Biomass monitor probes and bioreactors incorporating such probes

A bioreactor includes a plastic enclosure for containing a biological medium, the enclosure being integrally formed to have one or more elongate port extensions projecting outwardly from the enclosure and communicating from the exterior to the interior of the enclosure. A biomass impendence monitor probe is provided for use in conjunction with the bioreactor. The probe is pushed into one or more of the elongate ports in order to have an electrode arrangement positioned internally of the container. The probe has an elongate housing having an outer surface extending along and contiguous with the elongate inner surface of the port extension. The housing extends from the electrode end of the probe to a remote end. The housing is provided with an electrical connector connected to the electrode arrangement.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from GB 1006793.2, filed Apr. 23, 2010, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to biomass monitor probes and bioreactors incorporating such probes. The invention relates particularly to probes intended for use as single use monitor probes and bioreactors.

2. State of the Art

Different embodiments of single use biomass monitor probes, devices and bioreactors incorporating such probes are disclosed in, for example, WO2010/010313. An improved arrangement has now been devised.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a bioreactor arrangement comprising:i) an enclosure for containing a biological medium and including one or more elongate port extensions projecting outwardly from the enclosure and communicating from the exterior to the interior of the enclosure;ii) an impedance monitor probe being secured in one or more of the elongate ports in order to have an electrode arrangement positioned to monitor the biological medium, the impedance monitoring probe comprising an elongate housing having an outer surface extending along and contiguous with the elongate inner surface of the port extension, the housing extending from the electrode end of the probe to a remote end, the remote end being provided with an opening of a bore which extends at least part-way internally along the length of the elongate housing to an electrical connector connected to the electrode arrangement.

It is preferred that the port extension comprises a cylindrical port extension.

In one realisation of the invention, the monitor probe is positioned to have the electrode arrangement positioned internally of the enclosure.

In one embodiment, it is preferred that the enclosure for containing the biological medium comprises a flexible bag, pouch or wall and the one or more elongate cylindrical port extensions projecting outwardly from the container are formed integrally with the enclosure.

It is preferred that the elongate housing of the impedance monitor probe extends along the majority of the length of the elongate port extension. This provides for secure location in the port extension. Beneficially, the impedance monitor probe is pushed fitted into position in the one or more of the elongate ports, preferably via the external open end of the respective elongate port. This means that access for securing the probe in position is required from externally only of the bioreactor. There is no need to access the reactor from internally to fit the probe in position. Ties, clamps or other securing means may be applied to the exterior of the port extension in order to secure the engagement between the push fitted probe and the port extension.

Preferably the elongate housing extends beyond the outer end of the elongate port extension. This provides for convenient connection of the probe to other components.

Preferably, the impedance monitor probe of the bioreactor arrangement is formed of at least two-parts comprising a probe part and a connector part arranged to connect with the probe part, the connector part having an elongate proximal end part arranged to be inserted into the bore in the probe so as to facilitate electrical connection with the electrode arrangement; and a distal end housing part containing monitoring circuitry and/or electronic signal conditioning or processing means enabling a signal conditioning or processing operation to be conducted on the electrical signal from the probe.

According to a further aspect, the present invention provides an impedance monitoring probe part having a measurement electrode arrangement positioned at an end of the probe part, and comprising an elongate housing extending from the electrode end of the probe part to a remote end, the remote end being provided with an opening of a bore cavity which extends at least part-way internally along the length of the elongate housing to an electrical connector connected to the electrode arrangement.

The probe part housing is beneficially made of a plastics material that is sterilisable with the bioreactor and disposable.

It is preferred that the electrical connector is positioned at the end of the internal bore in the probe part housing. Beneficially, the electrical connector is positioned closer to the electrode end of the probe part than to the remote end. Most preferably, the electrical connector is positioned proximate the electrode end of the probe part.

Positioning the electrical connector closely adjacent to the electrode arrangement provides enhanced technical performance because it reduces the size of the electrical circuit in the disposable probe part. This is important because of calibration issues. Ideally, the circuitry in each probe part for connection to an electrical connector part (as described below) will be repeatably identical. Differences in the circuitry between different probe parts connected to the same connector, one after the other, can result in calibration issues. By keeping the monitoring circuitry in the disposable probe part to a minimum, the calibration issues are minimised because the major part of the monitoring circuitry is provided within the connector part of the two part probe.

