Xylulokinase activity in various yeasts includingSaccharomyces cerevisiae containing the cloned xylulokinase gene

Cellulosic biomass is an abundant and underused substrate for biofuel production. The inability of many microbes to metabolize the pentose sugars abundant within hemicellulose creates specific challenges for microbial biofuel production from cellulosic material. Although engineered strains of Saccharomyces cerevisiae can use the pentose xylose, the fermentative capacity pales in comparison with glucose, limiting the economic feasibility of industrial fermentations. To better understand xylose utilization for subsequent microbial engineering, we sequenced the genomes of two xylose-fermenting, beetle-associated fungi, Spathaspora passalidarum and Candida tenuis . To identify genes involved in xylose metabolism, we applied a comparative genomic approach across 14 Ascomycete genomes, mapping phenotypes and genotypes onto the fungal phylogeny, and measured genomic expression across five Hemiascomycete species with different xylose-consumption phenotypes. This approach implicated many genes and processes involved in xylose assimilation. Several of these genes significantly improved xylose utilization when engineered into S. cerevisiae , demonstrating the power of comparative methods in rapidly identifying genes for biomass conversion while reflecting on fungal ecology.

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“…Although some details are known (Fig. 1A) (2,3,(10)(11)(12), much of the mechanism of xylose fermentation remains unresolved.…”

mentioning

confidence: 99%

Comparative genomics of xylose-fermenting fungi for enhanced biofuel production

Wohlbach

Kuo

Sato

et al. 2011

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

169

156

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“…As early as 1988, D-xylulokinase sequences from S. cerevisiae and Pachysolen tannophilus have been described [162][163][164]. In the yeast genome project, the complete S. cerevisiae gene XK was identified [165].…”

Section: Xylulokinasementioning

confidence: 99%

“…However, the XK enzyme, which was described by Ho and Tsao in 1993, was found to be inactive [164,166]. In S. cerevisiae cells, it is known that the activity of XK limits the xylulose metabolism [162,163]. The overexpression of XK from S. cerevisiae (ScXK) along with XYL2 and XYL1 of P. stipitis in Saccharomyces sp.…”

Section: Xylulokinasementioning

confidence: 99%

“…Additionally, a mutation within the promoter region of phosphoglucose isomerase causes the reduction of the enzyme activity and accumulation of fructose-6-phosphate, which also causes increase in the ethanol yield by 15% [80]. In native S. cerevisiae, D-xylulokinase is not expressed meaningfully; however, it is crucial for xylulose metabolism as the ∆XK mutants have a defect to grow on xylulose [163]. Simultaneously, the XK overexpression can cause a defect on the growth of the yeast strain on xylulose [165].…”

Section: Xylulokinasementioning

confidence: 99%

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Bioethanol a Microbial Biofuel Metabolite; New Insights of Yeasts Metabolic Engineering

et al. 2018

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Scarcity of the non-renewable energy sources, global warming, environmental pollution, and raising the cost of petroleum are the motive for the development of renewable, eco-friendly fuels production with low costs. Bioethanol production is one of the promising materials that can subrogate the petroleum oil, and it is considered recently as a clean liquid fuel or a neutral carbon. Diverse microorganisms such as yeasts and bacteria are able to produce bioethanol on a large scale, which can satisfy our daily needs with cheap and applicable methods. Saccharomyces cerevisiae and Pichia stipitis are two of the pioneer yeasts in ethanol production due to their abilities to produce a high amount of ethanol. The recent focus is directed towards lignocellulosic biomass that contains 30-50% cellulose and 20-40% hemicellulose, and can be transformed into glucose and fundamentally xylose after enzymatic hydrolysis. For this purpose, a number of various approaches have been used to engineer different pathways for improving the bioethanol production with simultaneous fermentation of pentose and hexoses sugars in the yeasts. These approaches include metabolic and flux analysis, modeling and expression analysis, followed by targeted deletions or the overexpression of key genes. In this review, we highlight and discuss the current status of yeasts genetic engineering for enhancing bioethanol production, and the conditions that influence bioethanol production.

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“…8,9) However, ethanol production from xylose by means of these strains is insufficient, because S. cerevisiae has little XK activity. 10) The ethanol yield from xylose has been increased by overexpressing the XK encoding gene (XKS1) in S. cerevisiae strains carrying XYL1 and XYL2.…”

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confidence: 99%