Bioreactors centrifugal

The simplest devices have rakes mounted on the stirrer shaft located on the surface of the liquid. A more sophisticated device is the Funda-foam system , in which the foam is destroyed by centrifugal forces. The nutrient solution held in the foam flows back into the bioreactor, and the air released from the foam leaves the vessel. 

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

A continuous centrifugal bioreactor, in which cells are fluidized in balance with centrifugal forces, has been designed to allow high density cell cultivation and superior aeration without elutriation of the suspended cells (van Wie et al., 1991). Reactor performance was hampered by elutriation of biomass by evolved gas in an anaerobic fermentation, indicating that it may not be suitable in its present state for three-phase fermentations. Immobilization of the cells on denser particles may overcome this problem. 

In a spin-filter based stirred bioreactor, there are various forces acting on both the liquid medium and the cell particles gravity force, axial force due to impeller rotation, centrifugal force created by the spin-filter rotation, and radial force (drag) generated by the perfusion flux. 

With an adherent cell line, initially there will be few cells in the harvest and those that are recovered may be nonviable This is not necessarily a cause for concern, since viable cells will remain attached to the fibers With a nonadherent cell line, the first 50 mL of the initial harvests may yield a higher proportion of dead cells, because these tend to fall more rapidly to the bottom of the cartridge 29. In the early stages with a nonadherent cell line, too many cells may inadvertently be removed during harvesting After centrifugation, these cells may be suspended in the replacement medium and reintroduced into the bioreactor It is also possible to use cells from a well-established bioreactor to seed another... 

Voit H, Gotz F, Mersmann AB. Overproduction of lipase with Staphylococcus camosus (pLipPSl) under modified gravity in a centrifugal field bioreactor. Chem Eng Technol 1989 12 364-373. 

Fig. 1. Schematic diagram of a centrifugal impeller bioreactor (5 1). 1 Magnetic stirring device 2 gas in 3 head plate 4 agitator shaft 5 measurements of the liquid velocity profiles of the discharge flow were performed in the vertical direction across the width of the blades (the vertical dashed line) and at various radial distances from the impeller tip 6 sintered stainless sparger 7 centrifugal blade 8 draft tube 9 DO probe 10 centrifugal rotating pan...

Recently, Wang and Zhong successfully designed a novel centrifugation impeller bioreactor (Fig. 3) for shear-sensitive cell systems [35, 36]. They proved... 

The steps involved in purification include harvesting of the bioreactor, followed by inactivation of cells and concentration of the starting material, which is the cells, or the medium when the product is secreted. Concentration is achieved by using centrifugation or membrane filter systems by ultrafiltration. Cells are disrupted using the physical, chemical or enzymatic method that is best suited to the particular situation (Hopkins, 1991 Papoutsakis, 1991). 

Oxygen levels were regularly measured in samples taken from the bioreactor by means of a portable oximeter, to maintain the oxygen inside the bioreactor at 2-A mg O2/L. The exit stream of the reactor is impelled to the membranes by a centrifugal pump located at the exit (see Figure 41.2), at a rate of 56 m /h at 4 bar. 

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