A Laboratory Experiment to Demonstrate the Principles of Sedimentation in a Centrifuge:ESTIMATION OF RADIUS AND SETTLING VELOCITY OF BACTERIA

摘要

Sedimentation refers to the movement of particles in a fluid under the influence of an external force. Centrifugation is a subset of sedimentation where particles or macromolecules move through a liquid under the influence of a centrifugal force. Centrifugation is a ubiquitous unit operation in biotechnology, food, mineral processing, and many other industries. In the biotechnology industry centrifugation is used for rapid removal of cell particles from fermentation or cell culture media, removal of cell debris, and separation of protein precipitates. Commercial bioprocesses for the manufacture of penicillin, recombinant human insulin, monoclonal antibodies, therapeutic proteins, viral vaccines, bioethanol, and 1,3-propane diol use centrifugation for cell removal. Biological particles are relatively small (sub-micron to a few microns in diameter), and hence high rotational speeds are necessary for their separation. However, higher rotational speeds lead to greater shear stress. Particles separated using centrifugation in biotechnology are usually shear sensitive and hence require greater care during separation. Therefore, centrifuge operation in biotechnology is a tradeoff between separation efficiency and shear damage.