Demonstration of D-xylose reductase and D-xylitol dehydrogenase in Pachysolen tannophilus

Metabolic engineering of Saccharomyces cerevisiae for increased bioconversion of lignocellulose to ethanol

“…The activity of XYL1 was measured spectrophotometrically by monitoring the oxidation of NADPH at 340 nm in a reaction solution with following composition: 0.1 M sodium phosphate buffer (pH 7.0), 0.2 M xylose, and 0.15 mM NADPH [5]. The activity of XYL2 was determined by the method described previously [12].…”

“…In naturally xylose-utilizing yeasts such as Pichia stipitis, Pachysolen tannophilus and Candida shehatae, the main enzymatic steps in xylose metabolism are catalyzed by xylose reductase (XYL1) and xylitol dehydrogenase (XYL2). Xylose is first oxidized by XYL1 to xylitol, which is then oxidized by XYL2 to xylulose [5]. Since the S. cerevisiae cannot utilize xylose, but does utilize and ferment its isomer D-xylulose, the obvious first step to allow xylose metabolism is to introduce a heterologous pathway converting xylose to xylulose [6][7][8].…”

Production of Xylitol by the Thermotolerant Kluyveromyces marxianus IMB Strains

“…The procedure was modified from the one described by Smiley and Bolen [15]. All IMB yeast strains were grown in YPX medium containing 10 g/l yeast extract, 20 g/l peptone, and 20 g/l xylose for 18 h at 40°C and 220 rpm.…”

“…XR and XD are not available during glucose fermentation [15]. Xylose is reduced to xylitol, catalyzed by XR, and further oxidized to xylulose, catalyzed by XD.…”

Sequence and analysis of an aldose (xylose) reductase gene from the xylose‐fermenting yeast Pachysolen tannophilus

“…Of yeasts known to possess the uncommon ability to ferment xylose to ethanol, three have been studied in some detail: Candidu slzehutar (Ho et ul., 1990), Piclzia stipitis (du Preez et al, 1986;Slininger et cil., 1985) and PLicliysolen tunnojdii1ii.s (Smiley andBolen, 1982: Bolen et a/.. 1985;Ligthelm et a/., 1988). The xylose metabolic pathway operating in these three yeasts consists of conversion of xylose to xylitol by xylose reductase, conversion of xylitol to xylulose by xylitol dehydrogenase (D-xylulose reductase, EC 1.1.1.9), phosphorylation of xylulose followed by further conversion to ethanol via common enzymes of the pentose phosphate and Embden-MeyerhoffParnas pathways (Slininger et al, 1987).…”