"Large-scale submerged fermentations have been important for many years for the production of antibiotics, vitamins, enzymes, etc.; however, aeration studies have been severely restricted in these processes because of the unavailability of adequate oxygen sensing equipment.
A steam-sterilizable oxygen sensor of improved design was developed out of an investigation of several potential sensors. This rapidly responding galvanic probe made use of a lead anode, a silver cathode, an acetate buffer as the electrolyte, and a one mil Teflon® membrane as the diffusion barrier. Its sensitivity was approximately 40 µamps and full response required approximately 5 minutes.
Use was made of the steam-sterilizable oxygen sensor for the determination of the effect of impeller speed and aeration rate on the absorption coefficient of a small, 5 liter pilot-plant fermentor. It was found that the impeller speed had a more pronounced effect on this coefficient than the aeration rate. The oxygen sensor was also used in determining the effect of General Electric Antifoam 10 on the absorption coefficient. At a concentration of 0.071 per cent, the antifoaming agent decreased the aeration efficiency by approximately 60 per cent.
Amylase production by Aspergillus niger, glutamic acid production by Brevibacterium divaricatum, and gluconic acid production by Pseudomonas fluorescens were studied at various aeration efficiencies. It was found that for all fermentations, an increase in the aeration efficiency resulted in an increase in the rate of product formation as well as an increase in total yield.
Since the effect of dissolved oxygen on product formation by microorganisms was investigated, it was also of interest to determine the critical oxygen tension of these and other organisms. The critical oxygen tension of Myrothecium verrucaria and Torulopsis utilis was determined as was that of the three organisms previously mentioned. The critical oxygen tension for the bacteria, B. divaricatum and P. fluorescens, and yeast, T. utilis, was extremely low, while that of the fungus, A.niger, was high. M. verrucaria, although a fungus, exhibited a critical oxygen tension close to that of the bacteria and yeast"--Abstract, pages ii-iii.
Siehr, Donald J.
Grigoropoulos, Sotirios G.
Lorah, James R.
Wellek, Robert M.
Strunk, Mailand R., 1919-2008
Chemical and Biochemical Engineering
Ph. D. in Chemical Engineering
University of Missouri at Rolla
x, 189 pages
© 1966 Carl J. Wallace, All rights reserved.
Dissertation - Open Access
Imaging systems in chemistry -- Design
Oxygen -- Measurement
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Link to Catalog Record
Wallace, Carl J., "Aeration studies in submerged fermentations using a steam-sterilizable dissolved oxygen sensor of improved design" (1966). Doctoral Dissertations. 443.