Limitations of Oxygen Transfer in the
Warburg Apparatus
J. O. BRYANT, FWPCA Fellow
W. W. AKERS, Professor of Chemical Engineering
A. W. BUSCH, Professor of Environmental Engineering
Rice University
Houston, Texas
INTRODUCTION
The Warburg apparatus is widely used for measurement of both rate and
amount of oxygen uptake in biological studies. The rate of oxygen uptake is important even m studies concerned only with cumulative uptake because the apparent reaction stoichiometry can be distorted by physical limitations on the system
(1).
If the rate of oxygen uptake measured in the Warburg is to represent toe true
biochemical reaction rate, the controlling step in toe reaction sequence must be
toe biochemical reaction. In toe course of the reaction, oxygen must be transferred from the gas phase to the liquid phase because the organisms can use only
dissolved nutrients. The gas exchange step must not be the controlling process in
the reaction chain (Figure 1).
The purpose of this paper is to show that oxygen transfer rates can limit the
rate of biological reactions in toe Warburg system. This rate limitation can also
affect the apparent reaction stoichiometry. In addition, toe amount of oxygen
available in toe gas atmosphere of the system is shown to be a limit on experiment design in terms of the total amount of carbon which can be oxidized. However, rate limitations are shown to be manifested long before oxygen depletion is
critical in systems using air as toe gas phase.
PREVIOUS WORK
Monod (2) has reported that bacterial cells are uniform throughout toe exponential phase of growth. Martin (3) and Hershey (4) have reported that the
oxygen uptake per unit volume of cell material is constant. From these observations the conclusion can be made that oxygen uptake and bacterial growth should
demonstrate similar time progressions, i. e., an exponential function.
Several sources (5, 6, 7, 8,9,10) have reported arithmetic linear oxygen uptake as opposed to exponential oxygen uptake progressions for measurements made
using the Warburg system. Only conditions which supply an essential growth
nutrient at a constant, limiting rate can cause arithmetic linear growth (11, 12).
For the Warburg studies referenced above, all inorganic growth nutrients except
oxygen were reported to be present in excess in the liquid phase. Oxygen was
thus the only nutrient subject to a constant rate of addition.
As for toe question of whether oxygen limitation can cause arithmetic linear
growth, Volk and Myrvik (12) reported exponential growth for aerated bacterial
cultures but arithmetic linear growth in unaerated cultures. Dagley, et al (13)
reported that cell concentration reached a maximum in unaerated culture flasks
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