Effect of Nitrogen Source and Concentration on the Uptake of Peptides by a Lager Yeast in Continuous Culture

Continuous culture was used to demonstrate that both the type and the concentration of nitrogen source supplied in the medium influence the rate of peptide uptake by Saccharomyces cerevisiae NCYC 1324. Lower rates of peptide transport were observed in cells grown under ammonium- or allantoin-limitation or with excess ammonium or allantoin. Cells cultured in the chemostat with leucine (limiting or excess concentrations) exhibited the highest transport rates. Nitrogen starvation of ammonium-limited yeast cells removed the repressive effect of ammonium on peptide transport. The addition of leucine to ammonium- or allantoin-limited cells induced peptide transport. Physiological conditions that result in the repression, derepression, and induction of peptide transport in the lager brewing yeast S. cerevisiae NCYC 1324 were defined.