Acetoin production in growing Leuconostoc mesenteroides

Leuconostoc mesenteroides NCDO 518, provided with oxygen and pyruvate, pref erentially used oxygen as accessory electron acceptor and converted pyruvat e to acetoin. With glucose, 5.6 mM, as sole energy source only small amount s of acetoin were formed (0.08-0.21 mM). With glucose, 5.6 mM, and pyruvate , 20 mM, substantial amounts of acetoin were produced in growing, aerated c ultures at pH 5 (2.8 mM, equivalent to 0.5 mol [mol glucose fermented](-)1) . On exhaustion of glucose, growth ceased but metabolism of pyruvate contin ued with the formation of acetate and a little acetoin. In aerated cultures at pH 6 the general pattern was similar to that at pH 5 but less acetoin ( 0.6 mM) was formed during the growth phase and, after the exhaustion of glu cose, pyruvate was converted very slowly to acetate only. Leuc. mesenteroid es did not grow with pyruvate as sole energy source.