期刊
FEMS YEAST RESEARCH
卷 18, 期 1, 页码 -出版社
OXFORD UNIV PRESS
DOI: 10.1093/femsyr/fox096
关键词
Saccharomyces cerevisiae; sugar sensing/signaling; xylose; XR/XDH; GFP biosensor; cAMP/PKA; Snf3p/Rgt2p; SNF1/Mig1p; flow cytometry
资金
- Swedish Research Council (Vetenskapsradet) [2016-05297_VR]
- Brazilian National Council for Scientific and Technological Development (National Council for Scientific and Technological Development - CNPq)
- Vinnova [2016-05297] Funding Source: Vinnova
- Swedish Research Council [2016-05297] Funding Source: Swedish Research Council
One of the challenges of establishing an industrially competitive process to ferment lignocellulose to value-added products using Saccharomyces cerevisiae is to get efficient mixed sugar fermentations. Despite successful metabolic engineering strategies, the xylose assimilation rates of recombinant S. cerevisiae remain significantly lower than for the preferred carbon source, glucose. Previously, we established a panel of in vivo biosensor strains (TMB371X) where different promoters (HXT1/2/4p; SUC2p, CAT8p; TPS1p/2p, TEF4p) from the main sugar signaling pathways were coupled with the yEGFP3 gene, and observed that wild-type S. cerevisiae cannot sense extracellular xylose. Here, we expand upon these strains by adding a mutated galactose transporter (GAL2-N376F) with improved xylose affinity (TMB372X), and both the transporter and an oxidoreductase xylose pathway (TMB375X). On xylose, the TMB372X strains displayed population heterogeneities, which disappeared when carbon starvation was relieved by the addition of the xylose assimilation pathway (TMB375X). Furthermore, the signal in the TMB375X strains on high xylose (50 g/L) was very similar to the signal recorded on low glucose (<= 5 g/L). This suggests that intracellular xylose triggers a similar signal to carbon limitation in cells that are actively metabolizing xylose, in turn causing the low assimilation rates.
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