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Design of a system for the control of low dissolved oxygen concentrations: Critical oxygen concentrations for Azotobacter vinelandii and Escherichia coli
Author(s) -
Chen J.,
Tannahill A. L.,
Shuler M. L.
Publication year - 1985
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260270208
Subject(s) - azotobacter vinelandii , oxygen , chemistry , anaerobic exercise , limiting oxygen concentration , agitator , respiration , bioreactor , mesophile , environmental chemistry , chromatography , bacteria , biology , botany , nitrogen , mass transfer , physiology , nitrogenase , genetics , organic chemistry , nitrogen fixation
The physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory‐scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted with Azotobacter vinelandii and Escherichia coli . Critical oxygen concentrations for growth (that value of oxygen allowing growth at 97% of μ max ) were measured as 0.35 ± 0.03 mg/L for A. vinelandii and 0.12 ± 0.03 mg/L for E. coli. These values are significantly different from the commonly quoted values for critical oxygen concentrations based on respiration rates . Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO 2 limitation, we believe that the values reported in this work more closely represent reality.