The continuous culture of Clostridium thermocellum, a thermophilic bacterium capable of producing ethanol from cellulosic material, is demonstrated at elevated hydrostatic pressure (7.0 MPa, 17.3 MPa) and compared with cultures at atmospheric pressure. A commercial limitation of ethanol production by C. thermocellum is low ethanol yield due to the formation of organic acids (acetate, lactate). At elevated hydrostatic pressure, ethanol:acetate (E/A) ratios increased >102 relative to atmospheric pressure. Cell growth was inhibited by approximately 40% and 60% for incubations at 7.0 MPa and 17.3 MPa, respectively, relative to continuous culture at atmospheric pressure. A decrease in the theoretical maximum growth yield and an increase in the maintenance coefficient indicated that more cellobiose and ATP are channeled towards maintaining cellular function in pressurized cultures. Shifts in product selectivity toward ethanol are consistent with previous observations of hydrostatic pressure effects in batch cultures. The results are partially attributed to the increasing concentration of dissolved product gases (H 2, CO2) with increasing pressure; and they highlight the utility of continuous culture experiments for the quantification of the complex role of dissolved gas and pressure effects on metabolic activity.
|Number of pages||9|
|Journal||Applied Microbiology and Biotechnology|
|State||Published - Aug 2004|
Bibliographical noteFunding Information:
Acknowledgements The authors gratefully acknowledge the financial support of the National Science Foundation (Grant BES-9817069) and thank Eva Kaplan in the Department of Animal Sciences at the University of Kentucky, for her assistance with laboratory analysis.
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology