CHARACTERISTICS OF BUTANOL FERMENTATION BY A LOW-ACID-PRODUCING CLOSTRIDIUM-ACETOBUTYLICUM B18

Fermentation characteristics of Clostridium acetobutylicum B18 were st udied in batch experiments with and without pH control. This strain is shown to be potentially useful in simultaneous acetone-butanol-ethano l fermentation-separation systems because of its low acid production. In a pH-uncontrolled batch culture this strain produced mostly solvent s, including 15 g/l of butanol. Ethanol production was low. Strain B18 recycled organic acids more efficiently than other strains. In partic ular, butyric acid was completely recycled when glucose was not limiti ng. Yield of liquid products (solvents plus organic acids) and carbon recovery in total products (gas plus liquid) were 33.1-36.4 wt% and 90 -91 mol%, respectively, for 20-80 g/l of initial glucose. Glucose cons umption and the percentage of butanol among solvents were higher at 32 -degrees-C than at 37-degrees-C. Strain B18 required approximately 0.4 g/l of undissociated butyric acid at the onset of solvent production in pH-uncontrolled batch culture. The low undissociated butyric acid r equirement enabled this strain to produce 13.8 g/l of butanol at a con trolled pH of 6.0.