title: Hybridization and adaptive evolution of diverseSaccharomycesspecies for cellulosic biofuel production.
abstract: BACKGROUND
  Lignocellulosic biomass is a common resource across the globe, and its fermentation offers a promising option for generating renewable liquid transportation fuels. The deconstruction of lignocellulosic biomass releases sugars that can be fermented by microbes, but these processes also produce fermentation inhibitors, such as aromatic acids and aldehydes. Several research projects have investigated lignocellulosic biomass fermentation by the baker's yeastSaccharomyces cerevisiae. Most projects have taken synthetic biological approaches or have explored naturally occurring diversity inS. cerevisiaeto enhance stress tolerance, xylose consumption, or ethanol production. Despite these efforts, improved strains with new properties are needed. In other industrial processes, such as wine and beer fermentation, interspecies hybrids have combined important traits from multiple species, suggesting that interspecies hybridization may also offer potential for biofuel research.
  
  
  RESULTS
  To investigate the efficacy of this approach for traits relevant to lignocellulosic biofuel production, we generated synthetic hybrids by crossing engineered xylose-fermenting strains ofS. cerevisiaewith wild strains from variousSaccharomycesspecies. These interspecies hybrids retained important parental traits, such as xylose consumption and stress tolerance, while displaying intermediate kinetic parameters and, in some cases, heterosis (hybrid vigor). Next, we exposed them to adaptive evolution in ammonia fiber expansion-pretreated corn stover hydrolysate and recovered strains with improved fermentative traits. Genome sequencing showed that the genomes of these evolved synthetic hybrids underwent rearrangements, duplications, and deletions. To determine whether the genusSaccharomycescontains additional untapped potential, we screened a genetically diverse collection of more than 500 wild, non-engineeredSaccharomycesisolates and uncovered a wide range of capabilities for traits relevant to cellulosic biofuel production. Notably,Saccharomyces mikataestrains have high innate tolerance to hydrolysate toxins, while someSaccharomycesspecies have a robust native capacity to consume xylose.
  
  
  CONCLUSIONS
  This research demonstrates that hybridization is a viable method to combine industrially relevant traits from diverse yeast species and that members of the genusSaccharomycesbeyondS. cerevisiaemay offer advantageous genes and traits of interest to the lignocellulosic biofuel industry.
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: David
authors.identifier: 0000-0001-9912-8802
authors.initials: D
authors.lastname: Peris
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Ryan V
authors.initials: RV
authors.lastname: Moriarty
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: William G
authors.initials: WG
authors.lastname: Alexander
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: EmilyClare
authors.initials: E
authors.lastname: Baker
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Kayla
authors.initials: K
authors.lastname: Sylvester
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.|Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Sardi
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Quinn K
authors.initials: QK
authors.lastname: Langdon
authors.affiliation: Laboratorio de Microbiología Aplicada, Biotecnología y Bioinformática, Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales, IPATEC (CONICET-UNComahue), Centro Regional Universitario Bariloche, Bariloche, Río Negro Argentina.
authors.forename: Diego
authors.initials: D
authors.lastname: Libkind
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Qi-Ming
authors.initials: QM
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Feng-Yan
authors.initials: FY
authors.lastname: Bai
authors.affiliation: Departement des Sciences Biologiques, Université de Montréal, Montreal, QC Canada.|Département de Biologie, PROTEO, Pavillon Charles-Eugène-Marchand, Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Quebec City, QC Canada.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Leducq
authors.affiliation: Département de Biologie, PROTEO, Pavillon Charles-Eugène-Marchand, Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Quebec City, QC Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Charron
authors.affiliation: Département de Biologie, PROTEO, Pavillon Charles-Eugène-Marchand, Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Quebec City, QC Canada.
authors.forename: Christian R
authors.initials: CR
authors.lastname: Landry
authors.affiliation: UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal.
authors.forename: José Paulo
authors.initials: JP
authors.lastname: Sampaio
authors.affiliation: UCIBIO-REQUIMTE, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Gonçalves
authors.affiliation: Department of Genetics, Center for Genome Sciences and Systems Biology, Washington University in St. Louis, St. Louis, MO USA.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Hyma
authors.affiliation: Department of Genetics, Center for Genome Sciences and Systems Biology, Washington University in St. Louis, St. Louis, MO USA.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Fay
authors.affiliation: DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Trey K
authors.initials: TK
authors.lastname: Sato
authors.affiliation: Laboratory of Genetics, Wisconsin Energy Institute, J. F. Crow Institute for the Study of Evolution, Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI USA.|DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI USA.|Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI USA.
authors.forename: Chris Todd
authors.identifier: 0000-0001-5088-7461
authors.initials: CT
authors.lastname: Hittinger
keywords: AFEX-pretreated corn stover hydrolysate (ACSH); Ammonia fiber expansion (AFEX); Biodiversity; Bioethanol; Hybridization; Hydrolysate toxins; Saccharomyces; Xylose