Quantification of intracellular amino acids in batch cultures of Saccharomyces cerevisiae

The dynamics of intracellular amino acid pools were determined in batch cul tures of Saccharomyces cerevisiae. Immediate termination of metabolic activ ity was found to be necessary for accurate quantification of in vivo concen trations of intracellular amino acids, due to significant changes in most i ntracellular amino acid pools observed during extraction without an instant aneous stop of the metabolism. The method applied to batch-cultures of S. c erevisiae on glucose revealed complex dynamics in intracellular amino acid pools. The most drastic changes were observed during the diauxic shift and at the entry into the stationary phase. Even during phases of exponential g rowth on glucose and ethanol. cells showed significant variations in intrac ellular amino acid concentrations. The method presented can be used to inve stigate the physiology of yeast cultures, including industrially relevant b atch and fed-batch processes.