retained to the greatest extent in a simple manner such that the retention is easy to control and cancel.
In order to meet this object, the method, according to the invention, is characterized in that a filter surface comprising openings which are passable for the particles to be retained is oscillated in such a way as to impede the passage of these particles at least to a great extent.
The oscillations of the screen surface produce pressure waves in the liquid mixture, which pressure waves substantially prevent the biocatalysts and/or similar particles from passing through the screen openings, which are larger in comparison, and simultaneously suppress a plugging up of the openings by means of the formation of bridges. On the other hand, biologically inactive particles
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Maff David M.
Striker Michael J.
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