Optimal substrate feeding policy for fed-batch cultures of S. cerevisiae expressing bifunctional fusion protein displaying amylolytic activities

M. Mete Altintaş, Kutlu Ö Ülgen, Betül Kirdar, Z. Ilsen Önsan, Stephen G. Oliver

Research output: Contribution to journalArticlepeer-review

Abstract

The genetically modified Saccharomyces cerevisiae strain (YPB-G) which secretes a bifunctional fusion protein that contains both the Bacillus subtilis α-amylase and the Aspergillus awamori glucoamylase activities was used for the direct conversion of starch into ethanol. Starch was added instantaneously to the reactor at various discrete time instants (pulse feeding), or at a constant flow rate in either equal or unequal sub-intervals (intermittent feeding). Experiments with intermittent feeding of starch yielded poor biomass and ethanol yields. Pulse experiments were initiated with starch concentrations of 0, 10, 20, 40 and 50g/l, and then single, two or three feedings were made. Optimal feeding policy was found to depend heavily on initial conditions. Ethanol yields increased from 0.335 to 0.499(gethanol)/ (gsubstrate) upon decreasing the initial starch concentration from 50 to 10g/l and increasing the number of low starch containing pulses. Starch degradation rates were slower and fermentation times were longer for experiments initiated with minimal amounts (0 and 10g/l) of starch.

Original languageEnglish (US)
Pages (from-to)262-269
Number of pages8
JournalEnzyme and Microbial Technology
Volume33
Issue number2-3
DOIs
StatePublished - Aug 13 2003
Externally publishedYes

Keywords

  • Bifunctional fusion protein
  • Fed-batch fermentation
  • Recombinant yeast
  • Saccharomyces cerevisiae
  • Starch bioconversion

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Biochemistry
  • Applied Microbiology and Biotechnology

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