Abstract: A process is disclosed in which an amino acid-producing microorganism having an ability to assimilate lactic acid is aerobically cultivated in the presence of at least one lactic acid microorganism in an aqueous nutrient medium containing at least one carbohydrate which is assimilable by the lactic acid microorganism but nonassimilable or weakly assimilable by the amino acid-producing microorganism as the main carbon source and an accumulated amino acid is recovered from the culture broth. An industrially advantageous production of an amino acid has become feasible by utilizing inexpensive carbon sources or those organic substances in agricultural or livestock wastes that have heretofore not been effectively utilized.