The effect of the component concentrations of a synthetic medium on acetone and butanol fermentation by Clostridium acetobutylicum ATCC 824 was investigated. Cell growth was dependent on the presence of Mg, Fe, and K in the medium. Mg and Mn had deleterious effects when in excess. Ammonium acetate in excess caused acid fermentation. The metabolism was composed of two phases: an acid phase and a solvent one. Low concentrations of glucose allowed the first phase only. The theoretical ratio of the conversion of glucose to solvents, which was 28 to 33%, was obtained with the following medium: MgSO 4 , 50 to 200 mg/liter; MnSO 4 , 0 to 20 mg/liter; KCl, 0.015 to 8 g/liter (an equivalent concentration of K + was supplied in the form of KH 2 PO 4 and K 2 HPO 4 ); FeSO 4 , 1 to 50 mg/liter; ammonium acetate, 1.1 to 2.2 g/liter; para -aminobenzoic acid, 1 mg/liter; biotin, 0.01 mg/liter; glucose, 20 to 60 g/liter.

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