GB2054646A - A fermentor for cultures of micro-organisms - Google Patents

Abstract

A fermentor for growing micro- organisms has a container (17) into which a stirrer (12) projects from below and in whose upper region is located a rotatable froth separator (14). A guide cylinder (40) which is open at the top and bottom is arranged in the container to restrict the movement of the liquid stream by the stirrer (12). The froth separator (14) is arranged close beneath the upper wall (16) of the container (10) and at a vertical distance above the guide cylinder (40) and has fan- shaped vanes (38) for breaking up the froth. <IMAGE>

Description

SPECIFICATION A fermentor for cultures of micro-organisms.

The present invention relates to a fermentor for growing micro-organisms having a container into which a stirrer projects from below and in whose upper region is located a rotatable froth separator communicating with a gas outlet pipe, with a guide cylinder which is open at the top and bottom and is arranged coaxially in the container, a gas tube and with several attachments in the container wall for the supply and removal of gases or liquids and for the introduction of for example, probes.

In a known fermentor of this type (German Auslegeschrift No. 24 41 427), the container has a markedly curved cover which is drawn in toward the centre and a bottom which is also curved and drawn in toward the centre. A stirrer penetrates into the interior of the container through its bottom and into a guide cylinder arranged in the container. A nutrient solution for micro-organisms is introduced into the container and the air needed to propagate the micro-organisms is conveyed into the liquid through a gas tube. The stirrer produces a flow in the liquid-air mixture. This flow travels upwards in the annular space between the guide cylinder and container wall and is recirculated through the interior of the guide cylinder to the stirrer. Permanent movement and thorough mixing of the liquid-air mixture is thus maintained.Good and uniform permeation of the entire container cavity should be achieved due to the shape of the container walls.

As the nutrient liquid which is kept in vigorous movement and is thoroughly mixed with air or oxygen produces froth, a froth separator which projects into the guide cylinder is provided in the upper region. The froth separator consists of several funnel-shaped elements which are nested inside each other and which are driven by a rotor shaft. Due to the centrifugal force, the liquid settling on the walls of the funnel elements which are open at the bottom is spun outwards into and recirculated in the general liquid stream, while the gases contained in the froth rise in the interior of the froth separator and leave the container through a gas outlet pipe.

Although a fairly good degree of filling is already achieved in the known fermentor, it is possible for froth which cannot be reached by the froth separator to accumulate in the upper region of the container, Such deposits of froth assist wall growth which certain microbe cultures tend to form. The micro-organisms being deposited on the container wall form an adherent layer and no longer participate in the metabolism of the substrate.

An object of the invention is to propose a fermentor of the type mentioned at the outset which is to be filled virtually completely with a mixture of nutrient liquid and gas without the formation of permanently froth-filled zones, and in which the gas or the oxygen is contained in a uniform distribution in the liquid. In this way, culture wall growth is to be prevented and good utilisation of space for the growth of microbes is to be achieved.

According to the present invention there is provided a fermentor for growing micro-organisms with a container into which a stirrer projects from below and in whose upper region is located a rotating froth separator which communicates with a gas outlet pipe, with a guide cylinder which is arranged co-axially in the container and is open at the top and bottom, a gas tube and with a plurality of nozzles in the container wall for the supply or removal of gases or liquids and for the introduction of ancillary equipment, wherein the froth separator is arranged close beneath the upper wall of the container and at a vertical distance above the guide cylinder and has fanshaped vanes for breaking up froth formed during use.

Since the froth separator is arranged close beneath the upper wall of the container, no dead space is formed above the froth separator in which stationary or slowly moving froth can be retained.

The froth separator with its rotating parts is located in the immediate vicinity of the upper container wall leaving only a sufficient gap for reasons of tolerance between it and the upper container wall. Due to the vertical distance between the froth separator and the guide cylinder, the circulation of the liquid-gas mixture is not obstructed by the froth separator as the froth separator does not reduce the cross-section at any point of the revolution. A completely stirred fermentor without dead zones is obtained in this way with uniform filling of an intensively mixed substantially homogeneous gas-liquid mixture. A completely filled fermentor is particularly suitable for the growing of mycelia cultures which have a special tendency to wall growth if the filling is not complete.

Although the froth separator of the abovementioned known fermentor consists of a rotating member which operates solely by the centrifugal principle and spins the liquid particles, the fanshaped vanes of the froth separator in the fermentor according to the invention also break up the froth bubbles. This increases the effectiveness of the froth separator and prevents the formation of froth directly in the mixture at all points covered by the froth separator.

In order to break up the froth completely and uniformly, the vanes preferably have vertical openings or edges at differing distances from the rotational axis. In this way, the vanes of the froth separator do not dig uniform channels in the froth formation zone but, since the openings are alternately effective at differing points, the breaking up effect is uniform over the entire area of the froth separator.

