Bioreactors Cell concentration ranges

In the case of homogeneous bioreactors, the maximum cell concentration in perfusion cultures can attain 107-108 cells mL-1. When this operation mode is used in heterogeneous bioreactors, cell concentration in the cell compartment can approach the packing limit of tissues, which is in the order of 109 cells mL. Product concentrations reported for these processes vary considerably, but are most commonly in the range of 100— 500mgL 1. Culture duration can be in the range of several days up to several months (Bodeker, 1994). 

In this way, the use of bioreactors that allow high cell density cultures is of great importance as a tool to increase process productivity. Table 9.3 shows volumetric productivity values that can be obtained in the main types of industrial bioreactors, as well as the typical working volume and the cell concentration ranges that are usually attained. 

If 02 consumption were indeed zero order for a particular plant species, then it would appear that any phytoproduction process involving that species would require only that a minimum dissolved 02 concentration be maintained any concentration increase beyond that would be irrelevant. In the case of tobacco cells, any concentration greater than 15 % of air saturation would yield the same metabolic rate and, presumably, the same productivity of all metabolites. If, on the other hand, consumption is first order in the concentration range achievable in a practical bioreactor (equivalently, if Kf is comparable to working concentrations), then its concentration is an important control parameter in the bioreactor. However, Kobayashi et al. studied berberine production by suspended and immobilized cells of Thalictrum minus [50]. They assert that 02 uptake is a zero-order process but observed that berberine production depended on 02 availability. They controlled that availability by adjusting the speed of shaking of the culture flasks, thus varying the mass transfer coefficient for absorption of 02. 

Metabolomics is an extension of proteomics and describes the analysis of the catalytic activities that make up the metabolic activities of a cell. Metabolomics is at the core of biosystems engineering and its purpose is to analyze the metabolome (all metabolites, roughly in the range of 500- 2000) and their concentrations in the cell under given physiological conditions, as well as the dynamic response to changing environmental conditions (notably in a bioreactor). 

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