A further advantage is that, by keeping the amount of circuitry in the probe part to a minimum, the shadow cast by the metallic circuitry during gamma irradiation sterilisation is kept to a minimum. Additionally the cost of the probe part is also kept to a minimum.

In one embodiment, it is preferred that the electrical connector comprises one part of a male/female socket and pin electrical connector, preferably the socket part of a socket and pin electrical connector.

According to a further aspect, the present invention provides a two-part, impedance monitoring device comprising a single use disposable impedance monitoring probe as defined herein and in the appended claims; and a re-usable connector part arranged to connect with the disposable probe, the connector part having an elongate proximal end part arranged to be inserted into the bore in the probe so as to facilitate electrical connection with the electrode arrangement; and a distal end housing part containing an electrical circuit and/or electronic signal conditioning or processing means enabling a signal conditioning or processing operation to be conducted on the electrical signal from the probe.

In a preferred embodiment, the electronic signal conditioning or processing means provided in the distal end housing part comprises a pre-amplifier.

It is preferred that the connector part elongate proximal end part extends along substantially the entire length of the bore in the probe in order to facilitate electrical connection with the electrode arrangement of the probe.

According to a further aspect, the invention provides a bioreactor arrangement comprising:i) a flexible plastics enclosure for containing a biological medium the enclosure being integrally formed to have one or more elongate port extensions, projecting outwardly from the enclosure and communicating from the exterior to the interior of the enclosure;ii) an impedance monitor probe being pushed into one or more of the elongate ports in order to have an electrode arrangement positioned internally of the container, the impedance monitoring probe comprising an elongate plastics housing having an outer surface extending along and contiguous with the elongate inner surface of the cylindrical port extension, the housing extending from the electrode end of the probe to a remote end, the elongate housing being provided with an electrical connector connected to the electrode arrangement.

It is generally preferred that the bioreactor is sterilised with the impedance monitor probe already pushed into position in the one or more of the elongate ports.

The invention will now be further described in specific embodiments, by way of example only and with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, and initially toFIG. 1, there is shown a bioreactor1comprising a flexible plastics enclosure2typically in the form of a container or bag. Such bioreactors are known in the art to be used as single use bioreactors for use in fermentation, brewing or other biological processes. The flexible plastics enclosure2is typically gamma irradiated prior to use in order to sterilise the bioreactor. The bioreactor is typically disposed of following a single use and accordingly it is important to minimise the manufacturing and component costs of the product.

The container is provided with a series of elongate tube ports3, integrally formed with the enclosure and, in the embodiments ofFIGS. 1 and 2, projecting to extend outwardly from the wall of the enclosure2.

A two-part impedance monitoring device10is shown inFIG. 4. The monitoring device comprises a disposable probe part11and a connector part12. The disposable probe part11and re-usable connector part12are separable in service (i.e. after manufacture of the probe the probe part and the connector part can be separated). The disposable probe part11is in use arranged to be push fitted into a tube port3in the bioreactor enclosure2prior to sterilisation irradiation.

The probe part11has an electrode end14which is inserted into the bioreactor via the tube port3to be in contact with the culture in the bioreactor containing living cells (the biomass medium). The electrode end14includes an end surface15on which are mounted2pairs of platinum electrodes, which are formed as elongate strips at the distal end of the probe as shown most clearly inFIG. 4. The outer electrodes21bare used to pass current through the biomass media. The inner electrodes21aare used to sense the voltage across the gap between them. This arrangement is preferred over a simple 2 electrode arrangement in order to reduce the effect of polarisation that occurs at the current electrodes21b. A radio frequency (RF) electric current is applied to the biomass solution via the current electrodes21b, and the resultant voltage and current are sensed by the sensing electrodes2a.

In this impedance measurement technique, the voltage and current measurements obtained, an appropriate processor is able to determine the capacitance (pF) and conductance (mS) of the solution. These values are then scaled using the known probe characteristics to give conductivity (mS/cm) and capacitance (pF/cm). Capacitance (pF/cm) is proportionally related to the permitivity of the solution. The (RF) electric current is applied via the current electrodes21b, and the resultant voltage and current sensed by the sensing electrodes21a. Using the voltage and current measurements obtained, an appropriate processor is able to determine the capacitance (pF) and conductance (mS) of the solution. This impedance measurement technique is known in the art and described in, for example U.S. Pat. No. 4,810,650.

