Spore-inoculated penicillin fermentations using W 48–701 were carried out in two different types of equipment: stirred and aerated laboratory fermentors, or shaken flasks. The respiration of the mycelium was measured in Warburg manometers. The maximum oxygen demand in the fermentations occurred at approximately 40 hr. and the maximum Q of the mycelium at 24 hr. or earlier. During the whole phase of penicillin formation, respiration decreased steadily. Mycelium grown in the stirred and aerated vessels showed the highest respiration rate. In the shaken flasks the rate of solution of oxygen in the medium was found by polarographic methods to be insufficient to allow a respiration rate as high as that which occurred in the stirred and aerated vessels. Respiration in shaken flasks, however, was not directly limited by the rate of solution of oxygen but by the amount and kind of the respiratory enzymes which appear to be synthesized in proportion to the concentration of dissolved oxygen present during early growth.

Whereas the respiratory quotient () of mycelium from shaken-flask fermentations remained approximately unity throughout the fermentation, in the stirred and aerated vessels the . of the mycelium fell from unity to as low as 0·57, during the fermentation. The degree of aeration therefore appears to influence not only the quantity but also the kind of respiratory enzymes synthesized.


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