Characterisation of the gas-liquid mass transfer in shaking bioreactors

The maximum gas-liquid mass transfer capacity of 250 ml shaking flasks on o rbital shaking machines has been experimentally investigated using the sulp hite oxidation method under variation of the shaking frequency, shaking dia meter, filling volume and viscosity of the medium. The distribution of the liquid within the flask has been modelled by the intersection between the r otational hyperboloid of the liquid and the inner wall of the shaking flask . This model allows for thr calculation of the specific exchange area (a), the mass transfer coefficient (k(L)) and the maximum oxygen transfer capaci ty (OTRmax) for given operating conditions and requires no fitting paramete rs. The model agrees well with the experimental results. It was furthermore shown that the liquid film on the flask wall contributes significantly to the specific mass transfer area (a) and to the oxygen transfer rate (OTR). (C) 2001 Elsevier Science B.V. All rights reserved.