A comparison of three pH control methods for revealing effects of undissociated butyric acid on specific butanol production rate in batch fermentation of Clostridium acetobutylicum

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Yang, Xuepeng, Maobing Tu, Rui Xie, Sushil Adhikari, and Zhaohui Tong. 2013. AMB Express 3 (1): 1–8. doi:10.1186/2191-0855-3-3.

Type Journal Article
Author Xuepeng Yang
Author Maobing Tu
Author Rui Xie
Author Sushil Adhikari
Author Zhaohui Tong
URL http://dx.doi.org/10.1186/2191-0855-3-3
Volume 3
Issue 1
Pages 1-8
Publication AMB Express
ISSN 2191-0855
Date January 7, 2013
Journal Abbr AMB Expr
DOI 10.1186/2191-0855-3-3
Language English
Abstract pH control has been essential for butanol production with Clostridium acetobutylicum. However, it is not very clear at what pH level the acid crash will occur, at what pH level butanol production will be dominant, and at what pH level butyric acid production will be prevailing. Furthermore, contradictory results have been reported about required acidic conditions for initiation of solventogenesis. In this study, with the aim of further understanding the role of undissociated butyric acid in butanol production, we investigated the correlation between undissociated butyric acid concentration and specific butanol production rate in batch fermentation of Clostridium acetobutylicum by comparing three pH control approaches: NaOH neutralization (at 12, 24 or 36 h), CaCO3 supplementation (2, 5, or 8 g/l) and NaOAc buffering (pH 4.6, 5.0 or 5.6). By neutralizing the fermentation pH to ~5.0 at different time, we observed that neutralization should take place at the beginning of exponential phase (12 h), and otherwise resulting in lower concentrations of undissociated butyric acid, cell biomass and final butanol. CaCO3 supplementation extended cell growth to 36 h and resulted in higher butyrate yield under 8 g/L of CaCO3. In the NaOAc buffering, the highest specific butanol rate (0.58 h−1) was associated with the highest undissociated butyric acid (1.92 g/L). The linear correlation of the undissociated butyric acid with the specific butanol production rates suggested the undissociated butyric acid could be the major driving force for butanol production.

Keywords:

  • Acids
  • Biofuels
  • Butanol
  • Butyric acid
  • Clostridium acetobutylicum
  • Fermentation
  • Glucose
  • Growth
  • Ph
  • Solvents
  • Undissociated butyric acid

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