Project description:The aim of present study is to understand the impact of xylose utilization on the Saccharomyces cerevisiae physiology after initial genetic engineering and in a strain with an improved xylose utilization phenotype.
Project description:HMF and furfural were pulse added to xylose-utilizing Saccharomyces cerevisiae during either the glucose consumption phase or the xylose consumption phase. Transcriptome samples were collected before and one hour after pulsing of inhibitors.
Project description:In the present study transcriptome and proteome of recombinant, xylose-utilising S. cerevisiae grown in aerobic batch cultures on xylose were compared with glucose-grown cells both in glucose repressed and derepressed states. The aim was to study at genome-wide level how signalling and carbon catabolite repression differed in cells grown on either glucose or xylose. The more detailed knowledge about is xylose sensed as a fermentable carbon source, capable of catabolite repression like glucose, or is it rather recognised as a non-fermentable carbon source is important in achieving understanding for further engineering this yeast for more efficient anaerobic fermentation of xylose.
Project description:The xylose fermentation capability of an industrainl Saccharomyces cerevisiae strain was enhanced by adaptive evolution. Eight homozygots were generated by tetrads dissection. The underlying molecular basis of the enhanced xylose fermentation capability was analyzed.
Project description:Saccharomyces cerevisiae cannot metabolize non-glucose sugars including cellobiose, xylose, xylodextrins in nature, which are prevalent in plant cell wall. Here, one engineered S. cerevisiae strain, which expresses a cellodextrin transporter gene (cdt-1) and an intracellular β-glucosidase gene (codon-optimized gh1-1) from Neurospora crassa; XYL1 (xylose reductase gene), XYL2 (xylitol dehydrogenase gene), and XKS1 (xylulose kinase gene) from Scheffersomyces stipitis, as well as cdt-2 (coding for cellodextrin transporter 2), gh43-2 (coding for β-xylosidase) and gh43-7 (coding for a xylosyl-xylitol-specific β-xylosidase) from N. crassa, can utilize the above non-glucose sugars. We sequenced mRNA from exponential cultures of the engineered S. cerevisiae grown on glucose, cellobiose, xylose or xylodextrins as a single carbon source in both aerobic and anaerobic conditions in biological triplicate. Differences in gene expression between non-glucose sugar and glucose metabolism revealed by RNA deep sequencing indicated that non-glucose sugar metabolism induced mitochondrial activation and reduced amino acid and protein biosynthesis under fermentation conditions.
Project description:Xylose induced effects on metabolism and gene expression during anaerobic growth of an engineered Saccharomyces cerevisiae on mixed glucose-xylose medium were quantified. Gene expression of S. cerevisiae harbouring an XR-XDH pathway for xylose utilisation was analysed from early cultivation when mainly glucose was metabolised, to times when xylose was co-consumed in the presence of low glucose concentrations, and finally, to glucose depletion and solely xylose being consumed. Cultivations on glucose as a sole carbon source were used as a control. Genome-scale dynamic flux balance analysis models were developed and simulated to analyse the metabolic dynamics of S. cerevisiae in the cultivations. Model simulations quantitatively estimated xylose dependent dynamics of fluxes and challenges to the metabolic network utilisation. Increased relative xylose utilisation was predicted to induce two-directionality of glycolytic flux and a redox challenge already at low glucose concentrations. Xylose effects on gene expression were observed also when glucose was still abundant. Remarkably, xylose was observed to specifically delay the glucose-dependent repression of particular genes in mixed glucose-xylose cultures compared to glucose cultures. The delay occurred during similar metabolic flux activities in the both cultures. Xylose is abundantly present together with glucose in lignocellulosic streams that would be available for the valorisation to biochemicals or biofuels. Yeast S. cerevisiae has superior characteristics for a host of the bioconversion except that it strongly prefers glucose and the co-consumption of xylose is yet a challenge. Further, since xylose is not a natural substrate of S. cerevisiae, the regulatory response it induces in an engineered yeast strain cannot be expected to have evolved for its utilisation. Dynamic cultivation experiments on mixed glucose-xylose medium having glucose cultures as control integrated with mathematical modelling allowed to resolve specific effects of xylose on the gene expression and metabolism of engineered S. cerevisiae in the presence of varying amounts of glucose.
Project description:The molecular basis for glucose and xylose fermentation by industrial Saccharomyces cerevisiae is of interest to promote bioethanol production We used microarrays to investigate the transcriptional difference of a industrial strain cultured in both single sugar media and a mixed sugar medium of glucose and xylose
Project description:Xylose induced dynamic effects on metabolism and gene expression in engineered Saccharomyces cerevisiae in anaerobic glucose-xylose cultures
