Bioreactors bubble size distribution

Gas-Liquid Mass Transfer. Gas-liquid mass transfer within the three-phase fluidized bed bioreactor is dependent on the interfacial area available for mass transfer, a the gas-liquid mass transfer coefficient, kx, and the driving force that results from the concentration difference between the bulk liquid and the bulk gas. The latter can be easily controlled by varying the inlet gas concentration. Because estimations of the interfacial area available for mass transfer depends on somewhat challenging measurements of bubble size and bubble size distribution, much of the research on increasing mass transfer rates has concentrated on increasing the overall mass transfer coefficient, kxa, though several studies look at the influence of various process conditions on the individual parameters. Typical values of kxa reported in the literature are listed in Table 19. 

Furthermore, airlift bioreactor studies often use an effective riser diameter that is less than 0.15 m, which has been shown to influence the bubble size distribution in bubble columns (Kantarci et al., 2005). Not surprisingly, research work that compares ALR designs based on the bioreactor diameter uses smaller riser and downcomer columns and finds a strong bioreactor diameter dependence, noting... 

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