Separation of Particles,Streptomycetes,Filtration,Flocculation,Organic Polyelectrolytes,Foam Formation

	Separation of Particles - The first step in DSP is the separation of solids, usually cells, from the liquid medium. This is generally achieved as follows. Filtration. It is used for the separation of filamentous fungi and filamentous bacteria, e.g., streptomycetes, and often for yeast flocks. The various techniques of filtration employed are, surface filtration, depth filtration, centrifugal filtration, cross flow filtration, and rotary drum vacuum filtration.
Centrifugation. It may be used to separate bacteria and usually protein precipitates. But difficulties arise due to small differences in the densities of the particles and the medium. In addition, equipment cost, power consumption, temperature, etc. are the other disadvantages. Flocculation and Floatation. Flocculation, i.e., sticking together of cells, can be induced by inorganic salts, mineral hydrocolloids are organic polyelectrolytes. Since sedimentation rate of a particle increases with size, flocculated cells can be recovered by centrifugation.
In cases, where flocculation is not effective, very fine gas bubbles can be created by sparging, release of overpressure or electrolysis. The gas bubbles adsorb to and surround the cells, raising them to the surface of medium in form of foam (floatation); long chain fatty acids or amines promote stable foam formation. The cells collected in the foam are readily recovered. Flocculation and floatation are used for the most efficient recovery of microbial biomass in some single cell protein production systems.