Hydrodynamic stress capacity of microorganisms

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Abstract
A new experimental method has been developed for estimating the hydrodynamic stress capacity of microorganisms. In a test apparatus, stable continuous cultures of three types of green algae and two cyanobacteria were exposed to well‐defined hydrodynamic loads in a free jet. During and after the stress experiments the cultures showed a different response due to the damage in the jet. The results of these free‐jet experiments with short stress exposure were compared to those of stirring experiments in which hydrodynamic load was continuously generated by a stirrer. In both kinds of experiments distinct critical stress values could be determined below which no essential damage of the microorganisms cultures occurred. A correlation between the critical stress values in free‐jet and stirring experiments was found. It can be deduced that the free‐jet data, expressed as critical volumetric dissipated energy, are suitable for the calculation of hydrodynamic stress to which microorganisms might be exposed in biotechnical plants without suffering damage.