Comparison of the xylose reductase-xylitol dehydrogenase and the xylose isomerase pathways for xylose fermentation by recombinant Saccharomyces cerevisiae

Abstract

Background: Two heterologous pathways have been used to construct recombinant xylosefermenting Saccharomyces cerevisiae strains: i) the xylose reductase (XR) and xylitol dehydrogenase (XDH) pathway and ii) the xylose isomerase (XI) pathway. In the present study, the Pichia stipitis XR-XDH pathway and the Piromyces XI pathway were compared in an isogenic strain background, using a laboratory host strain with genetic modifications known to improve xylose fermentation (overexpressed xylulokinase, overexpressed non-oxidative pentose phosphate pathway and deletion of the aldose reductase gene GRE3). The two isogenic strains and the industrial xylosefermenting strain TMB 3400 were studied regarding their xylose fermentation capacity in defined mineral medium and in undetoxified lignocellulosic hydrolysate.

Unraveling the genetic basis of xylose consumption in engineered Saccharomyces cerevisiae strains

“…The xylA enzyme does not require cofactors and therefore does not have the redox bottleneck associated with the XR-XDH pathway. In addition, since it has lower accumulation of by-products, the total amount of ethanol that can be produced is higher10121314.…”

Ethanol Production from Traditional and Emerging Raw Materials

“…expressed in S. cerevisiae with much higher activity (Kuyper et al, 2003 ). However, also for this enzyme, the specific activity was too low to permit chromosomal integration (Karhumaa et al, 2007b and in fungi, the conversion of arabinose into metabolites of the pentose phosphate pathway (PPP) involves several more steps than the conversion of xylose (Fig. 23.6 ).…”

Beyond Genetic Engineering: Technical Capabilities in the Application Fields of Biocatalysis and Biosensors

“…Hence, much effort has been devoted to engineering strains of yeast which can ferment d-xylose and l-arabinose. Xylose fermentation can be achieved by expression of fungal xylose reductase plus xylitol dehydrogenase (Ho et al 1998) or bacterial xylose isomerase (Karhumaa et al 2007). Arabinose fermentation has proven more problematic, with cofactor imbalance generally leading to the major product being arabitol rather than ethanol (Karhumaa et al 2006), and attempts to engineer strains which could co-ferment mixtures of xylose and arabinose were still more difficult, requiring prolonged post-engineering selection (Wisselink et al 2009), though such strains have now been generated (Bettiga et al 2009;Bera et al 2010).…”