A large variety of different cell cultures were tested to find the best harvesting conditions for Sartoclear Dynamics® filters. The optimal conditions appeared to be similar for most cell lines. It was proven that the required amount of DE is relative to the amount of biomass in the culture. Further, it appeared that an acid precipitation of the smallest particles positively impacts the performance of the technology. The optimal conditions could be confirmed in a 1,000 L test which is described below.
- 1,000 Liters
- Chinese Hamster Ovary (CHO) line
- 10% Wet Cell Weight (WCW)
- Viability 80%
- Viable Cell Density (VCD) 30 Mil. Cells/mL
- 2M acetic acid
- pH reduced to pH 5.0
- DE | biomass ratio 1:4
- 25 kg Celpure®* C300 added in total
- Filtration area:
16 x 0,21 m2 = 3.36 m2
- Flow rate: 300 L/m2/h
- Final turbidity: 8 NTU
- Recovery: 92%
- DNA Removal: 93%
Cell Culture Preconditioning
In order to achieve ideal results and to use as little DE as possible, we recommend preconditioning the cell culture fluid. You can either add flocculants or lower the pH. This will create aggregates that are too big to migrate into the filter cake. This way, the cake stays permeable and the DE | biomass ratio can be reduced to about 1:4.
Best results were reported using organic acids such as 2M acetic acid to lower the pH to 5 for 45 minutes.
Adding Diatomaceous Earth (DE) for Filtration
How much Diatomaceous Earth do I need?
Adding diatomaceous earth to the filtration process has two purposes: Its porous structure keeps the filter cake permeable and it sieves out sub-micron particles to protect subsequent membrane filters.
The amount of Celpure®* C300 you mix into your cell culture is relative to your biomass. Based on a large number of tests with many different cell cultures we recommend the following DE|Biomas (WCW) ratios.
*Celpure® is a trademark of Advanced Minerals