Polarographic measurement of dissolved oxygen in yeast fermentations.

M1illions of cubic feet of air are sparged daily into a commercial baker's yeast fermentation to fulfill the oxygen demands of the organism. The costs for air compression are sizeable and, in some cases, the capacity of the air supply system may impose restrictions on the number or types of fermentations which can be scheduled. The rate of air supply required for each type of yeast fermentation has generally been established by a process of trial and error and is taken as the least amount of air needed for maximal yield. This approach is rather drawn-out and insensitive because the yields are affected by other variables which cannot be completely eliminated or appraised. Air requirements vary in different periods of a fermentation depending on the feed rate, yeast population, and so forth, and it is impractical to carry this empirical approach for air regulation far enough to completely prevent overaeration and attain maximal economy. Furthermore, this approach does little to minimize the risks of low yield or poor yeast quality resulting from improper aeration in fermentations following major operational or equipment changes. The objective of this work, therefore, was to investigate and develop techniques which could be employed to obtain more direct and accurate indications of the aeration conditions prevalent in active fermentations.