title: Evolved hexose transporter enhances xylose uptake and glucose/xylose co-utilization in Saccharomyces cerevisiae.
abstract: Enhancing xylose utilization has been a major focus in Saccharomyces cerevisiae strain-engineering efforts. The incentive for these studies arises from the need to use all sugars in the typical carbon mixtures that comprise standard renewable plant-biomass-based carbon sources. While major advances have been made in developing utilization pathways, the efficient import of five carbon sugars into the cell remains an important bottleneck in this endeavor. Here we use an engineered S. cerevisiae BY4742 strain, containing an established heterologous xylose utilization pathway, and imposed a laboratory evolution regime with xylose as the sole carbon source. We obtained several evolved strains with improved growth phenotypes and evaluated the best candidate using genome resequencing. We observed remarkably few single nucleotide polymorphisms in the evolved strain, among which we confirmed a single amino acid change in the hexose transporter HXT7 coding sequence to be responsible for the evolved phenotype. The mutant HXT7(F79S) shows improved xylose uptake rates (Vmax = 186.4 ± 20.1 nmol•min(-1)•mg(-1)) that allows the S. cerevisiae strain to show significant growth with xylose as the sole carbon source, as well as partial co-utilization of glucose and xylose in a mixed sugar cultivation.
authors.affiliation: Joint BioEnergy Institute, 5885 Hollis St, Emeryville, CA 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Reider Apel
authors.affiliation: Joint BioEnergy Institute, 5885 Hollis St, Emeryville, CA 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Mario
authors.initials: M
authors.lastname: Ouellet
authors.affiliation: Joint BioEnergy Institute, 5885 Hollis St, Emeryville, CA 94608, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Szmidt-Middleton
authors.affiliation: Joint BioEnergy Institute, 5885 Hollis St, Emeryville, CA 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.|Department of Bioengineering, University of California, Berkeley, CA 94720, USA.|Department of Chemical &Biomolecular Engineering, University of California, Berkeley, CA 94720, USA.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Keasling
authors.affiliation: Joint BioEnergy Institute, 5885 Hollis St, Emeryville, CA 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Aindrila
authors.initials: A
authors.lastname: Mukhopadhyay
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D014994:Xylose / Q000378:metabolism*
chemical_list: D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D002244:Carbon; D014994:Xylose; D005947:Glucose