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An engineered cryptic Hxt11 sugar transporter facilitates glucose-xylose co-consumption in Saccharomyces cerevisiae

Shin, H. Y., Nijland, J. G., de Waal, P. P., de Jong, R. M., Klaassen, P. & Driessen, A. J. M., 2-Nov-2015, In : Biotechnology for Biofuels. 8, 176, 13 p.

Research output: Contribution to journalArticleAcademicpeer-review

BACKGROUND: The yeast Saccharomyces cerevisiae is unable to ferment pentose sugars like d-xylose. Through the introduction of the respective metabolic pathway, S. cerevisiae is able to ferment xylose but first utilizes d-glucose before the d-xylose can be transported and metabolized. Low affinity d-xylose uptake occurs through the endogenous hexose (Hxt) transporters. For a more robust sugar fermentation, co-consumption of d-glucose and d-xylose is desired as d-xylose fermentation is in particular prone to inhibition by compounds present in pretreated lignocellulosic feedstocks.

RESULTS: Evolutionary engineering of a d-xylose-fermenting S. cerevisiae strain lacking the major transporter HXT1-7 and GAL2 genes yielded a derivative that shows improved growth on xylose because of the expression of a normally cryptic HXT11 gene. Hxt11 also supported improved growth on d-xylose by the wild-type strain. Further selection for glucose-insensitive growth on d-xylose employing a quadruple hexokinase deletion yielded mutations at N366 of Hxt11 that reversed the transporter specificity for d-glucose into d-xylose while maintaining high d-xylose transport rates. The Hxt11 mutant enabled the efficient co-fermentation of xylose and glucose at industrially relevant sugar concentrations when expressed in a strain lacking the HXT1-7 and GAL2 genes.

CONCLUSIONS: Hxt11 is a cryptic sugar transporter of S. cerevisiae that previously has not been associated with effective d-xylose transport. Mutagenesis of Hxt11 yielded transporters that show a better affinity for d-xylose as compared to d-glucose while maintaining high transport rates. d-glucose and d-xylose co-consumption is due to a redistribution of the sugar transport flux while maintaining the total sugar conversion rate into ethanol. This method provides a single transporter solution for effective fermentation on lignocellulosic feedstocks.

Original languageEnglish
Number of pages13
JournalBiotechnology for Biofuels
Volume8
Issue number176
Publication statusPublished - 2-Nov-2015

    Keywords

  • Sugar transport, Directed evolution, Lignocellulose conversion, Yeast, PERFORMANCE, INHIBITION, YEAST HEXOSE TRANSPORTERS, CANDIDA-INTERMEDIA, ETHANOL-PRODUCTION, FERMENTATION, STRAIN, GENES, METABOLISM, LIGNOCELLULOSE

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