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Transcriptomic response of the xylose-selective strain derived from E. coli BL21(DE3) growing on xylose or glucose

ABSTRACT: Different genetic engineering strategies have been proposed to obtain E. coli strains that selectively consume xylose. In this study, a previously reported strategy for obtaining a xylose-selective strain in E. coli K12 was applied to E. coli BL21 (DE3). While this approach resulted in the expected xylose-selective phenotype, a low xylose consumption rate was recorded when the strain was grown on a mixture of xylose and glucose. To enhance xylose consumption, a variant of the transcriptional activator XylR was expressed. The resulting strain not only exhibited an improved capacity to consume xylose but also slightly recovered the ability to consume glucose. The aim of the microarray analysis was to identify the transcriptional changes associated with glucose assimilation in the BL21(DE3) derived xylose-selective strain.

ORGANISM(S): Escherichia coli BL21(DE3)

PROVIDER: GSE277741 | GEO | 2024/10/01

REPOSITORIES: GEO

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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.

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Transcriptomic response of the xylose-selective strain derived from E. coli BL21(DE3) growing on xylose or glucose

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