title: Co-utilization of L-arabinose and D-xylose by laboratory and industrial Saccharomyces cerevisiae strains.
abstract: BACKGROUND
  Fermentation of lignocellulosic biomass is an attractive alternative for the production of bioethanol. Traditionally, the yeast Saccharomyces cerevisiae is used in industrial ethanol fermentations. However, S. cerevisiae is naturally not able to ferment the pentose sugars D-xylose and L-arabinose, which are present in high amounts in lignocellulosic raw materials.
  
  
  RESULTS
  We describe the engineering of laboratory and industrial S. cerevisiae strains to co-ferment the pentose sugars D-xylose and L-arabinose. Introduction of a fungal xylose and a bacterial arabinose pathway resulted in strains able to grow on both pentose sugars. Introduction of a xylose pathway into an arabinose-fermenting laboratory strain resulted in nearly complete conversion of arabinose into arabitol due to the L-arabinose reductase activity of the xylose reductase. The industrial strain displayed lower arabitol yield and increased ethanol yield from xylose and arabinose.
  
  
  CONCLUSIONS
  Our work demonstrates simultaneous co-utilization of xylose and arabinose in recombinant strains of S. cerevisiae. In addition, the co-utilization of arabinose together with xylose significantly reduced formation of the by-product xylitol, which contributed to improved ethanol production.
authors.affiliation: Department of Applied Microbiology, Lund University, P,O, Box 124, SE-22100 Lund, Sweden. Kaisa.Karhumaa@tmb.lth.se
authors.forename: Kaisa
authors.initials: K
authors.lastname: Karhumaa
authors.forename: Beate
authors.initials: B
authors.lastname: Wiedemann
authors.forename: Bärbel
authors.initials: B
authors.lastname: Hahn-Hägerdal
authors.forename: Eckhard
authors.initials: E
authors.lastname: Boles
authors.forename: Marie-F
authors.initials: MF
authors.lastname: Gorwa-Grauslund