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Coexistence of S. cerevisiae and E. coli in chemostat under substrate competition and product inhibition
Author(s) -
Davison Brian H.,
Stephanopoulos Gregory
Publication year - 1986
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.260281119
Subject(s) - chemostat , steady state (chemistry) , product inhibition , substrate (aquarium) , yeast , saccharomyces cerevisiae , ethanol , competition (biology) , escherichia coli , fermentation , acetic acid , non competitive inhibition , biochemistry , chemistry , biology , biophysics , bacteria , enzyme , organic chemistry , ecology , genetics , gene
A mixed culture of Saccharomyces cerevisiae and Escherichia coli was established in a stable coexistence steady state in a chemostat under constant operating conditions. The species competed for glucose, the growth‐limiting resource, and produced acetate and ethanol. The acetic acid was shown to be very inhibitory to E. coli in pure culture at pH 5 while ethanol inhibition was only marginal. No significant inhibition of S. cerevisiae growth was observed by either acetate or ethanol. Pure culture parameters were measured and used in the analysis. Linearized stability analysis for the case when both organisms produce the inhibitor showed that a transition through three stable outcomes was possible as the feed concentration is lowered. Experimental studies verified these predictions, and successive transitions from a yeast growth steady state, to a coexistence steady state, and to an E. coli growth steady state were obtained by lowering the glucose concentration in the feed from 10 to 5 to 2.5 g/L, respectively. This dynamic behavior is distinct from the outcomes of other competition–inhibition combinations and experimentally demonstrates for the first time that coexistence is possible due to substrate competition and product inhibition.