Project description:The main objective is to improve xylose fermentation by deletion of PHO13 gene in Xylose isomerase (XI) harboring yeast strains. Microarray analysis was performed to investigate effects of PHO13 deletion on the gene expression prolife of xylose-fermenting strains.
Project description:To select candidate promoters that function in the presence of xylose, we performed comprehensive gene expression analyses using xylose-utilizing yeast strains both during xylose and glucose fermentation.
Project description:The main objective is to improve xylose fermentation by deletion of PHO80 gene in recombinant xylose-fermenting yeast strains. Microarray analysis was performed to investigate effects of PHO80 deletion on the gene expression profile of xylose-fermenting strains.
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:A xylan ulitization locus in Polaribacter sp. Q13, named XUL-Q13, was predicted to be involved in mixed-linkage xylan utilization. To support this, Polaribacter sp. Q13 was cultivated separately in triplicates on mixed-linkage xylan (MX_1, MX_2, MX_3), xylose (X_1, X_2, X_3) and glucose (G_1, G_2, G_3) and their proteomes were analyzed. In addition, the proteome of the resting cells (T0) was also analyzed.
Project description:The xylose fermentation rate during xylose consumption phase after glucose depleted in glucose-xylose co-fermentation (defined as GX stage) was much lower than that when xylose was the sole carbon source (defined as X stage). BSGX001 and XH7 are two engineered strains that have the xylose-utilizing capacity. Here,we investigate the transcriptional differences between GX stage and X stage of BSGX001 and XH7, respectively.
Project description:The main objective is to improve xylose fermentation by deletion of PHO80 gene in recombinant xylose-fermenting yeast strains. Microarray analysis was performed to investigate effects of PHO80 deletion on the gene expression profile of xylose-fermenting strains. Samples for 2 strains (wild-type control, PHO80-deleted strain) were taken after 6h of xylose fermentation. Each sample was triplicated, resulting in a total of 6 samples.
Project description:Electro-fermentation is a new technique that could be used to influence the global metabolism in mixed-culture fermentation. In this study, a mixed-culture cathodic electro-fermentation of glycerol was investigated. Both microbial community structure and metabolic patterns were altered when compared to standard fermentation. This microbial population shift was more significant when the working electrodes were pre-colonized by Geobacter sulfurreducens, before electro-fermentation. The electro-fermenting microbial community was more efficient for producing 1,3-propanediol with an improved yield of 10% when compared with fermentation controls. Such improvement did not require high energy and total electron input represented < 1% of the total electron equivalents provided only by glycerol. A linear model was developed to estimate the individual metabolic pattern of each operational taxonomic unit. Application of this model compared to the experimental results suggests that the changes in global metabolism were supported by bacterial population selection rather than individual metabolism shift. This study shows for the first time that both fermentation pattern and bacterial community composition can be influenced by electro-fermentation conditions.
Project description:The xylose fermentation rate of thi2p deletion strains was higher than the control strains BSGX001 during xylose consumption phase after glucose depleted in glucose-xylose co-fermentation (defined as GX stage). BSGX001 was derived from the haploid strain CEN.PK113-5D, which is a engineered strains that have the xylose-utilizing capacity. Here,we investigate the transcriptional differences between BSGX001 (thi2Δ) and BSGX001 in GX stage.