CONTROLLED-PH BATCH BUTANOL-ACETONE FERMENTATION BY LOW ACID PRODUCING CLOSTRIDIUM-ACETOBUTYLICUM B18

C. acetobutylicum B18 produced a large amount of butanol over a wide r ange of pH (4.5-6.0). At pH 6.0 fermentation and cell growth were most active at pH 6.0, and the highest values of glucose consumption rate (4.37 g/L-h), butanol productivity (1.0 g/L-h), butyric acid recycle r ate (0.31 g/L-h), and cell growth rate (0.2 h-1) were obtained. There existed a critical pH between 6.0 and 6.5 above which cells switched t o organic acid producing mode. Clostridial stage appeared essential fo r solvent production by strain B18 but sporulation was not necessary f or solvent formation.