Aromatic lactic acid production by Bifidobacterium longum subsp. infantis is determined by cell density, substrate availability, and pH in vitro

at different concentrations of aromatic amino acids and pH levels to investigate the effect of these environmental factors on aromatic lactic acid production. We show that there is a linear relationship between aromatic lactic acid production and the exogenous aromatic amino acid concentration, that the production strongly follows cell density, and that pH regulates the preference toward producing different aromatic lactic acids. This knowledge may help inform strategies to enhance or direct beneficial aromatic lactic acid (ALA) production in the infant gut.