Practical considerations in the measurement of culture fluorescence.

We have examined practical considerations associated with the use of a commercially available fluorescence probe for in situ measurements in bioreactors. The optical path length of the measurement was first determined and a flow cell subsequently designed. The environment (agitation/aeration rates) of the probe was found to have a significant influence on the measurement. These effects were eliminated by placing the probe in a recycle loop using the flow cell. Fluorescence measurement in the recycle loop was verified to be representative of the cell sample and to not affect cell metabolism.