title: High butanol production by Clostridium saccharoperbutylacetonicum N1-4 in fed-batch culture with pH-Stat continuous butyric acid and glucose feeding method.
abstract: A pH-stat fed-batch culture by feeding butyric acid and glucose has been studied in an acetone-butanol-ethanol (ABE) fermentation using Clostridium saccharoperbutylacetonicum N1-4. The specific butanol production rate increased from 0.10 g-butanol/g-cells/h with no feeding of butyric acid to 0.42 g-butanol/g-cells/h with 5.0 g/l butyric acid. The pH value in broth decreases with butyric acid production during acidogenesis, and then butyric acid reutilization and butanol production result in a pH increase during solventogensis. The pH-stat fed-batch culture was performed to maintain a constant pH and butyric acid concentration in the culture broth, but feeding only butyric acid could not support butyric acid utilization and butanol production. Subsequently, when a mixture of butyric acid and glucose was fed, butyric acid was utilized and butanol was produced. To investigate the effect of the feeding ratio of butyric acid to glucose (B/G ratio), several B/G ratio solutions were fed. The maximum butanol production was 16 g/l and the residual glucose concentration in broth was very low at a B/G ratio of 1.4. Moreover, yields of butanol in relation to cell mass and glucose utilization were 54% and 72% higher in pH-stat fed-batch culture with butyric acid than that of conventional batch culture, respectively.
authors.affiliation: Laboratory of Microbial Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Tashiro
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Takeda
authors.forename: Genta
authors.initials: G
authors.lastname: Kobayashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
authors.forename: Ayaaki
authors.initials: A
authors.lastname: Ishizaki
authors.forename: Sadazo
authors.initials: S
authors.lastname: Yoshino