Evaluating the impact of Torulaspora delbrueckii and amino acid concentration on the nitrogen metabolism of Oenococcus oeni

This study investigates the impact of Saccharomyces cerevisiae and Torulaspora delbrueckii inoculation strategies and amino acid supplementation on nitrogen metabolism and malolactic fermentation (MLF) performance in Oenococcus oeni . Oenococcus oeni has low demand of nitrogen and typically prefers peptides over amino acids. In this work we studied the nitrogen metabolism (proteins, peptides, amino acids and biogenic amines (BA)) of three O. oeni strains. Higher initial amino acid concentrations generally accelerated MLF, particularly with the PSU-1 strain, which exhibited stuck fermentation in some conditions with low initial amino acid concentration related with coinoculation of yeasts. Nitrogen metabolism in O. oeni showed a preference for peptide-bound amino acids, and gene expression analyses highlighted a general upregulation in response to increased amino acid concentrations. BA production, particularly cadaverine and putrescine, was strain-dependent and associated with the presence of the odc gene. Besides, the production of 2-phenylethylamine was related with alcoholic fermentation (AF) inoculation strategy. Overall, the study demonstrates the complexity of nitrogen metabolism in O. oeni , emphasizing that it is influenced by both the yeast species used in AF and the initial amino acid composition, highlighting the importance of peptide composition, offering a potential tool for optimizing MLF in winemaking. • Nitrogen metabolism of Oenococcus oeni in Torulaspora delbrueckii wines was studied. • O. oeni consumed similar amount of amino acids regardless the initial concentration. • Peptide amino acids were those preferred by O. oeni in wine. • T. delbrueckii and increased amino acids upregulated nitrogen metabolism in O. oeni .