ISSN:
1573-0778
Keywords:
Air lift reactor
;
bubble column
;
bioreactor
;
oxygen gradients
;
scale-up
;
stirred vessel
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract An estimation is made of oxygen gradients in animal-cell bioreactors, using straightforward engineering calculations. Three types of bioreactor are considered: stirred vessel, bubble column and air lift, of sizes between 0.01 and 10 m3. First, the gradient is estimated in the stagnant layer surrounding a cell (15 μm), a microcarrier (185 μm) with 300 cells attached to it, a macroporous support (1.25 mm) containing 185,00 cells and one (6 mm) containing 4.25 million cells. It is assumed that oxygen consumption is 10−16 mole O2·cell−1·s−1, while mass transfer coefficients are obtained from Sherwood relations. Circulation and liquid-retention times of the bioreactors are compared with the oxygen-exhaust times of suspensions with 1012, 1013 and 1014 cells/m3 to estimate if oxygen gradients are likely to exist in the bulk-liquid phase. Finally, the gradient in the liquid film surrounding air bubbles is estimated using k l A-values obtained from empirical correlations. It is clear from all these estimations that in many situations severe gradients can be expected. The question remains, however, whether gradients should be avoided as much as possible, or may be tolerated to a certain extent or even created on purpose because of possible beneficial effects.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00744317
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