Supplements are available for figure 2: Figure supplement 1. Xylosyl-xylitol oligomers generated in
Supplements are accessible for figure 2: Figure supplement 1. Xylosyl-xylitol oligomers generated in yeast cultures with xylodextrins because the sole carbon supply. DOI: ten.cIAP custom synthesis 7554eLife.05896.012 Figure supplement 2. Xylodextrin metabolism by a co-culture of yeast strains to identify enzymatic source of xylosyl-xylitol. DOI: ten.7554eLife.05896.013 Figure supplement 3. Chromatogram of xylosyl-xylitol hydrolysis products generated by -xylosidases. DOI: 10.7554eLife.05896.We subsequent tested whether integration from the complete xylodextrin consumption pathway would overcome the poor xylodextrin utilization by S. cerevisiae (Figure 1) (Fujii et al., 2011). When combined together with the original xylodextrin pathway (CDT-2 plus GH43-2), GH43-7 enabled S. cerevisiae to grow additional swiftly on xylodextrin (Figure 4A) and eliminated accumulation of xylosyl-xylitol intermediates (Figure 4B and Figure 4–figure supplement 1). The presence of xylose and glucose significantly enhanced anaerobic fermentation of xylodextrins (Figure 5 and Figure 5–figure supplement 1 and Figure 5–figure supplement two), indicating that metabolic sensing in S. cerevisiae with the full xylodextrin pathway may require additional tuning (Youk and van Oudenaarden, 2009) for optimal xylodextrin fermentation. Notably, we observedLi et al. eLife 2015;4:e05896. DOI: 10.7554eLife.five ofResearch articleComputational and systems biology | EcologyFigure 3. Xylosyl-xylitol and xylosyl-xylosyl-xylitol production by a array of microbes. (A) Xylodextrin-derived carbohydrate levels noticed in chromatograms of intracellular metabolites for N. crassa, T. reesei, A. nidulans and B. subtilis grown on xylodextrins. Compounds are abbreviated as follows: X1, xylose; X2, xylobiose; X3, xylotriose; X4, xylotetraose; xlt, xylitol; xlt2, xylosyl-xylitol; xlt3, xylosyl-xylosyl-xylitol. (B) Phylogenetic tree on the organisms shown to generate xylosyl-xylitols during growth on xylodextrins. Ages taken from Wellman et al. (2003); Galagan et al. (2005); Hedges et al. (2006). DOI: ten.7554eLife.05896.015 The following figure supplement is offered for figure three: Figure supplement 1. LC-MSMS numerous reaction monitoring chromatograms of xylosyl-xylitols from cultures of microbes grown on xylodextrins. DOI: 10.7554eLife.05896.that the XRXDH pathway made substantially less xylitol when xylodextrins have been applied in fermentations than from xylose (Figure five and Figure 5–figure supplement 2B). Taken collectively, these outcomes reveal that the XRXDH pathway extensively utilised in engineered S. cerevisiae naturally has broad substrate specificity for xylodextrins, and full reconstitution on the naturally occurring xylodextrin pathway is necessary to enable S. cerevisiae to efficiently consume xylodextrins. The observation that xylodextrin fermentation was stimulated by glucose (Figure 5B) recommended that the xylodextrin pathway could serve more generally for cofermentations to improve biofuel production. We for that reason tested no matter whether xylodextrin fermentation could possibly be carried out simultaneously with sucrose fermentation, as a suggests to augment ethanol yield from sugarcane. In this scenario, xylodextrins ETB MedChemExpress released by hot water remedy (Hendriks and Zeeman, 2009; Agbor et al., 2011; Vallejos et al., 2012) might be added to sucrose fermentations making use of yeast engineered together with the xylodextrin consumption pathway. To test this concept, we employed strain SR8U engineered with all the xylodextrin pathway (CDT-2, GH43-2, and GH437) in fermentations combining sucrose and xylodextrin.