In order to prevent the formation of froth particularly in the vicinity of the cover wall of the container, the vanes are preferably erected on the upper side of a disc. The horizontal upper edges of the vanes are thus guided along parallel to the cover wall in the immediate vicinity of the cover wall so that the cover wall is kept free from froth.

The underside of the disc serves to guide the flow of the liquid-gas mixture. This can have one or more orifices through which gas can rise into the gas outlet pipe.

As the froth separator does not project into the guide cylinder, its diameter can be made sufficiently large for it to cover virtually the entire cover wall of the container. In this case, however it is not possible to introduce probes through the cover wall into the interior of the container.

Nevertheless, to allow probes to be introduced into the regions of high turbulence and to allow correcting means to be supplied in the case of a suitably large froth separator, it is proposed in an advantageous embodiment of the invention that numerous nozzles be arranged radially in an annular member arranged between a cylindrical container wall and the bottom wall. The nozzles lead into a region of high turbulence which is particularly suitable for the positioning of measuring probes, for example, for determination of the pH-value or of the oxygen partial pressure.

The liquid values can be determined representatively in this region. The membranes of the probes are prevented from being covered by organisms by the high turbulences. The addition of correcting means in the region of high turbulence is also particularly effective as a uniform distribution of the correcting means then takes place without delay.

The annular member can be designed as a flow guide body on its internal wall and, by means of its bulge of widened cross-section, can connect the cylindrical container wall and the bottom wall substantially without kinks so that the nozzles are inclined at an angle to the horizontal in the region of the bulge. This produces a structural shape which is particularly desirable in terms of flow and which can be produced using simple constructional elements. The fermentor can be produced from a cylindrical part which is sealed by a cover wall. The bottom wall also has a structurally simple design. The nozzles are located in the annular member where they are arranged radially so that they do not obstruct each other.

The concentration of the nozzles in the annular member means that other parts do not need corresponding shaping and that all or at least the majority of connecting devices such as tubes, cables etc., lead to the annular member. This makes the entire structure and also the connected pipes clearly visible and thus simplifies operations involving the fermentor.

A A preferred embodiment of the invention is described in more detail below by way of example with reference to the accompanying drawings, in which: Figure 1 shows a side view of a fermentor with stirrer drive and the drive of the froth separator; Figure 2 shows a longitudinal section through the fermentor according to Figure 1 on an enlarged scale; Figure 3 shows a cross-section along the line Ill-Ill in Figure 2; Figure 4 shows a section along the line lV-lV in Figure 3; Figure 5 shows a section along the line V-V in Figure 3; Figure 6 shows a plan view of the froth separator; and Figures 7a to 7d shows views of various vanes of the froth separator.

The fermentor shown in side view in Figure 1 comprises a reaction container 10 which is substantially cylindrical, a motor 11 for driving a stirrer 12 and a motor 13 for driving a froth separator 14. The reaction container 10 has a bottom plate 15 and a cover plate 16 between which the cylindrical body 17 is clamped by tie rods 18. The tie rods 18 extend outside the cylindrical body 17 between bottom plate 15 and cover plate 16 through which they penetrate and on whose exteriors they are clamped by screws 19.

Three horizontal cross-members 20 are arranged in the shape of a star and fixed on the underside of the bottom plate 1 5. These crossmembers 20 project outwards and are set on a support (not shown) bearing the entire fermentor.

The vertically arranged lower electric motor 11 for driving the stirrer 12 is connected to the bottom plate 15 by means of bearing bush 21.

The stirrer shaft 22 projects coaxially through the bearing bush 21 into the reaction container 10.

The vertically arranged upper electric motor 13 for driving the froth separator 14 is similarly connected to the cover plate 16 by means of a bearing bush 23. Shaft 24 for the froth separator 14 projects through the bearing bush 23.

Figure 2 shows the design of the reaction container 10 in more detail.

The end of the drive shaft 24 is screwed on to a hollow shaft 25 on whose lower end is located a flange 26 on which the froth separator 14 is fixed.

The hollow shaft 25 projects through a plate 27 which is mounted on the cover plate 16 and has an attachment 28 which penetrates through the cover plate 16. The cylindrical attachment 28 is sealed from the hollow shaft 25 by means of a sliding ring seal 29 and sealed from the cover plate 16 by a sealing ring 30.

The gas liberated at the froth separator 14 rises through a central opening 31 in the flange 26 and through the hollow shaft 25 into an annular space 32 in the bearing bush 23. In the region of the annular space 32 the bearing bush 23 is connected to a gas outlet 33 through which the gas which has entered the annular space 32 is discharged. The gas can be fed to an analyser which determines the composition of the gas continuously or at regular intervals. The annular space 32 is sealed at the top by a bearing and sealing plate 34 through which the shaft 24 projects in a sealed manner.

