title: Induction of Xylose Reductase and Xylitol Dehydrogenase Activities in Pachysolen tannophilus and Pichia stipitis on Mixed Sugars.
abstract: The induction of xylose reductase and xylitol dehydrogenase activities on mixed sugars was investigated in the yeasts Pachysolen tannophilus and Pichia stipitis. Enzyme activities induced on d-xylose served as the controls. In both yeasts, d-glucose, d-mannose, and 2-deoxyglucose inhibited enzyme induction by d-xylose to various degrees. Cellobiose, l-arabinose, and d-galactose were not inhibitory. In liquid batch culture, P. tannophilus utilized d-glucose and d-mannose rapidly and preferentially over d-xylose, while d-galactose consumption was poor and lagged behind that of the pentose sugar. In P. stipitis, all three hexoses were used preferentially over d-xylose. The results showed that the repressibility of xylose reductase and xylitol dehydrogenase may limit the potential of yeast fermentation of pentose sugars in hydrolysates of lignocellulosic substrates.
authors.affiliation: Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bicho
authors.forename: P Lynn
authors.initials: PL
authors.lastname: Runnals
authors.forename: J Douglas
authors.initials: JD
authors.lastname: Cunningham
authors.forename: Hung
authors.initials: H
authors.lastname: Lee