Engineering Parameters in Bioreactor’s Design: A Critical Aspect in Tissue Engineering
Table 2
Methods of measuring oxygen transfer rate.
Measurement method
Basis of the method
Pros
Cons
Ref.
Sulfite oxidation method
Monitoring pH changes during the oxidation of sodium sulfite to sodium sulfate controlled by oxygen depletion rate
(i) Simple and low cost (ii) Can be used for the determination of the interfacial area between gas and liquid (iii) Being accurate for minivolumes of less than 1 mL
(i) The kinetics of the homogeneous catalytic chemical reaction should be known (ii) Limited accuracy by visually determination of color change (iii) High salt concentration (usually 0.5 mol · L−1) reduces the maximum solubility of oxygen (iv) Not appropriate in large scale bioreactors (v) High surface tension causes the underestimation of potentially achievable OTR
Monitoring the dissolved O2 concentration during the aeration of the system
(i) Consistent measurement (ii) Does not depend on a zero or reference measurement
(i) Requiring a rapidly responsive, sterilizable, dissolved oxygen probe (ii) Limited application for minititerplates (MTPs) (iii) Not costly favorable
Monitoring by direct measurement of the rate of increasing dissolved oxygen concentration, after neutralizing the system by flushing nitrogen through the vessel to achieve an oxygen-free solution
(i) Can be applied to different media (for investigating the effect of media composition on oxygen mass transfer) (ii) Does not involve chemical reactions that could impact the measurement precision and the liquid film resistance
A nonrespiring system which is not in exact correspondence to real culturing conditions
Calculating the OTR by specifying the oxygen concentration difference between the inlet gas stream (O2, in) and the outlet gas stream (O2, out) using magnetomechanical exhaust gas analyzer (EGA)
(i) Continuous method (ii) Can be used to measure OTR in one to five parallel culture vessels