The froth separator 14 which is fixed on the underside of the flange 26 has a disc 35 which is at a vertical distance from the flange 26 and has a central opening 36. The outer rim 37 of the disc is inclined obliquely outwards so that the disc 35 forms a type of hood for collecting the rising gas.

Vertical vanes 38 which are arranged in the shape of a fan or star are located on the upper side of the disc 35. The upper edges of the vanes 38 are located in the immediate vicinity of the under side of the cover wall 1 6. The froth separator is of a diameter such that it extends over almost the entire internal cross-section area of the cylindrical body 17.

The guide cylinder 40 is arranged beneath the froth separator 14 at a vertical distance therefrom.

The guide cylinder 40 is double-walled in design.

The outer wall is designated by 41, the internal wall by 42 and the upper end wall by 43. The lower end wall of the guide cylinder is also sealed but two tubes 44 and 45 project through the lower end wall into the annular space in the guide cylinder 40. The tubes 44 and 45 stand on the bottom plate 15 and are joined to connecting pipes which project through the bottom plate 15.

The tube 45 is relatively short and ends in the lower region inside the guide cylinder 40 whereas the tube 44 is long and projects into the vicinity of the upper end of the annular space in the guide cylinder 40. The tubes 44 and 45 have openings 46 and 47 at their ends. The tube 45 acts as an inlet tube for a heating medium which enters the annular space of the guide cylinder 40, and the tube 44 forms the outlet tube for the heating medium. The flow-rate and the temperature of the heating medium can be regulated so that uniform conditioning of the liquid-gas mixture can be achieved by means of heat exchange on the walls 41 and 42 of the guide cylinder. In the sterilisation phase, steam can be charged through the annular space in the guide cylinder in the same way.

As shown in Figure 3, the external wall 41 of the guide cylinder 40 consists of three equal ring segments 50 in a plan view, each extending over an angle of 1200. The side edges of the ring segments 50 are bent outwards at right angles, forming flanges 49. The flanges 49 of the ring segments 50 are offset relative to each other and joined together. Each pair of flanges forms a vertical guide wall extending radially outwards from the external wall 41 of the guide cylinder 40 into the vicinity of the internal face of the cylindrical body 17.

The guide cylinder 40 which is supported by the tubes 44 and 45 and an additional tube 51 also standing on the bottom plate 15 (Figure 3) ends at a distance above the bottom plate 15. A gas tube 52 whose end is bent in the shape of a ring and co-axially surrounds the shaft 22 of the stirrer 12 is arranged just beneath the guide cylinder 40. The gas tube 52 serves to introduce oxygen, air or another suitable gas into the interior of the reaction container 10.

In the present embodiment, the stirrer 12 has two impeller wheels 53 and 55 which are fixed on the shaft 22 and are arranged spaced apart inside the guide cylinder 40. The impeller wheel 54 is located in the upper region of the guide cylinder 40 and the impeller wheel 53 in its lower region.

The blades of the two impeller wheels have the same oblique position so that both impeller wheels pump and propel the liquid-gas mixture in the same axial direction at any time. In the present case, the shaft 22 is rotated in such a way that the liquid-gas mixture is pumped downwards in the direction of the arrows 55 indicated in Figure 2 inside the guide cylinder 40, rises outside the guide cylinder 40 and flows back into the guide cylinder from above.

An annular member 56 having numerous nozzles 57 and 58 distributed in the shape of a star is located between the cylindrical body 17 and the bottom plate 15. In the present case, six nozzles 57 for the supply and discharge of gases or liquids and five nozzles 58 for the introduction of measuring probes are provided. The nozzles 57 and 58 are designed as tubular members which point obliquely upwards and outwards, the tubular members of the nozzles 58 for measuring probes being designed longer, for reasons of guidance, than the nozzles 57 which are either sealed by screwing in stoppers 59 or are connected to other units by screwing in pipe pieces.

Probes, for example, for measuring the pHvalue, for measuring the oxygen partial pressure, for measuring the pressure or the temperature, are introduced through the nozzles 58 into the interior of the reaction container. The nozzles 57 serve to supply air or other gases or to supply the fermentation substrate.

The annular member 56, whose shape is shown in detail in Figure 2, forms above the bottom of the reaction container 17 a lateral annular bulge 60 whose lower region is connected almost horizontally and almost without transition to the interior of the bottom wall 15 and whose upper region passes into the cylindrical wall of the cylindrical body 17 also almost without kinks. In the upper conical region of the bulge 60, which has an overall droplet or pear shape, the nozzles 57 and 58 merge into the interior of the reaction container 17. As the nozzles pass at right angles through the wall of the annular member 56, they run obliquely downwards into the interior of the reaction container.The measuring probes thus project into the region of high turbulence where the test values such as the pH-value and the oxygen partial pressure can be determined representatively for the entire container contents.

