Plasmid stability in a recombinant S cerevisiae strain secreting a bifunctional fusion protein

M. Mete Altnta, Betul Krdar, Z. Lsen Onsan, Kutlu O. Lgen

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The recombinant Saccharomyces cerevisiae strain, YPB-G, producing and secreting Bacillus subtilis α-amylase and Aspergillus awamori glucoamylase as a fusion protein yielded efficient utilisation of starch. A segregated population balance model has been used to determine the probability of plasmid loss and plasmid copy number. The kinetics of cell growth and product (fusion protein) formation were based on a genetically structured model. The predictions were compared with the experimental observations obtained for the unstable recombinant S cerevisiae cells in a 1.5 dm-3 batch bioreactor with 30 g dm3 initial starch under non-aerated conditions. The main advantage of the present model is that three different genetic classes were defined on the basis of the existence of plasmid and of the expression of the enzymes, ie cells containing plasmids and expressing the gene product, x1; cells containing plasmids and but not expressing the gene product, x2; and cells without plasmids, x3. It is confirmed by this model that the cells without plasmids outgrow and dominate in the fermentation medium (2.27 g dm-3 vs 0.51 g dm-3) as more and more glucose becomes available by the degradation of starch.

Original languageEnglish (US)
Pages (from-to)612-618
Number of pages7
JournalJournal of Chemical Technology and Biotechnology
Issue number6
StatePublished - 2001
Externally publishedYes


  • Bifunctional fusion protein
  • Plasmid copy number
  • Recombinant yeast
  • Segregational instability
  • Starch bioconversion

ASJC Scopus subject areas

  • Biotechnology
  • General Chemical Engineering
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Waste Management and Disposal
  • Pollution
  • Organic Chemistry
  • Inorganic Chemistry


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