Solventogenesis in Clostridium acetobutylicum fermentations related to carboxylic acid and proton concentrations

The mechanism primarily implicated in the solventogenesis process in batch fermentations of Clostridium acetobutylicum is examined in considerable detail. A variety of fermentations with or without pH control in the pH range of 3.7–6 have been carried out in order to examine which of a host of suspect parameters correlate with the initiation of solventogenesis. The parameters that did not correlate are the external (pH0) and intracellular (pHi) pH, and ΔpH, and the external or intracellular butyrate and acetate concentrations. Undissociated butyric acid (UBA) correlated well with the initiation of solventogenesis. A linear relationship between UBA and butanol concentrations was found at the onset of solventogenesis in all fermentations examined. The intercept of this linear relationship was 6–13mM UBA for the pH0 range of 3.7–5 and approximately zero for pH0 at or above 6. The required minimal UBA was interpreted as a dependency of the solventogenesis process on both H+ and butyrate concentrations. Undissociated acetic acid was found not to correlate with the initiation of solventogenesis. Addition of acetoacetate (AA) and propionate enhanced the effect of UBA on the solventogenesis process. The action of a nonmetabolizable (FCCP) and a metabolizable (AA) uncoupler on the ΔpH, pH0, pHi, and solventogenesis were also studied in order to gain further understanding of the solventogenesis mechanism.

[1]  E. Papoutsakis,et al.  The effect of pH on nitrogen supply, cell lysis, and solvent production in fermentations of Clostridium acetobutylicum , 1985, Biotechnology and bioengineering.

[2]  J. G. Morris,et al.  Production of Solvents by Clostridium acetobutylicum Cultures Maintained at Neutral pH , 1984, Applied and environmental microbiology.

[3]  H. Bahl,et al.  Nutritional Factors Affecting the Ratio of Solvents Produced by Clostridium acetobutylicum , 1986, Applied and environmental microbiology.

[4]  S. Gatenbeck,et al.  Intermediary Metabolism in Clostridium acetobutylicum: Levels of Enzymes Involved in the Formation of Acetate and Butyrate , 1984, Applied and environmental microbiology.

[5]  H. Rottenberg.  The measurement of membrane potential and deltapH in cells, organelles, and vesicles. , 1979, Methods in enzymology.

[6]  Eva R. Kashket,et al.  Uncoupling by Acetic Acid Limits Growth of and Acetogenesis by Clostridium thermoaceticum , 1984, Applied and environmental microbiology.

[7]  L. Huang,et al.  Transmembrane pH gradient and membrane potential in Clostridium acetobutylicum during growth under acetogenic and solventogenic conditions , 1985, Applied and environmental microbiology.

[8]  Carbon monoxide gasing leads to alcohol production and butyrate uptake without acetone formation in continuous cultures of Clostridium acetobutylicum , 1986 .

[9]  Cecil W. Forsberg,et al.  Influence of External pH and Fermentation Products on Clostridium acetobutylicum Intracellular pH and Cellular Distribution of Fermentation Products , 1986, Applied and environmental microbiology.

[10]  M. Huesemann,et al.  Transport of Substrates and Metabolites and Their Effect on Cell Metabolism (in Butyric‐Acid and Methylotrophic Fermentations) a , 1987, Annals of the New York Academy of Sciences.

[11]  Eva R. Kashket,et al.  Intracellular Conditions Required for Initiation of Solvent Production by Clostridium acetobutylicum , 1986, Applied and environmental microbiology.