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Influence of dilution rate and induction of cloned gene expression in continuous fermentations of recombinant yeast
Author(s) -
Da Silva Nancy Anderson,
Bailey James E.
Publication year - 1991
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.260370404
Subject(s) - inducer , yeast , dilution , saccharomyces cerevisiae , plasmid , lac operon , steady state (chemistry) , biology , biochemistry , fermentation , galactose , chemostat , expression vector , chemistry , microbiology and biotechnology , recombinant dna , gene , genetics , physics , bacteria , thermodynamics
The effects of growth rate on cloned gene product synthesis in recombinant Saccharomyces cerevisiae have been studied in continuous culture. The plasmid employed contains a yeast GAL10 ‐ CYC1 hybrid promoter directing expression of the E. coli lacZ gene. β‐Galactosidase production was therefore controlled by the yeast galactose regulatory circuit, and the induction process and its effects were studied at the various dilution rates. At all dilution rates plasmid stability decreased with induction of lacZ gene expression. In some instances, two induced “steady states” were observed, the first 10–15 residence times after induction and the second after 40–50 residence times. The second induced steady state was characterized by greater biomass concentration and lower β‐galactosidase specific activity relative to the first induced “steady‐state.” β‐Galactosidase specific activity and biomass concentration increased as dilution rate was reduced, and despite lower flow rate and plasmid stability, overall productivity (activity/L/hr) was substantially higher at low dilution rate. Important factors influencing all of the trends were the glucose and galactose (inducer) concentrations in the vessel and inducer metabolism.