French Press

The French pressure cell press, or French press, is an apparatus used in  biological experimentation to disrupt the plasma membrane of cells by passing them through a narrow valve under high pressure.

The French Press can also be used for disintegration of chloroplasts, homogenates of animal tissue, and other biological particles. It is capable of disrupting cell walls while leaving the cell nucleus undisturbed. The press uses an external hydraulic pump to drive a piston within a larger cylinder that contains the liquid sample. The highly pressurized sample is then squeezed past a needle valve. As the sample passes through the valve, the fluid experiences shear stress and decompression, causing cellular disruption.

A French press is commonly used to break the resilient plasma membrane and cell walls of bacteria and other microorganisms for isolation of proteins and other cellular components. The disruption of cells in a French press generates ‘inside-out’ membrane vesicles which are required for many in vitro biochemical assays.