Endogenous Xylose Pathway in
            <i>Saccharomyces cerevisiae</i>

Toivari, Mervi; Salusjärvi, Laura; Ruohonen, Laura; Penttilä, Merja

doi:10.1128/aem.70.6.3681-3686.2004

Cited by 121 publications

(102 citation statements)

References 46 publications

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“…The latter genes were also upregulated in the DS69473-Y353C mutant strain (see Table S2 in the supplemental material). However, the upregulation of SOR1 could also be caused by the increased influx of D-xylose into the cell, since D-xylose induces the expression of SOR1 (36). This may also apply to SOR2.…”

Section: Discussionmentioning

confidence: 99%

Improved Xylose Metabolism by a CYC8 Mutant of Saccharomyces cerevisiae

Nijland

Shin

Boender

et al. 2017

Appl Environ Microbiol

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Engineering Saccharomyces cerevisiae for the utilization of pentose sugars is an important goal for the production of second-generation bioethanol and biochemicals. However, S. cerevisiae lacks specific pentose transporters, and in the presence of glucose, pentoses enter the cell inefficiently via endogenous hexose transporters (HXTs). By means of in vivo engineering, we have developed a quadruple hexokinase deletion mutant of S. cerevisiae that evolved into a strain that efficiently utilizes D-xylose in the presence of high D-glucose concentrations. A genome sequence analysis revealed a mutation (Y353C) in the general corepressor CYC8, or SSN6, which was found to be responsible for the phenotype when introduced individually in the nonevolved strain. A transcriptome analysis revealed altered expression of 95 genes in total, including genes involved in (i) hexose transport, (ii) maltose metabolism, (iii) cell wall function (mannoprotein family), and (iv) unknown functions (seripauperin multigene family). Of the 18 known HXTs, genes for 9 were upregulated, especially the low or nonexpressed HXT10, HXT13, HXT15, and HXT16. Mutant cells showed increased uptake rates of D-xylose in the presence of D-glucose, as well as elevated maximum rates of metabolism (V max ) for both D-glucose and D-xylose transport. The data suggest that the increased expression of multiple hexose transporters renders D-xylose metabolism less sensitive to D-glucose inhibition due to an elevated transport rate of D-xylose into the cell. IMPORTANCEThe yeast Saccharomyces cerevisiae is used for second-generation bioethanol formation. However, growth on xylose is limited by pentose transport through the endogenous hexose transporters (HXTs), as uptake is outcompeted by the preferred substrate, glucose. Mutant strains were obtained with improved growth characteristics on xylose in the presence of glucose, and the mutations mapped to the regulator Cyc8. The inactivation of Cyc8 caused increased expression of HXTs, thereby providing more capacity for the transport of xylose, presenting a further step toward a more robust process of industrial fermentation of lignocellulosic biomass using yeast.KEYWORDS sugar transporter, xylose transport, evolutionary engineering, transcriptome, yeast A n increasing energy demand and concerns of obtaining this energy from fossil fuels have stimulated the development of liquid fuels from renewable feedstock. Bioethanol, mostly used as a fuel additive, produced from readily fermentable agricultural feedstocks, such as sugar cane and corn, is less desired because the production of these feedstocks requires large amounts of arable land and competes with the food supply (1). A more sustainable source of feedstock is lignocellulosic biomass from hardwood, softwood, and agricultural residues (2). However, a major drawback of lignocellulosic feedstocks is the inability of the most commonly used yeast in industry,

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Section: Discussionmentioning

confidence: 99%

Improved Xylose Metabolism by a CYC8 Mutant of Saccharomyces cerevisiae

Nijland

Shin

Boender

et al. 2017

Appl Environ Microbiol

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“…Indeed, mutants of S. pombe have been isolated that grow on galactose and constitutively express their GAL pathways (33), suggesting that S. pombe may respond to a different induction signal. Similarly, S. cerevisiae, although not classified as a xylose-using yeast (2), has been shown to grow on xylose when endogenous genes are overexpressed (34). The ability of Y. lipolytica to grow on D-xylose varies among strains (2,14,15), and it may be that the D-xylose pathways of C. tanzawensis and other yeasts, which possess XYL gene homologs but do not grow on D-xylose in classical assays (2), are likewise rewired.…”

