Utilization of specific power input measurements for optimization of culture conditions in shaking flasks

Shaking flasks are often used in early stages of bioprocess development, particularly in screening purposes. Their advantages include ease of handling and low cost. The direction of bioprocess development is strongly influenced by the performance of microorganisms at these early stages. Therefore shaking conditions must be monitored carefully for limitations, e.g. oxygen limitations, or 'out of phase' conditions. Product formation of the xanthan producing bacterium Xanthomonas campestris is severely impaired by 'out of phase' shaking conditions. This could be shown for different shaking diameters and filling volumes. The dimensionless phase number could successfully be applied to prevent unsuitable 'out of phase' conditions. Cultures of Pseudomonas putida CA3 grown at 'in phase' and 'out of phase' hydrodynamic states, but otherwise identical conditions, also shows a lower optical density for 'out of phase' conditions. With help of power consumption measurements these unsuitable shaking conditions can be detected and avoided. (C) 2003 Elsevier B.V. All rights reserved.