Studies on Oxygen Transfer in Submerged Fermentations

Abstract

The unsteady-state gas analysis method was applied satisfactorily to the studies on the effects of oxygen transfer in glutamic acid fermentation. The following points were clarified: 1) When the sulfite oxidation method was adopted as a measure of aeration effec-tiveness, sulfite rab, the rate of oxygen transfer into sulfite solution, could be applied most widely. 2) As long as cultures were performed sup-plying air as the oxygen source, the results of the fermentation were well correlated with the value of sulfite rab, though the behaviours of sulfite solution to oxygen were not the same as that of fermentation broths. 3) Under the condition of high oxygen supply, sulfite rab lost its ability as a measure of aeration. 4) In all cases, biological rab, the rate of oxygen transfer actually occurring in the fermentation broths, could be an useful measure of aeration effectiveness. 5) It was difficult to employ PL, the level of dissolved oxygen, as a criterion of aeration in glutamic acid fermentation. 6) The best measure of aeration effective-ness, therefore, was concluded to be biological Tab, the next being sulfite rab. 7) For controlling the rate of oxygen supply in shaken cultures, the method of chang-ing the partial pressure of gas-phase oxygen in flasks by selecting suitable types of plugs or by purging flasks with gas of different oxygen concentration was preferable. 8) The optimum aeration condition for glutamic acid fermentation was 7×10-7<biological rab, or 10×10-7< sulfite rab<15×10-7 (mol/ml.min). 9) Extremely high or low oxygen supply resulted in the low productivity of glutamic acid, though each condition was different in several points. 10) In the condition of slightly restricted oxygen supply, fermentation proceeded at the same rate as in the optimum condition and the yield of glutamic acid based on the amount of sugar consumed was lowered.