Facts
In comparison to a Levitronix^® pump, a 4-Piston Diaphragm Pump consists of multiple valves that restrict fluid motion to the desired direction. Valve interaction can lead to shear stress, which can result in reduced protein quality.

Test conditions
The Levitronix^® PuraLev^® 600SU and a 4-Piston Diaphragm Pump of corresponding hydraulic power were evaluated for their generation of shear stress and its effect on protein activity. A fixed volume of lysozyme was pumped in two identical closed-loop configurations. The flow rate of each pump was set to 10 and 20 lpm, and backpressures of 1.5, 2, 2.5 bar, respectively. Protein activity and size were measured at selected times and compared.

Results
Protein activity did not change significantly for the PuraLev^® 600SU during the entire test. The fluctuations are within an acceptable margin of error. In contrast, the 4‐piston diaphragm pump showed a significant decrease in protein activity in all tests.

Protein activity and size at 10 lpm and 1.5 bar