[Effect of the agitation intensity and concentration of surface-active substances on the rate of oxygen sorption by a model sulfite-albumin medium]. / Vliianie intensivnosti peremeshivaniia i kontsentratsii poverkhnostno-aktivnykh veshchestv na skorost' sorbtsii kisloroda model'noi sredoi sul'fit-al'bumin.

The physicochemical properties of a model medium consisting of two substances, sodium sulfite and albumin, were studied. It was shown that the presence of a SAS in the sulfite solution significantly lowered the rate of oxygen sorption by the model medium. The higher the SAS concentration, the lower the sorption rate. When yeasts were grown on sulfite liquor under conditions of the reduced medium the rate of their growth and respiration did not significantly depend on aeration within wide ranges of its variation. The experiments with the model medium demonstrated that the aeration independence was due to indifference to oxygen not of the cells but of the medium as the result of its physicochemical properties. The effect of sorption hysteresis was also studied on the model medium. It was revealed that the rate of oxygen desorption from the medium was lower than that of oxygen sorption by the same medium. The effect was not observed when a nonionic SAS was added to the medium and the isoelectric point was almost reached. The effect was connected with impairment of oxygen diffusion through the medium surface film. Interaction of the substances included in the model medium was of physical nature.

[Effect of oxygen on the growth, respiratory rate and morphology of Candida utilis cells in periodic and continuous cultures]. / O vliianii kisloroda na rost, skorost' dykhaniia i morfologiiu kletok Candida utilis v periodicheskikh i nepreryvnykh kul'turakh.

The aim of this work was to study how the concentration of oxygen dissolved in the cultural broth influenced the respiration and morphology of the yeast Candida utilis in batch and continuous cultures. Highly effective respiration was registered in cells growing for a certain period of time at low oxygen concentrations limiting the growth; the respiration was characterized by low values of the Michaelis constant kc and the critical concentration of dissolved oxygen Ccr. When passing from the low oxygen concentration to a high one, the character of cellular respiration changed abruptly in the cells whose growth was limited with oxygen for a long time. The morphology of the culture limited with oxygen was characterized by an increase in the percentage of elongated forms in the population. The respiration of the cells cultivated at high oxygen concentrations, when their growth was either non-limited or limited by glucose, was distinguished by high Ccr values and slow respiration rates at small oxygen concentrations while the dependence of the respiration rate on the concentration of oxygen had an about S-shaped character.