Measurement of K_La by a gassing‐in method with oxygen‐enriched air

Abstract

The dynamic gassing-out method using nitrogen for gas-liquid K(L)a measurements has been modified so that gassing-out is performed with air and gassing-in with oxygen-enriched air. This new method was proven theoretically valid for use in inert model systems and in actual fermentation systems. The K(L)a values were measured in a 1-m-high bubble column and compared with those obtained from the traditional gassing-in method for three different mixing models in batchwise contacting: mixed gas and liquid (MMB); plug-flow gas and mixed liquid (PMB); and plug-flow gas and plug-flow liquid (PPB). The K(L)a values obtained from the new method were consistent with those of the method of Bartholomew et al. Discrimination between the models appeared to be not important for the 1-m-high column, but the theoretical analysis revealed that it would become necessary for columns about 10 m and higher.

Determination of the volumetric mass transfer coefficient (kLa) using the dynamic “gas out–gas in” method: Analysis of errors caused by dissolved oxygen probes

“…Using the value of the microbial oxygen uptake rate obtained from the gas-out results, the oxygen interfacial concentration can be obtained from the intercept, which is (Cf -Qo2X/k,a). Alternately, since initially, under steady-state conditions,' Equation (3) can be integrated from the time, t,, at which the air flow is re-started to any subsequent time, t , to give'X2' Thus, k,a can be determined from the slope of ln(C,, -C,) versus t. If required, the oxygen interfacial concentration can then be obtained from Equation ( 5 ) and the value of the volumetric microbial oxygen uptake rate obtained from the gas-out results.…”

“…Steady state is first established with either air or nitrogen sparging and either oxygen or nitrogen is then substituted for the air or nitrogen . 4,5,7,10,16,18,20 As pointed out by Kim and Chang," * To whom all correspondence should be addressed performing an upstep with oxygen-enriched air is preferable to a downstep with nitrogen since it eliminates the risk of going below the critical dissolved oxygen concentration in actual microbial broths. A variant of this technique is the dynamic pressure method, where the pressure inside the bioreactor is increased causing an instantaneous increase in the interfacial oxygen concentration.…”

Hydrodynamics and mass transfer coefficients in a bubble column photo-bioreactor

“…The details of the method can be found in previous studies (Chang et al, 1989;Han and Al-Dahhan, 2007). The dissolved oxygen concentration [DO] was measured using an optical probe developed by Neo-Fox Ocean Optics, Florida, USA.…”

A Review of Dissolved Oxygen Concentration Measurement Methods for Biological Fermentations

“…Most oxygen measuring electrodes used in biological processes have response times that range from 3 to 100 seconds (Van't Riet and Tramper, 1991;Gaddis, 1999), which may result in the need to correct oxygen concentration data depending on the reactor dynamics. Many models have been developed to correct for τ e and are discussed in great detail in the literature (Lee and Tsao, 1979;Linek et al, 1979;Linek et al, 1981;Ruchti et al, 1981;Sobotka et al, 1982;Vardar and Lilly, 1982;Lee and Luk, 1983;Linek et al, 1984;Linek et al, 1985;Linek, 1988;Chang et al, 1989;Chisti, 1989;Kim and Chang, 1989;Linek et al, 1989;Linek et al, 1991;Van't Riet and Tramper, 1991;Linek et al, 1992;Tribe et al, 1995;Gaddis, 1999;Tobajas and Garcia-Calvo, 2000;Freitas and Teixeira, 2001;Lopez et al, 2006). Lee and Luk (1983) and Sobotka et al (1982) provide a good review of these model corrections.…”