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Toward pectin fermentation by Saccharomyces cerevisiae: Expression of the first two steps of a bacterial pathway for d-galacturonate metabolism

Paper ID Volume ID Publish Year Pages File Format Full-Text
23638 43459 2012 8 PDF Available
Title
Toward pectin fermentation by Saccharomyces cerevisiae: Expression of the first two steps of a bacterial pathway for d-galacturonate metabolism
Abstract

Saccharomyces cerevisiae cannot metabolize d-galacturonate, an important monomer of pectin. Use of S. cerevisiae for production of ethanol or other compounds of interest from pectin-rich feedstocks therefore requires introduction of a heterologous pathway for d-galacturonate metabolism. Bacterial d-galacturonate pathways involve d-galacturonate isomerase, d-tagaturonate reductase and three additional enzymes. This study focuses on functional expression of bacterial d-galacturonate isomerases in S. cerevisiae. After demonstrating high-level functional expression of a d-tagaturonate reductase gene (uxaB from Lactococcus lactis), the resulting yeast strain was used to screen for functional expression of six codon-optimized bacterial d-galacturonate isomerase (uxaC) genes. The L. lactis uxaC gene stood out, yielding a tenfold higher enzyme activity than the other uxaC genes. Efficient expression of d-galacturonate isomerase and d-tagaturonate reductase represents an important step toward metabolic engineering of S. cerevisiae for bioethanol production from d-galacturonate. To investigate in vivo activity of the first steps of the d-galacturonate pathway, the L. lactis uxaB and uxaC genes were expressed in a gpd1Δ gpd2Δ S. cerevisiae strain. Although d-tagaturonate reductase could, in principle, provide an alternative means for re-oxidizing cytosolic NADH, addition of d-galacturonate did not restore anaerobic growth, possibly due to absence of a functional d-altronate exporter in S. cerevisiae.

► First two enzymes of the bacterial galacturonate pathway functionally expressed in Saccharomyces cerevisiae. ► Codon-optimized galacturonate isomerase gene from Lactococcus lactis superior to 5 other bacterial genes. ► Attempts to demonstrate in vivo activity of complete galacturonate pathway in yeast unsuccessful.

Keywords
Pectin; d-Galacturonate; Ethanol; Metabolic engineering; d-Galacturonate isomerase; d-Tagaturonate reductase; Saccharomyces cerevisiae
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Toward pectin fermentation by Saccharomyces cerevisiae: Expression of the first two steps of a bacterial pathway for d-galacturonate metabolism
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 162, Issues 2–3, 31 December 2012, Pages 303–310
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us