Effect of Lactate on the Growth and Production of Diacetyl and Acetoin by Lactobacilli

Diacetyl and acetoin production and cell growth in Lactobacillus acidophilus CNRZ 232, Lactobacillus casei ssp. rhamnosus ATCC 7469, Lactobacillus brevis ATCC 14869, and Lactobacillus fermentum ATCC 9338 were studied. The first three species produced large amounts of diacetyl and acetoin when pyruvate was included in a medium with yeast extract, peptone, tryptone, and glucose. Lactobacillus fermentum failed to produce the compounds under consideration.Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus brevis utilized lactate as a carbon source. When lactate was added to the medium containing pyruvate, the diacetyl, acetoin, and biomass decreased in Lactobacillus casei and Lactobacillus brevis. In Lactobacillus acidophilus both compounds decreased somewhat, and bacterial growth increased, although it decreased again at high lactate concentrations. There was no production of diacetyl and acetoin at pH lower then 4.25 and only little at 4.25.