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- Title
Identification and characterization of a galacturonic acid transporter from Neurospora crassa and its application for Saccharomyces cerevisiae fermentation processes.
- Authors
Benz, J. Philipp; Protzko, Ryan J.; Andrich, Jonas M. S.; Bauer, Stefan; Dueber, John E.; Somerville, Chris R.
- Abstract
Background Pectin-rich agricultural wastes potentially represent favorable feedstocks for the sustainable production of alternative energy and bio-products. Their efficient utilization requires the conversion of all major constituent sugars. The current inability of the popular fermentation host Saccharomyces cerevisiae to metabolize the major pectic monosaccharide Dgalacturonic acid (D-GalA) significantly hampers these efforts. While it has been reasoned that the optimization of cellular D-GalA uptake will be critical for the engineering of D-GalA utilization in yeast, no dedicated eukaryotic transport protein has been biochemically described. Here we report for the first time such a eukaryotic D-GalA transporter and characterize its functionality in S. cerevisiae. Results We identified and characterized the D-GalA transporter GAT-1 out of a group of candidate genes obtained from co-expression analysis in N. crassa. The N. crassa Δgat-1 deletion strain is substantially affected in growth on pectic substrates, unable to take up D-GalA, and impaired in D-GalA-mediated signaling events. Moreover, expression of a gat-1 construct in yeast conferred the ability for strong high-affinity D-GalA accumulation rates, providing evidence for GAT-1 being a bona fide D-GalA transport protein. By recombinantly coexpressing D-galacturonate reductase or uronate dehydrogenase in yeast we furthermore demonstrated a transporter-dependent conversion of D-GalA towards more reduced (Lgalactonate) or oxidized (meso-galactaric acid) downstream products, respectively, over a broad concentration range. Conclusions By utilizing the novel D-GalA transporter GAT-1 in S. cerevisiae we successfully generated a transporter-dependent uptake and catalysis system for D-GalA into two products with high potential for utilization as platform chemicals. Our data thereby provide a considerable first step towards a more complete utilization of biomass for biofuel and value-added chemicals production.
- Subjects
NEUROSPORA crassa; SACCHAROMYCES cerevisiae; GALACTURONIC acid; FERMENTATION; MONOSACCHARIDES; BIOMASS energy
- Publication
Biotechnology for Biofuels, 2014, Vol 7, Issue 1, p1
- ISSN
1754-6834
- Publication type
Article
- DOI
10.1186/1754-6834-7-20