Format

Send to

Choose Destination
PLoS One. 2014 Sep 15;9(9):e107499. doi: 10.1371/journal.pone.0107499. eCollection 2014.

Engineering and two-stage evolution of a lignocellulosic hydrolysate-tolerant Saccharomyces cerevisiae strain for anaerobic fermentation of xylose from AFEX pretreated corn stover.

Author information

1
DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
2
DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America; Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
3
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
4
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
5
DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, United States of America; Biomass Conversion Research Laboratory, Department of Chemical Engineering and Materials Science, Michigan State University, Lansing, Michigan, United States of America.
6
DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, United States of America; School of Food and Bioengineering, Qilu University of Technology, Jinan, China.
7
Advanced Biofuels Process Demonstration Unit, Lawrence Berkeley National Laboratory, Emeryville, California, United States of America.
8
Deconstruction Division, Joint BioEnergy Institute, Emeryville, California, United States of America.
9
DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, United States of America; Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan, United States of America; Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing Michigan, United States of America; Division of Sustainable Process Engineering, Luleå University of Technology, Luleå, Sweden.
10
DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America; Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America; Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
11
DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America; Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.

Abstract

The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX)-pretreated corn stover hydrolysate (ACSH). We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH.

PMID:
25222864
PMCID:
PMC4164640
DOI:
10.1371/journal.pone.0107499
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center