The probe part11has an elongate housing13extending away from the electrode end14. The length of the probe part housing13is preferably such that, with the disposable probe part11retained in the tube port3of the bioreactor enclosure2, the distal end16of the probe part housing13is positioned outwardly beyond the end of tube port3. This makes connection with the connector part12more convenient. The internal diameter of the tube port3and the external diameter of the probe part housing13are matched such that the probe part is a secure push fit into the tube port3which resiliently grips the probe part housing13. This connection is enhanced because of the relatively long length of the tube port and the probe housing. This feature also means that the probe part11is stably mounted with respect to the bioreactor enclosure2. Plastic ties or clamps27may be used to enhance the securing of the probe part housing13in the tube port3.

The probe part11is push fitted into the respective tube port13from externally of the enclosure. This means that access to the interior of the enclosure is not required to fit the probe part into the tube port13.

The interior of the probe part housing13is provided with an internal bore17extending from an opening29in the distal end16of the probe part11internally along the length of the elongate housing13to an electrical connector19connected to the electrode arrangement. The internal bore has a relatively large diameter portion17astepping down to a relatively narrower diameter portion17bwhich comprises an electrical connector socket arranged to connect with an electrical connector pin31provided on the connector part12. In this way, even though the probe part11is relatively long and electrically connected to the connector part12, the location of electrical connection is close to the electrode arrangement which gives improved measurement performance.

The reason for this is that such an arrangement minimises the size of the electrical circuit in the disposable probe part11thereby minimising stray impedances which contribute system to errors. This is important because of calibration issues. Ideally, the circuitry in each probe part11for connection to the connector part12will be repeatably identical. Differences in the circuitry between different probe parts connected to the same connector, one after the other, can result in calibration issues. By keeping the monitoring circuitry in the disposable probe part11to a minimum, the calibration issues are minimised because the major part of the monitoring circuitry is provided within the connector part12of the two part device. A further advantage is that, by keeping the amount of circuitry in the probe part11to a minimum, the shadow cast by the metallic circuitry during gamma irradiation sterilisation is kept to a minimum. Additionally the cost of the probe part11is also kept to a minimum.

The pin connector31of the connector part is provided at the end of an elongate proximal end part33which is shaped and dimensioned to be a snug sliding fit into the internal bore17aof the probe part11. The shoulder36abuts against the seat24when the elongate proximal end part33of the connector part12is fully inserted home into the bore in the probe part11. This provides good rigidity and support between the probe part11and the connector part12. The distal part of the connector part12has an increased diameter housing part35and an internal cavity43which contains monitoring circuitry and typically signal processing electronics for carrying out initial signal conditioning or processing on the signal derived from the electrode arrangement. The end of the connector part12is provided with a proprietary socket/pin connector44for connection to a signal pre-amplifier (not shown connected).

The arrangement provides that the probe part11can be inserted into the tube port3prior to sterilisation and that it is easy to subsequently connect and disconnect the connector part12of the device. Separating the connection part12from the probe part11prior to sterilisation, and removing the bulk of the circuitry, minimises the risk of gamma radiation not reaching all parts of the probe part11in the sterilisation process. Therefore the probe part11and connector part12are separable in service. Consequently, the probe part11can be constructed to be single use and disposable with the bioreactor enclosure. The probe part11is manufactured of suitable materials such a plastics materials and the more expensive signal processing components are housed in the re-usable connector part12.

FIG. 3shows an alternative embodiment of a bioreactor in which the tube port103projects internally of the enclosure2. The probe part11is once again push fitted into the tube port3from externally of the enclosure2.

Advantageously, the bioreactor arrangement includes a two part arrangement, a monitoring probe part11and a connector part12, arranged such that the probe part11can be inserted into the tube port of a bioreactor whilst still enabling the connector part to be separated from the probe part. The circuitry in the probe part11is arranged to be minimal such that on removal of the connector the risk of gamma radiation not reaching all parts of the probe in the sterilisation process is minimised.

It will be readily appreciated that the embodiments described are explanatory only and other arrangements falling within the scope of the invention are envisaged. For example the electrodes provided on the external face could be replaced by concentric band electrodes positioned about the end of the probe part.