On the measurement and scaling of mixing time in orbitally shaken bioreactors

•Development of a robust and objective post processing procedure for DIMST measurements.•Comparison of mixing time in STR and OSR using identical experimental and data processing procedures.•Mixing time scaling law for OSR. Accurate determination of the mixing time in orbitally shaken bioreactors (OSRs) is essential for the optimization of mixing processes and minimization of concentration gradients that can be deleterious to cell cultures. The Dual Indicator System for Mixing Time (DISMT) was employed to measure mixing times in cylindrical and Erlenmeyer flask bioreactors. Various aspects of importance for the acquisition of accurate data from the measurement methodology are discussed, utilizing also comparisons of DISMT and pH probe results obtained in two stirred reactors. The OSR results are juxtaposed with data previously reported in the literature for both cylindrical reactors and Erlenmeyer flasks. The employment of a critical Froude number shows promise for the establishment of a scaling law for mixing time across the various types and sizes of shaken bioreactors.