Filtration

Cell-free substrate samples are removed from the bioreactor using the sampling probe on a filtration basis. The hydrophilized probe is mounted inside the bioreactor and subsequently sterilized along with the medium.

The membrane module of the probe is positioned in the turbulent zone of the reactor, near the agitator. A tubular membrane made of polypropylene with a pore size of 0.2 µm serves as sterile barrier. The filtrate flux does not exceed 1.5 mL/min.

After sampling, the cell-free sample can be used directly for analysis. The filtration probe is used when a sufficient reactor volume is available.

1.2 TRACE C2 - Automated online Sampling

The TRACE C2 Sampling is a universal online bioreactor sampling system which can automatically withdraw samples from up to four bioreactors. Both cell-containing samples and cell-free samples can be obtained.

1.3 TRACE single-use tubing sets

Depending on the sampling method, sterile tubing sets are available that are easily mounted on the device. They include all components for sampling, such as pumps, valves, filters and the corresponding connector the bioreactor or the sampling probe.

Solutions for rinsing and disinfection are automatically promoted through the tubing system to ensure optimum quality of the individual samples and to exclude contamination of the process.

2. Methods

For the diverse needs of an effective online process monitoring and sampling TRACE offers a wide range of methods which can be selected by the user according to the process conditions and measurement tasks.

Currently, the following methods for filtration probes are available:

1. Cell-free sampling by filtration
2. Cell-free sampling by filtration 4-channel
3. Cell-free sampling by filtration with backflush
4. Cell-free sampling by filtration with backflush 4-channel

2.1 Cell-free sampling by filtration

In filtration mode, the tubing is connected directly to a filtration probe which is installed in the bioreactor. The filtration probe enables the extraction of cell-free medium and at the same time it represents the sterile barrier between the reactor content and outside.
For sampling pump 1 draws the required amount of medium in selected intervals or at defined times and releases it via the "Sample (out)" port. Then the line is flushed with sterile filtered air to prevent carryover of individual samples.

Prior to sampling, the line “Sample (in)” is pre-rinsed with medium to obtain a representative sample. This purge time is preset.

After sampling and between individual samplings the lines are rinsed with buffer ("Buffer") and air ("Air"). Again, this process is automatic. The buffer solution and the medium-rinsing are disposed via the waste line ("Waste").

In addition to the times or intervals of sampling, the volume of the respective sample can be chosen in the range of 0.5 - 20 ml.

Settings:
- Sample volume
- Interval every x minutes, or the time of sampling.

2.2 Cell-free sampling by filtration 4-channel

In addition to the filtration system described in section 2.1, a 4-channel version of the tubing set can be used, in which up to 4 different reactors can be operated by TRACE C2 Sampling.

The particular sampling probe is then switched on via a selector valve, and the probes are activated one after another or at set points in time.

Settings (for each reactor individually):
- Sample volume
- Interval every x minutes, or the time of sampling

2.3 Cell-free sampling by filtration with backflush

In filtration mode, the tubing is connected directly to a filtration probe which is installed in the bioreactor. The filtration probe enables the extraction of cell-free medium and at the same time it represents the sterile barrier between the reactor content and outside.

In addition this method allows to flush the probe with a rinsing solution „Flush“(water or sterile fresh medium) counter to the removal direction. This backflushing can be useful for longer fermentations or long intervals between the individual withdrawals. Especially with small probes and less filtration membrane surface this option allows for regular flushing of the membrane pores.

For sampling pump 1 draws the required amount of medium in selected intervals or at defined times and releases it via the "Sample (out)" port. Then the line is flushed with sterile filtered air to prevent carryover of individual samples.

Prior to sampling, the line “Sample (in)” is pre-rinsed with medium to obtain a representative sample. This purge time is preset.

After sampling and between individual samplings the lines are rinsed with buffer ("Buffer") and air ("Air"). Again, this process is automatic. The buffer solution and the medium-rinsing are disposed via the waste line ("Waste").

In addition to the times or intervals of sampling, the volume of the respective sample can be chosen in the range of 0.5 - 20 ml. For membrane backflushing the user can specify a certain volume between 10 to 50 ml.

Settings:
- Sample volume
- Backflush volume
- Interval every x minutes, or the time of sampling

2.4 Cell-free sampling by filtration with backflush 4-channel

In addition to the filtration system described in section 2.3, a 4-channel version of the tubing set can be used, in which up to 4 different reactors can be operated by TRACE C2 Sampling. The particular sampling probe is then switched on via a selector valve, and the probes are activated one after another or at set points in time.

 

Settings (for each reactor individually):
- Sample volume
- Backflush volume
- Interval every x minutes, or the time of sampling