Overcoming inefficient cellobiose fermentation by cellobiose phosphorylase in the presence of xylose

Kulika Chomvong, Vesna Kordić, Xin Li, Stefan Bauer, Abigail E. Gillespie, Suk Jin Ha, Eun Joong Oh, Jonathan M. Galazka, Yong Su Jin, Jamie H.D. Cate

Research output: Contribution to journalArticlepeer-review


Background: Cellobiose and xylose co-fermentation holds promise for efficiently producing biofuels from plant biomass. Cellobiose phosphorylase (CBP), an intracellular enzyme generally found in anaerobic bacteria, cleaves cellobiose to glucose and glucose-1-phosphate, providing energetic advantages under the anaerobic conditions required for large-scale biofuel production. However, the efficiency of CBP to cleave cellobiose in the presence of xylose is unknown. This study investigated the effect of xylose on anaerobic CBP-mediated cellobiose fermentation by Saccharomyces cerevisiae. Results: Yeast capable of fermenting cellobiose by the CBP pathway consumed cellobiose and produced ethanol at rates 61% and 42% slower, respectively, in the presence of xylose than in its absence. The system generated significant amounts of the byproduct 4-O-β-d-glucopyranosyl-d-xylose (GX), produced by CBP from glucose-1-phosphate and xylose. In vitro competition assays identified xylose as a mixed-inhibitor for cellobiose phosphorylase activity. The negative effects of xylose were effectively relieved by efficient cellobiose and xylose co-utilization. GX was also shown to be a substrate for cleavage by an intracellular β-glucosidase. Conclusions: Xylose exerted negative impacts on CBP-mediated cellobiose fermentation by acting as a substrate for GX byproduct formation and a mixed-inhibitor for cellobiose phosphorylase activity. Future efforts will require efficient xylose utilization, GX cleavage by a β-glucosidase, and/or a CBP with improved substrate specificity to overcome the negative impacts of xylose on CBP in cellobiose and xylose co-fermentation.

Original languageEnglish (US)
Article number85
JournalBiotechnology for Biofuels
Issue number1
StatePublished - Jun 7 2014


  • Cellobiose
  • Cellobiose phosphorylase
  • Glucopyranosyl-xylose
  • Inhibition
  • Xylose

ASJC Scopus subject areas

  • General Energy
  • Management, Monitoring, Policy and Law
  • Biotechnology
  • Renewable Energy, Sustainability and the Environment
  • Applied Microbiology and Biotechnology


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