[Morphological changes in a chemostat culture of Candida utilis undergoing cyclic changes of pH and pO2]

The effect of cyclic pH and pO2 changes on the morphology of Candida utilis was studied with time intervals measured in minutes. The pH was varied from 4.5 to 2.6, the pO2 from 70% of the saturation to 0%. The morphology was studied both visually and using the technique of optical-structural computer analysis. The regime with pH changes increased the biomass yield. However, the averaged morphological characteristics showed that the growth was slightly inhibited. Therefore, the yeast population was very heterogeneous, some cells were inhibited while other cells were stimulated, which made the economic coefficient rise. The cells were also inhibited when they were exposed in the conditions of oxygen deficiency for a short period of time. However, the cells could not be inhibited if, at the same time, the pH was extremely low. Changes in the morphology were detected earlier than either the inhibition or stimulation of growth was recorded by measuring the weight of biomass.