title: Utilization of (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.
abstract: Lactococcus lactis subsp. lactis IL1403 was grown in medium containing unlabelled free amino acids and (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.
authors.affiliation: Competence Centre of Food and Fermentation Technologies, Akadeemia tee 15a, 12618, Tallinn, Estonia, kaspar.kevvai@tftak.eu.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Kevvai
authors.forename: Mary-Liis
authors.initials: ML
authors.lastname: Kütt
authors.forename: Ildar
authors.initials: I
authors.lastname: Nisamedtinov
authors.forename: Toomas
authors.initials: T
authors.lastname: Paalme
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D013294:Lactococcus lactis / Q000254:growth & development* / Q000378:metabolism*; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D010455:Peptides