Addition of sodium acetate to chemically defined MP2 medium was found to increase and stabilize solvent production by Clostridium beijerinckii BA101, a solvent-hyperproducing mutant derived from C. beijerinckii NCIMB 8052. C. beijerinckii BA101 demonstrated a greater increase in solvent production than C. beijerinckii NCIMB 8052 when sodium acetate was added to MP2 medium. In 1-1 batch fermentations, C. beijerinckii BA101 produced 32.6 g/l total solvents, with butanol at 20.9 g/l, when grown in MP2 medium containing 60 mM sodium acetate and 8% glucose. To our knowledge, these values represent the highest solvent and butanol concentrations produced by a solventogenic Clostridium strain when grown in batch culture.