Abstrict
A stirred gas bubble fermenter is provided with a cooler outside
the fermenter which is coupled to the fermenter through an overflow
exit. An overflow weir is connected to the inner wall of the fermenter
below the overflow exit and extends at least in the upward direction
of the fermenter. In a preferred embodiment, the overflow weir extends
above the upper extremity of the overflow exit. The fermenter may
further be provided with a guide plate arranged between at least
a portion of the overflow weir and at least a portion of the overflow
exit in order to more efficiently separate bubbles from a culture
broth in the fermenter.
Claims
What is claimed is:
1. In a stirred gas bubble fermenter having aeration means, a waste
gas outlet and an overflow exit, and provided with a cooler outside
the fermenter and coupled to the fermenter through said overflow
exit,
the improvement comprising:
an overflow weir connected to the inner wall of the fermenter below
said overflow exit and extending at least in the upward direction
of the fermenter so as to be opposite at least a portion of said
overflow exit; and
a guide plate arranged between at least a portion of said overflow
weir and at least a portion of said overflow exit to improve gas-liquid
separation.
2. The fermenter according to claim 1, wherein the shape of the
transverse section of said overflow weir is linear.
3. The fermenter according to claim 1, wherein the shape of the
transverse section of said overflow weir is round.
4. The fermenter according to claim 1, wherein said overflow weir
is generally, "L"-shaped in a vertical section, the horizontal
leg thereof being connected to said inner wall of said fermenter
below said overflow exit and the vertical leg thereof extending
upwardly opposite said overflow exit.
5. The fermenter according to claim 4, wherein said vertical leg
extends above the upper extremity of said overflow exit.
6. The fermenter according to claim 1, wherein said overflow weir
comprises a member extending upwardly and inclined away from the
inner wall of said fermenter.
7. The fermenter according to claim 6, wherein said upwardly extending
member extends above the upper extremity of said overflow exit.
8. The fermenter according to claim 1, wherein said overflow weir
extends above the upper extremity of said overflow exit.
9. The fermenter according to claim 1, wherein the shape of the
transverse section of said guide plate is linear.
10. The fermenter according to claim 1, wherein the shape of the
transverse section of said guide plate is round.
11. The fermenter according to claim 2, wherein the shape of the
transverse section of said guide plate is linear.
12. The fermenter according to claim 3, wherein the shape of the
transverse section of said guide plate is round.
13. The fermenter according to claim 1, wherein said guide plate
extends below the lower extremity of said overflow exit.
14. The fermenter according to claim 13, wherein said guide plate
extends above the upper extremity of said overflow weir.
15. The fermenter according to claim 14, wherein both said overflow
weir and said guide plate extend above the upper extremity of said
overflow exit.
16. The fermenter according to claim 1, wherein said guide plate
extends above the upper extremity of said overflow weir.
17. The fermenter according to claim 16, wherein both said overflow
weir and said guide plate extend above the upper extremity of said
overflow exit.
18. The fermenter according to claim 1, wherein the lower end of
said guide plate is situated lower than the upper extremity of said
overflow exit.
19. The fermenter according to claim 1 wherein said guide plate
cooperates with said overflow weir to define a tortuous path for
the exit fluid from the fermenter.
Description FIELD OF THE INVENTION
The present invention relates to a stirred gas bubble fermenter
provided with a cooler outside the fermenter. More particularly,
it relates to a fermenter in which bubbles can be separated from
a culture broth passed from the said fermenter to a cooler.
BACKGROUND OF THE INVENTION
In the method for culturing microorganisms such as yeast, bacteria,
etc., under aerobic conditions to produce microbial cells and for
producing useful substances such as antibiotics, amino acids, alcohols,
etc., research and development was made about the measures for providing
oxygen and for cooling culture broth heated during a fermentation
process, etc., in both batch and continuous fermentation systems
for the purpose of improving fermentation efficiency. For instance,
a method for controlling the temperature of a culture broth by providing
a cooling tube inside the fermenter is known. However, the diffusion
efficiency of air provided in the fermenter into the culture broth
is lowered in this method and, in addition, it has also the defect
that the effective area inside the fermenter is reduced. Therefore,
a fermentation process using a stirred gas bubble fermenter provided
with a cooler and a device for eliminating bubbles outside the fermenter
has also been proposed (ex. Japanese Patent Publication Gazette
No. 26040/1964).
By way of illustration, in controlling a culture broth to an appropriate
temperature by cooling it, it is necessary to remove bubbles in
the culture broth passed into a cooler as much as possible in order
to obtain a good cooling effect.
SUMMARY OF THE INVENTION
We have studied conditions for culturing microorganisms with a
stirred gas bubble fermenter. As a result, we have found that the
aforesaid problem can be solved by providing a relatively small-scale
weir of simple structure inside the fermenter.
In accordance with the present invention, in a stirred gas bubble
fermenter, bubbles are separated from a culture broth passed from
the fermenter to a cooler by providing an overflow weir extended
from the inner wall of the fermenter below the overflow exit to
the upper direction of the fermenter. In addition, the present invention
includes a fermenter provided with a guide plate between the aforesaid
overflow weir and overflow exit in order to separate bubbles from
the culture broth more efficiently.
BRIEF EXPLANATION OF THE FIGURES
FIGS. 1 and 2 illustrate typical embodiments of fermenters of the
present invention.
