Towards a single empirical correlation to predict kLa across scales and processes

Mathematical models are increasingly used in fermentation. Nevertheless, one of the major limitations of these models is that the parameters they include are process specific, e.g. the volumetric mass transfer coefficient (kLa). Oxygen transfer was studied in order to establish a single equation to predict kLa, and data from a range of processes – pilot and production scale – were extracted. On ‐ line viscosity was measured for all processes (56 batches). Off ‐ line rheological measurements were performed for the pilot scale processes (26 batches). The apparent viscosity was evaluated with 5 different calculations of the average shear rate. The experimental kLa value was determined with the direct method; however, eight variations of its calculation were evaluated. Several simple correlations were fitted to the measured kLa data. The standard empirical equation was found to be best for predicting kLa in all processes at pilot scale using off ‐ line viscosity measurements, and using the equation from Henzler and Kauling (1985) to evaluate the shear rate. In addition, a parameter set of the standard empirical equation was found that can predict oxygen transfer in Bacillus processes at all scales using on ‐ line viscosity measurements. A single correlation for all processes and all scales could not be established