Utilization of ^sup 15^N-labelled yeast hydrolysate in Lactococcus lactis IL1403 culture indicates co-consumption of peptide-bound and free amino acids with simultaneous efflux of free amino acids

• Published in: Antonie van Leeuwenhoek 2014-03, Vol.105 (3), p.511
• Main Authors: Kevvai, Kaspar, Kütt, Mary-liis, Nisamedtinov, Ildar, Paalme, Toomas
• Format: Article
• Language: English
• Subjects: Amino acids; Cell culture; Consumption patterns; Fermentation; Peptides; Yeast; Yeasts
• ISSN: 0003-6072; 1572-9699
• DOI: 10.1007/s10482-013-0103-2

Lactococcus lactis subsp. lactis IL1403 was grown in medium containing unlabelled free amino acids and ^sup 15^N-labelled yeast hydrolysate to gain insight into the role of peptides as a source of amino acids under conditions where free amino acids are abundant. A mathematical model was composed to estimate the fluxes of free and peptide-derived amino acids into and out of the intracellular amino acid pool. We observed co-consumption of peptides and free amino acids and a considerable efflux of most free amino acids during growth. We did not observe significant differences between the peptide consumption patterns of essential and non-essential amino acids, which suggests that the incorporation of a particular amino acid is more dependent on its availability in a readily assimilated form than the organism's auxotrophy for it. For most amino acids the contribution of peptide-bound forms to the formation of biomass was initially between 30 and 60 % with the remainder originating from free amino acids. During the later stages of fermentation we observed a decrease in the utilization of peptide-bound amino acids, thus indicating that the more readily assimilated peptides are gradually exhausted from the medium during growth.[PUBLICATION ABSTRACT]