FIG. 3 is a transverse section of the fermenter of FIG. 1.
FIG. 4 is a transverse section of a modification of the fermenter
of FIG. 1.
FIGS. 5-8 illustrate various types of overflow weirs which may
be provided.
FIG. 9 is a transverse section of the fermenter of FIG. 2.
FIG. 10 is a transverse section of a modification of the fermenter
of FIG. 2.
In the Figures, reference numerals 1, 2, 3, 4 and 5, respectively,
denote fermenter, overflow weir, overflow exit, guide plate and
cooler.
EMBODIMENTS OF THE INVENTION
Referring to FIG. 1, overflow weir 2 is provided inside fermenter
1. Overflow weir 2 comprises a first section which extends horizontally
from the inner wall of fermenter 1 below overflow exit 3, and a
second vertical section which extends upwardly from the first horizontal
section. The position of the upper end of the vertical section of
the overflow weir (i.e., weir height) should be decided depending
on the linear velocity of the culture broth passed from overflow
exit 3 to cooler 5. The weir height can be reduced when the linear
velocity is small.
The shape of the overflow weir in the transverse direction is arbitrary.
For instance, it may be linear, as illustrated in FIG. 3, or may
be round (overflow weir 2'), as in FIG. 4. Alternatively, the overflow
weir 2 may be wave-shaped, square-shaped, or mixed shape. It is
preferred to provide fermenter 1 with more than two coolers in the
case where the overflow weir has a round shape, etc., as indicated
in FIG. 4. The shape of the part where the overflow weir is set
up at the inner wall of fermenter 1 may be varied and FIGS. 5-8
are examples thereof.
The provision of guide plate 4 between overflow weir 2 and overflow
exit 3 as illustrated in FIG. 2 makes the separation of gas from
liquid more efficient. The shape of the longitudinal section for
the said guide plate is arbitrary. For example, it may be linear,
as in FIG. 2, wave-shaped, or other arbitrary shapes. In the same
way, the shape of the transverse section of guide plate 4 can be
decided arbitrarily, and it may be linear, as in FIG. 9, round,
as in FIG. 10, wave-shaped, square-shaped or mixed shape. The lower
end of guide plate 4 is preferably provided so that it may be situated
lower than the upper end of overflow exit 3.
The area, volume, etc., of the part where the overflow weir 2 and
the guide plate 4 overlap each other should be properly decided
taking into consideration factors such as the linear velocity of
culture fluid, etc. Thus, a favorable result can be obtained.
By the use of the fermenter of the present invention, a very favorable
cooling effect can be obtained because separation of gas and liquid
is done rapidly from the culture broth introduced into the overflow
weir, and the culture broth without bubbles is sent to a cooler
5 through the overflow exit 3. The separation of gas and liquid
is further made smooth by providing a guide plate 4. In addition,
the overflow weir occupies only an extremely small part of the fermenter
and so the influence on efficient area for fermentation is slight.
Furthermore, it is easy to provide a conventional fermenter with
an overflow weir and a guide plate in accordance with the present
invention, and there is no inconvenience in so modifying the fermenter
because of their simple structure. Particularly, concurrent provision
of the guide plate 4 makes further miniaturization possible.
Therefore, by cultivating microorganisms using the fermenter so
equipped, bubble separation from a culture broth introduced to a
cooler can be made advantageously, and thus fermentation can proceed
favorably. The production of useful substances such as antibiotics,
vitamins, amino acids, alcohols, organic acids, etc., and microbial
cells can be done advantageously.
Typical examples involving use of the fermenter of the present
invention are shown below.
EXAMPLE 1
A culture medium (700 liters) was placed in the fermenter (total
length 2800 millimeters, diameter 700 millimeters) as illustrated
in FIG. 1, provided with an overflow weir 480 millimeters in width
and 270 millimeters in height with a linear-shaped transverse section
(as in FIG. 3) at a point 170 millimeters below the lower end of
the overflow exit and a distance of 100 millimeters from the inner
wall. Seed culture (yeast: Candida utilis) obtained by cultivation
was added to this culture medium and continuous cultivation was
carried out under conditions of 32.degree. C. and 1-3.5 VVM (3.0
- 11.0 centimeters/second) of ventilation volume.
The exit pipe extending from the fermenter 1 to the cooler 5 was
made transparent for easy checking of the presence or absence of
bubbles in the culture broth sent to the cooler 5 through overflow
exit 3 to control the temperature during the culture process. As
a result, it was observed that no bubbles were contained in the
culture broth at the exit pipe except for a small amount in a few
cases when the linear velocity of culture broth passed into the
overflow weir was significantly large (more than 20 centimeters/second).
EXAMPLE 2
Yeast cells were produced in the same manner as in Example 1, except
that a guide plate of 280 millimeters width and 350 millimeters
height was provided at a distance 30 millimeters from the inner
wall and a point 80 millimeters between the lower end of the overflow
weir and the lower end of the guide plate as illustrated in FIG.
2.
As a result, no bubbles were contained in the culture broth at
the exit pipe even when the linear velocity of the culture broth
passed into the overflow weir was significantly large. The examination
of the position of the lower end of the guide plate 4 indicated
that a distance of from 20 to 130 millimeters from the bottom of
the overflow weir 2 provides a favorable result in the case of this
example.
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