Cell Lysis and Flocculation
Cell Lysis and Flocculation
If a product is synthesized intracellularly and not secreted by the producing cell, or if the product is to be extracted from plant, animal, or fungal tissue, it is necessary to remove the product from the cell or tissue by force. The choice of procedure is highly dependent on the nature of the product and the nature of the cell or tissue. It was seen in Chapter 1 that bioproducts represent a wide variety of chemical species. In this chapter, we also see that the sources of bioproducts—cells and tissues—are widely varied. For this reason, there exists a wide variety of methods for breaking, or lysing, cells and tissues, broadly classified as “chemical” and “physical” methods. Once cells have been suspended and/or broken open, the resulting suspension of solids must be separated from the liquid in which it is suspended. This separation process, filtration and/or sedimentation (the subjects of the next two chapters), is enhanced by having larger particles. Larger particles can be achieved by flocculation, a process whereby particles are aggregated into clusters, or flocs. In recent years, it has become desirable to isolate specific cell types from mixtures of suspended cells and to deliver the resulting cell subpopulation(s) to a process for which they, and only they, are required. Most examples come from in vivo sources such as blood and dispersed tissue cells. This aspect of cell processing, namely, cell purification, places special demands on separation processes that are capable of handling particulate matter under conditions that allow cells to remain alive. This chapter presents two major elements of cell processing: the science and engineering of cell rupture by physical and chemical methods and the flocculation of cells and subcellular particles in aqueous suspension. First, however, it is helpful to develop a broad appreciation for the variety and compositions of cells that are likely to be encountered in downstream bioprocessing.
Keywords: Gram-positive bacteria, Hamaker constant, animal cells, cell lysis, eukaryotic cells, lipids, penicillin, prokaryotic cells, protoplasts
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