Abstract

Corn stalks were used as a support to immobilize Clostridium thermobutyricum in a fermentation process for butyric acid production. The effects of pH and acetic acid concentration on butyric acid production were examined in a steady-state 25-day continuous flow operation. A metabolic shift was induced by changing pH of the medium. The maximum and the minimum ratio of butyric acid and acetic acid produced in the fermentation process were achieved at pH 7.0 and 5.0, respectively, and the maximum yield of butyric acid was observed at pH 6.0. The addition of acetate in the medium has resulted in an increased butyric acid final concentration. The maximum total butyric acid concentration of 15.82 g/l was obtained at pH 6.0 with 10 g/l acetic acid concentration in the medium. The cell adsorption and morphology change during the growth phase on corn stalk support were examined by the scanning electronic microscope (SEM).

Key words: Butyric acid, corn stalk, immobilized cells, Clostridium thermobutyricum.