The present disclosure is directed to a method for cultivating a Bordetella species, comprising: cultivating a Bordetella species under aerobic conditions in a liquid culture medium; and maintaining a pH of the liquid culture medium by using a strong acid, such as nitric acid, or using a first and second acid, wherein the first acid is an inorganic acid that dissociates essentially completely in water, such as nitric acid, hydrochloric acid or sulfuric acid, and wherein the second acid is an inorganic acid having an acid dissociation constant (pKa) of greater than 1, such as phosphoric acid. Methods for increasing the yield of Bordetella fimbrial agglutinogen 2 and fimbrial agglutinogen 3 (FIM2/3) in a supernatant fraction from a Bordetella culture are also provided.