E.Coli

Homogenizers, however, are the most commonly used devices to lyse large quantities of bacteria. A cell suspension is pumped through the minute orifice of a homogenizing valve at high pressure; this is followed by the sudden release of the pressure on the suspension, resulting in an instant expansion that provides the turbulence and liquid shear — combined with the high pressure — that breaks the cells.

The main disruptive factor in this process is the pressure applied to the sample and the subsequent pressure drop across the valve. This provides the impact and the shear stress, making the cells break in proportion to the operating pressure.

Compared with other methods, homogenization is both convenient and efficient, offering higher percentage cell disruption rates. Modern GEA homogenizers are able to work continuously, enabling large quantities of cells to be processed at high operational pressures, which eliminates the need to add deoxyribonuclease (DNase) to the cell suspension.

Suggested pressures for typical applications are 600–1000 bar with a single stage homogenizer; multiple passes (2–3) are generally required to achieve adequate lysis. It should be noted that high processing pressures result in a rise in operating temperatures. Cells should, therefore, be cooled (4 °C) prior to use to avoid inactivating proteins by foaming.

Fermenters, separators, decanters and cross-flow filtration technology for the gentle treatment of fragile cell cultures are also available from GEA. We understand that the careful treatment of living micro-organisms, sterility and efficiency are prerequisites to economical, reliable and efficient processing.