The use of dinoflagellate bioluminescence to characterize cell stimulation in bioreactors.

Bioluminescent dinoflagellates are flow-sensitive marine organisms that produce light emission almost instantaneously upon stimulation by fluid shear in a shear stress dose-dependent manner. In the present study we tested the hypothesis that monitoring bioluminescence by suspended dinoflagellates can be used as a tool to characterize cellular response to hydrodynamic forces in agitated bioreactors. Specific studies were performed to determine: (1) impeller configurations with minimum cell activation, (2) correlations of cellular response and an integrated shear factor, and (3) the effect of rapid acceleration in agitation. Results indicated that (1) at a volumetric mass transfer coefficient of 3 x 10(-4) s(-1), marine impeller configurations were less stimulatory than Rushton configurations, (2) bioluminescence response and a modified volumetric integrated shear factor had an excellent correlation, and (3) rapid acceleration in agitation was highly stimulatory, suggesting a profound effect of temporal gradients in shear in increasing cell stimulation. By using bioluminescence stimulation as an indicator of agitation-induced cell stimulation and/or damage in microcarrier cultures, the present study allows for the verification of hypotheses and development of novel mechanisms of cell damage in bioreactors.