Plasmid maintenance and protein overproduction in selective recycle bioreactors

Kimberly L. Ogden, Robert H. Davis

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


A new plasmid construct has been used in conjunction with selective recycle to successfully maintain otherwise unstable plasmid‐bearing E. coli cells in a continuous bioreactor and to produce significant amounts of the plasmid‐encoded protein β‐lactamase. The plasmid is constructed so that pilin expression, which leads to bacterial flocculation, is under control of the tac operon. The plasmid‐bearing cells are induced to flocculate in the separator, whereas cell growth and product synthesis occur in the main fermentation vessel without the inhibiting effects of pilin production. Selective recycle allows for the maintenance of the plasmid‐bearing cells by separating flocculent, plasmid‐bearing cells from nonflocculent, segregant cells in an inclined settler, and recycling only the plasmid‐bearing cells to the reactor. As a result, product expression levels are maintained that are more than ten times the level achieved without selective recycle. All experimental data agree well with theoretical predictions.

Original languageEnglish (US)
Pages (from-to)325-333
Number of pages9
JournalBiotechnology and Bioengineering
Issue number4
StatePublished - Feb 20 1991
Externally publishedYes


  • fermentations, continuous
  • flocculation
  • induction
  • protein overproduction
  • segregation

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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