Thang H. Vu, Applied Biochemistry and Food Science, Saga University, Honjo-cho 1, Saga 840-8502, Saga, Japan, Kohzo Kanda, Laboratory of Applied Microbiology, Department of Applied Biochemistry and Food Science, Faculty of Agriculture, Saga University, Honjo-cho 1, Saga 840-8502, Saga, Japan, and Genta Kobayashi, Department of Applied Biochemistry and Food Science, Saga University, 1, Honjo-cho, Saga, 840-8502, Japan.
Strain Clostridium saccharoperbutylacetonicum N1-4 has been demonstrated to possess several good fermentation characteristics in production of solvents from cassava. Minimization of costs associated with nutritional supplements is essential for economic large-scale production of solvents. This work compares the effects of various nitrogen sources on fermentation characteristics of cassava chips by Clostridium saccharoperbutylacetonicum N1-4. Fermentation of cassava chips in Tryptone-Yeast extract-Acetate (TYA) medium produced 15.5 g/L of butanol and 19.4 g/L of total solvents. Among different nitrogen sources added to medium, tryptone was the most efficient nitrogen source. When 7.7 g/L of tryptone was added, maximum butanol concentration was 17.8 g/L with butanol and solvent yield (based on potential glucose) was 0.36 and 0.42, respectively. In term of maximum total solvent and butanol concentration, corn steep liquor showed better results than that observed in fermentation using peptone. When 14 g/L of corn steep liquor powder was supplemented to the mash, maximum solvent and butanol concentration of 20.3 g/L and 15.9 g/L, respectively was reached after 42 h. The solvent yield (0.41) and butanol yield (0.32) was higher than those obtained with fermentation in TYA medium (0.38 and 0.30, respectively) and comparable with those obtained in fermentation using yeast extract. Yeast extract reduced significantly fermentation time to 32 h while urea prolonged that up to 60 h. It was also found that using urea increased maximum acetone concentration up to 5.0 g/L but prolong fermentation time to 60h whereas maximum butanol concentration was comparable with those observed in fermentation using yeast extract.
