[Conditions and dynamics of citrate, isocitrate and polyol excretion in yeast growth on glucose]

The dynamics of metabolite excretions by Candida guilliermondii, Candida zeylanoides and Torulopsis candida was studied during their batch cultivation in media with glucose excess and low concentrations of N, P or S sources; the latter were the growth limiting factors and determined the transition to phase of retardation and the stationary phase of growth. Growth limitation with the above components in the presence of a carbon source results in the following: (a) the growth becomes linear and the phase of retardation falls into two periods differing in the absolute growth rate which initially is relatively high but then decreases; (b) protein content drastically decreases while lipid content and in particular, of glycogen increases, i. e. the direction of biosynthetic processes changes; (c) intensive excretion of citrate and isocitrate begins and continues (including the stationary phase) until the carbon source is exhausted. In contrast to citrate and isocitrate, polyols are excreted throughout all growth phases (including the exponential one) and strictly periodically, i. e. these metabolites are repeatedly excreted and re-utilized. The fact that polyols are excreted during the exponential growth phase proves that their overproduction apparently is not connected with the limitation of the cultural growth.