Energetic benefits and rapid cellobiose fermentation by Saccharomyces cerevisiae expressing cellobiose phosphorylase and mutant cellodextrin transporters

Suk Jin Ha, Jonathan M. Galazka, Eun Joong Oh, Vesna Kordić, Heejin Kim, Yong Su Jin, Jamie H.D. Cate

Research output: Contribution to journalArticlepeer-review

Abstract

Anaerobic bacteria assimilate cellodextrins from plant biomass by using a phosphorolytic pathway to generate glucose intermediates for growth. The yeast Saccharomyces cerevisiae can also be engineered to ferment cellobiose to ethanol using a cellodextrin transporter and a phosphorolytic pathway. However, strains with an intracellular cellobiose phosphorylase initially fermented cellobiose slowly relative to a strain employing an intracellular Β-glucosidase. Fermentations by the phosphorolytic strains were greatly improved by using cellodextrin transporters with elevated rates of cellobiose transport. Furthermore under stress conditions, these phosphorolytic strains had higher biomass and ethanol yields compared to hydrolytic strains. These observations suggest that, although cellobiose phosphorolysis has energetic advantages, phosphorolytic strains are limited by the thermodynamics of cellobiose phosphorolysis (ΔG°=+3.6kJmol-1). A thermodynamic "push" from the reaction immediately upstream (transport) is therefore likely to be necessary to achieve high fermentation rates and energetic benefits of phosphorolysis pathways in engineered S. cerevisiae.

Original languageEnglish (US)
Pages (from-to)134-143
Number of pages10
JournalMetabolic Engineering
Volume15
Issue number1
DOIs
StatePublished - Jan 2013

Keywords

  • Β-glucosidase
  • Cellobiose
  • Cellodextrin transporter
  • Phosphorylase
  • Thermodynamics

ASJC Scopus subject areas

  • Bioengineering
  • Biotechnology
  • Applied Microbiology and Biotechnology

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