Shaken flasks by resonant acoustic mixing versus orbital mixing: Mass transfer coefficient kLa characterization and Escherichia coli cultures comparison

AbstractShaken flasks are widely applied in bioprocesses due to their flexibility and ease of operation. Resonant acoustic mixing (RAM) enables non-contact mixing by the application of low frequency acoustic energy, and is proposed as an alternative to solve oxygen limitations in orbital mixing (OM). The aim of this study is to experimentally determine empirical kLa correlations for RAM and compare it with OM by its measurement at different shaking frequencies, nominal flask volumes, and filling volumes. The maximum kLa here obtained were 131.3±5.1h−1 for OM and 435.4±11.7h−1 for RAM. Empirical correlations were validated for kLa as a function of shaking frequency and superficial area/filling volume ratio and rendered adequate values for the adjusted R2 with an accuracy of ±30%. Further, we compared the Escherichia coli kinetics of growth, glucose uptake, dissolved oxygen tension (DOT), and organic acids production in RAM and OM at two equivalent initial kLa. Similar E. coli kinetics were observed at an initial kLa of 46h−1, but not at 92h−1 where differences in DOT and culture parameters were found, mainly in growth rate and biomass yield on glucose, which is the result of different oxygen transfer rates due to the increased gas pressures in RAM