A study into the role of L-aspartic acid on the metabolism of L-malic acid and D-glucose by Oenococcus oeni

Aims: The purpose of this work was to study the effect of L-aspartic acid concentration on bacterial growth, D-glucose fermentation and L-malic acid consumption of Oenococcus œni NCFB 1707. Methods and Results: Bacterial cultures were performed in synthetic media. Bacterial growth, D-glucose fermentation and L-malic acid consumption were reduced when L-aspartic acid concentration became excessive. This inhibitory effect of high concentrations of L-aspartic acid on bacterial growth was also observed with several Oenococcus œni strains, except O. œni BL01. The L-aspartic acid inhibitory effect on bacterial growth could be reduced by increasing the concentration of L-glutamic acid. L-glutamic acid transport was found to be competitively inhibited by L-aspartic acid. In addition, an excessive amount of L-aspartic acid modified D-glucose metabolism, with an overproduction of acetic acid and reduced ethanol production. Conclusions: Since L-glutamic acid is an essential amio acid for the bacterial strain used, the L-aspartic acid inhibitory effect on bacterial growth could be linked to its involvement in an antagonistic interaction with L-glutamic acid. Significance and Impact of the Study: Such antagonistic interactions between amino acids in O. œni strains could be another explanation for the difficulties of inducing malolactic fermentation in wines.