The high turbulence in the region of the lower end of the guide cylinder also prevents the special electrodes from being covered with organisms.

The fact that correcting means are supplied through the nozzles 57 also into the region of high turbulence, allowing rapid and uniform distribution and mixing, is also advantageous. However, due to the large diameter of the froth separator 14, the passage of electrode through the cover wall of the reaction container which would otherwise be conventional is not possible in the fermentor illustrated.

Figure 4 shows the attachment of the tube 44 for the delivery of the heating medium to an external nozzle 61. The bottom plate 15 has a radial passage 62 issuing from its outer rim, on whose external end the nozzle 61 is screwed. The radial passage 62 communicates with an axial passage 63 in the bottom plate 15. The lower end of the tube 44 is located on the end of the axial passage 63. The seal is provided by an annular plate 64 screwed on to the bottom plate 15 containing a sealing ring.

In a similar manner, the tube 45 is connected to the nozzle 65 (Figure 3), through which the heating medium is supplied.

Some air or pure oxygen is introduced into the gas tube 52 through an attachment 66 in the wall of the annular member 56 as shown in Figure 5.

The attachment 66 is joined to a feed pipe 68 by means of a screw member 67. The screw member 67 has a tubular member 69 projecting into the gas tube 52. The gas introduced into the gas tube 52 issues through numerous holes in the gas tube 52 in the interior of the reaction container 10.

The fermentor is surrounded by an articulated sterilising sleeve 70 of mesh-form material which surrounds the tie rods 18 and the cylindrical body 17, as shown in Figure 2.

Figures 6 and 7a to 7d show details of the froth separator 14. The vanes 38 which are arranged in the shape of a fan, of which Figures 7a to 7d shows the vanes 381,382,283 and 384 respectively in a side view, are located vertically on the disc 35. The vanes have vertical openings or slits 72 extending from the edge of the disc 35 over a portion of the vane height. Figures 7a to 7d shows that the openings 72 are located at differing points on adjacent vanes. This prevents the formation of circular channels as the froth separator rotates and allows thorough whirling and breaking up of the froth in the formation phase. A step portion 73 which can also have differing positions and can form selectively a lefthand and a right-hand limit edge is located on the upper edge of each vane.According to Figure 7b, a lateral recess 74 is also provided on the outer rim of the vane 382.

The vanes 38 are welded on the upper side of the disc 35. In the central region, they are also centred and connected to each other by an annular horizontal plate 75 projecting into corresponding slits or recesses.

The division of phases by the froth separator allows the fermentor to be operated in the completely filled condition and, nevertheless, prevents liquid substrate from being entrained via the gas outlet pipe 33. The froth separator 14 rotates in the same direction as the impeller wheels 53 and 54 so that it does not obstruct the flow of material and does not form a drive member opposed to the substrate stream. When the fermentor is filled to about 80% with liquid substrate, the substrate is mixed homogeneously with the remaining portion of air producing uniform filling over the entire volume of the container.

Claims (9)

1. A fermentor for growing micro-organisms with a container into which a stirrer projects from below and in whose upper region is located a rotating froth separator which communicates with a gas outlet pipe, with a guide cylinder which is arranged co-axially in the container and is open at the top and bottom, a gas tube and with a plurality of nozzles in the container wall for the supply or removal of gases or liquids and for the introduction of ancillary equipment, wherein the froth separator is arranged close beneath the upper wall of the container and at a vertical distance above the guide cylinder and has fanshaped vanes for breaking up froth formed during use.

2. A fermentor according to Claim 1, wherein the ancillary equipment is one or more probes.

3. A fermentor according to Claim 1 or 2, wherein the vanes each have vertical openings or edges at differing distances from the rotational axis.

4. A fermentor according to Claim 1, 2 or 3, wherein the vanes are arranged vertically on the upper side of a disc.

5. A fermentor according to any preceding claim, wherein the plurality of nozzles are radially arranged in an annular member located between a cylindrical container wall and the bottom wall of the container.

6. A fermentor according to claim 5, wherein the internal wall of the annular member is a flow guide member and, by means of a bulge which is widened in cross-section, connects the cylindrical container wall and the bottom wall substantially without kinks, and the nozzles are inclined at an angle to the horizontal in the region of the bulge.

7. A fermentor according to any preceding claim wherein the guide cylinder has vertically projecting guide walls by means of which the annular space between the guide cylinder and the container wall is divided.

8. A fermentor according to any preceding claim, wherein the guide cylinder is a heat exchanger.

9. A fermentor for growing micro-organisms substantially as herein described with reference to and as illustrated in the accompanying drawings.