Exploring d-xylose oxidation in Saccharomyces cerevisiae through the Weimberg pathway

• Main Authors: Lisa Wasserstrom, Diogo Portugal-Nunes, Henrik Almqvist, Anders G. Sandström, Gunnar Lidén, Marie F. Gorwa-Grauslund
• Format: Article
• Language: English
• Published: SpringerOpen 2018-03-01
• Series: AMB Express
• Subjects: d-Xylose; Weimberg pathway; Saccharomyces cerevisiae; d-Xylonate dehydratase; Caulobacter crescentus; Iron–sulfur clusters
• Online Access: http://link.springer.com/article/10.1186/s13568-018-0564-9

Abstract Engineering of the yeast Saccharomyces cerevisiae towards efficient d-xylose assimilation has been a major focus over the last decades since d-xylose is the second most abundant sugar in nature, and its conversion into products could significantly improve process economy in biomass-based processes. Up to now, two different metabolic routes have been introduced via genetic engineering, consisting of either the isomerization or the oxido-reduction of d-xylose to d-xylulose that is further connected to the pentose phosphate pathway and glycolysis. In the present study, cytosolic d-xylose oxidation was investigated instead, through the introduction of the Weimberg pathway from Caulobacter crescentus in S. cerevisiae. This pathway consists of five reaction steps that connect d-xylose to the TCA cycle intermediate α-ketoglutarate. The corresponding genes could be expressed in S. cerevisiae, but no growth was observed on d-xylose indicating that not all the enzymes were functionally active. The accumulation of the Weimberg intermediate d-xylonate suggested that the dehydration step(s) might be limiting, blocking further conversion into α-ketoglutarate. Although four alternative dehydratases both of bacterial and archaeon origins were evaluated, d-xylonate accumulation still occurred. A better understanding of the mechanisms associated with the activity of dehydratases, both at a bacterial and yeast level, appears essential to obtain a fully functional Weimberg pathway in S. cerevisiae.