Agitation-Aeration in the Laboratory and in Industry

SummaryThis investigation used the glucose oxidase system to simulate oxygen transfer rate in fermentation broths. It was demonstrated that the fungal preparation contained sufficient lactonase activity 80 that D-glucono-8-lactone did not accumulate and that the rate of production of gluconic acid was proportional to the oxygen uptake rate. Enzyme concentrations of 1.5-2 g/l were found adequate to determine oxygen absorption rates in shake flasks while maintaining the dissolved oxygen concentration of low levels. The apparent Michaelis constant for oxygen, K,(Oz), was found to be 27% saturation with air; this value along with experimentally determined uptake rates could be used to calculate dissolved oxygen concentration in lieu of using a dissolved oxygen probe. Enzyme concentrations of 5 g/l were sufficient to give linear acid production and low dissolved oxygen concentrations in a bench-scale fermenter with no foaming or enzyme deactivation. The method is considered more valid and easier to employ than previously utilized techniques such as sulfite oxidation. Extension of the system to evaluating aeration effectiveness and scaleup of fermentation equipment is discussed.

Section: Determination Of the Apparent Michaelis Constant For Oxygenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Use of the glucose oxidase system to measure oxygen transfer rates

Hsieh

Silver

Máteles

1969

“…The process of mass transfer from gas to a liquid occurs in three steps according to Whitman's two-film theory of gas absorption (Finn, 1954;Lewis and Whitman, 1924;Whitman, 1962). The first step involves the transfer of the component from the bulk of the gas, through the gas boundary layer, and to the phase boundary between the gas and liquid.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic bubbler facilitates near complete mass transfer for sustainable multiphase and microbial processing

Baker

Crivellari

Gagnon

et al. 2016

A microfluidic device (channels <70 μm) was utilized to create micro-scale bubbles to significantly increase mass transfer efficiency at low flow rates. The convergence of one gas and two liquid channels at a Y-junction generates bubbles via cyclic changes in pressure. At low flow rates, the bubbles had an average diameter of 110 μm, corresponding to a volumetric mass transfer KL a of 1.43 h(-1) . Values of KL a normalized per flow rate showed that the microbubbler had a 100-fold increased transfer efficiency compared to four other commonly used bubblers. The calculated percentage of oxygen transferred was approximately 90%, which was consistent with a separate off-gas analysis. The improved mass transfer was also tested in an algae bioreactor in which the microbubbler absorbed approximately 90% of the CO2 feed compared to 2% in the culture with an alternative needle bubbling method. The microbubbler yielded a cell density 82% of the cell density for the alternative needle tip with an 800-fold lower flow rate (0.5 mL/min versus 400 mL/min) and a 700-fold higher ratio of biomass to fed carbon dioxide. The application of microfluidics may transform interfacial processing in order to increase mass transfer efficiencies, minimize gas feeding, and provide for more sustainable multiphase processes. Biotechnol. Bioeng. 2016;113: 1924-1933. © 2016 Wiley Periodicals, Inc.

“…Their low investment cost and ease of handling allow for a large number of fermentation experiments to be conducted in parallel. Cultivation of aerobic microorganisms, however, requires a sufficient oxygen supply to the culture media, because a limitation of oxygen could affect bacterial growth and product formation (Finn, 1954;Steel, 1958;Yamada et al, 1978). Impeded mass transfer from the culture medium also influences the removal rate of volatile compounds like CO 2 , ethanol, inducers, etc.…”

Section: Introductionmentioning

confidence: 99%

New method to determine the mass transfer resistance of sterile closures for shaken bioreactors

Anderlei

Mrotzek

Bartsch

et al. 2007

In this paper a novel and easily applied method to measure the mass transfer resistance of the sterile closures (e.g. cotton plug) of shaken bioreactors is introduced. This method requires no investment in special equipment (e.g. an oxygen sensor) and can be performed with the materials usually available in typical laboratories. The method is based on the model of Henzler et al. (1986), which mechanistically describes mass transfer through the sterile closure of a shaken bioreactor based on diffusion coupled with Stefan convection. The concentration dependency of the multi-component diffusion coefficients is taken into account. The water loss from two equivalent shaken bioreactors equipped with sterile closures during several days of shaking is measured. One flask contains distilled water, the other a saturated salt solution. From the water evaporation rate in each of the two flasks, the new model presented calculates the relative humidity in the environment, the average diffusion coefficient of oxygen in the sterile closure (D(O2)), and the diffusion coefficient of carbon dioxide (D(CO2)) . The diffusion coefficient of carbon dioxide (D(CO2)) only depends on the density and material properties of the sterile closure and not on the gas concentrations and is, therefore, an ideal parameter for the characterization of the mass transfer resistance. This new method is validated experimentally by comparing the diffusion coefficient of oxygen (D(O2)) to a measurement by the classic dynamic method; and by comparing the calculated relative humidity in the environment to a humidity sensor measurement.