Analysis of cellodextrin transporters from Neurospora crassa in Saccharomyces cerevisiae for cellobiose fermentation

Heejin Kim, Won Heong Lee, Jonathan M. Galazka, Jamie H.D. Cate, Yong Su Jin

Research output: Contribution to journalArticlepeer-review

Abstract

Saccharomyces cerevisiae can be engineered to ferment cellodextrins produced by cellulases as a product of cellulose hydrolysis. Direct fermentation of cellodextrins instead of glucose is advantageous because glucose inhibits cellulase activity and represses the fermentation of non-glucose sugars present in cellulosic hydrolyzates. To facilitate cellodextrin utilization by S. cerevisiae, a fungal cellodextrin-utilizing pathway from Neurospora crassa consisting of a cellodextrin transporter and a cellodextrin hydrolase has been introduced into S. cerevisiae. Two cellodextrin transporters (CDT-1 and CDT-2) were previously identified in N. crassa, but their kinetic properties and efficiency for cellobiose fermentation have not been studied in detail. In this study, CDT-1 and CDT-2, which are hypothesized to transport cellodextrin with distinct mechanisms, were introduced into S. cerevisiae along with an intracellular β-glucosidase (GH1-1). Cellobiose transport assays with the resulting strains indicated that CDT-1 is a proton symporter while CDT-2 is a simple facilitator. A strain expressing CDT-1 and GH1-1 (DCDT-1G) showed faster cellobiose fermentation than the strain expressing CDT-2 and GH1-1 (DCDT-2G) under various culture conditions with different medium compositions and aeration levels. While CDT-2 is expected to have energetic benefits, the expression levels and kinetic properties of CDT-1 in S. cerevisiae appears to be optimum for cellobiose fermentation. These results suggest CDT-1 is a more effective cellobiose transporter than CDT-2 for engineering S. cerevisiae to ferment cellobiose.

Original languageEnglish (US)
Pages (from-to)1087-1094
Number of pages8
JournalApplied Microbiology and Biotechnology
Volume98
Issue number3
DOIs
StatePublished - Feb 2014

Keywords

  • Cellodextrin transporters
  • Cellulosic ethanol
  • Engineered S. cerevisiae
  • Intracellular β-glucosidase

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology

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