Estimation of dissolved carbon dioxide concentrations in aerobic fermentations

Abstract

Dissolved carbon dioxide and bicarbonate ions in fermentation broths can (independently) inhibit or promote microbial growth and productivity. In research facilities with a large number of fermenters, dissolved carbon dioxide sensors tend not to be used, and as a result this variable will generally go unmonitored, making the meaningful analysis of data more difficult. For aerobic fermentations, mass transfer of carbon dioxide can be described in an analogous way to oxygen transfer. The mass transfer coefficient for carbon dioxide is 0.89 times that for oxygen. The maximum dissolved carbon dioxide concentration as a function of exit gas composition is compared with the concentration obtained by assuming equilibrium between the broth and exit gas. The difference between these two concentrations is typically 20–40% of the equilibrium concentration. In large fermenters, a degree of plug flow behavior in the gas and the generally lower specific aeration rates will serve to produce a better approach to equilibrium than for research fermenters.

Reconstruction of the O2 uptake rate and CO2 evolution rate on a time scale of seconds

“…Besides, it is noted that the algorithm that is presented in this article may also be used for other applications, such as, if one is interested in the carbon dioxide concentration and no dissolved carbon diox-Ž . ide sensor is available Royce and Thornhill, 1991 , or …”

Estimating cell specific oxygen uptake and carbon dioxide production rates for mammalian cells in perfusion culture

“…The corrected equilibrium constants K 1 and K 2 were 10 À6.30 and 10 À10. 23 , respectively, at 37 C.…”

Scale‐up analysis for a CHO cell culture process in large‐scale bioreactors

“…Since the unit of time (t) is hour, the volume ratio of the gas phase to the liquid phase (R V ) can be measured by volume of gas (L) sparged in 1-h period per liquid volume of cultures (L). The k L a CO 2 value was calculated from k L a O 2 value based on the k L a CO 2 =k L a O 2 ratio of 0.91 (Spérandio and Paul, 1997), which is derived from the ratio of liquid-phase diffusivities of CO 2 and O 2 (Royce and Thornhill, 1991). The measured k L a values for CO 2 and O 2 were reported in agreement with the k L a CO 2 =k L a O 2 ratio of 0.90-0.91 at low agitation speed (25 and 53 rpm) in a mineral culture medium (Spérandio and Paul, 1997).…”