Functional characterization of a xylose transporter in Aspergillus nidulans

Ana Cristina Colabardini, Laure Nicolas Annick Ries, Neil Andrew Brown, Thaila Fernanda Dos Reis, Marcela Savoldi, Maria Helena S. Goldman, João Filipe Menino, Fernando Rodrigues, Gustavo Henrique Goldman

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31 Citations (Scopus)

Abstract

Background: The production of bioethanol from lignocellulosic feedstocks will only become economically feasible when the majority of cellulosic and hemicellulosic biopolymers can be efficiently converted into bioethanol. The main component of cellulose is glucose, whereas hemicelluloses mainly consist of pentose sugars such as D-xylose and L-arabinose. The genomes of filamentous fungi such as A. nidulans encode a multiplicity of sugar transporters with broad affinities for hexose and pentose sugars. Saccharomyces cerevisiae, which has a long history of use in industrial fermentation processes, is not able to efficiently transport or metabolize pentose sugars (e.g. xylose). Subsequently, the aim of this study was to identify xylose-transporters from A. nidulans, as potential candidates for introduction into S. cerevisiae in order to improve xylose utilization. Results: In this study, we identified the A. nidulans xtrD (xylose transporter) gene, which encodes a Major Facilitator Superfamily (MFS) transporter, and which was specifically induced at the transcriptional level by xylose in a XlnR-dependent manner, while being partially repressed by glucose in a CreA-dependent manner. We evaluated the ability of xtrD to functionally complement the S. cerevisiae EBY.VW4000 strain which is unable to grow on glucose, fructose, mannose or galactose as single carbon source. In S. cerevisiae, XtrD was targeted to the plasma membrane and its expression was able to restore growth on xylose, glucose, galactose, and mannose as single carbon sources, indicating that this transporter accepts multiple sugars as a substrate. XtrD has a high affinity for xylose, and may be a high affinity xylose transporter. We were able to select a S. cerevisiae mutant strain that had increased xylose transport when expressing the xtrD gene. Conclusions: This study characterized the regulation and substrate specificity of an A. nidulans transporter that represents a good candidate for further directed mutagenesis. Investigation into the area of sugar transport in fungi presents a crucial step for improving the S. cerevisiae xylose metabolism. Moreover, we have demonstrated that the introduction of adaptive mutations beyond the introduced xylose utilization genes is able to improve S. cerevisiae xylose metabolism.

Original languageEnglish
Article number46
JournalBiotechnology for Biofuels
Volume7
Issue number1
DOIs
Publication statusPublished - 1 Apr 2014

Keywords

  • Aspergillus nidulans
  • Saccharomyces cerevisiae
  • second generation bioethanol
  • xylose transporters

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology
  • Renewable Energy, Sustainability and the Environment
  • Energy(all)
  • Management, Monitoring, Policy and Law

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    Colabardini, A. C., Ries, L. N. A., Brown, N. A., Dos Reis, T. F., Savoldi, M., Goldman, M. H. S., Menino, J. F., Rodrigues, F., & Goldman, G. H. (2014). Functional characterization of a xylose transporter in Aspergillus nidulans. Biotechnology for Biofuels, 7(1), [46]. https://doi.org/10.1186/1754-6834-7-46