Section: Discussionmentioning

confidence: 99%

Comparative genomics of biotechnologically important yeasts

Riley

Haridas

Wolfe

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

303

394

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Ascomycete yeasts are metabolically diverse, with great potential for biotechnology. Here, we report the comparative genome analysis of 29 taxonomically and biotechnologically important yeasts, including 16 newly sequenced. We identify a genetic code change, CUG-Ala, in Pachysolen tannophilus in the clade sister to the known CUG-Ser clade. Our well-resolved yeast phylogeny shows that some traits, such as methylotrophy, are restricted to single clades, whereas others, such as L-rhamnose utilization, have patchy phylogenetic distributions. Gene clusters, with variable organization and distribution, encode many pathways of interest. Genomics can predict some biochemical traits precisely, but the genomic basis of others, such as xylose utilization, remains unresolved. Our data also provide insight into early evolution of ascomycetes. We document the loss of H3K9me2/3 heterochromatin, the origin of ascomycete mating-type switching, and panascomycete synteny at the MAT locus. These data and analyses will facilitate the engineering of efficient biosynthetic and degradative pathways and gateways for genomic manipulation.genomics | bioenergy | biotechnological yeasts | genetic code | microbiology Y easts are fungi that reproduce asexually by budding or fission and sexually without multicellular fruiting bodies (1, 2). Their unicellular, largely free-living lifestyle has evolved several times (3). Despite morphological similarities, yeasts constitute over 1,500 known species that inhabit many specialized environmental niches and associations, including virtually all varieties of fruits and flowers, plant surfaces and exudates, insects and other invertebrates, birds, mammals, and highly diverse soils (4). Biochemical and genomic studies of the model yeast Saccharomyces cerevisiaeessential for making bread, beer, and wine-have established much of our understanding of eukaryotic biology. However, in many ways, S. cerevisiae is an oddity among the yeasts, and many important biotechnological applications and highly divergent physiological capabilities of lesser-known yeast species have not been fully exploited (5). Various species can grow on methanol or n-alkanes as sole carbon and energy sources, overproduce vitamins and lipids, thrive under acidic conditions, and ferment unconventional carbon sources. Many features of yeasts make them ideal platforms for biotechnological processes. Their thick cell walls help them survive osmotic shock, and in contrast to bacteria, they are resistant to viruses. Their unicellular form is easy to cultivate, scale up, and harvest. The objective of this study was, therefore, to put yeasts with diverse biotechnological applications in a phylogenomic context and relate their physiologies to genomic SignificanceThe highly diverse Ascomycete yeasts have enormous biotechnological potential. Collectively, these yeasts convert a broad range of substrates into useful compounds, such as ethanol, lipids, and vitamins, and can grow in extremes of temperature, salinity, and pH. We compared 29 yeast genome...

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“…It has been shown that over-expression of these native S. cerevisiae genes using endogenous promoters enabled a specific growth rate of 0.01 h -1 on d-xylose in shake flasks [64]. However, in these shake-flask cultures this engineered yeast strain converted d-xylose into xylitol with a yield of 55%.…”

Section: Native D-xylose-metabolising Enzymes In S Cerevisiaementioning

confidence: 99%

“…However, in these shake-flask cultures this engineered yeast strain converted d-xylose into xylitol with a yield of 55%. Under anaerobic conditions, precluding respiratory NAD + regeneration, the strain overexpressing the endogenous enzymes was unable to utilise d-xylose [64].…”

Section: Native D-xylose-metabolising Enzymes In S Cerevisiaementioning

confidence: 99%