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Influence of the pH on (open) mixed culture fermentation of glucose: A chemostat study
Author(s) -
Temudo Margarida F.,
Kleerebezem Robbert,
van Loosdrecht Mark
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21412
Subject(s) - formate , fermentation , chemostat , chemistry , mixed acid fermentation , metabolic flux analysis , industrial fermentation , dehydrogenation , product inhibition , biochemistry , metabolism , lactic acid fermentation , bacteria , lactic acid , catalysis , biology , non competitive inhibition , genetics , enzyme
Catabolic products from anaerobic fermentation processes are potentially of industrial interest. The volatile fatty acids and alcohols produced can be used as building blocks in chemical processes or applied directly as substrates in a mixed culture process to produce bioplastics. Development of such applications requires a predictable and controllable product spectrum of the fermentation process. The aim of the research described in this paper was (i) to investigate the product spectrum of an open mixed culture fermentation (MCF) process as a function of the pH, using glucose as substrate, and (ii) to relate the product spectrum obtained to generalized biochemical and thermodynamic considerations. A chemostat was operated under carbon and energy limitation in order to investigate the pH effect on the product spectrum in a MCF process. A transition from CO 2 /H 2 production at lower pH values to formate production at higher pH values was observed. The ratio of CO 2 /H 2 versus formate production was found to be related to the thermodynamics of formate dehydrogenation to CO 2 /H 2 . This transition was associated with a shift in the catabolic products, from butyrate and acetate to ethanol and acetate, likely due to a decrease in the oxidation state of the electron carriers in the cell. The product spectrum of the MCF process as a function of the pH could largely be explained using general biochemical considerations. Biotechnol. Bioeng. 2007; 98: 69–79. © 2007 Wiley Periodicals, Inc.