[Effect of input nitrogen concentrations on Candida utilis growth in continuous culture with pulsed carbon feed]

The yeast Candida utilis IBPMY-405 was cultivated in a synthetic medium at a dilution rate of 0.05 h-1 in the regime of pulse glucose feed. The periodicity of glucose additions was determined by the current signal of an optical density sensor. Changes of the signal in the course of time were of a periodical character with the constant frequency and amplitude of fluctuations as long as the experimental conditions remained the same. Three concentrations of ammonium nitrogen were used (0.152, 0.064 and 0.043 g/l) to assay the number of cells in a unit volume of the culture, the percentage of budding cells, the quantity of nitrogen assimilated per cell, the consumption of oxygen, the increment of optical density in response to the addition of glucose (delta x) and the time taken by optical density to increase (tx). The parameters of phase I in the cycle of changes in optical density (tx and delta x) were found to depend on how the culture was supplied with nitrogen. As this supply decreased, tx increased and delta x decreased. The respiration rate and the percentage of budding cells underwent cyclic fluctuations while the overall quantity of cells per unit volume of the culture remained constant. An attempt has been made to substantiate the applicability of the parameters tx and delta x for testing the culture and rapidly identifying nitrogen limitation during continuous cultivation of Candida utilis in the regime of plus feed with source of carbon.